Atividade antinociceptiva e estudo toxicológico de extrato aquoso de Egletes viscosa Lessa (Asteraceae)

Egletes viscosa Less (Asteraceae), popularly known as "macela" or "macela-da-terra", is a plant widely used in popular medicine due to its anti-inflammatory, bactericidal, antidiarrhoea, mio-relaxant, antispasmodic, antinociceptive, digestive, and anti-viral properties. Phytochemical screening of aqueous extract of Egletes viscosa (AEEV) revealed the high presence of flavonoids. This study examined the oral antinociceptive potential of AEEV in rodents using different concentrations (100, 200, and 400 mg/kg, p.o.). The results showed significant antinociceptive action when tested in writhing (200 and 400 mg/kg-p<0.05) and in the second phase of formalin tests (200 mg/kg-p<0.01 and 400 mg/kg-p<0.001). The inhibition (%) of extract in the writhing test was 63.4, 56.7, and 79.2% respectively for 200, 400, and acetyl salicylic acid (300 mg/kg); for the formalin test (second phase) results were 66.1, 84.7, and 96.2% respectively for 200, 400, and acetyl salicylic acid (300 mg/kg). Collectively, these observations suggest that AEEV is effective against continuous inflammatory pain. AEEV was well tolerated. In an acute toxicity test, oral administration of 5 g/kg of AEEV was performed and no mortality rate was observed. Similarly, in a subchronic toxicity study, no mortality was observed after 30 days of daily oral administration of 100 mg/kg of AEEV. There was no significant difference in the body and organ weights between control and experimental animals in both acute and subchronic toxicity tests. Pathological assays did not reveal any evidence of detectable differences in the gross appearance, as well as in the architectural or cellular pattern characteristics of the internal organs of the animals in both acute and subchronic tests. Nevertheless, significant differences were verified between males of the experimental and control groups regarding the levels of hemoglobin and leukocytes. In conclusion, AEEV did not induce any hazardous effects on the majority of the parameters studied. Additionally, an antinociceptive activity of the extract was verified. However, the increase in the levels of hemoglobin and leukocytes should be investigated in more detail.