Studies On The Secondary Metabolites And Bioactivities From Manihot Esculenta

Cassava (Manihot esculenta Crantz) is a major source of calorie in the tropics, whose roots can be processed into various foods. Cassava was widely cultivated in tropical regions around the world and also distributed in Hainan, Guangdong, Guangxi, Guizhou, Yunnan, Fujian, and Taiwan provinces, etc. In many countries, cassava has been used as an ethanol biofuel feedstock, as well as a traditional medicine to cure diarrhoea, fever, headache, aches and acariasis. However, few studies on chemical constituents and their pharmacological activity from Manihot esculenta were reported. In this paper, secondary metabolites from Manihot esculenta were isolated and identified, and their antibacterial activities were evaluted. Our works are very important to the development and sustainable utilization of cassava.Fourteen compounds were isolated from the EtOAc fraction of ethanol extract of stems of Manihot esculenta by column chromatography, and their structures were identified by physicochemical and spectral data (UV, IR, MS,1D NMR,2D NMR) as yucalexin P-23(1), thecacorin C (2), sporogen AO-2(3), yucalexin P-21(4), amentoflavone (5),(+)-Decursinol-4d (6), ceplignan (7), indole-3-carboxylic acid (8),3,9,13-megastigmanetriol (9), methylcholestane-3β,5α,6β,-triol (10), longifoamide-B (11), Protocatechuic acid (12), Catalpinic acid (13) and furan (14). Among them, compounds1and2were new diterpenoid, compound3was new sesquiterpene and compounds5-14were isolated from Manihot esculenta for the first time. The antimicrobial activities of all the compounds were examined by the filter paper disc agar diffusion method. Compounds4,6,8,9,11,13, and14showed inhibitory activity against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA). Compound10demonstrated inhibitory activity against MRSA. Compound12exhibited inhibitory activity against S. aureus.Four compounds were isolated by column chromatography from the EtOAc fraction of ethanol extract of cassava roots, and their structures were indentified by physicochemical and spectral data (UV, IR, MS,1D and2D NMR) as1-methoxy-2-propanol-β-D-galactosidase (15), D-(+)-trehalose (16), lactic acid (17) and succinic acid (18). Among them, compound15was new natural product, and the others were isolated from cassva for the first time.The antimicrobial activities of all the compounds were examined by the filter paper disc agar diffusion method. The ethanol extract and petroleum, EtOAc, n-BuOH and water fraction and compounds17&18showed inhibitory activity against MRSA. The petroleum fraction, EtOAc fraction, n-BuOH fraction and compounds17&18showed inhibitory activity against S. Aureus.All the fractions of cassava were examined for their antioxidant activity by the DPPH method. And the results showed that all the fractions contributed to the antioxidant activity., of which activity of the ethyl acetate fraction is the highest, with its EC50is9.6μg/ml.