Volume 97, Issue 5 - Special Issue: Virtual Conference on Chemistry and its Applications 2024 (VCCA-2024); Guest Editor: Ponnadurai Ramasami

This study investigated the catalytic potential of metal-loaded gamma alumina catalysts in the ozonation of 1,2-dichlorobenzene (DCB) under ambient reaction conditions. Different metal (Fe, Ni, and V) loaded gamma alumina catalysts were synthesized via wet impregnation technique and characterized using ICP-OES, FT-IR, BET, XRD, TEM, and SEM techniques. To identify the reaction products, Fourier transform infrared (FT-IR) spectroscopy and gas chromatography-mass spectrometry (GC-MS) techniques. The ozonation of 1,2-dichlorobenzene was studied within a glass reactor, where each substrate was exposed to ozone for varying time durations between 3 and 24 h. The catalytic performance of a range of metal-loaded γ-Al 2 O 3 catalysts was assessed by examining their conversion and selectivity capabilities. During the oxidative degradation of 1,2-dichlorobenzene, 3,4-dichloro-2,5-furandione ( DHF ) and mucochloric acid ( MCA ) were identified as the ozonation products. Among the studied catalysts, 2.5 % Ni/γ-Al 2 O 3 exhibited outstanding catalytic activity towards the conversion of 1,2-dichlorobenzene yielding a significant 65 % conversion of 1,2-dichlorobenzene after 24 h of ozonation.

In this present work, α-amylase isolated from Aspergillus fumigatus was successfully modified using glyoxylic acid. The enzyme was isolated through centrifugation and purified using (NH 4 ) 2 SO 4 salt deposition and dialysis. The purified α-amylase exhibited a purity level 17.79 times higher than that of the crude extract. The study also found that the optimum pH for α-amylase was 5.0, while for the α-amylase/glyoxylic acid an optimum pH of 5.5 was observed. Both the native and modified α-amylase showed an optimum temperature of 55 °C. The native α-amylase has the K M values of 11.55 mg mL −1 substrate and V max of 10.76 mol mL −1  min −1 . In contrast, the α-amylase/glyoxylic acid complex has the K M values ranging from 14.67 to 16.73 mg mL −1 substrate and V max ranging from 7.07 to 9.32 mol mL −1  min −1 . The residual activity of the native enzyme after incubation for 100 min at 60 °C was 9.34 %, while the modified enzyme exhibited residual activities ranging from 28 to 59 %. The Δ G i for the native α-amylase was 104.333 kJ mol −1 , while for the modified enzyme, the values in the range of 105.825–106.314 kJ mol −1 were found. Another important finding is significantly higher stability of the modified enzyme compared to the native enzyme, α-amylase, as evidenced by an increase in half-life ( t ½ ) ranging from 1.71 to 2.05 times.

Determining phosphate (PO 4 −3 ) and sulphate (SO 4 −2 ) is highly significant in agricultural sciences and practices for the sustainable growth of crops. Their deficiencies have reflective properties on the transcriptome and many metabolic pathways. Therefore, this study planned to monitor concentrations of both ions for the first time through conductometric titration using BaCl 2 . For this purpose, the leaves of Spinacia oleracea L., Thorn Apple , and Rangoon Creeper plants were collected from Karachi and transported to the Department of Chemistry, University of Karachi, where they were washed thoroughly to remove any dust particles, dried, and crushed in deionized water and filtered. A known concentration of barium chloride (BaCl 2 ) as a single reagent was prepared to be applied to an aqueous plant extract test sample containing an unknown amount of phosphate and sulphate ions. The 50 ml of extract was taken into the beaker and subjected to titration with a known concentration of BaCl 2 conductometrically. Results showed that as precipitation started, the conductivity of the extract solution decreased with the addition of the BaCl 2 and reached a point where further addition did not affect it. The precipitate was tested two times, initially and at the end of the reaction, by adding HCl and HNO 3 to validate the presence of these ions in leaves aqueous extract. Chemical analysis of the precipitate initially suggested that phosphate is separated first due to its low solubility product (Ksp) value and then sulphate. Moreover, the concentration of both ions at the end of the reaction was determined through the derivative graph of the conductivity curve and standard curve method after the separation of ions by HCl and HNO 3 . It was concluded that this simple technique may be used to ascertain the concentration of both ions required for plant growth under various stress conditions.

This study examines the oxidative breakdown of an antipsychotic drug risperidone utilizing a metalloporphyrin catalyst in a controlled, constrained amount of time and moderate reaction conditions. Analyzing products and tracking the oxidative degradation process using LC-MS/MS analysis gave precise information on the reaction products and defined structural changes. The study investigated the fragmentation patterns of risperidone’s oxidative breakdown products, delving into the mechanisms underlying each fragmentation pathway. Our work highlights the creation of site-specific metabolites. Risperidone-N-oxide was identified as a significant oxidative product along with minimal quantities of in vivo metabolite, 9-hydroxyrisperidone.

The intercalation of organic molecules into Layered Double Hydroxides has emerged as a promising technique for enhancing the functional properties of these materials for various applications. In this study, we report the successful triple intercalation of 2-methyl-4-chlorophenoxyacetic acid (MCPA), 3,4-dichlorophenoxyacetic acid (3,4D), and 2,4,5-trichlorophenoxybutyric acid (TBA) into LDHs using the ion exchange method. The intercalation process was carefully optimized to achieve the simultaneous incorporation of these three distinct organic molecules within the LDH interlayers. Characterization of the intercalated LDH materials was performed using X-ray diffraction, Ultraviolet-Visible spectroscopy, and Direct Injection Mass Spectrometry to confirm the successful incorporation of MCPA, 3,4D, and TBA, and to determine the percentage loading of these herbicides into the LDH structure. The XRD results demonstrated a significant increase in the interlayer spacing from 8.9 to 29.8 Å, confirming the successful intercalation of the organic molecules. UV–VIS analysis revealed percentage loadings of 57, 40, and 29 % for TBA, 3,4D, and MCPA, respectively. DIMS analysis further supported the successful triple intercalation, with characteristic m / z peaks at 200, 220, and 282 corresponding to MCPA, 3,4D, and TBA, respectively. This triple intercalation strategy offers a novel approach to designing multifunctional LDH materials with potential applications in controlled release systems for herbicides, environmental remediation, and catalysis. The synergistic effects of MCPA, 3,4D, and TBA within the LDH structure contribute to enhanced stability, prolonged release duration, and improved efficacy. This suggests potential applications in controlled-release herbicide formulations, reducing environmental contamination and ensuring targeted weed control.

uMhlathuze River in KwaZulu-Natal, South Africa, is a critical freshwater resource supporting industrial, agricultural, and domestic activities. However, its water quality is under threat from various anthropogenic pressures. This review synthesises existing literature to assess the river’s water quality, focusing on key contaminants, spatial and temporal trends, ecological impacts, and socio-economic implications. Key pollutants identified include elevated levels of nitrates (>10 mg/L), phosphates (>2 mg/L), heavy metals such as lead (Pb > 0.01 mg/L) and chromium (Cr > 0.05 mg/L) (Nsibande et al. Afr. J. Aquat. Sci. 2024, 262–274, 3.), and microbial contaminants with faecal coliforms exceeding 1,000 CFU/100 mL (Mthembu et al., Afr. J.  Microbiol. Res. 2012, 2020–2026, 9.). Seasonal variations exacerbate these issues, with higher pollutant loads observed during rainy periods due to increased runoff from industrial, agricultural, and urban areas. Figures illustrating contaminant trends by season or location could complement these findings. The degraded water quality has led to declines in biodiversity, including fish and aquatic macroinvertebrates, and poses significant public health risks for communities reliant on the river for drinking water and sanitation. Maps of pollution hotspots and biodiversity loss would aid in visualizing these impacts. Key knowledge gaps include inconsistent sampling methodologies, insufficient long-term data, and the absence of a region-specific Water Quality Index (WQI). This review highlights the need for standardised WQI frameworks, advanced monitoring technologies, and pollution tracking mechanisms to address these challenges. Additionally, socio-economic studies and community-based conservation initiatives are recommended to mitigate pollution impacts and improve water resource sustainability. These findings serve as a foundation for targeted research and policy actions to protect and sustainably manage the uMhlathuze River system.

Cow urine (CU) – a natural bio-organic waste product with immense medicinal value has been traditionally used by human beings for centuries. Researchers have reported the multi-purpose usage of CU in various sectors such as agriculture, medical, emulsified diesel fuel, and electricity generation. The beneficial effect of CU is mainly attributed to its composition which depends on multiple factors such as dietary habit, demography, breed type etc. The CU consists of many useful elements and enzymes which are essential for maintaining the ecological balance and well-being of human society. In spite of its limited benefits, there is still a lack of knowledge on the scientific usage of CU. In this investigation, antioxidant, scavenging activity, and reducing power assay of CU from adult, pregnant, lactating cow and its calf are assessed. The quantity of bio-chemical constituents in CU of adult, pregnant, lactating cow, and calf varied significantly. The concentration of urea, urea nitrogen, uric acid, calcium and creatinine was high in pregnant CU raw sample. Whereas, the amount of sodium and chlorine were high in lactating CU sample. Total phenol concentration was found to be high in adult CU raw sample, followed by calf and pregnant CU raw samples, which is responsible for the antimicrobial activity. Results show highest potent antioxidant activity on the inhibition of DPPH, superoxide anion, nitric oxide, hydroxyl free radicals, and better reducing ability in lactating CU raw sample as compared to other CU samples. In general, the raw CU sample showed better radical scavenging activity whereas distilled CU samples have better Fe 3+ reducing power assay.

Biofilm formation by Klebsiella pneumoniae, Acinetobacter baumannii, and methicillin-resistant Staphylococcus aureus (MRSA) significantly contributes to antimicrobial resistance (AMR), complicating infections associated with medical devices. This study investigates the potential of α-Amylase, DNase I, and Proteinase K in disrupting extracellular polymeric substances (EPS) within biofilms to enhance biofilm inhibition. Molecular docking studies revealed a strong interaction between α-Amylase and cellulose (−3.58 kcal/mol), suggesting effective targeting of biofilm polysaccharides. Biofilm inhibition was quantified using the crystal violet microtiter plate assay, and structural changes were visualized through confocal laser scanning microscopy (CLSM). The checkerboard synergy assay showed that enzyme combinations achieved up to 90 % biofilm inhibition, significantly outperforming individual enzymes (50–70 %). Notably, α-Amylase + DNase I and α-Amylase + Proteinase K exhibited synergy (FICI ≤ 0.5) in MRSA and A. baumannii , while DNase I + Proteinase K showed limited activity in A. baumannii (FICI = 2.0), suggesting biofilm composition differences influence enzymatic activity. Confocal microscopy analysis revealed that biofilm thickness was reduced by 50 % in K. pneumoniae and by 60 % in A. baumannii , further supporting enzyme-mediated biofilm disruption. These findings highlight the potential clinical applications of enzymatic therapy, particularly in preventing ventilator-associated pneumonia (VAP) by inhibiting biofilm formation and disrupting preformed biofilms in endotracheal tubes and improving antimicrobial efficacy. This study establishes α-Amylase as a potent biofilm-disrupting agent, with synergistic enzyme therapy offering a viable strategy to combat biofilm-associated infections. Currently, we are focusing on optimizing enzyme formulations for clinical application and evaluating their combination with antibiotics to enhance therapeutic outcomes.

The eco-friendly synthesis of nanoparticles has attained magnificent recognition in the present century due to its emphasis on reducing the environmental impact of chemical processes. The study investigated the utilization of a bioflocculant for the synthesis of silver nanoparticles to test their antimicrobial effect against two pathogenic microorganisms. Characterization techniques including UV–vis spectroscopy, Fourier-transform infrared, scanning electron microscopy, and dispersive X-ray spectroscopy were utilized in the present study to learn about the different properties of the synthesized nanoparticles. UV-visible spectroscopy viewed absorption bands at 250 nm and 435 nm for the bioflocculant and silver nanoparticles, respectively. Functional groups including alcohols, carboxylic, amine, aromatic compounds, sulfates, and halo compounds were observed for the bioflocculant FT-IR. Silver IR spectra showed absorption peaks indicating alcohols, alkenes, sulfonyl chloride, and halo compounds. SEM spectrum of the bioflocculant and silver nanoparticles presented spherical and flak-like morphologies, respectively. The SEM-EDX analysis of the silver nanoparticles showed elemental silver with 59.64 wt% previously not present from the bioflocculant before synthesis. The bioflocculant was not effective against the tested strains and AgNPs were effective against Escherichia coli in a concentration-dependent manner. These results show that a bioflocculant can be used to synthesize AgNPs with antibacterial potential.

The emergence of resistance in pathogenic bacteria to synthetic antibiotics is a critical global issue. This study aims to isolate antibacterial compounds from endophytic fungi and characterize the secondary metabolites from the white turi plant ( Sesbania grandiflora (L.) Pers.) as a novel source of natural antimicrobial agents to combat the growing problem of antibiotic resistance. The research involved isolating fungi, testing bioactivity, and purifying and characterizing bioactive compounds. Nine endophytic fungal isolates were obtained from the plant’s stem, seed, leave, and flower tissues. The isolate with the strongest antibacterial activity (Code: Bt-12), was derived from the stem tissue, showing 48.49 % inhibition against Staphylococcus aureus and 42.06 % against Pseudomonas aeruginosa using the microdilution method. Purification using vacuum liquid chromatography (VLC) identified the NV42 fraction as having the most significant antibacterial effect, with inhibition zone of approximately 12.5 mm for S. aureus and 8 mm for P. aeruginosa using the disc diffusion method. Liquid chromatography-mass spectrometry (LC-MS/MS) characterization identified the highest peaks from three selected fractions at retention times of 7.65, 15.27, and 7.69, with corresponding molecular formulas of C 23 H 31 N 2 O 2 , C 38 H 74 NO 14 , and C 23 H 31 N 2 O 2 , respectively and were classified as alkaloid secondary metabolites. This research successfully identified the predicted bioactive compounds that inhibit the growth of pathogenic bacteria, providing valuable insights into potential antibacterial agents derived from endophytic fungi in turi plants.

The study compares TiO 2 NPs synthesized via conventional chemical methods using Titanium Tetra Isopropoxide (TTIP) precursor versus an eco-friendly green synthesis approach using Moringa oleifera seed (MOS) extracts. Two standard fabrication routes-sol-gel and hydrothermal were employed for both chemical synthesis (CS) and green synthesis (GS) processes. The as-formed TiO 2 nanoparticles from all four synthesis conditions (CS-sol gel, CS-hydrothermal, GS-sol gel, GS-hydrothermal) exhibited a spherical shape and pure rutile crystal structure with slight variations in mean diameter based on the synthesis technique. Optical absorptions showed bandgap energies ranging from 3.14–3.28 eV and 2.24–2.59 eV for CS- and GS-TiO 2 systems respectively. The lower bandgap energy of green synthesized TiO 2 suggests higher visible light absorption, confirmed through diffuse reflectance spectroscopy where GS-TiO 2 NPs had higher base absorbance levels. The synthesized TiO 2 NPs were employed as catalysts for methylene blue (MB) dye degradation under UV and sunlight irradiation. Intriguingly, the results indicated that the degradation of MB dye under sunlight irradiation demonstrated superior efficiency compared to UV irradiation. In conclusion, the green-synthesized TiO 2 NPs showcased excellent optical properties and demonstrated enhanced photocatalytic performance in the degradation of MB dye, with an efficiency approaching 64 %.

The costs of producing electrocatalysts needed for proton exchange membrane water electrolyzers can be reduced by using less expensive metals, such as ruthenium, instead of the commercially used IrO. This reduction is needed for two reasons: 1) although South Africa has the central reserves globally, iridium is a scarce element that is mined with other platinum group metals (PGMs), and 2) iridium is 4 times more expensive in comparison to platinum. Hence, efficient bimetallic (IrM oxides where M = gold or ruthenium) electrocatalysts are needed for water splitting in acidic conditions. This paper reports on the commercial benchmark IrO and compares its electrocatalytic activity to the lab-synthesized IrRu and IrAu oxide composite mixtures. The benchmark catalyst IrO reported an onset potential of 1.23 V compared to the IrRu blended mixtures, with an average overpotential of 0.15 V. The IrAu oxide composites reported a slightly higher value of 0.28 V. The Tafel slopes for IrO were found to be 69.6 mV/decade, the IrAu oxides prepared reported an average of 52.61 mV/decade and the IrRu oxides an average of 65.65 mV/decade. Therefore, the IrAu showed good activity and OER stability compared to the commercial catalyst.

A Second harmonic generation (SHG) microscope optimized for biomaterials was developed. The set-up has a non-collinear counter propagating geometry, that allows for the polarization tuning of incoming and outgoing beams. The developed microscope has a resolution of 1.1 µm/line pair. It makes use of a highly sensitive and high-resolution CCD camera that allows for the imaging of delicate biomaterial samples in short acquisition times without burning. This is the first and only functional SHG microscope set-up in the Philippines.