[Two new protoberberine alkaloids from Stephania hernandifolia]

The 95% ethanol extract of Stephania hernandifolia was isolated and purified by column chromatography on silica gel and Sephadex LH-20, RP-18 medium-pressure liquid chromatography, and semi-preparative high performance liquid chromatography. The chemical structures of the compounds were identified by NMR and high-resolution mass spectrometry. Four alkaloids were isolated and identified as(-)-8-oxo-2,3,4,10,11-pentamethoxyberberine(1),(-)-8-oxo-11-hydroxy-2,3,4,10-tetramethoxyberberine(2), N-trans-feruloyl tyramine(3), and N-cis-feruloyl tyramine(4). Compounds 1 and 2 were new protoberberine alkaloids, while compounds 3 and 4 were amide alkaloids. All the four compounds were separated from this plant for the first time. The inhibitory activities of compounds 1, 3, and 4 against α-glycosidase were measured by the enzymatic reaction in vitro with 4-nitrophenyl-α-D-glucopyranoside(PNPG) as the substrate. Compounds 3 and 4 showed inhibitory activities against α-glucosidase, with median inhibition concentration(IC_(50)) values of(7.09±0.42) and(31.25±1.14) μmol·L~(-1), respectively.