A xylan from the fresh leaves of Piper betle: Structural characterization and studies of bioactive properties

A pure water soluble xylan (PS-I) with an average molecular weight ~1.1 × 10⁵ Da was isolated from the hot water extraction of fresh leaves of Piper betle (paan). The xylan was found to be composed of xylose, galactose and methyl galacturonate in a molar ratio of nearly 3:1:1. The repeating unit was composed of a backbone containing three (1 → 4)-α-D-Xylp residues, one of which was branched at O-2 position with the side chain consisting of (1 → 4)-α-D-GalpA6Me and terminal β-D-Galp residues. This xylan exhibited macrophage, splenocyte, and thymocyte stimulatory activities. In vitro antioxidant studies demonstrated that the xylan has DPPH radical scavenging potential (EC₅₀ = 148 μg/mL), ABTS radical quenching activity (EC₅₀ = 188 μg/mL) and ferrous ions chelating activity (EC₅₀ = 370 μg/mL). These findings elicit the need for further exploration of the xylan as a natural antioxidant and a potent immunostimulating agent.