Identification of compounds from Palicourea rigida leaves with topical anti-inflammatory potential using experimental models.

Palicourea rigida Kunth is traditionally used for the treatment of skin diseases, kidney pains and ovarian inflammation. Based on these traditional uses, this study evaluated the topical anti-inflammatory activity of the ethanol extract from P. rigida leaves (EEPR) and identified bioactive compounds. Ear edema was induced in Swiss mice by the topical application of Croton oil, arachidonic acid, phenol and capsaicin. Histopathological analysis and myeloperoxidase and N-acetyl-β-D-glucosaminidase activities were determined. EEPR was characterized by UHPLC-UV-MS HPLC and the isolated compound was identified through 1H and 13C nuclear magnetic resonance and mass fragmentation. Interaction profiles between quercetin 3-O-β-D-glucoside and cyclooxygenase-1 and -2 were established by molecular docking. EEPR significantly inhibited ear edema induced by Croton oil (p < 0.001), arachidonic acid (p < 0.01), phenol (p < 0.001) and capsaicin (p < 0.01 or p < 0.001). Histopathological analysis showed a reduction of edema, inflammatory cell infiltration and vasodilation. Additionally, the myeloperoxidase and N-acetyl-β-D-glucosaminidase activities were decreased (p < 0.001). From spectroscopic data, quercetin 3-O-β-D-glucoside was the identified compound. This compound can to interact with cyclooxygenase-1 and -2 through van der Waals interactions and dipole-dipole and hydrogen bonding's, demonstrating inhibition of these enzymes. The results indicate that EEPR is a source of active compounds with topical anti-inflammatory activity, justifying the traditional use of P. rigida and showing that this species has a therapeutic potential to treat skin inflammatory processes.