Opioid-like activity of Psychotria brachypoda

Abstract

Strong opioid-like analgesic activity has been detected in alkaloids from Psychotria colorata (Willd ex R. & S.) Muell. Arg., used by Amazonian caboclos of Brazil as a pain killer. The present work was undertaken to study Psychotria brachypoda (Muell. Arg.) Britton in regard to the presence of alkaloids and potential analgesic activity. The leaf ethanol extract is rich in alkaloids and was evaluated for analgesia (mouse tail-flick), effects on body temperature and acute toxicity. In the tail-flick test the extract was active in a dose-effect pattern (i.p. 350 mg/kg comparable to 6 mg/kg of morphine) and the activity was reversed by naloxone. The body temperature decreased significantly. Sedation, blepharoptosis, but not loss of righting reflex were observed in acute toxicity test. These results show that the ethanol extract of P. brachypoda is rich in alkaloids with opioid-like analgesic activity. These data indicate the pertinence of isolating these alkaloids and further characterizing their pharmacological profile. Psychotria alkaloids can be regarded as potential templates for new analgesic compounds.