A pectic arabinogalactan was obtained from the leaves of Andrographis paniculata by aqueous extraction
followed by -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 -d-Galp main chain, substituted at O-6 by (1→6)-linked -d-Galp
side chains. The latter residues were substituted at O-3 by (1→5)- and (1→3)-linked -l-Araf chains,
and non reducing end-units of -l-Araf and -d-Galp. 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 × 106/M. Thus, this study is an important step forward to investigate the
involvement of arabinogalactan in processes including interaction with biologically important transport
proteins.
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