The Role of Singlet Oxygen in Photoreactivity and Phototoxicity of Curcumin

• Published in: Photochemistry and photobiology 2023-01, Vol.99 (1), p.57-67
• Main Authors: Wolnicka‐Glubisz, Agnieszka, Olchawa, Magdalena, Duda, Mariusz, Pabisz, Pawel, Wisniewska‐Becker, Anna
• Format: Article
• Language: English
• Subjects: Animals; Cholesterol; Cosmetics; Curcumin; Curcumin - pharmacology; Cytotoxicity; Dermatitis, Phototoxic; Food additives; Food dyes; Irradiation; Light; Light irradiation; Liposomes; Mammalian cells; Mammals; Membrane potential; Membrane proteins; Membranes; Mitochondria; Oximetry; Oxygen; Oxygen consumption; Oxygen enrichment; Phototoxicity; Radiation; Singlet Oxygen; Toxicity
• ISSN: 0031-8655; 1751-1097
• DOI: 10.1111/php.13666

Curcumin is a plant‐derived yellow‐orange compound widely used as a spice, dye and food additive. It is also believed to have therapeutic effects against different disorders. On the other hand, there are data showing its phototoxicity against bacteria, fungi and various mammalian cells. Since the mechanism of its phototoxic action is not fully understood, we investigated here the phototoxic potential of curcumin in liposomal model membranes and in HaCaT cells. First, detection of singlet oxygen (1O2) luminescence proved that curcumin generates 1O2 upon blue light irradiation in organic solvent and in liposomes. Then, HPLC‐EC(Hg) measurements revealed that liposomal and cellular cholesterol is oxidized by 1O2 photogenerated by curcumin. Enrichment of liposome membranes with curcumin significantly increased the oxygen photo‐consumption rate compared to the control liposomes as determined by EPR oximetry. Cytotoxicity measurements, mitochondrial membrane potential analyses and protein hydroperoxides detection confirmed strong phototoxic effects of curcumin in irradiated HaCaT cells. These data show that since curcumin is advertised as a valuable dietary supplement, or a component of cosmetics for topical use, caution should be recommended especially when skin is exposed to light. Although the dual aspect of curcumin's activity (therapeutic and phototoxic) has been known in literature; the mechanism of its phototoxic action is not fully understood. The purpose of this study was to analyze the phototoxic potential of curcumin in liposomal model membranes and in HaCaT cells. The results indicate that the photoreactivity of curcumin could be related to photogeneration of singlet oxygen upon blue light irradiation and oxidation of liposomal and cellular lipids and cellular proteins.