ANTIBACTERIAL ACTIVITIES AND PHYTOCHEMICAL PROPERTIES OF EXTRACTS OF AIR POTATO (DIOSCOREA BULBIFERA) AGAINST SOME PATHOGENIC BACTERIA

Abstract

Dioscorea bulbifera Linn has been documented to be effective in treating several complicated ailments in many parts of the world, but remain an underutilized tuber in this part of world, Nigeria both for food and medicinal purposes. The present study, hence evaluated the antibacterial activities of ethanolic and aqueous extract of parts of the tuber against ten (10) clinical pathogens, using agar well diffusion. The bioactive constituents in these tubers were also determined using standard techniques. The proximate composition of the bulbils of the tuber ranged as follow; moisture content (4.58 - 4.61%); ash (4.46 - 4.52%); crude protein (8.29 - 8.44%); fat (1.96 - 1.99%); fibre (2.22 - 2.28%) and carbohydrate (78.31 -78.34%); while those of the peel of the tuber ranged as follow; moisture content (3.68 - 3.74%); ash (9.00 - 9.11%); crude protein (8.47 - 8.50%); fat (2.98 - 3.02%); fibre (22.67 - 22.58%) and carbohydrate (53.05 - 53.20%). The tuber was recorded to contain higher amount of saponin with the average of 24 mg/g, followed by cardiac glycosides with 13.13 mg/g, terpenoid with 8.48 mg/g, flavonoids followed with 5.36 mg/g and tannin with 4.21 mg/g was the least among the bioactive ingredients. Except for Proteus vulgaris, Serratia liquefaciens, Micrococcus luteus, Bacillus cereus and Citrobacter freundii, other test organisms were susceptible to the effect of the ethanolic extract of the peel of D. bulbifera at 500 μg/mL. High inhibition zones (between 17 and 22 mm) were recorded against 80% of the test organisms at 1000 μg/mL, except for 15 mm zone recorded against Bacillus cereus. The Minimum Inhibitory Concentrarion (MIC) and the Minimum Bactericidal Concentration (MBC) of extract of D. bulbifera ranged in respect to the part (peel and bulbil) from 125 μg/mL to 500 μg/mL; and 250 μg/ml to 1000 μg/mL for peels and bulbils respectively. Antibacterial activity of the ethanolic and aqueous extracts of the bulbils of D. bulbifera was however, not significant in this present study compared to that of the peel. This study therefore, affirmed that the peel of D. bulbifera is a novel source of bioactive compounds which do not only enhance the antibacterial properties, but also ascertain its good health-promoting qualities.