Comparable studies of two polysaccharides from leaves of Acanthopanax senticosus: Structure and antioxidation

Two pectin-polysaccharides, ASP-B2 (Mw, 5.32 kDa) and B3 (Mw, 30.51 kDa), were obtained from Acanthopanax senticosus leaves. An HILIC-UPLC-ESI--HCD-MS/MS technique was introduced for structural elucidations of skeletal structure of pectin-polysaccharides in addition to empolying SEC-MALLS, GC-MS, UPLC-ESI+-MS, methylation analysis, FT-IR and NMR methods. Skeletal structure of ASP-B2 was characterized by combining HG smooth region and RG hairy region with a 2:1 chain length ratio, wheres ASP-B3 had a distinguishing 3:1 chain length ratio (HG:RG). HG were defined as repeated →4GalA1→, and RG were featured by repeated →4GalA1 → 2Rhap1 → with branched points at C-3, C-4 and C-3,4 of rhamnosyl. Side chains mainly consisted of galactans, arabinans and arabinogalactans. Both showed a random coil conformation and no triple-helix conformation. ASP-B2 and B3 possess stronger DPPH and hydroxyl radical scavenging activities, with a relatively low reducing power. Thus, two polysaccharides can be further explored as novel natural antioxidant.