Isolation and structural features of an antiradical polysaccharide of Capsicum annuum that interacts with BSA

Abstract Red peppers, Capsicum annuum , are used worldwide as spices, foods and medicines. Herein, we have analyzed an antiradical polysaccharide isolated from red peppers through successive acetate buffer extraction. This macromolecule was purified using graded precipitation with ethanol, α-amylase treatment, deproteination and anion-exchange chromatography. This highly-branched polysaccharide (360 kDa) was esterified with phenolic acids and contained a (1,3)-linked-β-Gal p chain substituted at O -6 by (1,6)-linked-β-Gal p residues. The latter was substituted at O -3 by (1,5)- and (1,3,5)-linked-α-Ara f residues, and non-reducing end-units of α-Ara f and β-Gal p. The antiradical potential of this polysaccharide was comparable to standard antioxidants. The phenolic acid residues were the functional sites. This polysaccharide could form complex with bovine serum albumin having binding constant K  = 5.24 × 10 6 /M and change its microenvironment. Thus, aqueous extraction method provides a macromolecule that stimulates biological responses; this emphasizes the significance of red pepper as dietary antioxidant.