Background: Cancer is a leading cause of morbidity and mortality worldwide. Bauhinia strychnifolia Craib leaves is used in Thai traditional medicine for detoxification. Its leaves contain total phenolic content and also exhibit high antioxidant activity. However, there has been no report on cytotoxicity testing from its leave extracts. Thus, the present study aims to investigate its cytotoxic activity against cancer cell lines.
Objective: To study cytotoxicity from the ethanolic extracts of B. strychnifolia leaves and its vacuum liquid chromatography fraction against cholangiocarcinoma cell line (KKU-M156) and two types of colon adenocarcinoma cell lines (SW480, LS174T).
Material and Method: In vitro cytotoxic activity of the ethanolic extracts against three human cancer cell lines were investigated by using sulforhodamine B (SRB) assay.
Results: The 95% ethanolic extract of dried leaves showed the higher cytotoxic activity against KKU-M156, SW480, and
LS174T than 50% ethanolic extract of dried leaves. The chloroform fraction from the 95% EtOH extract of dried leaves showed the best cytotoxicity against KKU-M156 and SW480 with IC50 value of 5.79+0.47 and 6.90+0.14 μg/ml, respectively.
Conclusion: The chloroform fraction from the 95% ethanolic extract of dried leaves was the most effective fraction against bile duct and colon cancer cell lines, thus this extract should be further investigated for active compounds possessing those observed cytotoxic activity.

Keywords: Bauhinia strychnifolia, Detoxification, Thai traditional medicine, Cytotoxic activity, Sulforhodamine B (SRB) assay