| Affiliation: | a Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan
b School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada Suruga-ku, Shizuoka 422-8526, Japan
c School of Pharmacy, Kyushu University of Health and Welfare, 1714-1 Yoshino Nobeoka, Miyazaki 882-8508, Japan
d Center for Clinical Pharmaceutical Sciences, School of Pharmacy, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan
e Faculty of Pharmaceutical Sciences, Sojo University, 4-22-1 Ikeda, Kumamoto 860-0822, Japan |
) generated from both the xanthine/xanthine oxidase (X/XO) system and activated neutrophils was investigated by electron paramagnetic resonance spectroscopy, combined with 2-ethoxycarbonyl-2-methyl-3,4-dihydro-2H-pyrrole-1-oxide (EMPO). The findings show that the presence of normal-physiological serum concentrations of IS (0.1-10 μM) resulted in decreased formation of EMPO-superoxide adduct without affecting XO activity. Furthermore, IS showed scavenging activity against cell-derived 
generated from activated neutrophils. In addition, IS also eliminated hydroxyl radicals. These findings suggest that IS acts as a novel endogenous antioxidant under normal-physiological conditions.