Antinociceptive activity of Buddleja globosa (matico) in several models of pain
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Ethnopharmacological relevance: Leaf extracts of Buddleja globosa (Buddlejaceae) are used in Chilean folk medicine for wound healing. The anti-inflammatory (topic and per as), analgesic (per os) effects and the antioxidant activity of Buddleja globosa were for the first time reported by us. Aim of the study: Assess the antinociceptive activity of the methanol sequential and global extracts using complementary chemical and thermal models of pain, characterize pharmacologically the antinociception induced, evaluate seasonal influence to support Buddleja globosa medicinal use. Materials and methods: Global methanol, sequential methanol and ethanol (leaves collected in autumn and summer) extracts were evaluated for oral and topic analgesia in tail flick, formalin and writhing models, verbascoside and 7-O-luteolin glucoside were assayed in tail flick and writhing. Ibuprofen was used as reference. For characterization of induced antinociception, naltrexone, naltrindole, tropisetron, nor-binaltorphimine, prazosin, yohimbine, atropine, and N-nitro-L-arginine methyl ester were used as antagonists and inhibitors drugs. Results: Seasonal influence was observed since autumn extract resulted less active. Extracts showed a dose-dependent antinociceptive activity in all assays, the highest effects were obtained for the formalin and writhing test. Verbascoside was more active than ibuprofen in the writhing test (67.6% and 50.0% at equimolar doses) and showed similar effects in the tail flick (topic and oral) near 25% at equivalent doses - ED25 or EC25 - to ibuprofen. Luteolin 7-O-glucoside was slightly more active in the tail flick test and nearly half active than verbascoside in the writhing assay. Effectiveness was higher for the sequential than for global alcoholic extracts, and can be increased by selective blocking of opioid receptors. Global methanol extract seems modulated only by naltrexone. Conclusions: Analgesic effect of Buddleja globosa is here demonstrated validating its use in traditional medicine. Season influence is important to be considered.