Purification and Identification of Compounds with In Vitro Antitumor Activity from Rabdosia Serra (Maxim) Hara

Objective: To find the antitumor compounds from Rabdosia Serra (Maxim) Hara, phytochemical isolation procedures were performed by bioassay-guided fractionation. Methods: The ethanol extract of Rabdosia serra (Maxim) Hara was fractionated by organic solvents-petroleum ether, benzene, ethyl acetate and butanol in sequence. The in vitro antitumor activity against human hepatoma cell line HepG2 and human leukemia cell line HL60 was determined by modified MTT (methyl thiazolyl tetrazolium) method. Undergoing SIC (silver ion chromatography), preparative HPTLC (high performance thin layer chromatography) and preparative HPLC (high performance liquid chromatography), a compound with high in vitro antitumor activity was purified from the benzene fraction. The structure of the compound was elucidated on the basis of spectral data from UV (ultraviolot-visible), IR (infrared), ¹³C-NMR (nuclear magnetic resonance), ¹H-NMR and MS (mass spectrometry). Results: Of the 5 fractions obtained from ethanol extract, benzene fraction exhibited the highest bio-activity against both cancer cell lines, its inhibitory rates against HepG2 and HL60 cell proliferation were up to 80% and 100% at the concentration of 100mug/mL, respectively. While the higher polarity fractions, i.e. butanol and aqueous fractions, almost presented no cytotoxicity. 3 sub-parts, denoted by II-5-1, II-5-2 and II-5-3, were gotten after purifying the benzene fraction. The bioassay results indicated that the compound with high cytotoxicity was II-5-3, its inhibitory rates against HepG2 and HL60 cell proliferation were 51.2% and 65.3% at the concentration of 12.5mug/mL, respectively. The structure of II-5-3 was elucidated as 1alpha, 7alpha, 12alpha, 14beta, 20alpha-pentahydroxy-haur-16-en-15-one. Conclusion: The antitumor constituents of Rabdosia Serra (Maxim) Hara exist in low polarity fractions, and by further purification of benzene fraction, an ent-kaurene diterpene compound, namely ent-1alpha, 7- alpha, 12alpha, 14alpha, 20alpha-pentahydroxy-haur-16-en-15-one, was obtained and tested to be having high in vitro antitumor activity.