Thesis (M.Sc.) --Chulalongkorn University, 2009

The present study evaluated the cytotoxic activity potential of 24 crude extracts obtained from 22 plant species used in the Thai traditional medicine against MCF-7 (human breast cancer cells) and SW-620 (human colon cancer cells). The cytotoxic activity was analyzed by incubating the cancer cells with the plant ethanol extracts at the doses of 0.1, 1, 10, 25, 50, 75, 100, 500 and 1,000 µg/ml, respectively for 72 hours. The 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay was used to determine cytotoxicity of the harvested cells in comparison with the DMSO control group. The plant extracts that showed a significantly cytotoxicity was/were verified from the IC [subscript 50] value of less than 30 g/ml. The leaf extract of Suregada multiflorum showed the highest cytotoxicity against MCF-7 cells with IC[subscript 50] value of 23.80 g/ml. The ethanolic extract of Stephania erecta (tuberous root), Streblus asper (seed), Suregada multiflorum (leaf), Piper nigrum (seed), Piper nigrum (fruit), Stephania venosa (tuberous root), Betula alnoides (whole stem), Diospyros rhodocalyx (stem bark) and Cyperus rotundus (rhizome), exhibited cytotoxicity against SW-620 cells with IC [subscript 50] values of 5.08, 5.55, 5.90, 14.60, 14.78, 15.73, 23.83, 29.34, and 29.47 μg/ml, respectively. The ethanolic extracts of Betula alnoides, Streblus asper, Stephania erecta, Stephania venosa and Suregada multiflorum extract showed the positive selectivity (Selectivity index) against SW-620 cells. The study provided information on some of the Thai rejuvenating herbs with potential anti-proliferation effect against the studied cancer cell lines