Molecular basis of scavenging effect of zonisamide on hydroxyl radical in vitro

Zonisamide (ZNS), a commonly used anticonvulsant, scavenged hydroxyl radicals at a clinically relevant concentration. Reactants of ZNS with hydrogen peroxide and with hydrogen peroxide plus UV irradiation, yielding hydroxyl radicals, were analyzed by the LC/MS technique. Many small fragments were found in the both reactions, suggesting that ZNS was decomposed not only by hydroxyl radicals but also by hydrogen peroxide. Furthermore, mass-fragment-grams showed that m/z: 213 (ZNS itself) was decreased markedly and m/z: 118 (may be a decomposed product by ring cleavage of ZNS) was detected specifically by treatment with hydroxyl radical. These data suggested that ZNS may react directly with free radicals.