Interaction with bovine serum albumin of an anti-oxidative pectic arabinogalactan from Andrographis paniculata

Abstract A pectic arabinogalactan was obtained from the leaves of Andrographis paniculata by aqueous extraction followed by α-amylase treatment, deproteination, and anion exchange chromatography. Methylation analysis, Smith degradation, and NMR spectroscopy indicated that it was a highly branched arabinogalactan containing a (1 → 3)-linked β- d -Gal p main chain, substituted at O -6 by (1 → 6)-linked β- d -Gal p side chains. The latter residues were substituted at O -3 by (1 → 5)- and (1 → 3)-linked α- l -Ara f chains, and non reducing end-units of α- l -Ara f and β- d -Gal p . This homogeneous arabinogalactan (36 kDa), which contained phenolic acids, showed dose-dependent anti-oxidative properties. The phenolic acid moieties might be the functional sites. This arabinogalactan can form a complex with bovine serum albumin having binding constant K  = 6.48 × 10 6 /M. Thus, this study is an important step forward to investigate the involvement of arabinogalactan in processes including interaction with biologically important transport proteins.