Structure and biological activities of a pectic polysaccharide from Mosla chinensis Maxim. cv. Jiangxiangru

• A pectic polysaccharide was purified from Mosla chinensis Maxim. cv. Jiangxiangru.
• Structural characterization of MP-A40 was elucidated by methylation and 1D/2D NMR.
• The backbone of MP-A40 was 1,4-linked α-d-GalpA and 1,4-linked α-d-GalpA6Me (32%).
• MP-A40 could inhibit the growth of K562 cells.
• MP-A40 increased production of NO from RAW264.7 in a dose-dependent manner.

A water-soluble pectic polysaccharide (MP-A40) was isolated and purified from Mosla chinensis Maxim. cv. Jiangxiangru for the first time, with a molecular weight of 32,600 Da. MP-A40 was comprised of 68.63% galacturonic acid and 13.05% neutral sugar. In addition, arabinose, galactose, rhamnose, mannose and glucose composed the neutral sugar in a relative ratio of 4.94, 3.07, 2.13, 1.62 and 1.29% of the dry weight of MP-A40, respectively. Structural characterization of MP-A40 was investigated by methylation analysis and 1D/2D NMR spectroscopy. From the results, the structure of MP-A40 was revealed as follows: 1,4-linked α-d-GalpA and 1,4-linked α-d-GalpA6Me interspersed with rare t-Araf (0.60%), t-Rhap (1.67%) and t-GalpA (10.15%). Esterification assay showed that about 32% of the carboxylic groups in GalA residues existed as methyl ester. In addition, MP-A40 could inhibit the growth of human leukemic cell line K562 and stimulate nitric oxide production from RAW 264.7 macrophages both in dose-dependent manners.