Abstract: The protective effects of variant concentrations of low molecular weight chitosan (LMWC) (5, 10, 20, 40 and 80 mg/L) on cadmium-induced oxygen free radicals and the possible mechanisms were investigated in freshwater crab Sinopotamon yangtsekiense. The oxygen free radicals included superoxide anion radical (O·2), hydroxyl radical (· OH) and hydrogen peroxide (H2O2) in hepatopancreas, gill and heart. The crabs were exposed to cadmium (Cd2+) (58 mg/L) and LMWC together for 96 hours. The results showed that Cd2+ could increase the production of oxygen free radicals and decrease the oxidative damage obviously. LMWC at the high dose (40 mg/L and 80 mg/L) could remarkably inhibit the production of oxygen free radicals and improve the state of oxidative stress. Furthermore, the dose-effect relationship is significant. According to these results, it is concluded that LMWC has certain scavenging effects on the oxygen free radicals induced by cadmium.

Key words: Sinopotamon yangtsekiense, low molecular weight chitosan, oxygen free radicals, antioxidant, cadmium