A Novel Pectin-Like Glycopeptide Isolated from the Fruit of Fructus Mori Impedes Aggregation and Production of Aβ42

The fruit of Fructus Mori is food and medicine, which has been demonstrated to have a significant neuroprotective effect. However, the effective constituent remains unknown. We speculate that the glycopeptide in the extract of the fruit has similar activity. To address this hypothesis, we isolated a novel pectin-like glycopeptide (FMP-6-S4) with a molecular weight of 11.23 kDa from the fruit. It contains about 20% of peptide comprising 17 amino acids and 80% glycan consisting of L-rhamnose (L-Rha), D-galactose (D-Gal), D-galacturonic acid (D-GalA), L-arabinose (L-Ara) and d-glucose (D-Glc) in molar ratios of 7.25:4.62:77.66:5.62:4.85. The backbone of the glycan part consisted of 1,4-linked α-D-GalpA and 1, 2-linked α-L-Rhap, while the branches were composed of hexenuronic acid (HexA) substituted at the C-3 position of partial galacturonic acid, and traces of galactose, glucose, and arabinose were substituted at the C-4 position of rhamnose. The in vitro experiments revealed that FMP-6-S4 might inhibit Aβ42 (β-amyloid peptides 42) aggregation and decrease Aβ42 production by modulating APP (amyloid precursor protein) processing.