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

Two pectin-polysaccharides, ASP-B₂ (M_w, 5.32 kDa) and B₃ (M_w, 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.