Glinus oppositifolius (L.) Aug. DC. (Aizoaceae) is a Malian medicinal plant used against various types of illnesses related to the immune response, like joint pains, inflammations, fever, malaria and wounds. Two pectin type polysaccharides, GOA1 and GOA2, being isolated from a 50 degrees C water extract from the aerial parts of Glinus oppositifolius were investigated for their activity towards the complement system and different leukocyte subsets because of the assumed effects on conditions related to the immune system. The polysaccharide polymer in GOA1 was shown to contain considerable amounts of the neutral sugars arabinose (26.4 mol%) and galactose (42.9 mol%), and methylation analysis indicated the presence of arabinogalactans type I (AG-I) and type II (AG-II). GOA2 was rich in galacturonic acid (68.3 mol%), along with rhamnose, arabinose and galactose. Structural studies indicated that rhamnose and galacturonic acid might constitute a rhamnogalacturonan backbone, often found in pectic substances, with side chains consisting of arabinose and galactose. Both GOA1 and GOA2 were shown to exhibit potent dose-dependent complement fixating activities, and induced chemotaxis of macrophages, T cells and NK cells.