Ethnopharmacological relevance: Lippia lacunosa Mart. & Schauer is an endemic plant from the Serra do Espinhaço mountain range located on the Atlantic plateau, Brazil. It is known as "chá de pedestre" and "rosmaninho" in folk medicine. This species has a characteristic mango aroma and is widely used by the population for flu, colds, sinus infections, coughing, relaxing baths, and foot baths after long walks. It is often confused with and, therefore, used interchangeably with L. rotundifolia and L. pseudothea.
Aim of the study: This study aimed to increase scientific knowledge on the ethnopharmacological use of Lippia lacunosa through the evaluation of the micromolecular composition and anti-inflammatory and antinociceptive activities of the hexane and ethanolic extracts, essential oil, and fractions in mice.
Materials and methods: The chemical profile of L. lacunosa extracts and fractions were obtained by chromatographic methods such as Ultra-Performance Liquid Chromatography (UPLC), Gas Chromatography (GC), Column Chromatography (CC), and Thin Layer Chromatography (TLC). Carrageenan-induced paw edema was used to investigate the anti-inflammatory activity in mice. Mechanical allodynia induced by carrageenan and hot plate tests were employed to evaluate the antinociceptive activity.
Results: The main constituents found in the essential oil were the monoterpenes myrcene (13.81%), linalool (6.84%), ipsenone (21.2%), and myrcenone (25.44%); and sesquiterpenes elemol (7.30%) and spathulenol (3.15%). The chromatograph fractionation of essential oil yielded a fraction rich in the main compounds (F33), ipsenone and mircenone. In experimental models of paw edema and mechanical allodynia induced by carrageenan (600 μg, 30 μL, i.pl.), the administration of hexane extract, essential oil (50 or 100 mg/kg, p.o.) or majority fraction (10 mg/kg, p.o.) reduced paw edema. The ethanolic extract (100 mg/kg) reduced mechanical allodynia only in the 2 nd h of evaluation. On the other hand, the hexane extract (50 or 100 mg/kg) and essential oil (100 mg/kg), as well as the majority fraction (10 mg/kg), reduced mechanical allodynia throughout the evaluation period. The hexane extract, essential oil, and majority fraction F33 also reduced the heat-induced nociceptive response. Also, majority fraction F33 did not affect the time mice spent in the rota-rod apparatus.
Conclusions: The elucidation of the composition of the essential oil and the demonstration of the activity of L. lacunosa in experimental models of acute inflammation and also in models of nociceptive and inflammatory pain can help to increase knowledge on the ancient ethnopharmacological use by the Bandeirantes, aiming at the evaluation of the species as a candidate for herbal medicine or phytopharmaceutical in the treatment of patients with inflammatory and painful conditions.
Keywords: Chá de pedestre; Essential oil; Inflammation; Lippia lacunosa; Pain.
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