Characterization of a biologically active pectin from Plantago major L.

PMII isolated from the leaves of Plantago major L. is a pectin type polysaccharide with anti-complementary activity. It is highly esterified and partly O-acetylated with regions of 1,4 linked polygalacturonic acid and at least two different hairy regions. The galactose side chains are linked to position 4 of rhamnose in the main chain. The structure of the galactan side chains is complex, but 1,3,6 linkages are dominating in one of the isolated hairy regions. Arabinose is attached to position 3 and 6 of galactose. In the other hairy region arabinose is attached to position 3 of galacturonic acid. De-esterification and de-acetylation do not alter the anti-complementary activity of PMII. Different parts of PMII were shown to have different activities. The smooth regions are only slightly active in contrast to the hairy regions which had significantly higher activity. The hairy regions of highest molecular weight (PVa) with 1,3,6 linked galactose side chains were found to be the most active fraction. The importance of arabinose for the activity seems to depend on the site of substitution. Removal of arabinose terminally linked to galactose increases the activity slightly while removal of arabinose linked to the galacturonic acid backbone decreases the activity. Copyright (C) 1996 Elsevier Science Ltd