Inhibition Activities of Extracts from Aloe spp.with Different Solvents against Alternaria brassicae

Antimicrobal substance of Aloe vera was extracted with methanol,ethanol,acetone,ethyl acetate,chloroform,benzene,petroleum ether and n-hexane,respectively.The results showed that the production of antimicrobial substance increased with the increase of solvent polarity.The antifungal activities of the extracts from Aloe with different solvents against Alternaria brassicae were tested by growth rate mensuration.The results indicated that the growth inhibition rates of Alternaria brassicae by the extracts with petroleum ether,n-hexane and ethyl acetate were 71.4 %,71.3 % and 62.4 %,respectively,higher than the other extracts.Therefore ethyl acetate was considered as the most suitable solvent for extracting antifungal substance based on both of the antifungal activity and yield rate.Inhibition effects of methanol,ethanol,acetone and ethyl acetate on Alternaria brassicae and dissolved activities of methanol,acetone and ethyl acetate to extracts from Aloe were tested.The results showed that different extracts from Aloe could easily dissolved in ethyl acetate and ethyl acetate had the lowest inhibition activity on Alternaria brassicae.Therefore ethyl acetate-water(7∶3,v/v) mixture was selected to dissolve different extracts from Aloe for further bioassay.In addition,2 ‰-1 % Tween 20 were used as surfactant for enhancing the uniformity of the ethyl acetate-dissolved extracts in PDA plates.The inhibition rates of the extracts from 7 Aloe species on Alternaria brassicae were determined.Aloe arborescens and Aloe vera showed higher activities than the others.