In vitro antimicrobial activity of zimmu (Allium sativum L. 'Allium cepa L.) leaf extract

The fungitoxic effect of various medicinal plants belonging to different families was evaluated in vitro on Rhizoctonia solani, the rice sheath blight pathogen. Of the various plant extracts, the leaf extract of zimmu (Allium cepa x Allium sativum) showed the maximum antifungal activity against R. solani and recorded an inhibition zone of 12 mm. The leaf extract of zimmu was also effective in inhibiting the growth of other agronomically important fungal and bacterial pathogens viz., Aspergillus flavus, Curvularia lunata, Alternaria solani, Xanthomonas oryzae pv. oryzae, Xanthomonas campestris pv. malvacearum and Xanthomonas axonopodis pv. citri. The antimicrobial compound was dissoluble in methanol and the methanolic extract showed the absorption maxima at 210 nm and 230 nm. Phenolic compounds were present in greater amounts in methanol extract of zimmu. TLC analysis showed the appearance of two blue spots at R _f= 0.65 and R_f= 0.90. The compounds eluted at R _f= 0.65 and R_f= 0.90 by preparative TLC exhibited strong antifungal activity against R. solani.