Studies on the Natural Antifungal compounds from Yam tubers (Dioscorea Alata. L.)
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Date
1986
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Publisher
Obafemi Awolowo University, Ile Ife, Nigeria
Abstract
In order to investigate the biochemical basis of natural resistance of yam peel to fungal infection,
a preliminary chromatographic bioassay of four varietal species of Dioscorea; Manihot
esculentum Crantz; Solanum aethiopicum Linn.; and Xanthosoma sagittifolium Schott was
undertaken. The studies revealed the presence of antifungal compounds from the peel extracts of
the root crops. Four prominent antifungal components were obtained from the peels of Dioscorea
alata L. out of which the component at Rf 0.38 was fully characterized. The component was
identified with the aid of nuclear magnetic resonance, mass spectroscopy and colour reaction as
sitosterol. It is a white crystalline solid with a melting point of 138oC.
The antifungal activity of the compounds against the germination of spores of four yam
pathogens showed a percentage inhibition of below 57% at a concentration of 50 ug/ml while
inhibition on the elongation of ferm- tubes of Fusarium moniliforme was as high as 82% at the
same concentration. However, the ED50 for inhibition of germ-tube elongation in the yam
compounds for the same organism was below 27 ug/ml.
β- sitosterol was found to have an effective inhibitory dosage against the yam pathogens and the
test fungus ranging between 1.21 - 2.4 x 10-4M. The role of the yam compounds at high
concentrations in disease resistance is discussed. The antifungal compounds have weak
bacteriostatic properties with no definite pattern against both gram - positive and Gram -
negative bacteria.
Description
133p
Keywords
Biochemical, Chromatographic, Antifungal, Nuclear magnetic resonance, Spectroscopy, Pathogens, Microbes