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We have recently screened plant constituents for inhibitory effects on arachidonate metabolism and have found some arachidonic acid analogues such as capsaicin of Capsicum annuum L. and the ajones of Allium sativum L. to be powerful in vitro inhibitors (1, 2) of prostaglandin synthase (GO) and 5-lipoxygenase (5-LO). In continuation of this screening program we have extended our investigations to some naturally occurring alkamides and alkylated phenol derivatives, Concentration (tM) 25 40 50 60 80 100 Spilanthol 18.4 30.9

From the water extract of the roots of Urtica dioica (stinging nettle) a polysaccharide fraction was isolated which revealed activity in the carrageenan rat paw edema model and lymphocyte transformation test. Ion exchange chromatography and gel filtration of this fraction afforded 4 different polysaccharides, one of which reduced dose dependent hemolysis in the classical pathway of the complement test. The Urtica dioica lectin (UDA) was reisolated and found to stimulate the proliferation of human lymphocytes.

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).