Browsing by Author "Wagara, Isabel N."

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    Antifungal activity of flavonoids isolated from Monanthotaxis littoralis against mycotoxigenic fungi from maize
    (American Journal of Chemistry and Application, 2014) Chepkirui, Clara; Matasyoh, Josphat C.; Wagara, Isabel N.; Nakavuma, Jesca
    This study evaluated the antifungal activity of a mixture of two closely related flavonoids namely 3, 7, 5’- trihydroxy anthocynidines and 3, 5-dihydroxy-7-methoxy anthocynidines isolated from Monanthotaxis littoralis (Annonaceae) against mycotoxigenic fungi from three genera (Aspergillus, Fusarium and Penicillium) isolated from maize samples. Dry leaves of Monanthotaxis littoralis was extracted with methanol, suspended in water and extracted with ethyl acetate. Column chromatography and Preparative Thin Layer Chromatography (PTLC) was used to purify the compounds. 1D and 2D NMR and Mass Spectroscopy were used to elucidate the structures of the compounds isolated. The extent of inhibition of fungal growth was dependent on the concentration of the flavonoids. The highest activity of the flavonoids was that against Aspergillus ochraceus with inhibition zone of 20.17 mm and MIC of 1 mg/ml. The activity of the flavonoids against the mycotoxigenic fungi had Minimum Inhibitory Concentration (MIC) values ranging from 1 mg/ml to 4 mg/ml. These results show that the two flavonoids from M. littoralis have antifungal activities against fungi that are the producers of poisonous mycotoxins found in foods. These compounds are potential antimicrobials that can be used in food preservation systems to inhibit the growth of moulds and retard subsequent mycotoxin production
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    Chemical composition of Cymbopogon citratus essential oil and its effect on mycotoxigenic Aspergillus species
    (African Journal of Food Science, 2011) Matasyoh, Josphat C.; Wagara, Isabel N.; Nakavuma, Jesca L.; Kiburai, Anderson M.
    This study evaluated the antifungal activity of essential oil of Cymbopogon citratus (Poaceae) against five mycotoxigenic species of the genus Aspergillus (Aspergillus flavus, Aspergillus parasiticus, Aspergillus ochraceus, Aspergillus niger and Aspergillus fumigatus) isolated from maize samples. The oil of C. citratus was obtained by hydro-distillation and analysed by Gas Chromatography – Mass Spectrometry (GC-MS). The oil was dominated by monoterpene hydrocarbons which accounted for 94.25% of the total oil and characterised by a high percentage of geranial (39.53%), neral (33.31%), and myrecene (11.41%). The antifungal activity tests showed that the oil was active against all the five Aspergillus species. The extent of inhibition of fungal growth was dependent on the concentration of the oil. The activity of the oil against the mycotoxigenic fungi had Minimun Inhibitory Concentration (MIC) values ranging from 15 to 118 mg/ml. These results show that the essential oil of C. citratus has antifungal activities against fungi that are the producers of poisonous mycotoxins found in foods. This oil can be used in food preservation systems to inhibit the growth of moulds and retard subsequent mycotoxin production.
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    Toxicity Studies on Anti-fungal Essential Oils Extracted from Selected Aromatic Plants from Mabira and Kakamega Forests, East Africa
    (European Journal of Medicinal Plants, 2016) Nakavuma, Jesca L.; Matasyoh, Josphat C.; Wagara, Isabel N.; Kalema, John; Alinaitwe, Lordrick
    In a bid to explore for grain bio-preservatives, essential oils extracted from Cymbopogon citratus, Rosmarinus officinalis, Monanthataxis littoralis and Aframomum angustifolium, that were earlier established to have anti-mold activity, were evaluated for their biosafety by determining the oral LD50. Methods: The essential oils were extracted by hydro-distillation from aromatic plants collected from Kakamega and Mabira forests in Kenya and Uganda, respectively. Acute oral toxicity was established using mice by determining the LD50; after which sub-acute toxicity studies were performed. The animals were observed for behavioural changes; and the gross and histopathological effects, if any, on the intestinal mucosa, spleen, lungs, liver, kidney and heart were noted. Results: The oral LD50 for Cymbopogon citratus, Rosmarinus officinalis, Monanthataxis littoralis and Aframomum angustifolium essential oils were established as 7,046.90; 4,723.33; 13,335.82; and 17,539.82 (mg/kg body weight), respectively. In all cases, increased breathing rates were observed, however Rosemary also caused lethargy and convulsions. Grossly, no changes were seen in the liver, kidney, lungs, heart and spleen from both the control and the treated mice except for Monanthataxis littoralis where the lungs and liver seemed changed; and the urinary bladder distended. However, the latter effects were noted at higher doses than the established oral LD50. Histopathologically, thickened intestinal mucosa lining; tubular degeneration and proteinuria in the kidneys; vascular congestion, focal necrosis and hydropic degeneration of hepatocytes in the liver, were encountered. Conclusion: Basing on the oral LD50 in mice, all oils were safe and can be explored further as antimold grain preservatives. However, Rosmarinus officinalis was marginally safe as per the OECD guidelines. The histopathological effects of Monanthataxis littoralis essential oil need to be investigated further.