In vitro antioxidant and immunostimulating activities of polysaccharides from Ginkgo biloba leaves.

Ginkgo biloba leaves (GBLs) are used as herbal dietary supplements and medicine worldwide. In this study, crude GBL polysaccharides (GBPSs) were extracted and further purified on a DEAE (diethylaminoethanol) Sepharose Fast Flow column to obtain GBPS-2 and GBPS-3. The molecular weights of GBPS-2 and GBPS-3 were 672 and 723 kDa, respectively. GBPS-2 and GBPS-3 were typical acidic heteropolysaccharides, composed of mannose (Man), rhamnose (Rha), glucuronic acid (GlcA), galacturonic acid (GalA), glucose (Glc), galactose (Gal), and arabinose (Ara) (molar ratio: 0.08:0.12:0.16:0.06:0.11:1.00:0.32) and Man, Rha, GlcA, GalA, Gal, and Ara (molar ratio: 0.92:1.00:0.83:0.11:0.42:0.23), respectively. GBPS-2 and GBPS-3 exhibited limited scavenging abilities for the hydroxyl and 2,2‑diphenyl‑1‑picrylhydrazyl radicals as well as noticeable scavenging effects on superoxide radicals and 2,2'‑azino‑bis(3‑ethylbenzothiazoline‑6‑sulphonic acid) radicals. Furthermore, GBPS-2 and GBPS-3 significantly increased the phagocytosis of macrophages and promoted the production of NO, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6. Thus, GBPS-2 and GBPS-3 exhibit potential application as functional food supplements.