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.
Keywords: Antioxidant activity; Chemical analysis; Fractionation; Lonicera japonica; Polysaccharide.
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