Two pairs of new biflavonoid enantiomers from Dysosma versipellis
Five biflavonoids were isolated and purified from the ethanol extract of Dysosma versipellis by silica gel column chromatography,Sephadex LH-20 column chromatography,and preparative HPLC.Their structures were identified as(+)-dysosmabiflavonoid H(1a),(-)-dysosmabiflavonoid H(1b),(+)-dysosmabiflavonoid Ⅰ(2a),(-)-dysosmabiflavonoid Ⅰ(2b),podoverine F(3)by extensive spectroscopic analysis(MS,UV,IR,NMR)and electronic circular dichroism(ECD)calculations.Compounds 1a and 1b,2a and 2b are two pairs of new biflavonoid enantiomers.Compounds 2,2a,and 2b showed significant DPPH scavenging capacity with IC50 values of 8.87,10.18,11.35 μmol/L,respectively,in comparison with trolox(IC50,14.95 μmol/L).Compounds 2,2a,and 2b displayed more potent DPPH radical scavenging activity than compounds 1,1a,1b,and trolox,respectively.The preliminary structure-activity relationship exhibited that the catechol hy-droxyl group in B ring of flavonoids is essential for DPPH radical scavenging activity.
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