Studies on the preparation, crystal structure and bioactivity of ginsenoside compound K

Microbial transformation of Panaxnotoginseng saponins (PNS) using Aspergillus niger afforded, as the main metabolite, ginsenoside compound K (20-O-beta-glucopyranosyl-20(S)-protopanaxadiol). Its structure was determined spectroscopically and by X-ray analysis, and this is the first time the crystal structure of ginsenoside has been reported. In comparison with ginsenoside Rb1, the pro-drug for this metabolite, compound K exhibits potent cytotoxic activity against tumor cell lines. The mean concentrations of compound K needed to inhibit the proliferation of cells by 50% (IC50) were 12.7, 11.4, 8.5 and 9.7 microM for mouse high-metastatic melanoma (B16-BL6), human hepatoma (HepG2), human myeloid leukemia (K562) and human high-metastatic lung carcinoma (95-D) cell lines, respectively. The data show that ginsenoside compound K is a good antitumor drug candidate.