Antinociceptive and anti-inflammatory activities of an aqueous extract of Chiliotrichum diffusum

The flowers of the Chiliotrichum diffusum (G. Forst.) Kuntze, Asteraceae, have long been used in traditional medicine and rituals. In this study, the anti-inflammatory and antinociceptive activities of a decoction of the flowers were evaluated and a phytochemical analysis was performed by HPLC-DAD. In order to evaluate the antinociceptive activity, the acetic acid-induced abdominal writhing and hot plate tests were used. The anti-inflammatory activity was evaluated using carrageenan-induced rat paw oedema. The decoction induced a significant anti-inflammatory effect (inhibition of 56.0% at 3 h) and produced significant inhibition on nociception in the acetic acid test (ED50 35 mg/kg i.p.; ED50 709 mg/kg p.o.). In the hot plate test, the antinociceptive activity of the extract employed at 500 mg/kg i.p. was significantly suppressed by pretreatment with naloxone (5 mg/kg). HPLC analysis showed the presence of chlorogenic acid, caffeic acid, hyperoside, isoquercitrin, quercitrin, afzelin, quercetin, apigenin and kaempferol. The decoction of C. diffusum proved to have antinociceptive and anti-inflammatory effects that may be related to the presence of the flavones, flavonols and phenolic acids identified. The opiod system seems to be involved in the mechanism of antinociception of the extract.