Bioassay-guided evaluation of anti-inflammatory and antinociceptive activities of Rhododendron ponticum L. leaves

Aim: Rhododendron ponticum L. is used for the treatment of inflammatory diseases and to alleviate rheumatic pain and against toothache in Turkish traditional medicine. The present study was to evaluate the anti-inflammatory and antinociceptive effects of R. ponticum leaves using in vivo models, and isolation and chemical characterization of the biologically active constituents.

Methods: Carrageenan-induced hind paw edema model was used for anti-inflammatory activity and p-benzoquinone induced abdominal contractions model for the antinociceptive activity. Bioassay-guided fractionation procedures were used for isolation and chemical characterization of the biologically active constituents.

Results: The ethyl acetate fraction displayed marked anti-inflammatory (28.4–40.7% inhibition) and antinociceptive (50.7% inhibition) acitivity as compared to references. Flavonols [a mixture of hyperoside and isoquercitrin (1) and, quercitrin (2)] as well as one flavanon glycoside [6-C-glycosylnaringenin (3)] were isolated from ethylacetate fraction and their structures were elucidated by spectral techniques. In addition, the anti-inflammatory activity TPA-induced mouse ear edema model was employed for the isolated compounds. Compounds 1 and 2 showed a potent activity profile against all the in vivo models employed, while 3 was only possessed significant activity against carrageenan-induced edema. All flavones were investigated according to anti-inflammatory activity, compounds 1–3 were found to show significant inhibitory activity on carrageenan-induced edema, while except from compound 3 they did not display potent inhibitory activity on TPA-induced ear edema model.

Conclusion: Results of the present study have supported the utilization of the plant in Turkish folk medicine and revealed that flavones are the major anti-inflammatory and antinociceptive principles of the plant.