Changes in chemical properties and bioactivities of turmeric pigments by photo-degradation
Yu Na Jung, Jungil Hong
Abstract
<abstract> Turmeric pigments have attracted a great attention for their variety of physiological functions. The pigments are, however, chemically unstable under various conditions including light irradiation. In this study, changes in chemical characteristics and bioactivities of turmeric pigments under light were investigated. Chemical changes of turmeric oleoresin (20 µg/mL) and curcumin (20 μM) significantly proceeded under irradiation by a regular household fluorescent light (27 W, 30 cm distance). After 24 h irradiation, color intensity of turmeric and curcumin decreased by 65.4 and 63.0%, respectively. Among three curcuminoids in turmeric, bisdemethoxycurcumin was the most resistant to decomposition by light. Scavenging activities of the irradiated turmeric pigments against 2, 2-diphenyl-2-picrylhydrazyl radical and intracellular reactive oxygen species were significantly less pronounced. The activity against 2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid radical was, however, significantly enhanced after photo-degradation. Cytotoxic effects of turmeric oleoresin after 24 h irradiation on HCT 116 colon cancer cells decreased, while those of curcumin was enhanced after photo-degradation. Our results indicates that chemical properties and bioactivities of turmeric pigments can be modulated under light, and the phenomena should be considered in various processing and storage conditions for the pigment-containing foods. </abstract>