Immunologically Active Polysaccharides and Lectins from the Aqueous Extract ofUrtica dioica

Abstract

From the aqueous extract of Urtica dioica L., (Urticaceae), five immunologically active polysaccharides (RP1 to RP 5) and a mixture of lectins (UDA = Urticadioica agglutinin), described for the first time by Peumans et al. (1), were isolated using ion exchange chromatography and gel filtration (2, 3). Poiysaccharides RP1 (Mr = 15000) and RP2 (Mr = 50000) possess the basic structure of 1,4-a-glucans with 1,6-a-branches, the polysaccharide RP2 with an additional low content of glucuronic acid. Both poiysaccharides exert significant concentration-dependent activities (95.5% reduction of hemolysis at a concentration of 1 mg/mi) in the classical and the alternative complement test according to Yamada et ai. (4). Polysaccharides RP3 (Mr = 200000) and RP4 (Mr = 18000) were found to be acidic rhamnogalacturonans with arabinogalactan sidechains. RP4 showed high activity in the 61Cr release test (5) and down to a concentration of 1.5 ig/ml a pronounced stimulation ( 500 U) in the TNF test using tumor target cells (6). The structure of RP5 (Mr = 70000) can be characterized as an arabinogalactan with a high content of glucuronic acid. A mixture of RP1 and RP4 exerted antiphlogistic properties in the rat paw edema model (7) in a concentration of 40 mg/kg (63.6% reduction within 22 h).UDA was isolated from fresh and dried roots by affinity chromatography on chitin according to Peumans et a!. (1).