Cytotoxic Epimeric Ginsenosides from the Flower Buds of Panax Ginseng

Three pairs of ginsenoside epimers, including three new compounds (2, 3 and 5), were isolated from the flower buds of Panax ginseng. The structures of the isolated compounds were elucidated on the basis of considerable spectroscopic analyses and comparison with the reported data. All six compounds were evaluated for their cytotoxicties against three human cancer cell lines, HL-60, MGC80-3 and Hep-G2. Compounds 1, 3, and 6 with S configurations at C-24 or C-20 showed moderate inhibitory activities with IC50 values of 25.32, 18.76, and 38.64 mu M in HL-60 cells, respectively. Our findings showed that different configurations of these isolated ginsenosides had a significant impact on the antitumor activity, and S epimers were higher than R.