Avicennia marina(Forsk.) Vierh. is one of the most widespread mangroves species of the world. The plant is widely used in the treatment of skin disease, ailments and wounds. Researchers have so far focused their attentions on its medicinal functions and chemical constituents. HAM-3-Ⅱb-Ⅱ, an acidic polysaccharides was obtained from Avicennia Marina by a series step of extraction, isolation and purification. The structure was studied by periodate oxidation, Smith degradation, partial hydrolysis and methylation analysis. The results show that HAM-3-Ⅱb-Ⅱ is an acidic pectin-type belong to RGI family, the backbone of main chain contained homogalacturonan fragments as “smooth regions” with 1,4-α-D-GalpA and rhamnogalacturonan segments as “hairy regions” with repeating unit of →4)-α-D-GalpA-(1→2)-α-L-Rhap-(1. T-, 1,6-, 1,3,6-, 1,4-, 1,4,6-D-Galp and T-, 1,2-, 1,3-, 1,5-, 1,2,5-, 1,3,5-Araf are linked as arabinogalactan type Ⅰ, arabinogalactan type Ⅱ, galactan and arabinan at the cite of O4 of Rha in the form of the side chain. Hence, HAM-3-Ⅱb-Ⅱ was considered a new bioactive pectin from Avicennia Marina.
