Anti-inflammatory activities and mechanisms of action of the petroleum ether fraction of Rosa multiflora Thunb. hips

Ethnopharmacological relevance: The hip of Rosa multiflora Thunb. has been traditionally used as a dietary supplement and a herbal remedy for the treatment of various diseases including cold, flu, inflammation, osteoarthritis, rheumatoid arthritis and chronic pain in China. Aims of the study: To explore the anti-inflammatory ingredient of the hip of R. multiflora Thunb. and its mechanism of action. Materials and methods: The ethanol extract of the hip of R. multiflora Thunb. was fractioned with petroleum ether, ethyl acetate and water, and each fraction was screened for anti-inflammatory activity in xylene-induced mouse ear edema model. Three more models, acetic acid-induced mouse vascular permeation, cotton pellet-induced rat granuloma, and carrageenan-induced rat hind paw edema were also employed to verify the anti-inflammatory effect of the identified fraction. To explore the mechanism of action, the activity of inducible nitric oxide synthase (iNOS) and the level of nitric oxide (NO) in sera, as well as mRNA expression level of cyclo-oxygenase-2 (COX-2) in inflammatory tissues of rats with carrageenan-induced hind paw edema were measured. GC-MS technology was applied to identify the active components in the active fraction. Results and conclusions: The petroleum ether fraction (PEF) was identified to be the active fraction in inflammation animal models (i.e., oral administration of PEF (168.48, 42.12 and 10.53 mg/kg) evoked a significantly (P < 0.001) dose-dependent inhibition of the xylene-induced mice ear edema). Down-regulating COX-2 expression (P < 0.001) and reducing NO production (P < 0.05) through inhibiting iNOS activity (P < 0.001) may be the partial mechanism of action of PEF. GC-MS analysis indicated that unsaturated fatty acids are enriched in PEF and may be responsible for the anti-inflammatory activity of PEF and this herb. The results of this study provide pharmacological and chemical basis for the application of the hip of R. multiflora Thunb. in inflammatory disorders.