Yeast mannans protect liposomes against peroxidation but do not scavenge free radicals

The mannans from Candida albicans serotype A, Candida dubliniensis, Candida tropicalis and Saccharomyces cerevisiae protected liposomes against peroxidation by OH radicals in a concentration-dependent manner. The most efficacious antioxidant was mannan from C. albicans serotype A with antioxidant activity ∼49% comparable with known antioxidant carboxymethylated glucan (∼46%). The natural antioxidant α-tocopherol exhibited 90% protection of liposomes. The mannans and glucans scavenged negligible amount of free radicals in the common 2,2-diphenyl-1-picrylhydrazyl test. It seems likely that protection of liposomes against OH radicals by polysaccharides is not due to their scavenging properties, but may be caused by a sterical hindrance. The polysaccharides containing flexible β-linkages are more effective protectors of liposome peroxidation than these polysaccharides that contain α-linkages only.