Photodegradation of Turmeric Oleoresin Under Fluorescent Light and White LED: Impacts on the Chemical Stability, Bioactivity, and Photosensitizing Property of Curcuminoids.

Turmeric oleoresin (TO), a natural pigment derived from rhizomes, is valued for its health benefits, which are primarily attributed to its rich curcuminoid content (curcumin, demethoxycurcumin, and bisdemethoxycurcumin). Despite these benefits, curcuminoids are known to be light-sensitive and possess photosensitizing properties. This study investigated the impact of common light sources, fluorescent light and white LED (both at 10 W/m), on the chemical stability, antioxidant activity, cytotoxicity, and photosensitizing properties of TO. Exposure to both light sources significantly reduced TO's color and fluorescence intensity, with white LED causing greater instability. HPLC analysis confirmed a decrease in individual curcuminoid levels, with curcumin degrading most rapidly under both conditions. The DPPH radical scavenging activity of irradiated TO decreased compared to fresh or dark-stored turmeric, whereas its ABTS radical scavenging activity increased upon light exposure. Photosensitizing potency, measured by formazan decolorization and lipid peroxide formation, declined as TO decomposed under light. Conversely, the cytotoxicity of TO against B16F10 melanoma cells was significantly enhanced under light exposure, though this effect was diminished significantly after 24 h of pre-irradiation. These findings underscore the instability of turmeric pigment under common lighting conditions, which should be a crucial consideration when processing, storing, and distributing turmeric-containing products.