Interaction of Retinoic Acid Radical Cation with Lysozyme and Antioxidants: Laser Flash Photolysis Study in Microemulsion

All‐trans retinoic acid ( ATRA ) plays essential roles in the normal biological processes and the treatment of cancer and skin diseases. Considering its photosensitive property, many studies have been focused on the photochemistry of ATRA . In this study, we investigated the transient phenomena in the laser flash photolysis ( LFP ) of ATRA in microemulsion to further understand the photochemistry of ATRA . Results show that 355 nm LFP of ATRA in both acidic and alkaline conditions leads to the generation of retinoic acid cation radicals ( ATRA •+ ) via biphotonic processes. The employment of microemulsion system allows us to investigate the reaction of hydrophobic ATRA •+ with molecules of different polarity. Therefore, we studied the reaction activity of ATRA •+ to many hydrophobic and hydrophilic molecules. Results show that ATRA •+ can efficiently interact with lysozyme, tyrosine, tryptophan and many antioxidants, such as curcumin (Cur), vitamin C ( VC ) and gallic acid ( GA ). The apparent rate constants of these reactions were measured and compared. These findings suggest that ATRA •+ is a reactive transient product which may pose damage to lysozyme, and antioxidants, such as Cur, VC and GA , may inactivate ATRA •+ by efficient quenching reactions.