Preparative separation of flavonoids in plant extract of S milacis G labrae R oxb. by high performance counter‐current chromatography

Four flavonoids, isoastilbin, astilbin, isoengelitin, and engelitin were isolated and purified simultaneously from S milacis G labrae R oxb. for the first time by high performance counter‐current chromatography using a system consisting of n ‐hexane– n ‐butanol–water (1:2:3, v/v/v). A total of 392.6 mg of astilbin, 71.4 mg of isoastilbin, 47.4 mg of engelitin, and 10.3 mg of isoengelitin were purified from 1.89 g of the ethyl acetate extract of S milacis G labrae R oxb. in six runs, each at over 94.51% purity as determined by HPLC . The structures of the four compounds were identified by their retention time, the LC ‐ ESI ‐ MS n in the negative ion mode, and confirmed by 1 H‐NMR experiments. The characteristic LC‐ESI‐MS fragmentation patterns of the four compounds were discussed.