Antitumor Effects Of Alkaloidal Compounds From Gelsemium Elegans Benth And Their Preliminary Mechanisms

BACKGROUND Gelsemium elegans Benth (G. Benth.), which is indigenous in China, belongs to the genus Gelsemium of Loganiaceae. G. Benth. is abundant in Fujian, Zhejiang and Guangxi provinces and so on. The clinical and basic researches indicated that the total alkaloid of G. Benth possess antitumor property.However, the therapeutic dosage was close to the toxic dosage which handicapped the application.In recent years antitumor effect of monomeric alkaloids of G. Benth have been paid more attention to by researchers but the mechanism remains unclear. Therefore,in the present study we further investigated the antitumor effect of monomeric alkaloids of G. Benth both in vitro and in vivo and the mechanisms involved in the anticancer activity,with the purpose of providing dosage reference and theory basis for development of new chemotherapeutic agents that can prevent and treat cancer with low toxicity.OBJECTIVE To investigate the antitumor effect and mechanisms of alkaloidal compounds from Gelsemium elegans Benth.METHODS 1. Four alkaloid compounds were assessed for cytotoxic activity in vitro using the microculture 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay for cellular viability.2. The antitumor activity of alkaloid compounds were evaluated in the kunming mice bearing H22 hepatoma. Tumor growth inhibiton was observed. 3.Cells treated with alkaloid compounds at various concentrations and different time were abserved under fluorescence microscopy and ethidium bromide/acridine orange (EB/AO) double staining were used to evaluate the morphological change of sw480 cell lines before and after the treatment.The flow cytometry(FCM) was used to investigate the apoptotic rate and the changes of cell cycle distribution of apoptosis cells treated with alkaloid compounds at various concentrations.RESULTS 1.The results of MTT demonstrated that Koumine, Gelsemine, Gelsenicine and Gelsevirine could significantly inhibite the proliferation of human carcinoma cell line SW480 and MGC80-3 in a dose-dependent manner. The 50% inhibiting concentration (IC50) of Koumine, Gelsemine, Gelsenicine and Gelsevirine on SW480 cells were 0.45±0.10,0.76±0.28,0.52±0.22 and 1.41±0.06 mmol?L-1 respectively, and were 0.82±0.19,1.20±0.33,1.14±0.23 and1.22±0.11 mmol?L-1 respectively on MGC80-3 cells. Koumine, Gelsemine and Gelsenicine also could inhibite the proliferation of TE-11 and HepG2 cells in a dose-dependent manner. IC50 of Koumine, Gelsemine and Gelsenicine on TE-11 cells were 0.74±0.05, 1.94±0.30 and 1.73±0.35 mmol?L-1 respectively, and were 1.26±0.32, 1.82±0.35 and 1.79±0.54 mmol?L-1 respectively on HepG2 cells. 2. Koumine significantly inhibited the growth of mice implanted solid tumor of H22 hepatoma in a dose-dependent manner,the inhibitory rates at dose of 4mg/kg, 2mg/kg, 1mg/kg were 40.29%,36.57% and 22.89% respectively; Gelsemine could inhibite H22 tumor in a dose-dependent manner and the inhibitory rates at dose of 4mg/kg was 28.91% but Gelsevirine showed no significant inhibitory effect on H22; 3. Using flow cytometry a sub-G1 peak of apoptotic cells was detected in cell cycle analysis. Furthermore, a dose related increase in the percentage of cells in S phase and a concomitant decrease in the percentage of cells in G1 phase was observed in cells exposed for 48h. This suggested that koumine inhibited cell growth by specific blocking of the progression of cells through S-phase of the cell cycle and inducing apoptosis of tumor cells.CONCLUSION The in vitro and in vivo anticancer effects of alkaloidal compounds from Gelsemium elegans Benth indicated that it has sufficient potential to warrant further investigation. Moreover, inducing cell cycle arrest and leading to tumor cells apoptosis might be one of the possible mechanisms involved in the anticancer activity.