Structural analysis and in vitro fermentation characteristics of an Avicennia marina fruit RG-I pectin as a potential prebiotic

Avicennia marina (Forssk.) Vierh. is a highly salt-tolerant mangrove, and its fruit has been traditionally used for treating constipation and dysentery . In this study, a pectin (AMFPs-0-1) was extracted and isolated from this fruit for the first time, its structure was analyzed, and the effects on the human gut microbiota were investigated. The results indicated that AMFPs-0-1 with a molecular weight of 798 kDa had a backbone consisting of alternating →2)-α-L-Rha p -(1→ and →4)-α-D-Gal p A-(1→ residues and side chains composed of →3-α-L-Ara f -(1→-linked arabinan with a terminal β-L-Ara f , →5-α-L-Ara f -(1→-linked arabinan, and →4)-β-D-Gal p -(1→-linked galactan that linked to the C-4 positions of all α-L-Rha p residues in the backbone. It belongs to a type I rhamnogalacturonan (RG-I) pectin but has no arabinogalactosyl chains. AMFPs-0-1 could be consumed by human gut microbiota and increase the abundance of some beneficial bacteria, such as Bifidobacterium , Mitsuokella , and Megasphaera , which could help fight digestive disorders . These findings provide a structural basis for the potential application of A. marina fruit RG-I pectic polysaccharides in improving human intestinal health.