Fractionation and antioxidant activities of the water-soluble polysaccharides from Lonicera japonica Thunb.

L. japonica has been used as food and healthy beverage due to the good nutrition. Although the chemical compounds have been extensively studied, polysaccharide compositions remain unclear. In this study, water-soluble polysaccharides of L. japonica were fractionated into one neutral fraction (LJP-N) and four acidic fractions (LJP-A-1 ~ LJP-A-4) by a combination of ion-exchange and gel permeation chromatographies. The structures and antioxidant activities of these factions were determined by HPLC, FT-IR and the radical scavenging activities, anti-hemolysis inhibitory ability, protective effect against DNA damage. Results showed that LJP-N was a starch-like glucan with some arabinogalactan; acidic fractions were all pectic polysaccharide, with the average molecular weights approximately ranging from 19.0 to 383.8 kDa. LJP-A-2 ~ LJP-A-4 were similar to each other, mainly composed of GalA (>50%) with some Gal and Ara residues, while LJP-A-1 mainly composed of Gal and Ara (>70%). LJP-A-3 was defined as HG-type pectic polysacchride, with a trace of RG-I domain by NMR experiment. The antioxidant activity of LJP fractions showed different activities, and LJP-A-3 and LJP-A-4 exhibited noticeable antioxidant activities by six kinds of evaluated methods comparable with others. The results indicated that LJP-A-3 and LJP-A-4 could be used as a potential natural source of antioxidant.