The Role of Singlet Oxygen in Photoreactivity and Phototoxicity of Curcumin

Abstract

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 ( 1 O 2 ) luminescence proved that curcumin generates 1 O 2 upon blue light irradiation in organic solvent and in liposomes. Then, HPLC-EC(Hg) measurements revealed that liposomal and cellular cholesterol is oxidized by 1 O 2 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.

Tetraacetyl riboflavin derivative mediates caspase 3/7 activation via MAPK in A431 cells upon blue light influence

“…However, to be convinced of the validity of this hypothesis, it would be necessary to investigate, whether 3MeTARF molecule interacts with biomembranes and penetrates into the cells, as the location of the sensitizer is an important factor. Photosensitizers like curcumin, despite lower quantum yield of singlet oxygen generation (0.04 compared to chlorophyll), trigger lethal effect, due to permeability through the cell membrane 17 . Its hydrophobic molecule readily penetrates into the cell, where via 1 O 2 generating, oxidizes cholesterol and proteins, leading to rapid phototoxic effect, even at its relatively low concentrations 17 .…”

“…The plates were illuminated at room temperature through a lid, using 50 W LED lamps emitting 438 nm blue light (PXM sp.k. Zupnik M., Poland) for 15 min 10,17 . Nonirradiated cells were kept in the dark under similar conditions.…”

“…Zupnik M., Poland) for 15 min. 10,17 Nonirradiated cells were kept in the dark under similar conditions.…”

“…17 Its hydrophobic molecule readily penetrates into the cell, where via 1 O 2 generating, oxidizes cholesterol and proteins, leading to rapid phototoxic effect, even at its relatively low concentrations. 17 On the other hand, the hydrophobic nature of curcumin, makes low its bioavailability, compared to that of Rfl, which limits the use of curcumin as a potential photosensitizer in PDT.…”

Elucidation of Molecular‐level Mechanisms of Oxygen Atom Reactions with Chlorine Ion in NaCl Solutions using Molecular Dynamics Simulations Combined with Density Functional Theory

“…In addition, the singlet oxygen atom also plays an important role in photochemistry. [23][24][25] In this study, we performed MD simulations combined with density functional theory (DFT) to study the reaction mecha-nisms for oxygen atom and chlorine ion in NaCl solutions. Considering the ground and first excited states of the oxygen atom, we examined four bulk systems, O( 3 P)-NaCl-63H 2 O, O( 1 D)-NaCl-63H 2 O, O( 3 P)-4NaCl-63H 2 O, and O( 1 D)-4NaCl-63H 2 O. MD simulations were performed on 256 trajectories that underwent sixty-four initial configurations of every system.…”