Gastroprotective effect and structure of a rhamnogalacturonan from Acmella oleracea

A methyl esterified rhamnogalacturonan was isolated from the plant Acmella oleracea. Its structure was elucidated by methylation analysis and NMR spectroscopy. It inhibited ethanol-induced gastric ulcers in rats with an ED50 of 1.5mg/kg. [Display omitted] ► A methyl esterified rhamnogalacturonan was isolated and characterized from Acmella oleracea. ► The rhamnogalacturonan is partially substituted by side-chains of type II arabinogalactans. ► The polysaccharide reduced ethanol-induced gastric lesions in rats with an ED50 of 1.5mg/kg. ► Rhamnogalacturonan of A. oleracea may be a gastroprotective agent. The plant Acmella oleracea (L.) R.K.Jansen (Asteraceae), locally known as jambu, is widely used in Legal Amazon in local dishes and in folk medicine. A polysaccharide (SC) was isolated from this plant, following aqueous extraction, which contained uronic acid, galactose, arabinose, rhamnose, and glucose in a 15:2:1:1:0.5 molar ratio and had a Mw 226,000g/mol. Methylation analysis and NMR spectroscopy indicated that SC is a rhamnogalacturonan composed of a long chain of →4)-6-OMe-α-d-GalpA-(1→, interspersed with some α-l-Rhap residues, partly substituted by side-chains of type II arabinogalactans. SC significantly inhibited ethanol-induced gastric ulcers in rats with an ED50 of 1.5mg/kg, indicating that SC acts as gastroprotective agent.