Isolation, characterization, and activity of the polysaccharides in Bulbophyllum kwangtumgense Schltr

A microwave-assisted method was used to extract the polysaccharide from Bulbophyllum kwangtumgense Schltr, and the optimum extraction conditions were determined by orthogonal experiments. The purified polysaccharide component BKP-1 had an obvious polysaccharide characteristic structure on the infrared spectrum and was mainly composed of xylose and glucuronic acid at a ratio of 0.568:0.432. Its molecular weight distribution (polydispersity index was 0.58) was uniform with 1.92× 10 6  Da. The main structural skeleton of BKP-1 was →4)-β-D-Xylp-(1 → [4)-β-D-Xylp-(1] 4  → 4)-α-D-GlcAp-(1 → [4)-α-D-GlcAp-(1] 2 →. BKP-1 could clear certain free radicals, among which the hydroxyl free radical scavenging ability was the best, with a clearance rate of 61.46 %. Furthermore, BKP-1 significantly modulated the secretion of both pro-inflammatory and anti-inflammatory cytokines at a concentration of 125 μg/mL. Notably, the mechanism BKP-1 exhibiting inhibitory effects were related to regulating of the NF-κB signaling pathway.