Antcin C is a bioactive compound isolated from Antrodia cinnamomea, a rare and expensive medicinal fungus endemic to Taiwan. Up to date, the absolute structure of antcin C has not been solved. In this study, the phenylglycine methyl ester (PGME) derivatives of antcin C were prepared. From NMR analysis the absolute configuration of (S)-antcin C (1) and (R)-antcin C (2) were determined. By MTT assay, (S)-antcin C presented cytotoxicity against Hep G2 and MCF-7 cells, with IC50 values of 14.5 and 12.8 μg/mL, respectively. However, (R)-antcin C did not show significant cytotoxicity. Our results showed that the configuration at C25 for antcin C is very important for its cytotoxicity. From a quality control point of view, it is necessary to identify and quantify the R- and S- enantiomers in the A. cinnamomea products.
