Chemistry

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Start date: 2000End date: 2009Subject: search.filters.subject.essential oils

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    Physicochemical changes of stored cowpea, Vigna unguiculata, treated with selected essential oils to control cowpea bruchid, Callosobruchus maculatus (F.)
    (Journal of Food, Agriculture & Environment., 2006) Rubasinghege, G.R.S.; Paranagama, P.; Abeywickrama, K.
    Cowpea (Vigna unguiculata) seeds were treated with essential oils of C. citratus,C. nardus, C. zeylanicum, M. minutum and a standard pesticide (pirimiphos methyl) as fumigant toxicants. At the end of the four month storage period, physical and chemical properties of cowpea from each storage system were analyzed. Variation of physicochemical properties among treated storage systems was insignificant with one exception; 20±5% of moisture was lost in samples treated with essential oils due to absorption of treated oil. Higher protein, fat and dietary fiber contents were reported from essential oil-treated samples compared to those treated with pirimiphos methyl. With lower toxicity to humans and other mammals and less or no significant variation in physicochemical properties, the selected essential oils can be used as fumigant toxicants against Callosobruchus maculatus (F.).
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    Deterrent effects of some Sri Lankan essential oils on oviposition and progeny production of the cowpea bruchid, Callosobruchus maculatus (F.)(Coleoptera; Bruchidae)
    (2003) Paranagama, P.; Adhikari, C.; Abeywickrama, K.P.; Bandara, P.
    Essential oils extracted from five plant materials were tested on oviposition and progeny production of F1 adult of cowpea bruchid, Callosobruchus maculatus on cowpea seeds. All oils tested showed a significant inhibition of oviposition and F1 adult emergence compared to the control during no-choice tests. Cymbopogon citratus and C. nardus showed higher effect on oviposition and F1 adult emergence than the essential oils of Alpinia calcarata, Cinnamomum zeylanicum and Murraya koinigii. In the choice test, the percentage ovipositions in all oils treated samples (except 10 mg of M. koinigii) were significantly lower than that of the control and ethanol treated samples. The percentage eggs deposited decreased with increasing doses of the oils ranging from 10 to 160 mg. The percentage of eggs laid was zero in samples treated with 40 mg of C. nardus or A. calcarata, 80 mg of C. citratus and 160 mg of C. zeylanicum. The essential oils of M. koinigii showed the lowest effect on oviposition when compared to other four essential oils.
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    Fungicidal and anti-aflatoxigenic effects of the essential oil of Cymbopogon citratus (DC.) Stapf. (lemongrass) against Aspergillus flavus Link. isolated from stored rice
    (The Society for Applied Microbiology, 2003) Paranagama, P.A.; Abeysekera, K.H.T.; Abeywickrama, K.P.; Nugaliyadde, L.
    Aims: To develop a natural fungicide against aflatoxigenic fungi, to protect stored rice, using the essential oil of lemongrass. Methods and Results: Aspergillus flavus Link. was isolated from stored rice and identified as an aflatoxigenic strain. Lemongrass oil was tested against A. flavus and the test oil was fungistatic and fungicidal against the test pathogen at 0Æ6 and 1Æ0 mg ml)1, respectively. Aflatoxin production was completely inhibited at 0Æ1 mg ml)1. The results obtained from the thin layer chromatographic bioassay and gas chromatography indicated citral a and b as the fungicidal constituents in lemongrass oil. During the fumigant toxicity assay of lemongrass oil, the sporulation and the mycelial growth of the test pathogen were inhibited at the concentrations of 2Æ80 and 3Æ46 mg ml)1, respectively. Conclusion: Lemongrass oil could be used to manage aflatoxin formation and fungal growth of A. flavus in stored rice. Significance and Impact of the Study: Currently, fungicides are not used to control fungal pests or mycotoxin production on stored rice. Rice treated with the essential oil of lemongrass could be used to manage fungal pests as well as the insect pests in stored rice. The essential oil is chemically safe and acceptable to consumers, as synthetic chemical fungicides can cause adverse health effects to consumers.