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Possible mechanism of anti-inflammatory activity and safety profile of aqueous and ethanolic leaf extracts of Pistia stratiotes Linn (Araceae)
Pistia stratiotes is used extensively in inflammatory disorders in several countries including Ghana. The aim of the study was to investigate the anti-inflammatory property and possible mechanism of action of aqueous and ethanolic leaf extracts of Pistia stratiotes and to ascertain its safety for use. In separate experiments, acute inflammation was induced in the right hind paws of rats using carrageenan, histamine, serotonin, prostaglandin E, and bradykinin. Paw thickness (an indication of inflammation) were measured plethysmographically. Animals were grouped and treated with diclofenac, chlorpheniramine, and granisetron (reference anti-inflammatory agents), or aqueous and ethanolic extracts of Pistia stratiotes at doses of 30, 100, and 300 mg/kg orally. Control groups received distilled water. Paw thicknesses was measured at 30 or 60 min intervals for 2.5 to 4 h for the various procedures. The extracts at all doses signifi-cantly reduced (P. 0.05-0.001) paw thickness in all the models of inflammation except the 300 mg/kg doses in carrageenan and serotonin-induced inflammation. The anti-inflammatory effects of the extracts were comparable to the reference drugs. Acute and delayed toxicity test revealed that the aqueous extract causes hemolysis of red blood cells (reduced count and presence of uro-bilinogen in urine) and possible acute kidney function impairment (proteinuria and microalbu-minuria). The aqueous and ethanolic extracts of P. stratiotes have anti-inflammatory activity in acute inflammation induced with carrageenan, through the inhibition of histamine, serotonin, prostaglandin, and bradykinin. Hematological profile as well as liver and kidneys function should be monitored when used orally for the treatment of inflammatory disorders.