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The objective of the present study was to investigate the antioxidant activity and immunostimulating property of glucosamine (GlcN) using various in vitro and in vivo tests. Results showed that GlcN possessed excellent antioxidant activities as manifested by strong chelating effect on ferrous ions and protection of macromolecules such as protein, lipid, and deoxyribose from oxidative damage induced by hydroxyl radicals. The immunostimulating effects of GlcN were further evaluated through various immunological tests. GlcN showed excellent activity of enhancing splenocyte proliferation. Neutral red pinocytosis and NO production in mouse peritoneal macrophages were significantly augmented. Oral administration of GlcN to mice for 20 days significantly enhanced the serum antibody level in mice in response to sheep red blood cells (SRBC), increased the relative organ weight of spleen and thymus tissue, and promoted the delayed-type hypersensitivity (DTH) against SRBC as compared with control group. In conclusion, the present investigation reveals GlcN is biologically functional in antioxidative activities and immunostimulating properties.

The protective effects of chitosan oligosaccharide (COS), d-glucosamine (GlcNH(2)) and N-acetyl-d-glucosamine (GlcNAc) on carbon tetrachloride (CCl(4))-induced hepatotoxicity and the possible mechanisms that involved were investigated in male ICR mice. CCl(4) (20mg/kg body weight, i.p.) administration induced marked increase in serum AST and ALT activities, primed liver lipid peroxidation, depleted sulfhydryl content, impaired total antioxidant capabilities and induced genotoxicity 24h after administration. Pretreatment with COS, GlcNH(2), and GlcNAc (1.5g/kg body weight, i.g.) for 12 consecutive days prior to CCl(4) challenge significantly induced metallothionein (MT) expression. Thus, the antioxidant defensive system in the body was strengthened to counteract the oxidative damage induced by the succedent CCl(4) administration. Serum AST and ALT activities were effectively decreased. Hepatic malondialdehyde formation was inhibited and sulfhydryl contents, total antioxidant capabilities were markedly restored. Genotoxicity as reflected by DNA fragmentation, however, was not mitigated by pretreatment with COS, GlcNH(2), and GlcNAc. Histophathologic results of liver also confirmed their hepato-protective effects. Pretreatment with COS, GlcNH(2), and GlcNAc also could significantly decrease serum creatinine and uric acid levels and inhibit lipid peroxidation in kidney homogenate. Our results suggest that pretreatment with COS, GlcNH(2), and GlcNAc can efficiently protect mice against CCl(4)-induced toxicity.