Six new dammarane-type triterpene saponins from Panax ginseng flower buds and their cytotoxicity

Background: Panax ginseng has been used for a variety of medical purposes in eastern countries for more than two thousand years. From the extensive experiences accumulated in its long medication use history and the substantial strong evidence in modern research studies, we know that ginseng has various pharmacological activities, such as antitumor, antidiabetic, antioxidant, and cardiovascular system–protective effects. The active chemical constituents of ginseng, ginsenosides, are rich in structural diversity and exhibit a wide range of biological activities. Methods: Ginsenoside constituents from P. ginseng flower buds were isolated and purified by various chromatographic methods, and their structures were identified by spectroscopic analysis and comparison with the reported data. The 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H- tetrazolium bromide method was used to test their cytotoxic effects on three human cancer cell lines. Results: Six ginsenosides, namely 6'–malonyl formyl ginsenoside F1 (1), 3β–acetoxyl ginsenoside F1 (2), ginsenoside Rh24 (6), ginsenoside Rh25 (7), 7β–hydroxyl ginsenoside Rd (8) and ginsenoside Rh26 (10) were isolated and elucidated as new compounds, together with four known compounds (3–5 and 9). In addition, the cytotoxicity of these isolated compounds was shown as half inhibitory concentration values, a tentative structure–activity relationship was also discussed based on the results of our bioassay. Conclusion: The study of chemical constituents was useful for the quality control of P. ginseng flower buds. The study on antitumor activities showed that new Compound 1 exhibited moderate cytotoxic activities against HL-60, MGC80-3 and Hep-G2 with half inhibitory concentration values of 16.74, 29.51 and 20.48 μM, respectively. Keywords: 7β–hydroxyl ginsenoside Rd, Acylated ginsenosides, Cytotoxicity, Dammarane–type triterpene saponin, Panax ginseng flower buds