芦荟不同溶剂提取物对白菜黑斑病菌的抑菌活性研究

用甲醇、乙醇、丙酮、乙酸乙酯、氯仿、苯、石油醚、正己烷8种溶剂对库拉索芦荟的抗菌活性物质进行提取,提取产率随溶剂极性的增强而提高.以白菜黑斑病菌为测试菌,用生长速率法测定芦荟各种溶剂粗提物的抑菌活性,当提取物浓度为10mg/mL时,各种溶剂粗提物均表现一定的抑菌效果,其中以石油醚、正己烷和乙酸乙酯的粗提物抑菌效果最好,分别为71.4 %、71.3 %和62.4 %.从抑菌效果及提取产率两方面考虑,乙酸乙酯为提取芦荟抑菌活性物质的最佳溶剂.通过测定甲醇、乙醇、丙酮、乙酸乙酯4种溶剂1 %～10 %系列浓度对白菜黑斑病菌的抑制作用及甲醇、丙酮、乙酸乙酯3种溶剂对各种芦荟粗提物的溶解性,确立用乙酸乙酯-水(7∶ 3,v/v)溶解各种粗提物进行生物测定,既能较好地溶解各种粗提物,又对测试菌的抑制作用相对较小.试验研究还筛选了2 ‰～1 %吐温20作表面活性剂乳化乙酸乙酯使其与所溶解的粗提物能均匀分布到PDA培养基中,保证了测定结果的准确性与稳定性.通过测定库拉索芦荟等7种芦荟水浸提物的抑菌活性,认为树芦荟、库拉索芦荟的抑菌效果最好.

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.