Antinociceptive, antiinflammatory and antidiabetic effects of Leonotis leonurus (L.) R. BR. [Lamiaceae] leaf aqueous extract in mice and rats

The present study was undertaken to investigate the antinociceptive, antiinflammatory, and antidiabetic properties of the aqueous leaf extract of Leonotis leonurus (L.) R. BR. (Lamiaceae) in mice and rats, to scientifically appraise some of the plant's ethnomedical uses, and its safety and efficacy. The leaf powder of the plant was Soxhlet extracted with distilled water and used. The antinociceptive effect of the plant's extract was evaluated by the "hot-plate" and "acetic acid" test models of pain in mice, while the antiinflammatory and antidiabetic effects of the leaf extract were investigated in rats, using fresh egg albumin-induced paw edema, and streptozotocin (STZ)-induced diabetes mellitus, respectively. Morphine (MPN, 10 mg/kg i.p.), diclofenac (DIC, 100 mg/kg i.p.), and chlorpropamide (250 mg/kg p.o.) were used, respectively, as reference analgesic, antiinflammatory, and hypoglycemic agents for comparison. L. leonurus leaf aqueous extract (LLE, 50-800 mg/kg i.p.) produced dose-dependent and significant (p < 0.05-0.001) antinociceptive effects against thermally and chemically induced nociceptive pain stimuli in mice. LLE (50-800 mg/kg i.p.) also significantly (p < 0.05-0.001) inhibited fresh egg albumin-induced paw edema, and caused significant (p < 0.05-0.001) hypoglycemic effects in rats. It is suggested that the analgesic effects of LLE (50-800 mg/kg i.p.) may be peripherally and centrally mediated. The different flavonoids, diterpenoids, polyphenolics, and other chemical constituents of the plant may be involved in the observed antinociceptive, antiinflammatory, and antidiabetic effects of the plant's extract. However, the results of this experimental animal study suggest that the aqueous leaf extract of L. leonurus possesses antinociceptive, antiinflammatory, and hypoglycemic properties, and thus lend pharmacological credence to the suggested folkloric uses of the herb in the management and/or control of painful, arthritic, and other inflammatory conditions, as well as for adult-onset, type-2 diabetes mellitus in some communities of South Africa.