Abstract

Antioxidants act as quenchers or scavengers of oxidative free radicals and singlet oxygen (O-1(2)); these compounds are effective in the treatment of diseases associated with oxidative stress and food preservation. We studied the antioxidant activity of hesperidin which was isolated from mandarin (Citrus reticulata) fruit peels against singlet oxygen (O-1(2)). High-performance liquid chromatography with diode array detection was used for chemical characterization. The total singlet oxygen quenching rate constants of the hesperidin was measured by using the Stern-Volmer model. Results showed an overall quenching rate constant with a value of 6.43 x 10(7) M-1 s(-1) for O-1(2), which for the best of our knowledge has not been reported before. Furthermore, quantum chemical calculations were performed to get insight into the molecular and electronic structure properties of this antioxidant, which confirms that the quenching mechanism through energy transfer is rarely probable and that O-1(2) could interact with the methoxy phenyl charge rich fragment of the molecule.