Glucans exhibit weak antioxidant activity, but stimulate macrophage free radical activity

Polymeric carbohydrates have been reported to modulate inflammatory respons es in vitro and in vivo. Previous reports suggest that certain carbohydrate polymers, such as (1-->3)-beta -D-glucans, may possess free radical scaven ging activity. If glucans are free radical scavengers then it might explain , in part, the ability of these ligands to modulate inflammatory responses. The present study examined the free radical scavenging activity of a varie ty of carbohydrate polymers and the effect of the polymers on free radical levels in a murine macrophage cell line. All of the carbohydrates exhibited concentration dependent antioxidant effects (EC50 range = 807 to 43 mug/ml ). However, the antioxidant activity for the carbohydrates was modest in co mparison with PDTC (EC50 = 0.13 mug/ml) and the carbohydrate concentration required for antioxidant activity was high ((X) over bar EC50 = 283 mug/ml) . The antioxidant ability of the polymers was greater (p < .05) than their monosaccharide constituents, i.e., dextrose EC50 = 807 vs. glucan sulfate E C50 = 43 <mu>g/ml. Coincubation of glucans with murine J774a.1 cells increa sed free radical levels when compared to controls. Therefore, the weak free radical scavenging activity of glucan polymers cannot explain their modula tory effect on inflammatory responses in tissue culture and/or disease mode ls of inflammation. (C) 2001 Elsevier Science Inc.