Structure elucidation of bioactive pectins from Opilia celtidifolia (Guill. & Perr.) Endl. Ex Walp. (Opiliaceae)

Many plants contain polysaccharides that exhibit biological activities of different kinds. Immunostimulatory, antitumor, antiviral, antibacterial and anti-inflammatory activities are among the numerous demonstrated biological proprieties [1]. Polysaccharides from the leaves of Opilia celtidifolia (Oc), a medicinal plant used in wound healing processes in traditional medicine in Mali (West Africa), possesses a potent activity in the complement system. The activity was tested using the inhibition of haemolysis of human sensitized erythrocytes [2]. A pure pectin fraction PMII, with Rhamnogalacturonan (RG) type I structure, from the leaves of Plantago major L. was used as positive control. Oc polysaccharides were more active than PMII. The ICH ₅₀ of the most active fraction was 0.6µg/mL while that of PMII was 8.6µg/mL. We elucidated the structure of these active polysaccharides. They were water soluble; they were purified by gel filtration and anion exchange chromatography. The structure was determined by enzymatic degradation followed by methylation using GC-MS. The monosaccharide composition determined by gas chromatography and a positive reaction with the Yariv-β-glucosyl reagent coupled with the GC-MS results indicated that the active polysaccharides are pectic type and contain some structural elements associated with arabinogalactans type II.

References: 1. Paulsen, B.S., and Barset, H. (2005), Adv. Polym. Sci. 186: 69–101. 2. Michaelsen, T.E. et al. (2000), Scand. J. Imm. 52: 483–490.