Search

The determination of the crystal and molecular structure of organic compounds has contributed immensely towards the area of crystal engineering. This contributes towards the understanding of the molecular geometry and the different intermolecular interactions which control crystal packing. An approach which quantifies the energetics associated with the formation of different “molecular pairs” is of importance to recognize the hierarchy of intermolecular interactions present in the crystal. We intend to explore different computational tools which contribute towards the field of crystal engineering. In this regard, the crystal structure of 7-hydroxy-4-methyl-2H-chromen-2-one and its hydrate were re-determined and their crystal packing were analyzed in terms of the interaction energy of different intermolecular interactions, calculated by PIXEL method, contributing towards the stabilization of the crystal packing. The system is so chosen such that it allows the analysis of weak interactions like C–H···O, C–H···π, π···π, lp···π etc. in the presence of strong O–H···O hydrogen bonds and also allows for a systematic exploration of the effect of solvent (water in the present case) on the crystal packing. The calculation of the lattice energy reveals that the anhydrous form is 7 kcal/mol more stable than the corresponding hydrate. The major stabilization towards the crystal packing were observed to come from strong O–H···O=C hydrogen bonds (9 kcal/mol) in case of the anhydrous form while in case of its hydrate, water acts as both an acceptor and a donor of the hydrogen bonds, the interaction energy ranging from 5 to 9 kcal/mol. The weak C–H···O hydrogen bond were found to be the second highest contributor (I.E = 3.5–5.5 kcal/mol) towards the stabilization of the packing in both the crystal structures. The main differences in the crystal packing were observed in the presence of weaker interactions in their crystal packing. The weak C–H···π, O(lp)···C=O interactions were observed in the crystal packing of the anhydrous form while the π···π, O(lp)···π interactions stabilize the crystal packing in case of its hydrate. This phenomenon were further well supported by the analysis of the Hirshfeld surfaces mapped with different properties, 2D-fingerprint plots, electrostatic potential mapped on the Hirshfeld surface and electron density isosurface (calculated by ab initio calculation at DFT-D3/B97-D) at both solid state and optimized geometry.

Photodynamic therapy (PDT) represents a novel treatment that uses a photosensitizer (PS), light source (laser) of an appropriate wavelength and oxygen to induce cell death in cancer cells. The aim of this study was to investigate the photodynamic effects of aluminum tetrasulfophthalocyanines (AlTSPc) and zinc (ZnTSPc) tetrasulfophthalocyanines activated with a 672nm wavelength laser on melanoma cancer, dermal fibroblast and epidermal keratinocyte cells. Each cell line was photosensitized with either AlTSPc or ZnTSPc for 2 h before using a diode laser with a wavelength of 672nm to deliver a light dose of 4.5 J/cm2to the cells. The cell viability of melanoma cells were decreased to approximately 50% with concentrations of 40 g/ml for AlTSPc and 50 g/ml for ZnTSPc. These PS concentrations caused a slight decrease in the cell viability of fibroblast and keratinocyte cells. Both photosensitizers in the presence of high concentrations (60 g/ml-100 g/ml) showed cytotoxicity effects on melanoma cells in its inactive state. This was not observed in fibroblast and keratinocyte cells. Cell death in PDT treated melanoma cells was induced by apoptosis. Therefore, AlTSPc and ZnTSPc exhibit the potential to be used as a PS in PDT for the treatment of melanoma cancer.

Phenolic compounds from plants offer a means for both the prevention and detoxification of mycotoxins that affect human health. This research investigates the control of fungal growth and toxin production by Fusarium verticillioides with plant phenolic compounds, namely chlorophorin, iroko and maakianin, benzoic acid, caffeic acid, ferulic acid, and vanillic acid. Inhibition by these compounds of fungal growth was determined by the agar overlay method and their effect on fumonisin B1 (FB1) production was determined by high-performance liquid chromatography. Chlorophorin was the most effective compound in inhibiting fungal growth, followed by iroko, maakianin, vanillic acid and caffeic acid. Chlorophorin also was the most effective compound in reducing toxin production (94% reduction), followed by caffeic acid, ferulic acid, vanillic acid and iroko, which reduced FB1 levels by 90-91%. The widespread occurrence of fumonisins world-wide and the lack of adequate prevention of fumonisins require 'biologically safe' alternatives to prevent the transfer of fungi and their health hazardous toxins into our daily foods and environment.

This study was undertaken to determine the effectiveness of modified atmospheres and packaging materials on the growth of Penicillium expansumand patulin production in apples. Granny Smith apples were surface sterilized with 76% ethanol and inoculated with 0.1 ml of a 1.1 × 107spore/ml P. expansumspore suspension. The apples were packaged either in polyethylene (PE) or polypropylene (PP) and treated with three different gas combinations, viz., 58% CO2/42% N2, 48% CO2/52% N2, and 88% CO2/12% N2, and were then incubated for 14 days at 25°C. Fungal growth was monitored every 2 to 4 days by measuring radial growth from the point of inoculation. After the 14th day, apples were pulped, and patulin was extracted, purified, and quantified by high-performance liquid chromatography. PP did not inhibit fungal growth in any of the atmospheres tested, and it only inhibited patulin production in atmospheric gas and 58% CO2/42% N2. PE was very effective and inhibited fungal growth by four- or fivefold, depending on the modified atmosphere. Patulin production in PE-packaged apples was almost completely inhibited by all three gas combinations. Gas chromatographic analysis of the PE-packaged samples before and after the incubation period showed that CO2levels dropped and N2levels increased for all of the atmospheres tested. Our studies showed conclusively that PE is an excellent packaging material for the storage of apples since it inhibited the growth of P. expansum, thereby allowing <3.2 μg/ml of patulin to be produced, regardless of gaseous environment.

The effect of nine different oils was evaluated on the growth of Aspergillus parasiticusand Fusarium moniliforme. The experimental design to examine the inhibition of mycotoxins involved the incorporation of each of seven oils into broth and patty cultures. The fungal mycotoxin was identified by high-pressure liquid chromatography. Clove oil (eugenol) was the most inhibitory to the growth of A. parasiticusand F. moniliforme, followed by cinnamon (cinnamic aldehyde), oregano (thymol and carvacol) and mace oils (myristin). Neem and eucalyptus oil (cineole) did not affect fungal growth. The feasibility of implementing the results of this study to control mycotoxin toxicity was examined by costoring whole and ground cloves with mycotoxin-infected grain. Addition of both whole and ground cloves markedly reduced the aflatoxin contamination of the grain. These results clearly suggest that commonly occurring mycotoxigenic fungi can be controlled with clove oil (eugenol), thus spice oil successfully inhibited the growth of A. parasiticusand F. moniliforme, regulated the production of fumonisins, and prevented the formation of aflatoxins. The social implication of this finding is that rural communities can prevent the formation of fungal toxins in contaminated grain by simple measures.

Traditionally brewed alcoholic beverages are regularly consumed by most ethnic black South Africans. Maize and barley, both of which are used for producing locally brewed alcoholic beer, are frequently contaminated by mycotoxin-producing moulds. The study was undertaken to investigate whether these toxins are present in raw grains and the traditional beers imbibed by the local black African population. It was established that the raw ingredients (sorghum, sorghum malt grains, maize grits), commercially produced traditional beers (Utshwala and Utshwala special) and home-brewed beers (Umqombotha, Isiqatha, Imfulamfula) were contaminated by bacteria and fungi (both yeasts and moulds). The contaminating moulds were isolated and identified. The contaminated samples were analysed for aflatoxins B1, B2, G1 and G2, zearalenone, citrinin, deoxynivalenol, and ochratoxin A using a multi-mycotoxin thin-layer chromatography screening method and the toxins were quantified by high-performance liquid chromatography. Grain samples were infected by Aspergillus flavus, A. alliaceus, A. clavatus, Penicillium spp., Rhizopus spp. and Mucor spp. Sorghum malt grain samples contained the toxin zearalenone. No mycotoxin-producing fungi were present in the fermented beers but two of six commercial beer samples contained aflatoxins (200 and 400 μ gl-1) and 45% (13 of 29) of the home-brewed beers had zearalenone (range 2.6-426 μgl-1) and/or ochratoxin A (3-2340 μgl-1).

Patulin is a mycotoxin produced by a number of molds involved in fruit spoilage. This compound is carcinogenic and teratogenic. Various methods are currently used to reduce the levels of patulin in apple juice, namely, charcoal treatment, chemical preservation (sulfur dioxide), gamma irradiation, fermentation, and trimming of fungus-infected apples. Many of these processes are expensive and time-consuming. Therefore, there is a need to find a convenient and economical process to control patulin levels. This study was undertaken to evaluate the effectiveness of several clarification processes for the reduction of patulin. Clarification was carried out on a laboratory scale. Apple pulp was spiked with patulin, pressed, and clarified using four different processes, namely, fining with bentonite, enzyme (pectinase)treatment, paper filtration, and centrifugation. Patulin was recovered from the clarified juice by liquid-liquid extraction, and solid-phase chromatography was used for sample cleanup prior to analysis by high-performance liquid chromatography (HPLC). The minimum detectable limit using HPLC was 20 μg/liter. Pressing followed by centrifugation resulted in an average toxin reduction of 89%. Total toxin reduction using filtration, enzyme treatment, and fining were 70, 73, and 77%, respectively. Patulin reduction was due to the binding of the toxin to solid substrates that was verified by analyzing the clarified juice as well as the filter cake, pellet, and sediment. The combined concentrations correlated to the spiked concentration. These results reveal that clarification was successful in the reduction of patulin levels in apple juice. However, clarification resulted in high levels of patulin in the pressed pulp after filtration and centrifugation, and this could be harmful if they are used as animal feeds.