Characterization of a pectin from Lonicera japonica Thunb. and its inhibition effect on Aβ42 aggregation and promotion of neuritogenesis

Pectin is a class of complex polysaccharides and recognized for its potential bioactivities. In this study, we showed that a pectic polysaccharide, LFA03-a, was extracted from Lonicera japonica Thunb. flowers and purified with DEAE-cellulose and Sephacryl S-100HR. LFA03-a was composed of rhamnose, arabinose, galactose and galacturonic acid in the molar ratio of 18.1:25.3:36.8:19.5. Its structure was determined to possess a rhamnogalacturonan I (RG-I) backbone consisting of α-l-1,2-Rhap and α-d-1,4-GalAp disaccharide repeating unit, substituted at O-4 of l-rhamnose. The side chain was involved with β-d-1,4-Galp, β-d-1,3-Galp, β-d-1,3,6-Galp and branched α-l-1,5-Araf. Fluorescence spectroscopic analysis with thioflavine T (ThT) and atomic force microscopy (AFM) results showed that LFA03-a inhibited Aβ42 aggregation in a dose dependent manner and impeded Aβ42 oligomerization and fibril formation. In addition, LFA03-a mildly induced the differentiation of PC12 cells and promoted neuritogenesis.The results suggested that pectin LFA03-a might be a potential targeted therapeutic drug for Alzheimer's disease.