The ethanol extract of Leonurus sibiricus L. induces antioxidant, antinociceptive and topical anti-inflammatory effects

Ethnopharmacological relevance: Leonurus sibiricus L. (Lamiaceae), popularly known as motherwort, or "erva-de-macae" or "rubim" in Brazil, is a plant used for the treatment of inflammatory conditions, but few studies have evaluated this anti-inflammatory activity or other activities that may be relevant. Aim of the study: This study was undertaken to investigate the antioxidant, antinociceptive and topical anti-inflammatory effects of the ethanol extract of L. sibiricus (EELs). Materials and methods: Chromatographic analysis, determination of total phenolic and flavonoid contents and in vitro antioxidant assays were performed, while the formalin test and ear inflammation induced by 12-0-tetradecanoylphorbol-13-acetate (TPA) were performed in mice. Results: We observed that total phenolic and flavonoids content in EELs were respectively 60.1 mg of gallic acid equivalent/g of extract and 15.4 mg of catechin equivalent/g of extract. Chlorogenic, caffeic, p-coumaric and ferulic acids, as well as quercetin were identified in EELS. This extract also led to the consumption of the radicals 2,2-diphenyl-1-picrylhydrazyl, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) and nitric oxide, increased the ferric reducing/antioxidant power (FRAP) and inhibited the spontaneous or FeSO4-induced in vitro lipid peroxidation. In the formalin test, oral pretreatment with EELs (400 mg/kg) reduced (p < 0.001) the licking/biting time in the second phase, but not in the first phase. In the ear inflammation induced by TPA, the concomitant topical administration of EELs (0.3-3 mg/ear) significantly reduced the edema, myeloperoxidase activity, levels of tumoral necrosis factor-alpha and interleukin-1 beta and lipoperoxidation, as well as increased FRAP in ear tissue when compared to vehicle-treated ears. Conclusions: These results indicate that EELS has antioxidant, antinociceptive and topical anti-inflammatory activities, supporting the use of this plant in folk medicine.