Volume 67, Issue 6

In this paper, enzymatic methods for the synthesis of 5-hydroxy-2-(hydroxymethyl)-4H-pyran-4-one (kojic acid) esters are reviewed. Important process parameters related to the synthesis of kojic acid esters such as the type of immobilized lipase, solvent, temperature, initial water activity, water content, pH, metal salts, enzyme loading, substrates mole ratio, and acyl donors are highlighted and discussed. The properties of kojic acid esters related to their solubility, stability, cytotoxicity, depigmenting activity, tyrosinase inhibitory, metal-chelating, anti-oxidant, and other biological activities are also highlighted. At present, kojic acid and its esters are widely used in cosmetic and skin health industries as skin whitening agents. The advantages and disadvantages of various kojic acid esters are compared and possible industrial applications of these derivatives are also discussed.

Synthesis of the fragrant compound Calone 1951® from 4-methyl catechol and methyl bromoacetate entails three successive reactions: the Williamson reaction, Dieckmann condensation, and hydrolysis-decarboxylation reaction. In this paper, the synthesis of 4-methylcatechol dimethylacetate (MCDA) via the Williamson reaction by adding KI as catalyst was investigated. It was found that the addition of an appropriate amount of KI can significantly increase the product yield due to generation of methyl iodoacetate via the reaction between KI and methyl bromoacetate. The synthesised MCDA as well as Calone 1951® were first characterised by melting points, HPLC, IR, and NMR analyses. Next, the effect of the key operating factors on MCDA synthesis by the Williamson reaction was investigated and the optimum operating conditions were obtained via a group of orthogonal experiments. The verification experiments demonstrated that, under the optimum operating conditions, the MCDA yield could be increased from 78.5 % to 95.4 % by the addition of an appropriate amount of KI; the corresponding yield of Calone 1951® increased to 68 %.

HgCO3·2HgO (mercury oxide carbonate), along with partly unreacted reactants, was obtained by exploring the behaviour of the Hg2Cl2/HgO binary system in supercritical CO2 (scCO2) at 200°C, 22000 kPa in the presence and absence of water, using a self-made laboratory-scale system. The reaction of pure HgO with scCO2 aimed at the synthesis of HgCO3 (mercury carbonate), also yielded the same product. Meanwhile, with a small amount of water present in the Hg2Cl2/HgO-scCO2 system, at 200°C, 22000 kPa, the mineral terlinguaite (Hg4O2Cl2) was obtained instead of mercury oxide carbonate. Repeating this reaction under the same conditions, but in the absence of CO2, again resulted in the synthesis of terlinguaite, leading to the assumption that the scCO2 had no influence on the synthesis of terlinguaite. This study reveals a new moisture-free laboratory method and conditions for the permanent fixation of CO2 by HgO. This method bears two benefits: 1) it can be introduced to reduce the Hg content in flue gas and fly ash emitted from coal-burning power plants and municipal waste incinerators; 2) it can contribute to CO2 mineralisation in montroydite (HgO) geological formations as mercury oxide carbonate.

Everyday domestic activity is a significant source of water pollution. The presence of six household micropollutants in an urban wastewater treatment plant (WWTP) was assessed in wastewater and sludge. A multi-target analytical method was developed for the quantification of ibuprofen, erythromycin, ofloxacin, 4-nonylphenol, 5-chloro-2-(2,4-dichlorophenoxy)phenol (triclosan), and sucralose. The micropollutants were extracted from the liquid and solid phases and their concentrations were determined by LC-MS/MS. The efficiency of micropollutants’ removal within a conventional activated sludge process was assessed. From 50 % to 90 % of ibuprofen and erythromycin was removed from the wastewater liquid phase. Their removal can be attributed to biological degradation as they were not found adsorbed on the outlet sludge. Ofloxacin and triclosan were removed from the liquid phase with similar efficiencies; however, they were adsorbed on the sludge, so it was not possible to determine their removal mechanism (whether biodegradation or displacement to solid phase/sequestration). Sucralose was not removed from wastewater (3 μg L−1 in inlet and outlet liquid phase) and not adsorbed on the sludge. 4-Nonylphenol concentrations were sometimes higher in the WWTP outlet water; this may relate to the degradation of alkylphenol ethoxylates in the wastewater treatment process. 4-Nonylphenol was always present in the outlet sludge.

2-(2-Aminoethylamino)ethanol (L) reacts with cupric bromide in dimethylformamide to give a mononuclear complex of Cu(II) [L2Cu]Br2, with six-coordinate distorted octahedral geometry, in which two molecules of tridentate (N,N,O) ligand are involved. The structure was confirmed by spectroscopic methods, elemental and thermogravimetric analyses, and magnetic measurements. Optimization of possible configurations indicated the formation of the trans structure of the complex. Experimental results indicate that the investigated complex, bis[2-(2-aminoethylamino)ethanol] copper(II) bromide, behaves as a semiconductor in the studied temperature range of 298–388 K. Gas sensing properties of the film for the volatile organic compounds (VOCs): acetone, tetra-chloromethane, chloroform, ethanol, and methanol, were also investigated as a function of vapor concentration and temperature in dark. The film showed maximum sensitivity to tetrachloromethane and ethanol vapors at room temperature. Responses of the film to the tested gases are reversible.

The mechanism of α-acetyl-γ-butyrolactone (ABL) synthesis from γ-butyrolactone (GBL) and ethyl acetate (EtOAc) was explored by detecting the material changes involved and the enthalpies of formation of the synthons, products, and possible intermediates were calculated using the density functional theory. GBL forms a carbanion of γ-butyrolactone by losing an α-H under strongly alkaline conditions. ABL is then obtained via two reaction mechanisms. One of the reaction mechanisms involves direct reaction of the carbanion of GBL with EtOAc to produce ABL. The other involves the formation of a carbanion of α-(2-hydroxy-tetrahydrofuran-2-yl)-γ-butyrolactone through the reaction of two molecules of GBL, and the subsequent combination of this anion with EtOAc to produce ABL. ABL is thus formed through the above two kinds of competitive ester condensation reactions. It is unnecessary to take into account synthons’ local thickness, and their self-condensation under these conditions. Both reactions of the carbanion of GBL with EtOAc and GBL are exothermic, so the control of their reaction rate is the key to their security. Considering the reasons above, this work applied synthon as the solvent, and avoided environmental pollution by alkylbenzene; also, accidents such as red material and fire were avoided by specific surface area of sodium metal control. Effective isolation of the organic and aqueous phases was performed using the salting out method. Thus, an environmentally friendly, safe, simple, and efficient new method for the synthesis of ABL with the yield higher than 90 % has been established.

The anti-cancer properties of naturally occurring (2R, 3R)-(−)-1-methoxyspirobrassinol methyl ether (I) and their synthetic amino or piperidyl analogues II inspired us to study the synthesis of new target compounds III with a C—C bond in the 2-position of indole rather than a C—N or C—O bond (I or II respectively). The goal was achieved via electrophilic-nucleophilic 3,2-difunctionalisation of 1-methoxybrassinin (IV) in the presence of bromine and the Grignard reagent leading to the formation of cis- and trans-C—C analogues of I. Finally, the anti-cancer activities of the new compounds were measured and compared with I and II in order to show the importance of a heteroatom in the 2-substituted indole on the anti-cancer activity of spirobrassinols.

Tandospirone (I), developed as an anxiolytic drug, is an aryl-piperazine compound that binds to both 5-HT1A and dopamine D4 receptors. Palladium-catalysed hydroarylation reactions of tandospirone analogues containing an oxygen bridge and 3-(trifluoromethyl)phenyl or 2,3-dichlorophenyl groups were studied in order to find a new stereoselective access to a series of new exo-aryl(hetaryl)-substituted derivatives with potential biological activity.

Methyl-2-arylidene hydrazine-carbodithioate has not been of particular interest to researchers even though its metal complexes are extensively reported on due to their biological activity. This study examined the cytostatic and antiviral activity of twelve methyl-2-arylidene hydrazinecarbodithioates reported by many researchers as intermediates for the synthesis of thiosemicarbazides and the preparation of their metal complexes. Compounds IIc, IIi, and IIl with tridentate ligand features were found to have the lowest IC50 value (6.5 μM, ≈ 1 μM, and 0.8 μM, respectively) against HL60 human promyelocytic leukemia cells. They were also most inhibitory to human embryonic lung (HEL) fibroblast proliferation (5.3 μM, 17 μM, and 2.6 μM). Compound IIc and IIl show antiviral activity against wild-type herpes simplex virus (HSV), varicella zoster virus (VZV), and acyclovirresistant HSV; however, these activities were observed at concentrations at which the compounds also markedly inhibit HL60 and HEL cell proliferation.

In the event of genotoxic impurities in drug products, knowledge of the origin and fate of these components is of particular importance. In the present study, commercially available proguanil tablets (Paludrine®) were investigated in respect of formation of the main degradation product, 4-chloroaniline (PCA), which is known to be genotoxic. The investigations made use of high performance liquid chromatography coupled with fluorescence detection (HPLC-FLD) and gas chromatography coupled with flame ionisation detection (GC-FID) systems. In addition, proposals for the structure of further proguanil degradation products were developed based on results obtained by mass spectroscopy (HPLC-MS). Database analysis using DEREK, MCASE, and Vitic was performed to obtain an initial toxicological evaluation of the proposed chemical structures. Finally, the absence of the newly established structures in stored proguanil tablets was verified.

The biocatalytic production of pravastatin from compactin by hydroxylation has found many applications in health care and pharmaceuticals. Actinomadura macra, Actinomadura madurae, and Actinomadura livida can efficiently bioconvert compactin to pravastatin. The fermentation broth (Penicillium citrinum fermented media) harvested on the eighth day contained 388.90 mg L−1 of compactin and an undetectable level of mycotoxin (citrinin). Bioconversion by A. macra was highest (87 %) in the yeast extract-amended medium. The anti-actinomadura effects of citrinin reduce the bioconversion capacity of Actinomadura. The in situ hydroxylation of compactin produced by P. citrinum represents a preferable alternative for the use of purified compactin, as a way to reduce cost and time processing.

The contents of Ca, Cu, Fe, K, Mg, Mn, Na, and Zn in fruiting bodies of the highly-prized matsutake mushroom (Tricholoma matsutake) from twelve widely separated sites in Southwest China were determined using AAS. The results for dried mushrooms showed that the mean contents (mg kg−1) of the determined elements decreased in the following order: K (440–2000), Na (150–740), Ca (90–850), Mg (90–680), Zn (20–180), Fe (13–78), Cu (0.34–45), Mn (0.09–7.6).