Structural analysis and antioxidant activity of an arabinoxylan from L. (Garcke).

L. (Garcke) is extensively used in traditional medicinal systems to treat various ailments. In the present study, an alkali-soluble polysaccharide (MAP) was isolated from the leaves of in 1.15% (w/w) yield. MAP was composed of l-rhamnose, l-arabinose, d-xylose, d-glucose and d-galactose in a 1.00 : 6.04 : 19.88 : 1.07 : 3.03 molar ratio along with d-glucuronic acid (1.95). Methylation/linkage analysis revealed a backbone of →4)-β-d-Xyl(1→ (30.09 mol%) with a side chain of →3)-α-l-Ara(1→ (15.21 mol%) residues. The structure of MAP was elucidated by a combination of degradative and derivatization techniques, including hydrolysis, alditol acetate derivatization, methylation, GC-MS, partial hydrolysis, ESI-MS and NMR (1D, 2D) spectral analysis. Based on correlation analysis, MAP was found to be an arabinoxylan comprising a backbone of →4)-β-d-linked Xyl(1→ with branching at O-2 by a →3)-α-l-Ara(1→ and →3)-β-d-Xyl(1→ chain. MAP also exhibited ferric ion reducing activity, with a reducing power of 0.914 ± 0.01 ( = 0.972) at 1 mg mL concentration, which showed dose-dependent behavior. MAP can be utilized as a potential antioxidant.