Natural arsenal of Magnolia sarcotesta: insecticidal activity against the leaf-cutting ant Atta mexicana (Hymenoptera: Formicidae)

Dennis Adrián Infante-Rodríguez; Jorge Ernesto Valenzuela-González; Neptalí Ramírez-Marcial; Suria Gisela Vásquez-Morales

doi:10.1515/flaent-2024-0049

Article Open Access

Natural arsenal of Magnolia sarcotesta: insecticidal activity against the leaf-cutting ant Atta mexicana (Hymenoptera: Formicidae)

Dennis Adrián Infante-Rodríguez , Jorge Ernesto Valenzuela-González , Neptalí Ramírez-Marcial and Suria Gisela Vásquez-Morales

Published/Copyright: June 12, 2025

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From the journal Florida Entomologist Volume 108 Issue 1

Abstract

Atta mexicana (F. Smith) (Hymenoptera: Formicidae) is a significant agricultural pest in Mexico. This study tested the insecticidal activity of ethanol extracts from the sarcotesta of three Magnolia (Magnoliaceae) species endemic to Mexico against A. mexicana. Contact and ingestion bioassays were performed using various ethanol extract concentrations. After 72 h of exposure, Magnolia pugana (Iltis & A.Vazquez) A.Vazquez & Carvajal showed the highest contact toxicity at 2.0 mg/mL, 0.2 mg/mL, and 0.02 mg/mL, with a lethal concentration to 90 % mortality (LC₉₀) of 0.02 mg/mL. Magnolia perezfarrerae A.Vázquez & Gómez-Domínguez exhibited toxicity at 2.0 mg/mL and 0.2 mg/mL, with LC₉₀ = 0.1 mg/mL, while Magnolia vovidesii A.Vázquez, Domínguez-Yescas & L.Carvajal showed toxicity at 4.0 mg/mL and 0.04 mg/mL, with LC₉₀ = 0.4 mg/mL. The ethanol extracts also demonstrated significant toxicity by ingestion. The most effective concentrations for M. pugana was 2.0 mg/mL with LC₉₀ = 0.24 mg/mL, while for M. perezfarrerae, they were 2.0 mg/mL, 0.2 mg/mL, and 0.02 mg/mL (LC₉₀ = 0.06 mg/mL). For M. vovidesii, the most effective concentrations were 4.0 mg/mL, 0.4 mg/mL, and 0.04 mg/mL (LC₉₀ = 0.07 mg/mL). Chemical analysis revealed the presence of alkaloids, terpenes, and phenols in the extracts. This study suggests that the tested Magnolia sarcotesta extracts have great potential as effective botanical pesticides against A. mexicana, implying promising insights for developing agricultural pest management strategies.

Resumen

Atta mexicana (F. Smith) (Hymenoptera: Formicidae) es una plaga agrícola significativa en México. Este estudio evaluó la actividad insecticida de los extractos etanólicos de la sarcotesta de tres especies de Magnolia (Magnoliaceae) endémicas de México contra A. mexicana. Se realizaron bioensayos de contacto e ingestión utilizando diversas concentraciones de extractos etanólicos. Después de 72 horas de exposición, Magnolia pugana (Iltis & A.Vázquez) A.Vázquez & Carvajal mostró la mayor toxicidad por contacto a 2.0 mg/mL, 0.2 mg/mL y 0.02 mg/mL, con una concentración letal de 90 % (LC₉₀) de 0.02 mg/mL. Magnolia perezfarrerae A.Vázquez & Gómez-Domínguez presentó mayor toxicidad a 2.0 mg/mL y 0.2 mg/mL, con LC₉₀ = 0.1 mg/mL, mientras que Magnolia vovidesii A.Vázquez, Domínguez-Yescas & L.Carvajal mostró toxicidad a 4.0 mg/mL y 0.04 mg/mL, con LC₉₀ = 0.4 mg/mL. Los extractos etanólicos también demostraron una toxicidad significativa por ingestión. Las concentraciones más efectivas para M. pugana fueron 2.0 mg/mL con LC₉₀ = 0.24 mg/mL, mientras que para M. perezfarrerae, las concentraciones más efectivas fueron 2.0 mg/mL, 0.2 mg/mL y 0.02 mg/mL (LC₉₀ = 0.06 mg/mL). Para M. vovidesii, las concentraciones más efectivas fueron 4.0 mg/mL, 0.4 mg/mL y 0.04 mg/mL (LC₉₀ = 0.07 mg/mL). El análisis químico reveló la presencia de alcaloides, terpenos y fenoles en los extractos. Este estudio sugiere que los extractos de sarcotesta de Magnolia evaluados tienen un gran potencial como pesticidas botánicos efectivos contra A. mexicana, lo que implica perspectivas prometedoras para el desarrollo de estrategias de manejo de plagas agrícolas.

Keywords: Magnoliaceae; botanical pesticides; bioprospecting; plant extracts; Attini ants

Palabras clave: Magnoliaceae; insecticidas botánicos; bioprospección; extractos vegetales; hormigas Attini

1 Introduction

Plant bioprospecting aims to discover new drugs, phytochemicals, and other useful compounds (Infante-Rodríguez et al. 2022). Botanical pesticides offer several environmental benefits over synthetic pesticides due to their low risk to non-target organisms, as they biodegrade and break down rapidly in the environment (Campos et al. 2019). Although they have a brief residual action, certain botanical pesticides are being implemented as barrier treatments. In these instances, effectiveness is achieved through behavioral effects such as repellence and deterrence, rather than acute toxicity (Kelm et al. 1997).

Despite being seen as more environmentally friendly, botanical insecticides can negatively affect biodiversity, as they often contain bioactive compounds harmful to both target pests and beneficial insects, such as pollinators (Xavier et al. 2015). For example, neem extracts are toxic to bees (Lopes Amaral et al. 2016). With increasing insecticide resistance, botanical insecticides, which consist of mixtures of active compounds, offer an advantage over synthetic chemicals (Shivanandappa and Rajashekar 2014). However, they still must be used cautiously within an integrated pest management approach to avoid ecological imbalances and resistance issues (Guleria and Tiku 2009).

Some plants produce secondary metabolites with a great variety of chemical and functional properties, alkaloids, terpenes, and phenols are usually the main groups recorded with insecticidal, deterrence, or antifeeding effects on insects (Rattan 2010). The Magnolia genus (Magnoliaceae) is recognized for producing a variety of bioactive compounds extracted from its bark, polyfollicles, flowers, and leaves (Poivre and Duez 2017). Some endemic Magnolia species from Mexico, such as Magnolia vovidesii A.Vázquez, Domínguez-Yescas & L.Carvajal and Magnolia schiedeana Schltdl., have demonstrated insecticidal activity when ethanol extracts of their leaves or seeds with sarcotesta are applied to adults of the Mexican fruit fly, Anastrepha ludens Loew (Diptera: Tephritidae) (Flores-Estéves et al. 2013; Vásquez-Morales et al. 2015). Similarly, a novel lignan, (+)-epimagnolin A, derived from the flower buds of Magnolia fargesii (Finet & Gagnep.) W.C. Cheng has shown growth inhibitory effects against Drosophila melanogaster Meigen (Diptera: Tephritidae) larvae (Miyazawa et al. 1994). Furthermore, a powder extract of Magnolia tamaulipana Vazquez has been found to inhibit egg laying and food intake in adult female Tetranychus urticae C.L.Koch (Trombidiformes: Tetranychidae), with efficacy increasing in line with the extract concentration, showing optimal results between 500 and 1,000 μg/mL, suggesting its potential as a control agent for spider mites (Chacón-Hernández et al. 2020). Additionally, Magnolia citrata Noot. & Chalermglin has exhibited insecticidal activity against the yellow fever mosquito Aedes aegypti (L.; Diptera: Culicidae) and attractant properties for the Mediterranean fruit fly Ceratitis capitata Wiedemann (Diptera: Tephritidae) (Luu-Dam et al. 2021). Similarly, the ethanolic leaf extract of Magnolia alejandrae García-Mor. & Lamonico has shown promising acaricidal potential for controlling Tetranychus merganser Boudreaux (Trombidiformes: Tetranychidae), containing phytochemicals such as phenolic compounds, alkaloids, and terpenes. Mites treated with 15 % (v/v) of the extract exhibited a 33.3 % mortality at 72 h and a notable reduction in oviposition rates, leading to a decrease in the growth rate of the mite population (Olazaran-Santibañez et al. 2024). These findings highlight the potential of Magnolia species and their extracts as effective biocontrol agents.

It has been reported that repellent and toxic compounds against ants (Solenopsis invicta Buren × S. richteri Buren hybrid fire ants; Hymenoptera: Formicidae) can be isolated from some Magnolia species. For example, the essential oil of Magnolia grandiflora L., as well as its individual components 1-decanol and 1-octanol, were significantly more repellent than N,N-diethyl-meta-toluamide, known as DEET, which is the most commonly used ingredient in insect repellents (Ali et al. 2022). 1-decanol and 1-octanol, present in the essential oil of the seeds, were toxic to fire ant workers. 1-decanol, with a lethal concentration to 50 % mortality (LC₅₀) of 140.6 μg/g, was the most toxic natural compound, followed by 1-octanol (LC₅₀ = 486.8 μg/g). Bifenthrin, with an LC₅₀ of 0.018 μg/g, was much more toxic than these natural compounds. The repellency and toxicity of 1-decanol make it a natural compound of interest for further study under field conditions (Ali et al. 2022).

Among the herbivorous insects, leaf-cutting ants (Hymenoptera: Attini: Myrmicinae) are represented by the genera Atta (Fabricius), and Acromyrmex (Mayr). These ants are ecologically and economically important species in the Neotropics because they cause damage to numerous crop plant species, generating losses of millions of dollars annually (Wirth et al. 2003). The main method used to control Atta species is the application of baits impregnated with sulfluramid, this compound was classified as an organic pollutant highlighting the urgent need to seek new active ingredients with greater ecological and environmental safety (Teixeira et al. 2023). Therefore, the investigation of botanical pesticides rich in alkaloids, terpenes, and phenols has gained momentum serving as an agroecological alternative for leaf-cutting ant control (Bueno et al. 2005; Boulogne et al. 2012; Infante-Rodríguez et al. 2020).

Plant extracts from the bark, branches, roots, and flowers of selected Magnolia species have been used to treat a variety of illnesses and diseases, including anxiety, insomnia, depression, diabetes, cardiovascular, liver, and bowel disease (Lee et al. 2011), and palliative care in some kinds of cancer (Morshedloo et al. 2017). The potential of extracts, essential oils, and secondary metabolites extracted from fruit, peel, seed, and sarcotesta from certain Magnolia species as biopesticides for agricultural insect pest management has been studied (Hernandez-Rocha & Vazquez-Morales 2023). However, as far as we know the toxic effects of M. vovidesii, Magnolia pugana (Iltis & A.Vazquez) A.Vazquez & Carvajal, and Magnolia perezfarrerae A.Vázquez & Gómez-Domínguez, against leaf-cutting ants have not yet been studied.

As the sarcotesta of certain Magnolia species have insecticidal properties; it was expected that the sarcotesta of the endemic Mexican species evaluated in the present study could be toxic or deterrent to leaf-cutting ants. Therefore, to prospect botanical insecticidal agents sourced from natural reservoirs, which hold promise for future pest management approaches, the main aims of this study were (i) evaluate the insecticidal effect of ethanol extracts of the sarcotesta from three Magnolia species endemic to Mexico against the leaf-cutting ant Atta mexicana F. Smith (Hymenoptera: Formicidae), and (ii) qualitatively identify and characterize the chemical constituents present in the ethanol extracts of Magnolia sarcotesta.

2 Materials and methods

2.1 Plant material

Leaves and polyfollicles were collected from three populations at different sites in Mexico during August 2022 and January and April 2023 (Figure 1). M. vovidesii was collected from the Coyopolan community in Ixhuacán de los Reyes, Veracruz (19.36863971 °N, 97.08292572 °W, 1,570 m a.s.l.). The plant material of M. perezfarrerae was collected in the community of Ocuilapa de Juárez, located in the municipality of Ocozocoautla de Espinosa, Chiapas (16.8491667 °N, 93.40972222 °W, 959 m a.s.l.). Lastly, the plant material of M. pugana was collected at the Centro Universitario de Ciencias Biológicas y Agropecuarias (CUCBA) of the University of Guadalajara, situated in Zapoapan, Jalisco (20.7475 °N, 103.512777 °W, 1,670 m a.s.l.). Taxonomic determination was conducted by Suria Gisela Vásquez-Morales and verified by curators of the herbarium XAL at the Instituto de Ecología A.C. (INECOL). Additionally, duplicate specimens of M. pugana (Voucher No. XAL0150849), and M. vovidesii (Voucher No. XAL72936) were placed in the herbarium XAL, and a duplicate specimen of M. perezfarrerae (Voucher No. 23948), was placed in the herbarium CH at El Colegio de la Frontera Sur.

Figure 1:

Magnolia structures collected in the present study: (a–c) polyfollicle, leaves, and seeds of Magnolia vovidesii Vázquez, Domínguez-Yescas & L. Carvajal, (d–f) polyfollicle, leaves and seeds of Magnolia perezfarrerae A.Vázquez & Gómez-Domínguez, and (g–i) polyfollicle, flower and seeds of Magnolia pugana (Iltis & A.Vázquez) A.Vázquez & Carvajal. Photo credit: DAIR and SGVM.

2.2 Ethanol extract of sarcotesta

The sarcotesta extract was prepared according to the protocol of Vásquez-Morales et al. (2022) with minor modifications. First, the seeds of each Magnolia species were extracted from the polyfollicles, and then the sarcotesta was removed manually. The sarcotesta from each species was placed in separate paper bags and dried in a drying cabinet (Mermmet Incubator IN30, Germany) at 40 °C for 7 days until completely dehydrated. Following that, it was pulverized in a mortar. The sarcotesta extracts were prepared for each species by maceration of 50 g of pulverized sarcotesta and 250 mL of ethanol (96 %, 1:5 w.v⁻¹). The ethanol extracts of sarcotesta were subsequently stored at 25 ± 2 °C for 6 days. The ethanol extracts of sarcotesta were filtered, and the solvent was collected in a 500 mL Erlenmeyer flask. The ethanol extracts of sarcotesta were concentrated in a rotary evaporator (Büchi, model R-300, Switzerland) at 60 °C. A final extract volume of 10–20 mL was obtained, with extraction yields of 2 mg/mL from M. pugana and M. perezfarrerae, and 4 mg/mL from M. vovidesii.

2.3 Qualitative chemical profiles determination of sarcotesta extract

2.3.1 Thin layer chromatography

Thin layer chromatography (TLC) was performed using solvents of four polarities: hexane (100 %), acetone (100 %), ethanol (100 %), and methanol (100 %). For this, 1 mL of each ethanol extract of sarcotesta tested was dissolved in 1 mL of each solvent, and an aliquot of 20 μL of each sample was applied on silica gel aluminum TLC plates, coated with fluorescent indicator F254 (Merck KEGaA, 64271, Darmstadt, Germany). The plates were developed in the different solvents for 10 min and were revealed using vanillin. Finally, the retention factor (Rf) was estimated for each visible spot, using the equation:

Rf = dte dts

where dte is the distance traveled by the extract and dts is the distance traveled by the solved tested.

2.4 Analyses of secondary metabolites by qualitative tests

To detect the presence of different secondary metabolites in each species studied, we used the protocol described by Dominguez (1973), and Vásquez-Morales et al. (2022). A total of 1 mg samples of the methanolic extract from each species were subjected to phytochemical analysis to ascertain the presence of alkaloids, terpenoids, steroids, phenolics, flavonoids, and tannins. All qualitative assays were performed in triplicate. The results were classified according to the formation of precipitates for alkaloids and tannins, and color intensity for phenols, terpenes and steroids, and flavonoids. Additionally, the presence of foam for saponins also was tested. Based on visual inspection, the samples were categorized as absent, low, medium, or high concentration.

2.5 Insecticidal activity assays

2.5.1 Experimental colonies

Fertilized queens without wings (n = 400) were collected after the nuptial flight in June 2022 in Silao (21.0075000 °N, 101.5075000 °W) and Guanajuato city (21.0108333 °N, 101.2694444 °W) and were kept until they became established in the insectary at Botany and Invertebrates Laboratory of the Department of Biology, Division Natural and Exact Sciences of the University of Guanajuato, in Guanajuato, Mexico. A total of 10 nests were established under laboratory conditions with a relative humidity of 60 ± 10 % and a temperature of 25 ± 2 °C. The nests received a diet to maintain their symbiotic fungal gardens based on oat flakes (Avena sativa L.; Poaceae), cornflakes (Kellogg´s^®), bougainvillea leaves (Bougainvillea spectabilis Willd.; Nyctaginaceae) and, rose leaves and petals (Rosa spp.; Rosaceae).

2.6 Determination of susceptibility of leaf-cutting ant workers to ethanol extract of Magnolia sarcotesta

2.6.1 Contact bioassay

Foraging ants derive only approximately 10 % of their nutrition from the mutualistic fungal mycelium, with the remainder (90 %) likely obtained from plant sap, which is rich in carbohydrates (Silva et al. 2003). Based on this information, the bioassays were standardized before contact exposure. The foraging ants for each bioassay were carefully captured from the insectarium colonies, stored in buckets, and transported to the laboratory. Afterward, the leaf-cutting ants were given a 12-h acclimatization period and given a solution of water and corn syrup (10 %) (Karo^®, Fresh Meadows, New York) ad libitum, which is rich in fructose. The solution was placed in glass vials sealed with cotton plugs. All of this was done with the premise that during the contact exposure experiment to the Magnolia extracts, the ants would not be fed and hydrated. The bioassay was performed following the World Health Organization (WHO) Standard Procedure for Impregnation of Filter Papers for Insecticide Susceptibility Testing (WHO 2022) with minor modifications. Circular filter paper discs with a diameter of 5.5 cm were cut and placed inside Petri dishes measuring 60 × 15 mm. Each paper disc was impregnated with one of the following treatments: 1 mL distilled water (negative control), 1 mL spinetoram (Palgus TM, Dow Agrosciences, Mexico) at 0.43 mg/mL (positive control), and for the M. pugana and Magnolia pererezfarrerae species, ethanol extracts of sarcotesta was analyzed in six concentrations (2 mg/mL, 0.2 mg/mL, 0.02 mg/mL, 0.002 mg/mL, 0.0002 mg/mL, and 0.00002 mg/mL). In addition, six concentrations (4 mg/mL, 0.4 mg/mL, 0.04 mg/mL, 0.004 mg/mL, 0.0004 mg/mL, and 0.00004 mg/mL) were tested for M. vovidesii. Each treatment involved 20 workers of leaf-cutting ants, and we recorded daily mortality at 3 h, 24 h, 48 h, and 72 h. The mortality (M) percentage of dead leaf-cutting ant workers was calculated using the formula:

M % = Number of dead ants 20 × 100

Abbott’s correction (CM) was then applied using the formula to account for the natural death of individuals:

CM % = M % sample − M % negative control 100 − M % negative control × 100

The experiment was made in triplicate, and leaf-cutting ant workers who were unresponsive to the touch of a toothpick were classified as dead.

2.6.2 Ingestion bioassay

Before the start of the experiment, the ants were divided into groups of 20 individuals per treatment and deprived of food and water for 24 h. The bioassay was performed with one of the following treatments: 1 mL purified water (negative control), 1 mL spinetoram (Palgus TM, Dow Agrosciences, Mexico) at 0.43 mg/mL (positive control), and for the M. pugana and M. pererezfarrerae species, ethanol extracts of sarcotesta was analyzed in five concentrations (2 mg/mL, 0.2 mg/mL, 0.02 mg/mL, 0.002 mg/mL, and 0.0002 mg/mL). In addition, five concentrations (4 mg/mL, 0.4 mg/mL, 0.04 mg/mL, 0.004 mg/mL, and 0.0004 mg/mL) were tested for M. vovidesii. For each replicate (n = 3), a microcentrifuge tube sealed with cotton wool containing 1 mL of each treatment was placed in 100 mL plastic bottles with lids. Each treatment involved 20 leaf-cutting ant workers, and we recorded daily mortality at 3 h, 24 h, 48 h, and 72 h. The percentages of mortality and the corrected mortality were estimated in the same way as in the contact experiment.

2.7 Statistical analysis

Mortality data were expressed as the mean ± SD (n = 3) and analyzed using the nonparametric Kruskal-Wallis test with subsequent Dunn’s post-hoc test for group comparisons. All statistical analyses were conducted with the Agricolae library (De Mendiburu 2010) in R software version 4.1.2 (R Core Team 2020). Furthermore, to find the lethal concentrations to 50 % and 90 % mortality against leaf-cutting ants a logistic regression model was employed using the drc package version 2.6-10 (Ritz et al. 2015) in R software v. 4.1.2 (R Core Team 2020).

3 Results

3.1 Contact bioassay

3.1.1 Mortality of A. mexicana in response to ethanol extracts of M. pugana sarcotesta

Ethanol extracts of M. pugana sarcotesta at concentrations of 2.0 mg/mL, 0.2 mg/mL, and 0.02 mg/mL were 100 % effective as insecticides against A. mexicana (H = 22.872; df = 7; P < 0.01) after 72 h exposure (Table 1). These results were equal to the mortality observed with spinetoram (positive control), with corrected mortality of 100 %. The concentration of 0.002 mg/mL showed moderate toxicity (42.59 ± 12.83 %; mean ± standard deviation), while concentrations of 0.0002 mg/mL and 0.00002 mg/mL showed very low insecticidal efficacy with mortality of 16.66 ± 5.55 % and 11.11 ± 0 %, after 72 h exposure, respectively (Figure 2). The LC₅₀ and LC₉₀ values for M. pugana were estimated to be 0.002 mg/mL and 0.02 mg/mL, respectively (Table 2).

Figure 2:

Abbott’s adjusted mortality percentage of Atta mexicana after 72 h contact exposure to six concentrations of ethanol extracts of the sarcotesta of Magnolia pugana and Magnolia perezfarrerae, at 2.0 mg/mL (C1), 0.2 mg/mL (C2), 0.02 mg/mL (C3), 0.002 mg/mL (C4), 0.0002 mg/mL (C5), and 0.00002 mg/mL (C6), and Magnolia vovidesii at 4.0 mg/mL (C1), 0.4 mg/mL (C2), 0.04 mg/mL (C3), 0.004 mg/mL (C4), 0.0004 (C5), and 0.00004 mg/mL (C6),with positive control of spinetoram at 0.43 mg/mL (C+), and water (C-).

Table 1:

Effectiveness of ethanolic extracts of Magnolia sarcotesta as a botanical pesticide by contact against Atta mexicana at six concentrations. Mortality percentages over time and the corrected mortality (Mean ± SD) are presented. PC = positive control, spinetoram, NC = negative control, water, C1–C6 = tested concentrations of ethanolic extracts of sarcotesta from the species tested. Superscript letters indicate significant differences among treatments (P < 0.05; Kruskal-Wallis test with subsequent Dunn’s post-hoc test for group comparisons).

Treatments	Concentration (mg/mL)	Mortality (3 h)	Corrected mortality (3 h)	Mortality (24 h)	Corrected mortality (24 h)	Mortality (48 h)	Corrected mortality (48 h)	Mortality (72 h)	Corrected mortality (72 h)
Magnolia pugana

PC	0.43	78.33 ± 18.92a	77.96 ± 19.25a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a
NC	0	1.66 ± 2.88cd	–	5.00 ± 8.66cd	–	5.00 ± 8.66b	–	11.66 ± 11.54e	–
C1	2.0	55.00 ± 43.58ab	54.23 ± 44.32ab	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a
C2	0.2	23.33 ± 7.63ab	22.03 ± 7.76ab	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a
C3	0.02	15.00 ± 13.22bc	13.55 ± 13.45bc	78.33 ± 11.54b	77.19 ± 12.15b	78.33 ± 11.54b	77.35 ± 9.80b	80.00 ± 8.66a	100 ± 0a
C4	0.002	0 ± 0d	0 ± 0d	8.33 ± 5.77cd	3.50 ± 6.07c	8.33 ± 5.77c	20.54 ± 14.97c	30.00 ± 13.22b	42.59 ± 12.83b
C5	0.0002	0 ± 0d	0 ± 0d	11.66 ± 5.77c	7.01 ± 6.07c	20.00 ± 8.66cd	9.43 ± 9.80cd	20.00 ± 8.66c	16.66 ± 5.55c
C6	0.00002	0 ± 0d	0 ± 0d	3.33 ± 5.77d	0 ± 0c	3.33 ± 5.77e	0 ± 0e	3.33 ± 5.77d	11.11 ± 0.00d

Magnolia perezfarrerae

PC	0.43	28.33 ± 12.58^a	27.11 ± 12.79ab	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a
NC	0	1.66 ± 2.86b	–	3.33 ± 5.77c	–	6.66 ± 11.54b	–	28.33 ± 40.72b	–
C1	2.0	63.33 ± 18.92^a	62.71 ± 19.25^a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a
C2	0.2	8.33 ± 14.43b	7.09 ± 13.69b	51.66 ± 42.52ab	50.00 ± 43.99ab	88.33 ± 20.20a	87.50 ± 21.65a	96.66 ± 2.88a	95.34 ± 4.02a
C3	0.02	10.0 ± 17.32b	9.6 ± 16.63b	18.33 ± 23.26ab	16.66 ± 23.25bc	25.00 ± 21.79b	22.02 ± 19.26b	41.66 ± 28.43b	27.13 ± 25.72b
C4	0.002	1.66 ± 2.88b	1.13 ± 1.96b	5.0 ± 5.0c	2.87 ± 3.59c	5.00 ± 5.00b	1.19 ± 2.06b	6.66 ± 2.88bc	0 ± 0b
C5	0.0002	1.66 ± 2.88b	1.13 ± 1.96b	1.66 ± 2.88c	0.57 ± 0.99c	6.66 ± 7.63b	2.97 ± 5.15b	23.33 ± 28.43b	12.40 ± 21.48b
C6	0.00002	1.66 ± 2.88b	1.13 ± 1.96b	20.00 ± 26.45bc	18.39 ± 26.10bc	23.33 ± 36.17b	20.83 ± 36.08b	35.00 ± 43.58ab	26.35 ± 45.65b

Magnolia vovidesii

PC	0.43	78.33 ± 18.92^a	77.96 ± 19.25a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a
NC	0	1.66 ± 2.88cd	–	5.00 ± 8.66d	–	25.00 ± 26.45cd	–	29.69 ± 39.28cd	–
C1	4.0	55.0 ± 43.58ab	54.23 ± 44.32ab	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a
C2	0.4	23.33 ± 7.63ab	22.03 ± 7.76ab	36.66 ± 24.66ab	33.33 ± 25.96b	76.76 ± 20.20ab	68.88 ± 26.94^a	86.66 ± 12.58ab	81.03 ± 17.89ab
C3	0.04	15.0 ± 13.23bc	14.12 ± 12.49bc	30.00 ± 20.00bc	26.31 ± 21.05b	46.66 ± 27.53bc	33.33 ± 29.05b	53.33 ± 16.07bc	33.62 ± 22.86bc
C4	0.004	0 ± 0d	0 ± 0d	8.33 ± 5.77cd	3.50 ± 6.07c	8.33 ± 5.77d	0 ± 0c	16.08 ± 14.32cd	1.72 ± 2.98d
C5	0.0004	0 ± 0d	0 ± 0d	3.33 ± 2.88d	0 ± 0c	5.00 ± 5.00d	0 ± 0c	7.66 ± 7.19d	0 ± 0d
C6	0.00004	0 ± 0d	0 ± 0d	5.00 ± 5.00d	1.75 ± 3.03c	11.66 ± 10.40cd	0 ± 0c	15.00 ± 5.00cd	0 ± 0d

Table 2:

Lethal concentration to 50 % and 90 % mortality by contact (LC) of ethanol extracts of Magnolia sarcotesta against Atta mexicana at 72 h of exposure. The confidence interval (CI), the lower limit (LL), and the upper limit (UL).

Plant species	Effective concentration	Estimate (mg/mL)	SE	CI 95 %
				LL	UL
Magnolia pugana	LC₅₀	0.002	0.00043496	0.00118093	0.00302509
	LC₉₀	0.02	0.00847184	0.00069491	0.03661391
Magnolia perezfarrerae	LC₅₀	0.04	0.0187337	−0.0044551	0.0749724
	LC₉₀	0.1	0.1752145	−0.2471832	0.4956929
Magnolia vovidesii	LC₅₀	0.04	0.0097318	0.0214940	0.0627548
	LC₉₀	0.4	0.1846595	−0.0094683	0.7734530

3.1.2 Mortality of A. mexicana in response to ethanol extracts of M. vovidesii sarcotesta

The results show that concentrations of 4.0 mg/mL and 0.4 mg/mL of sarcotesta ethanol extract were effective against A. mexicana with 100, and 81 ± 17.89 % mortality after 72 h exposure (H = 20.764; df = 7; P < 0.01), respectively, while the concentration of 0.04 mg/mL showed moderate toxicity with 33.62 ± 22.86 % mortality. Concentrations of 0.004 mg/mL, 0.0004 mg/mL, and 0.00004 mg/mL showed very low or no insecticidal efficacy with corrected mortality of 1.72 ± 2.98 %, 0 ± 0 %, 0 ± 0 %, respectively (Table 1). The spinetoram treatment (positive control) had a corrected mortality of 100 ± 0 % (Figure 2). The LC₅₀ and LC₉₀ values for M. vovidesii were estimated to be 0.04 mg/mL and 0.4 mg/mL, respectively (Table 2).

3.1.3 Mortality of A. mexicana in response to ethanol extracts of M. perezfarrerae sarcotesta

In the case of ethanol extracts of M. perezfarrerae sarcotesta, only the concentrations of 2.0 mg/mL and 0.2 mg/mL were effective as insecticides against A. mexicana with 100 % and 95.34 ± 4.02 % mortality, respectively, after 72 h exposure (H = 19.012; df = 7; P < 0.01), similar to that observed in the spinetoram treatment (positive control, 100 %) (Table 1). Concentrations of 0.02 mg/mL, 0.002 mg/mL, 0.0002 mg/mL, and 0.00002 mg/mL showed very low toxicity with corrected mortality of 27.13 ± 25.72 %, 0 ± 0 %, 12.4 ± 21.48 %, and 26.35 ± 45.65 %, respectively (Figure 2). The LC₅₀ and LC₉₀ values for M. perezfarrerae were estimated to be 0.04 mg/mL and 0.1 mg/mL, respectively (Table 2).

3.2 Ingestion bioassay

3.2.1 Mortality of A. mexicana in response to ethanol extracts of M. pugana sarcotesta

The results of the ingestion assay suggest that ethanol extracts of Magnolia spp. sarcotesta may also be active by consumption. Differences in median mortality at 72 h were observed among leaf-cutting ant workers exposed to ethanol extract of M. pugana sarcotesta by ingestion (H = 19.021; df = 6; P < 0.01) (Table 3). The concentration of 2.0 mg/mL had a mortality of 100 ± 0 %, the positive control spinetoram also had a mortality of 100 ± 0 %. The concentration of 0.2 mg/mL had a mortality of 86.54 ± 8.81 %. The concentration of 0.02 mg/mL had a mortality of 55.77 ± 29.60 %, and the concentrations of 0.002 mg/mL, and 0.0002 mg/mL had mortalities of 11.54 ± 3.33 %, and 9.62 ± 6.66 %, respectively (Figure 3). The 50 % and 90 % lethal concentrations were estimated at 0.02 mg/mL and 0.24 mg/mL, respectively (Table. 4).

Table 3:

Effectiveness of ethanolic extracts of Magnolia sarcotesta as a botanical pesticide by ingestion against Atta mexicana at six concentrations. Mortality percentages over time and the corrected mortality (Mean ± SD) are presented. PC = positive control, spinetoram, NC = negative control, water, C1–C6 = tested concentrations of ethanolic extracts of sarcotesta from the species tested. Superscript letters indicate significant differences among treatments (P < 0.05; Kruskal-Wallis test with subsequent Dunn’s post-hoc test for group comparisons).

Treatments	Concentration (mg/mL)	Mortality (3 h)	Corrected mortality (3 h)	Mortality (24 h)	Corrected mortality (24 h)	Mortality (48 h)	Corrected mortality (48 h)	Mortality (72 h)	Corrected mortality (72 h)
M. pugana

PC	0.43	0 ± 0b	0 ± 0b	75.00 ± 8.66ab	74.58 ± 8.81ab	91.66 ± 10.40ab	90.91 ± 11.35ab	100 ± 0a	100 ± 0a
NC	0	0 ± 0b	–	1.66 ± 2.86cd	–	8.33 ± 10.40c	–	8.33 ± 10.40d	–
C1	2.0	6.66 ± 2.88a	6.66 ± 2.88a	98.33 ± 2.88^a	98.31 ± 2.94^a	98.33 ± 2.88ab	98.18 ± 3.15ab	100 ± 0a	100 ± 0a
C2	0.2	28.33 ± 24.66^a	28.33 ± 24.66^a	73.33 ± 46.18^ab	72.88 ± 46.97ab	100 ± 0a	100 ± 0a	88.33 ± 7.63b	86.54 ± 8.81b
C3	0.02	11.66 ± 20.20ab	11.66 ± 20.20ab	40.00 ± 43.30b	38.99 ± 44.03b	60.00 ± 26.45b	56.37 ± 28.86c	61.66 ± 25.65b	55.77 ± 29.60b
C4	0.002	0 ± 0b	0 ± 0b	1.66 ± 2.88cd	1.13 ± 1.96cd	8.33 ± 10.40c	0 ± 0e	23.33 ± 2.88c	11.54 ± 3.33c
C5	0.0002	0 ± 0b	0 ± 0b	0 ± 0d	0 ± 0d	11.66 ± 5.77c	3.64 ± 6.30d	21.66 ± 5.77c	9.62 ± 6.66c

M. perezfarrerae

PC	0.43	6.66 ± 11.54a	6.66 ± 11.54a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a
NC	0	0 ± 0a	–	0 ± 0e	–	0 ± 0c	–	6.66 ± 5.77c	–
C1	2.0	18.33 ± 15.27a	18.33 ± 15.27a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a
C2	0.2	5.0 ± 5.0a	5.00 ± 5.00a	85.00 ± 15.00a	85.00 ± 15.00a	100 ± 0a	100 ± 0a	100 ± 0a	100 ± 0a
C3	0.02	3.33 ± 5.77a	3.33 ± 5.77a	11.66 ± 2.88bc	11.66 ± 2.88bc	96.66 ± 5.77a	96.66 ± 5.77a	91.66 ± 14.43a	91.07 ± 15.46b
C4	0.002	1.66 ± 2.88a	1.66 ± 2.88a	18.33 ± 5.77b	18.33 ± 5.77b	8.33 ± 5.77b	8.33 ± 5.77b	50.00 ± 20.0b	46.42 ± 21.42b
C5	0.0002	0 ± 0a	0 ± 0a	5.00 ± 5.00de	5.00 ± 5.00de	10.00 ± 5.00b	10.00 ± 5.00b	51.66 ± 20.20b	48.21 ± 21.65b

M. vovidesii

PC	0.43	0 ± 0a	–	15.00 ± 25.98ab	15.00 ± 25.98	95.00 ± 8.66a	95.00 ± 8.66	100 ± 0a	100 ± 0a
NC	0	0 ± 0a	–	0 ± 0ab	–	0 ± 0b	–	1.66 ± 2.88c	–
C1	4.0	0 ± 0a	–	100 ± 0a	100 ± 0	100 ± 0a	100 ± 0	100 ± 0a	100 ± 0a
C2	0.4	0 ± 0a	–	61.66 ± 16.07ab	61.66 ± 16.07	96.66 ± 5.77a	96.66 ± 5.77	100 ± 0a	100 ± 0a
C3	0.04	0 ± 0a	–	63.33 ± 55.07ab	63.33 ± 55.07	75.00 ± 43.30b	75.00 ± 43.30	100 ± 0a	100 ± 0a
C4	0.004	0 ± 0a	–	0 ± 0b	0 ± 0	5.00 ± 5.00b	5.00 ± 5.00	50.00 ± 21.79b	49.15 ± 22.16b
C5	0.0004	0 ± 0a	–	1.66 ± 2.88ab	1.66 ± 2.88	10.00 ± 13.28b	10.00 ± 13.28	45.00 ± 48.0b	44.06 ± 49.03b

Figure 3:

Abbott’s adjusted mortality percentage of Atta mexicana after 72 h exposure by ingestion to five concentrations of ethanol extracts of the sarcotesta of Magnolia pugana and Magnolia perezfarrerae at 2.0 mg/mL (C1), 0.2 mg/mL (C2), 0.02 mg/mL (C3), 0.002 mg/mL (C4), 0.0002 mg/mL (C5), and Magnolia vovidesii at 4.0 mg/mL (C1), 0.4 mg/mL (C2), 0.04 mg/mL (C3), 0.004 mg/mL (C4), 0.0004 (C5), and 0.00004 mg/mL (C6), with positive control of spinetoram at 0.43 mg/mL (C+) and water (C-).

Table 4:

Lethal concentration to 50 % and 90 % mortality by ingestion (LC) of ethanol extracts of Magnolia sarcotesta against Atta mexicana at 72 h of exposure. The confidence interval (CI), the lower limit (LL), and the upper limit (UL).

Plant species	Effective concentration	Estimate (mg/mL)	SE	CI 95 %
				LL	UL
Magnolia pugana	LC ₅₀	0.02	0.0050825	0.005481	0.0274412
	LC ₉₀	0.24	0.1783327	−0.140378	0.6301504
Magnolia perezfarrerae	LC ₅₀	0.001	0.00045918	0.00010663	0.0020906
	LC ₉₀	0.06	0.043302	−0.038251	0.14885
Magnolia vovidesii	LC ₅₀	0.001	0.0010079	−0.00096688	0.0033881
	LC ₉₀	0.07	0.10591	−0.15523	0.30238

3.2.2 Mortality of A. mexicana in response to ethanol extracts of M. vovidesii sarcotesta

The ethanol extracts of M. vovidesii sarcotesta showed significant variations in mortality by ingestion (H = 17.362; df = 6; P < 0.01). Ethanol extract of M. vovidesii sarcotesta at concentrations of 4.0 mg/mL, 0.4 mg/mL, and 0.04 mg/mL showed uniform mortality of 100 ± 0 %, indicating an increased insecticidal effect by ingestion, which was comparable to the mortality of spinetoram at 100 ± 0 % (Table 3). In contrast, concentrations 0.004 mg/mL and 0.0004 mg/mL displayed comparatively lower mortality, with 49.15 ± 22.16 % and 44.06 ± 49.03 %, respectively (Figure 3). The 50 % and 90 % lethal concentrations were estimated at 0.001 mg/mL and 0.07 mg/mL, respectively (Table 4).

3.2.3 Mortality of A. mexicana in response to ethanol extracts of M. perezfarrerae sarcotesta

In the case of the ethanol extracts of M. perezfarrerae sarcotesta by ingestion, the highest three concentrations of 2.0 mg/mL, 0.2 mg/mL, and 0.02 mg/mL were the most effective against A. mexicana workers with mortality of 100 ± 0 %, 100 ± 0 %, and 91.07 ± 15.46 %, respectively (H = 18.512; df = 6; P < 0.01) (Table 3). Concentrations of 0.002 mg/mL and 0.0002 mg/mL had intermediate toxicity with mortality of 46.42 ± 21.42 % and 48.21 ± 21.65 %, respectively. As expected, the treatment with spinetoram also had a mortality of 100 ± 0 % (Figure 3). The 50 % and 90 % lethal concentrations were estimated at 0.001 mg/mL and 0.06 mg/mL, respectively (Table 4).

3.3 Qualitative chemical profile determination of plant extracts

Diverse phytochemical spots traveled various distances on samples up the TLC plate, based on the chosen solvent system. Compared to high polar solvents such as acetone, ethanol, and methanol; hexane (a low polar solvent) resulted in a better separation of compounds on the TLC plate. Our results showed that the sarcotesta extract of the test species had a greater amount of low polar compounds. However, mobile phases containing higher polarity solvents such as acetone, ethanol, and methanol did not provide satisfactory separation of compounds migrating up the TLC plate (Table 6).

Table 5:

Qualitative phytochemical analysis of specialized metabolites of ethanol extracts of Magnolia sarcotesta. Symbols (−), (+), (++), (+++) indicate absence, a low, moderate, or high presence of each type of metabolite group in samples.

	Alkaloids	Terpenes and steroids	Phenols	Flavonoids	Tannins	Saponins
Magnolia pugana	+++	+++	+	+++	–	–
Magnolia perezfarrerae	+++	+++	++	+	–	+
Magnolia vovidesii	++	++	+	++	–	–

Table 6:

The retention factor (Rf) of individual compounds found in the ethanolic extract of Magnolia sarcotesta in different solvent systems, solvents are sorted in ascending order of polarity.

Polarity	Solvent	Retention factor (Rf)
		Magnolia pugana	Magnolia perezfarrerae	Magnolia vovidesii
Low polarity	Hexane	0.30	0.05	0.08
		0.15	0.08	0.12
		0.17	0.16	0.19
		0.28	0.43	0.37
		0.4		0.45
		0.55
		0.64
		0.67
Hight polarity	Acetone	0.64	0.51	0.64
	Ethanol	0.52	0.82	0.52
	Methanol	0.62	0.5	0.56

The qualitative phytochemical analysis indicated the presence of a complex matrix of phytochemicals in the sarcotesta extract of each Magnolia species tested in this study. The presence of alkaloids, terpenes, phenols, and flavonoids is reported. The tannin test was negative, and saponins were only detected in the M. perezfarrerae extracts. M. pugana and M. perezfarrerae had a higher content of alkaloids and terpenes; a high content of flavonoids in M. pugana also was observed (Table 5).

4 Discussion

In this study, we evaluated the efficacy of ethanol extracts of sarcotesta derived from M. pugana, M. perezfarrerae, and M. vovidesii on the survival of the leaf-cutting ant A. mexicana. One of our main results showed that ethanol extracts of sarcotesta of M. vovidesii, M. perezfarrerae, and M. pugana had insecticidal effects by contact and ingestion against A. mexicana. Magnolias have a high insecticide potential against Tephritidae; for example, the ethanol extract of M. vovidesii and M. schiedeana sarcotesta had an insecticidal effect by ingestion using concentrations of 1 mg/mL to 0.001 mg/mL on A. ludens (Flores-Estévez et al. 2013; Vásquez-Morales et al. 2015). On the other hand, sarcotesta extracts of M. vovidesii, M. perezfarrerae, and M. pugana also were active by ingestion in A. ludens, and A nastrepha obliqua Macquart (Diptera: Tephritidae) at the same concentrations (Vásquez-Morales et al. 2022). In the current study, at 0.2 mg/mL, ethanol extract of M. pugana and M. perezfarrerae sarcotesta showed high contact toxicity to A. mexicana after 72 h. In the case of M. vovidesii, a higher level of contact toxicity was observed at 0.4 mg/mL. Sarcotesta concentration values were lower than the corresponding value for spinetoram (0.43 mg/mL), which served as the positive control in the experiment. Spinetoram, a multicomponent tetracyclic macrolide in the spinosyn insecticide class, was designed to control lepidopteran larvae, leaf-miners, and thrips in various crops (Sparks et al. 2020).

The spinosyns are produced from fermentation of Saccharopolyspora spinosa Mertz & Yaho (Pseudonocardiaceae) and Saccharopolyspora pogona (NRRL30141; Pseudonocardiaceae) and have been reported to exhibit insecticidal potential against various insect pests of agriculture and urban environments including pest ants (Kirst 2010). When compared with many other insecticides, spinosyns generally show greater selectivity toward target insects and lesser activity against many beneficial predators as well as mammals and other aquatic and avian animals. Their insecticidal spectrum, unique mode of action, and lower environmental effect make them useful new agents for modern integrated pest management programs (Kirst 2010).

Some spinosyns, such as spinosin A and spinosin D (Spinosad^®), have been used in field treatments for the control and agroecological management of A. mexicana in central Mexico (Serratos-Tejeda et al. 2017). Spinetoram^® offers several advantages over Spinosad^® for ant control, particularly in agricultural settings. It is more effective against a wider range of species, including those that have developed resistance to Spinosad^® (Chen et al. 2020). In addition, Spinetoram^® is more stable under varying environmental conditions, meaning it remains active longer, providing extended protection. Both Spinosad^® and Spinetoram^® have been used to control some ant pests such as Camponotus sericeus Fabricius (Hymenoptera: Formicidae) where it has shown higher toxic activities than insecticides such as bifenthrin, methomyl, bendiocarb, chlorpyrifos, profenophos, temephos, deltamethrin, permethrin, acetamiprid, imidacloprid, thiamethoxam, abamectin, emamectin, chlorfenapyr, and fipronil (Khan et al. 2021). Overall, Spinetoram^® was a good choice to be used as positive control in the experiments. However, this insecticide should be used cautiously due to recent studies indicating its toxicity to zebrafish (Chen et al. 2020).

The compounds found in M. grandiflora seed essential oil (1-decanol, and 1-octanol) showed significantly higher repellency against Ae. aegypti at 156 to 39 and 19.5 to 4.9 μg/g, the LC₅₀ was estimated at 625 μg/g (Ali et al. 2020). M. grandiflora seed essential oil also had repellence or toxic effects against the hybrid fire ant (S. invicta × S. richteri) where 1-decanol (with LC₅₀ = 140.6 μg/g) was the most toxic natural compound followed by 1-octanol (LC₅₀ = 486.8 μg/g) at 24 h post-treatment (Ali et al. 2022). This suggests that Magnolia seed extracts could have a high insecticidal potential for pest control of Diptera and Hymenoptera species (Lee et al. 2011; Luu-Dam et al. 2021; Ali et al. 2022).

The results of the ingestion bioassays also showed that, depending on the concentration used, the ethanol extract of sarcotesta of M. pugana, M. perezfarrerae, and M. vovidesii can produce mortality of 9.62–100 %, 48.21–100 % and 44.06–100 % at 72 h post-exposure, respectively. This result suggests that sarcotesta extract might contain compounds that can function as a stomach poison like those suggested by Wang et al. (2016), where lignans such as honokiol and magnolol extracted from Magnolia denudata Desr. seeds were larvicidal against third-instar larvae of Culex pipiens L. (Diptera: Culicidae), Ae. aegypti, Aedes albopictus Skuse (Diptera: Culicidae), and Anopheles sinensis Wiedemman (Diptera: Culicidae). Honokiol (LC₅₀ = 6.13–7.37 mg/L) was highly effective against larvae of all four mosquito species. It can destroy the midgut of Ae. aegypti larvae, mainly damaging the midgut epithelium, resulting in variably dramatic degenerative midgut responses through sequential epithelial disorganization (Wang et al. 2016).

The use of plant extracts can affect leaf-cutting ants, and their symbiont fungus, most of the reported toxic compounds also have been alkaloids, terpenes, and phenols (Van Bael et al. 2011; Infante-Rodríguez et al. 2020) and around 277 chemical compounds had been reported in Magnolia plant structures such as fruit, peel, seed, and sarcotesta. Fruit with seeds is the plant structure with the largest number of exclusive chemical compounds (122 compounds), followed by seedless fruit or peel (46 compounds), seed (42 compounds), and sarcotesta (five compounds); around 69 % of the compounds were terpenes, phenols, and alkaloids (Hernandez-Rocha and Vásquez-Morales 2023). Among the terpenes described in Magnoliaceae (Ahmed and Abdelgaleil 2005), sesquiterpene lactones are recognized as characteristic components of the vegetative structures. These lactones play a crucial role in plant defense, and they act as insecticides and reduce the appetite of herbivores for these plants (Srivastava et al. 1990).

After 72 h of exposure, M. pugana showed the highest contact toxicity with an LC₉₀ of 0.02 mg/mL. M. perezfarrerae and M. vovidesii also showed toxicity, with LC₉₀ values of 0.1 mg/mL and 0.4 mg/mL, respectively. The ethanolic extracts were toxic by ingestion, with an LC₉₀ of 0.24 mg/mL for M. pugana, 0.06 mg/mL for M. perezfarrerae, and 0.07 mg/mL for M. vovidesii. Alkaloids, terpenes and phenols were identified in the extracts. These results highlight the potential of Magnolia extracts as botanical pesticides against A. mexicana, with promising applications in agricultural pest management.

Volatile and non-volatile components of the unripe fruits of Magnolia ovata (A. St.-Hil.) Spreng. were investigated and analyzed by gas chromatography coupled to flame ionization detector (GC/FID) and gas chromatography coupled to mass spectrometry (GC/MS) (Barros et al. 2012). The oil in the sample was rich in spathulenol (19.3 %), and hexadecanoic acid (52.0 %). Extracts of the dried fruit contained 14 known compounds including nine lignoids (magnovatin A, magnovatin B, acuminatin, licarin A, oleiferin A, oleiferin C, kadsurenin M, 4-O-demethylkadsurenim M and 7-epi-virolin), two sesquiterpene lactones (parthenolide and michelenolide) and three alkaloids (lysicamine, lanuginosine and O-methylmoschatoline) (Barros et al. 2012). Curiously, spathulenol is a terpene that has shown a larvicidal effect on mosquitoes (Mathew and Thoppil 2011). Also, spathulenol has significant properties on Coleoptera as a fumigant (IC₅₀ of 15 μg/mL), toxicant (LC₅₀ of 9–26 µg/insect), and contact toxicant/repellent (LD₅₀ of 18 µg/adult; 45 % mortality at 10 %; 54–100 % repellency at 3–79 nL/cm² (2–4 h)) (Muñoz-Acevedo et al. 2024). Diverse secondary metabolites also have been isolated in seeds of other species of Magnolia, these include neolignans (magnolol and honokiol), lignans (yangambine and syringaresinol) phenylpropanoids (coniferine, syringine), flavonoids (rutin) and sesquiterpenes (costunolid) (Vásquez-Morales et al. 2015).

The regulation of leaf-cutting ant queens is of great importance for the prevention of new colony formation. However, the study of this phenomenon in laboratory conditions presents several challenges, primarily due to the monogynous nature of the colonies and the difficulty in obtaining enough successful foundress queens before nuptial flights, which occur between May and June in Mexico. It has been observed in the present study that laboratory colonies, particularly those that are relatively young, may not produce gynes. Prior research on Atta nest founding has demonstrated that gynes can establish claustral nests, cultivate fungal gardens, and nourish larvae. However, fungal gardens have been observed to fail in some instances before worker emergence (Fernández-Marín and Wcislo 2005). Consequently, our attention has been directed toward the forager caste, which is tasked with gathering plant material to cultivate the mutualistic fungus (Infante-Rodriguez et al. 2020). We suggest that a reduction in the foraging capacity of these workers can disrupt colony homeostasis, resulting in a decline in fungal gardens, a reduction in the worker population, and, in some cases, trigger a colony collapse.

One limitation with the study was that the negative control indicated that mortality was elevated at 72 h (with a mortality of 11.66 % for M. pugana, 28.33 % for M. perezfarrerae, and 29.69 % for M. vovidesii), which is why the adjusted mortality was reported to prevent an overestimation of mortality obtained in the treatments. A longer hydration period may potentially yield more favorable results. This aspect will be considered in future experimental designs to enhance the validity of the outcomes.

Overall, this study confirmed that sarcotesta extracts of three endemic Magnolia species of Mexico show insecticidal activity against foragers of the leaf-cutting ant A. mexicana. It should be noted that, to date, no studies have been conducted that compare the toxic or residual effects of compounds found in Mexican magnolias against groups of pollinators, such as native bees and other insect pollinators of cultivated plants. This is important in future studies, as bees represent a highly abundant member of numerous ecosystems and are critical for the pollination of almost 80 % of all flowering plants (Nicholls and Altieri 2012). Among the tested species, the sarcotesta extracts of M. pugana and M. perezfarrerae were more toxic than those of M. vovidesii, by contact, in the case of ingestion exposure M. perezfarrerae and M. vovidesii were the most efficient. We found that the sarcotesta extract is a complex matrix of phytochemicals of low and mean polarity. In addition, the qualitative test found that alkaloids, terpenes, and phenols were the most characteristic chemical groups found in ethanol extracts of the sarcotesta of Mexican Magnolia species. These metabolites can act as effective insecticides to control a wide range of pests; in addition, they play several roles in plant defense against fungi, viruses, bacteria, and herbivores (Ninkuu et al. 2021). These compounds often have specific mechanisms of action that affect the nervous system, development, or reproduction of insects, leading to their death or inhibiting their ability to cause harm in herbivorous insects (Boulogne et al. 2012).

Corresponding authors: Dennis Adrián Infante-Rodríguez and Suria Gisela Vásquez-Morales, Departamento de Biología, División de Ciencias Naturales y Exactas, Universidad de Guanajuato, Noria Alta SN, Noria Alta, AP 36050, Guanajuato, México, E-mail: da.infante@ugto.mx (D.A. Infante-Rodríguez), sg.vasquez@ugto.mx (S.G. Vásquez-Morales)

Funding source: Infante-Rodríguez D. A. acknowledges the postdoctoral fellowship granted by the Consejo Nacional de Humanidades, Ciencia y Tecnología (CONAHCYT)

Award Identifier / Grant number: CVU 409930

Acknowledgments

We would like to thank the Universidad de Guanajuato and the Consejo Nacional de Humanidades, Ciencia y Tecnología (CONAHCYT).

Research ethics: Not applicable.
Informed consent: Not applicable.
Author contributions: DAIR and SGVM conceptualization, funding, methodology, investigation, formal analysis, writing-original draft. NRM and JEVG writing-review, editing the original draft, and interpretation of bioassay.
Use of Large Language Models, AI and Machine Learning Tools: None declared.
Conflict of interest: None declared.
Research funding: Infante-Rodríguez D.A. acknowledges the postdoctoral fellowship granted by the Consejo Nacional de Humanidades, Ciencia y Tecnología (CONAHCYT) (CVU 409930).
Data availability: The data is available from the corresponding author upon request.

References

Ali, A., Chen, J., and Khan, I. (2022). Toxicity and repellency of Magnolia grandiflora seed essential oil and selected pure compounds against the workers of hybrid imported fire ants (Hymenoptera: Formicidae). J. Econ. Entomol. 115: 412–416, https://doi.org/10.1093/jee/toab262.Search in Google Scholar PubMed

Ali, A., Tabanca, N., Demirci, B., Raman, V., Budel, J.M., Baser, K.H.C., and Khan, I.A. (2020). Insecticidal and biting deterrent activities of Magnolia grandiflora essential oils and selected pure compounds against Aedes aegypti. Molecules 25: 1359, https://doi.org/10.3390/molecules25061359.Search in Google Scholar PubMed PubMed Central

Ahmed, S.M. and Abdelgaleil, S.A. (2005). Antifungal activity of extracts and sesquiterpene lactones from Magnolia grandiflora L. (Magnoliaceae). Int. J. Agric. Biol. 7: 638–642.Search in Google Scholar

Barros, L.F., Ehrenfried, C.A., Riva, D., Barison, A., de Mello-Silva, R., and Stefanello, M.E.A. (2012). Essential oil and other constituents from Magnolia ovata fruit. Nat. Prod. Commun. 7: 1934578X1200701030, https://doi.org/10.1177/1934578x1200701030.Search in Google Scholar

Boulogne, I., Petit, P., Ozier-Lafontaine, H., Desfontaines, L., and Loranger-Merciris, G. (2012). Insecticidal and antifungal chemicals produced by plants: a review. Environ. Chem. Lett. 10: 325–347, https://doi.org/10.1007/s10311-012-0359-1.Search in Google Scholar

Bueno, F.C., Godoy, M.P., Leite, A.C., Bueno, O.C., Pagnocca, F.C., Fernandes, J.B., Hebling, M.J.A., Bacci, Jr M., Vieira, P.C., and Silva, MFGF (2005). Toxicity of Cedrela fissilis to Atta sexdens rubropilosa (Hymenoptera: Formicidae) and its symbiotic fungus. Sociobiology 45: 389–399.Search in Google Scholar

Campos, E.V., Proença, P.L., Oliveira, J.L., Bakshi, M., Abhilash, P.C., and Fraceto, L.F. (2019). Use of botanical insecticides for sustainable agriculture: future perspectives. Ecol. Indic. 105: 483–495, https://doi.org/10.1016/j.ecolind.2018.04.038.Search in Google Scholar

Chacón-Hernández, J.C., Arredondo-Valdés, R., Anguiano-Cabello, J.C., Ordaz-Silva, S., Hernández-Juárez, A., and Reyes-Zepeda, F. (2020). Effect of Magnolia tamaulipana extract on egg laying and food intake of Tetranychus urticae (Acari: Tetranychidae). Int. J. Acarol 46: 108–110, https://doi.org/10.1080/01647954.2019.1702097.Search in Google Scholar

Chen, B., Zhang, H., Jia, K., Li, E., Shouhua, Z., Yu, H., Cao, Z., Xiong, G., Hu, C., and Lu, H. (2020). Effects of spinetoram on the developmental toxicity and immunotoxicity of zebrafish. Fish Shellfish Immunol. 96: 114–121, https://doi.org/10.1016/j.fsi.2019.11.066.Search in Google Scholar PubMed

De Mendiburu, F. (2010). Agricolae: statistical procedures for agricultural research, R package ver. 1.0-9. http://CRAN.R-project.org/package=agricolae (consulted July 2022).Search in Google Scholar

Dominguez, X.A. (1973). Phytochemical research methods, 4th ed. Editorial Limusa, Mexico.Search in Google Scholar

Fernández-Marín, H. and Wcislo, W.T. (2005). Production of minima workers by gynes of Atta colombica Guérin-Ménéville (Hymenoptera: Formicidae: Attini) that lack a fungal pellet. J. Kans. Entomol. Soc. 78: 290–292, https://doi.org/10.2317/0402.19.1.Search in Google Scholar

Flores-Estévez, N., Vásquez-Morales, S.G., Cano-Medina, T., Sánchez-Velásquez, L.R., Noa-Carrazana, J.C., and Díaz-Fleischer, F. (2013). Insecticidal activity of raw extracts from Magnolia dealbata Zucc on a Tephritidae pest. J. Environ. Sci. Health, Part B 48: 585–589.10.1080/03601234.2013.774933Search in Google Scholar PubMed

Guleria, S. and Tiku, A. (2009). Botanicals in pest management: current status and future perspectives. In: Peshin, R., and Dhawan, A.K. (Eds.). Integrated pest management: innovation-development process. Springer, Dordrecht, pp. 317–329.10.1007/978-1-4020-8992-3_12Search in Google Scholar

Hernandez-Rocha, J.V. and Vásquez-Morales, S.G. (2023). The potential of Magnolia spp. in the production of alternative pest control substances. Molecules 28: 4681, https://doi.org/10.3390/molecules28124681.Search in Google Scholar PubMed PubMed Central

Infante-Rodríguez, D.A., Monribot-Villanueva, J.L., Mehltreter, K., Carrión, G.L., Lachaud, J.P., Velázquez-Narváez, A.C., Vásquez-Reyes, V.M., Valenzuela-Gónzalez, J.E., and Guerrero-Analco, J.A. (2020). Phytochemical characteristics of leaves determine foraging rate of the leaf-cutting ant Atta mexicana (Smith) (Hymenoptera: Formicidae). Chemoecology 30: 147–159, https://doi.org/10.1007/s00049-020-00306-4.Search in Google Scholar

Infante-Rodríguez, D.A., Landa-Cansigno, C., Gutiérrez-Sánchez, A., Murrieta-León, D.L., Reyes-López, C., Castillejos-Pérez, A.B., and Guerrero-Analco, J.A. (2022). Análisis fitoquímico y actividad antidiabética, antibacteriana y antifúngica de hojas de Bursera simaruba (Burseraceae). Acta Bot. Mex. 129: e2109, https://doi.org/10.21829/abm129.2022.2109.Search in Google Scholar

Kelm, M.A., Nair, M.G., and Schutzki, R.A. (1997). Mosquitocidal compounds from Magnolia salicifolia. Int. J. Pharmacogn. 35: 84–90.10.1076/phbi.35.2.84.13279Search in Google Scholar

Khan, H.A.A., Zafar, R., and Nasir, I. (2021). Toxicity of seventeen insecticides to Camponotus sericeus (Hymenoptera: Formicidae). J. Asia-Pac. Entomol. 24: 217–220, https://doi.org/10.1016/j.aspen.2020.11.017.Search in Google Scholar

Kirst, H. (2010). The spinosyn family of insecticides: realizing the potential of natural products research. J. Antibiotics 63: 101–111, https://doi.org/10.1038/ja.2010.5.Search in Google Scholar PubMed

Lee, Y.J., Lee, Y.M., Lee, C.K., Jung, J.K., Han, S.B., and Hong, J.T. (2011). Therapeutic applications of compounds in the Magnolia family. Pharmacol. Therapeut. 130: 157–176, https://doi.org/10.1016/j.pharmthera.2011.01.010.Search in Google Scholar PubMed

Lopes Amaral, R., Venzon, M., Martins Filho, S., and Lima, M.A.P. (2016). Does ingestion of neem-contaminated diet cause mortality of honey bee larvae and foragers? J. Apicult. Res. 54: 405–410, https://doi.org/10.1080/00218839.2016.1159821.Search in Google Scholar

Luu-Dam, N.A., Tabanca, N., Estep, A.S., Nguyen, D.H., and Kendra, P.E. (2021). Insecticidal and attractant activities of Magnolia citrata leaf essential oil against two major pests from Diptera: Aedes aegypti (Culicidae) and Ceratitis capitata (Tephritidae). Molecules 26: 2311, https://doi.org/10.3390/molecules26082311.Search in Google Scholar PubMed PubMed Central

Mathew, J. and Thoppil, J.E. (2011). Chemical composition and mosquito larvicidal activities of Salvia essential oils. Pharm. Biol. 49: 456–463, https://doi.org/10.3109/13880209.2010.523427.Search in Google Scholar PubMed

Miyazawa, M., Ishikawa, Y., Kasahara, H., Yamanaka, J.I., and Kameoka, H. (1994). An insect growth inhibitory lignan from flower buds of Magnolia fargesii. Phytochemistry 35: 611–613, https://doi.org/10.1016/S0031-9422(00)90572-7.Search in Google Scholar

Morshedloo, M.R., Quassinti, L., Bramucci, M., Lupidi, G., and Maggi, F. (2017). Chemical composition, antioxidant activity and cytotoxicity on tumour cells of the essential oil from flowers of Magnolia grandiflora cultivated in Iran. Nat. Prod. Res. 31: 2857–2864, https://doi.org/10.1080/14786419.2017.1303699.Search in Google Scholar PubMed

Muñoz-Acevedo, A., González, M.C., Alonso, J.E., and Flórez, K.C. (2024). The repellent capacity against Sitophilus zeamais (Coleoptera: Curculionidae) and in vitro inhibition of the acetylcholinesterase enzyme of 11 essential oils from six plants of the Caribbean region of Colombia. Molecules 29: 1753, https://doi.org/10.3390/molecules29081753.Search in Google Scholar PubMed PubMed Central

Nicholls, C.I. and Altieri, M.A. (2012). Plant biodiversity enhances bees and other insect pollinators in agroecosystems. A review. Agron. Sustain. Dev. 33: 257–274, https://doi.org/10.1007/s13593-012-0092-y.Search in Google Scholar

Ninkuu, V., Zhang, L., Yan, J., Fu, Z., Yang, T., and Zeng, H. (2021). Biochemistry of terpenes and recent advances in plant protection. Int. J. Mol. Sci. 22: 5710, https://doi.org/10.3390/ijms22115710.Search in Google Scholar PubMed PubMed Central

Olazaran-Santibañez, F.E., Heinz-Castro, R.T., Rivera, G., Rocandio-Rodríguez, M., Navarrete-Carriola, D.V., Zapata-Campos, C.C., Moreno-Ramírez, Y.R., and Chacón-Hernández, J.C. (2024). Evaluation of ethanol extract of Magnolia alejandrae (Magnoliales: Magnoliaceae) against Tetranychus merganser (Acari: Tetranychidae). J. Entomol. Sci. 59: 193–210, https://doi.org/10.18474/JES23-58.Search in Google Scholar

Poivre, M. and Duez, P. (2017). Biological activity and toxicity of the Chinese herb Magnolia officinalis Rehder and E. Wilson (Houpo) and its constituents. J. Zhejiang Univ. Sci. B 18: 194–214, https://doi.org/10.1631/jzus.B1600299.Search in Google Scholar PubMed PubMed Central

R Core Team (2020). R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria, Available at: https://www.r-project.org/.Search in Google Scholar

Rattan, R.S. (2010). Mechanism of action of insecticidal secondary metabolites of plant origin. Crop Prot. 29: 913–920, https://doi.org/10.1016/j.cropro.2010.05.008.Search in Google Scholar

Ritz, C., Baty, F., Streibig, J.C., and Gerhard, D. (2015). Dose-response analysis using R. PLOS ONE 10: e0146021, https://doi.org/10.1371/journal.pone.0146021.Search in Google Scholar PubMed PubMed Central

Serratos-Tejeda, C., Aragón-García, A., Pérez-Torres, B.C., and López-Olguín, J.F. (2017). Alternativa agroecológica para el manejo de Atta mexicana en Puebla, México. Southwest. Entomol. 42: 261–273, https://doi.org/10.3958/059.042.0123.Search in Google Scholar

Shivanandappa, T. and Rajashekar, Y. (2014). Mode of action of plant-derived natural insecticides. In: Singh, D. (Ed.). Advances in plant biopesticides. Springer, New Delhi, pp. 323–345.10.1007/978-81-322-2006-0_16Search in Google Scholar

Silva, A., Bacci, Jr. M., Gomes de Siqueira, C., Correa Bueno, O., Pagnocca, F.C., and Aparecida Hebling, M.J. (2003). Survival of Atta sexdens workers on different food sources. J. Insect Physiol. 49: 307–313, https://doi.org/10.1016/s0022-1910(03)00004-0.Search in Google Scholar PubMed

Sparks, T.C., Crouse, G.D., Benko, Z., Demeter, D., Giampietro, N.C., Lambert, W., and Brown, A.V. (2020). The spinosyns, spinosad, spinetoram, and synthetic spinosyn mimics ‐ discovery, exploration, and evolution of a natural product chemistry and the impact of computational tools. Pest Manag. Sci. 77: 3637–3649, https://doi.org/10.1002/ps.6073.Search in Google Scholar PubMed

Srivastava, R.P., Proksch, P., and Wray, V. (1990). Toxicity and antifeedant activity of a sesquiterpene lactone from Encelia against Spodoptera littoralis. Phytochemistry 29: 3445–3448, https://doi.org/10.1016/0031-9422(90)85254-d.Search in Google Scholar

Teixeira, F.V., de Melo Souza, T.R., Castellani, M.A., da Silva Camargo, R., Forti, L.C., de Paula, V.F., Silva de Matos, C.A.O., Nipato, Ó.B., Moreira, A.A., Sabattini, J.A., et al.. (2023). Bioactivity of plant extracts against Atta sexdens (Hymenoptera: Formicidae) workers by ingestion. Int. J. Trop. Insect Sci. 43: 1227–1236, https://doi.org/10.1007/s42690-023-01030-6.Search in Google Scholar

Van Bael, S.A., Estrada, C., and Wcislo, W.T. (2011). Fungal-fungal interactions in leaf-cutting ant agriculture. Psyche: J. Entomol. 2011: 617478–617479, https://doi.org/10.1155/2011/617478.Search in Google Scholar

Vásquez-Morales, S.G., Flores-Estévez, N., Sánchez-Velásquez, L.F., Pineda-López, M.R., Viveros-Viveros, H., and Díaz-Fleischer, F. (2015). Bioprospecting of botanical insecticides: the case of ethanol extracts of Magnolia schiedeana Schltl. applied to a tephritid, fruit fly Anastrepha ludens Loew. J. Entomol. Zool. Stud. 3: 01–05.Search in Google Scholar

Vásquez-Morales, S.G., Alvarez-Vega, E.A., Infante-Rodríguez, D.A., Huchin-Mian, J.P., and Pedraza-Reyes, M. (2022). Evaluación de extractos de árboles endémicos (Magnolia spp.) de México contra la plaga de la mosca de la fruta y estudio fitoquímico preliminar. Polibotánica 53: 167–182, https://doi.org/10.18387/polibotanica.53.11.Search in Google Scholar

Wang, Z., Perumalsamy, H., Wang, M., Shu, S., and Ahn, Y.J. (2016). Larvicidal activity of Magnolia denudata seed hydrodistillate constituents and related compounds and liquid formulations towards two susceptible and two wild mosquito species. Pest Manag. Sci. 72: 897–906, https://doi.org/10.1002/ps.4064.Search in Google Scholar PubMed

Wirth, R., Herz, H., Ryel, R.J., Beyschlag, W., and Hölldobler, B. (2003). Herbivory of leaf-cutting ants: a case study on Atta colombica in the tropical rainforest of Panama, 2. Springer-Verlag, Berlin.10.1007/978-3-662-05259-4Search in Google Scholar

WHO (World Health Organization) (2022). Standard operating procedure for testing insecticide susceptibility of adult mosquitoes in WHO bottle bioassays, Downloaded from: https://www.who.int/publications/i/item/9789240043770.Search in Google Scholar

Xavier, V.M., Message, D., Picanço, M.C., Chediak, M., Júnior, P.A.S., Ramos, R.S., and Martins, J.C. (2015). Acute toxicity and sublethal effects of botanical insecticides to honey bees. J. Insect Sci. 15: 137, https://doi.org/10.1093/jisesa/iev110.Search in Google Scholar

Received: 2024-06-27

Accepted: 2025-02-14

Published Online: 2025-06-12

This work is licensed under the Creative Commons Attribution 4.0 International License.

Articles in the same Issue

https://doi.org/10.1515/flaent-2024-0049

Keywords for this article

Magnoliaceae; botanical pesticides; bioprospecting; plant extracts; Attini ants

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