Scalamic enantiomers and racemates of minor lignanoid from an aqueous extract of the stems with hooks of Uncaria rhynchophylla

From an aqueous extract of the stems with hooks of Uncaria rhynchophylla, eight pairs of scalemic enantiomers of minor lignanoid (+)-/(-)-1 - (+)-/(-)-6、(+)-/(-)-9, and (+)-/(-)-10 as well as two pairs of racemic enantiomers (+)-/(-)-7 and (+)-/(-)-8 were isolated and chirally separated by column chromatographic techniques over macroporous adsorbent resin, MCI resin, Toyopearl HW-40, silica gel, and Sephadex LH-20, together with flash and chiral HPLC techniques. Their structures including the absolute configurations were determined by spectroscopic data analysis and theoretic calculations of electronic circular dichroism (ECD) spectra. Among them, chiral separation and absolute configurational determination of the optical active compounds (+)-/(-)-1 - (+)-/(-)-7 are reported for the first time, while the occurrence of scalemic enantiomers (+)-/(-)-9 and (+)-/(-)-10 in nature are discovered for the first time. Preliminary bioassay showed that (+)-8 and (-)-8 inhibited acetaminophen (APAP) induced HepG2 cell damage at a concentration of 10 μmol·L^-1.