Immunological activities and structure of pectin from Centella asiatica

Centella asiatica, is mainly found in the south of Asia and the southern hemisphere. The pectin was extracted from C. asiatica and isolated by anion-exchange and gel-filtration chromatography with TLC and GLC analyses. It contained arabinose, rhamnose, galactose, xylose and galacturonic acid. The structural features were elucidated by partial acid hydrolysis, enzymatic degradation, methylation, carboxyl-reduction, NMR spectroscopy and ESI-MS experiments. The backbone was presumed to contain 1, 4-linked α-d-GalA and 1, 2/1, 2, 4-linked α-l-Rha with RG-I and homogalacturonan (HG) types. The side chains were neutral chains including arabinosyl, arabinogalactosyl and xylosyl chains. Most of the side chains were attached to Rha, while partial residues were presumed to link to GalA. 14% GalA residues in backbone contained acetyl groups. With deacetylation and carboxyl-reduction, the pectin and its degraded product showed immuno-stimulating activity to different extent in vitro. These results indicated that the carboxyl and acetyl groups play important roles in the expression of immunological activity.