Anti-proliferation and radiation-sensitizing effect of an anthocyanidin- rich extract from purple-shoot tea on colon cancer cells

Abstract

Teas are known to have several health promoting benefits due to polyphenol contents. Two varieties of tea cyanins, Purple-Shoot Tea (not registered) and TTES No. 12, were selected, dehydrated or prepared to green tea to evaluate the anti-proliferative and radiation-sensitizing effects on colon cancer cells. The tea cyanins were extracted by using three drying treatments which are freeze-dried, hot-air dried and green tea manufacturing. The composition analysis showed that the extracts of purple-shoot teas contained more polyphenols, flavonoids, condensed tannins, anthocyanins and proanthocyanidins than TTES No. 12 under various tea processes. Lyophilized tea samples had better antioxidant capacities and reducing power than those of samples from hot-air dried and green tea manufacturing. Anti-proliferation results from HT-29, Colo 320DM and CT-26 cell lines showed that Purple-shoot tea had prominent inhibitory activities which might be correlated to its antioxidative properties. The cell cycle studies confirmed that Purple-shoot tea arrested colon cancer cell at G0/G1 phase. Tested tea samples had radiation-sensitizing effect on the CT-26 cell with 2Gy Co-60 irradiation. Higher anthocyanidin and anthocyanin contents in Purple-shoot tea may contribute to enhanced cytotoxicity and induction of apoptosis after irradiation. The radiation-sensitive effect of Purple-shoot tea on carcinoma cells suggested that nature compounds such as tea polyphenol can be utilized to reduce the dosage in radiotherapy in the future.