Chemical constituents in Thunbergia from Africa

Objective: To investigate the chemical compounds from the ethanol extract with inhibitory effects against aldose reductase from Thunbergia.Method: Guided by anti-aldose reductase assay,compounds from the bioactive fraction(ethyl acetate extract) were separated and purified by various chromatographic methods including silica gel,Sephadex LH-20,and reversed-phase HPLC.Their structures were indentified based on analysis of the spectroscopic data including 1D and 2D NMR data.Result: Eight compounds were obtained and identified as 8-hydroxy-8-methyl-9-methene-cyclopentane-1,4,6-trihydroxy-tetrahydronaphthalene-12-one,named as thunbergia A(1),3,4-dihydro-4,5,8-trihydroxy-2-(3-methyl-2-butenyl)naphthaoxiren-1(2H)-one(2),8-(β-gluco pyranosyloxy)-3,4-dihydro-2-(3-methyl-2-butenyl)naphtha oxiren-1(2H)-one(3),galangin(4),quercetin(5),luteolin(6),5,6,3′,4′-tetrahydroxy-3,7-dimethoxy-flavone(7) and upeol(8).Conclusion: Thunbergia A was a new derivative of tetrahydronaphthalene,and compounds 2 and 3 were separated from the genus Thunbergia for the first time.