Bioassay-guided isolation of anti-inflammatory and antinociceptive principles from a folk remedy, Rhododendron ponticum L. leaves.

BACKGROUND

Rhododendron ponticum L. (Ericaceae) is used for the treatment of inflammatory diseases and to alleviate rheumatic pain and against toothache in Turkish traditional medicine.

OBJECTIVE

To evaluate the anti-inflammatory and antinociceptive effects of Rhododendron ponticum leaves using in vivo models, and isolation and chemical characterization of the biologically active constituents through bioassay-guided fractionation procedures.

METHODS

Carrageenan-induced hind paw edema model was used for anti-inflammatory activity and p-benzoquinone induced abdominal contractions model for the antinociceptive activity assessment.

RESULTS

The ethylacetate fraction displayed marked anti-inflammatory (28.4-40.7% inhibition) and antinociceptive (50.7% inhibition) effects as compared to reference compounds. Through bioassay-guided fractionation and isolation procedures flavonol glycosides [a mixture of hyperoside and isoquercitrin (1) and quercitrin (2)] along with one flavanone glycoside [6-C-glycosylnaringenin (3)] were isolated as the active ingredients of ethylacetate extract against carrageenan-induced edema and p-benzoquinone-induced writhes and their structures were elucidated by spectral techniques. 1 and 2 also showed a significant anti-inflammatory activity against 12-O-tetradecanoyl-13-acetate (TPA)- induced mouse ear edema model.

CONCLUSIONS

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