Cytotoxic and antioxidant activities of Thai medicinal plants for cancer treatment

Fifteen Thai medicinal plants, ingredients of a Southern Thai traditional formula for cancer treatment [1], were selected to be tested for their antioxidant and cytotoxic activity against five types of human cancer cell lines; large cell lung carcinoma (COR-L23), liver (HepG2), skin (C32), breast (MCF7) and prostate cancer (PC3) cell lines and one type of normal human cell line, fibroblast cells (10FS). DPPH assay [2] was used to test free radical scavenging activity and SRB assay [3] was used to test cytotoxic activity. The procedures which were used for preparation of water and ethanolic were similar to those practiced by Thai traditional doctors. It found that the ethanolic extract of Rhinacanthus nasutus roots showed the highest cytotoxic activity against prostate, skin, liver and breast (IC₅₀=2.01, 10.09, 8.1 and 3.98µg/ml) and a high activity against COR-L23 and 10FS (IC₅₀ =5.05 and 10.1µg/ml, respectively). Dioscorea membranacea root extract showed the highest cytotoxic activity against lung cancer cell lines (IC₅₀ =4.63µg/ml) but it exhibited low cytotoxic activity against prostate, skin, liver and breast cancer cell lines. The extract of Curcuma zedoaria showed cytotoxic activity against lung and prostate cancer (IC₅₀ =6.05 and 17.84µg/ml, respectively). Two ethanolic extracts (Dioscorea membranacea and Curcuma zedoaria) showed specific activity against lung cancer cell lines and less cytotoxic activity against normal cell (IC₅₀=66.05 and 55.05µg/ml, respectively). The water extract of all plants exhibited no activity against all types of human cells. The antioxidant activity of the water extracts of Terminaila bellerica showed the highest antioxidant activity (EC₅₀=0.125µg/ml), Erythrophleum teysmannii and Sapindus rarak showed the second highest value and same value of antioxidant activity in this test (EC₅₀=0.625µg/ml). Four ethanolic extracts (Curcuma zedoaria, Dioscorea membranacea, Erythrophleum teysmannii and Smilax corbularia) also showed strong antioxidant activity (EC₅₀<20µg/ml).

Acknowledgement: Prince of Songkhla University for the financial support

References: 1. Itharat, A. et al. (1997) Wisdom of Thai traditional medicine, Prince of Songkla University, P126. 2. Yamasaki, K. (1994) Chem.Pharm.Bull. 42:1663–1665. 3. Skehan, P. et al. (1990)J. Natl. Cancer Inst. 82: 1107–1112