Pharmacological potential of Palicourea rigida kunth: A possible participation of flavonoid compounds

Palicourea rigida Kunth (Rubiaceae), also called “bate-caixa” or “douradao”, has been used as antihypertensive, antiulcerogenic, anti-inflammatory and analgesic by traditional communities. Pharmacological potential of the ethanol extract from P. rigida (EEPR) and two quercetin derivatives were investigated. Using the high performance liquid chromatography (HPLC) assay, EEPR was analyzed. Phenolic contents (total phenolic and flavonoids) were quantified by spectrophotometric methods. 2,2-diphenyl-1-pycrilhydrazil (DPPH), iron reducing power and β-carotene/linoleic acid bleaching tests were applied to estimate the antoxidant capacity of EEPR. Nociception (acetic acid-induced writhing, formalin and hot plate) and inflammation (carrageenan-induced paw edema and pleurisy) assays were performed. Molecular docking was used to measure the interactions’ profiles of ligands (rutin and quercetin) and cyclooxigenases (COX-1 and COX-2). HPLC analysis identified rutin and quercetin derivatives. Expressive levels of total phenolic and flavonoids and a promising antioxidant effect were measured. EEPR, rutin and quercetin reduced the abdominal contortions. EEPR was effective against both phases of formalin, while rutin and quercetin inhibited the second phase. The latency time on hot plate significantly increased after treatment with EEPR. Inflammatory parameters (paw edema, exudate volume and leukocyte infiltrate) were diminished by EEPR, rutin and quercetin. The molecular docking showed that rutin and quercetin are capable of complexing with COX-1 and COX-2 favorably through physical-chemical interactions. The results suggest that EEPR showed a relevant pharmacological potential, which may be related to action of rutin and quercetin derivatives.   Key words: Palicourea rigida, rutin, quercetin, antioxidant, antinociception, inflammation.