Toxicity and antinociceptive effects of Hamelia patens

Abstract

Many medicinal herbs are used in folk medicine without taking into account their toxicity. Hamelia patens Jacq. (Rubiaceae), a Mexican endemic species, is used for the empirical treatment of pain. The aim of this work was to evaluate the toxicity and antinociceptive effects of ethanolic extracts of H. patens leaves. The toxicity of H. patens leaves (500–5000mg/kg) was evaluated in acute (14 days) and subacute (28 days) assays. In the subacute assay, a blood analysis (both hematology and chemistry) was carried out. The antinociceptive effects of H. patens leaves (50–200mg/kg) were evaluated using thermal-induced nociception (hot plate) and the chemical-induced nociceptive tests (acid acetic and formalin). In the acute toxicity test, the LD50 estimated for H. patens leaves was 2964mg/kg i.p. and >5000mg/kg p.o., whereas in the subacute test HPE did not affect hematological or biochemical parameters. In chemical-induced nociception models, H. patens (100 and 200mg/kg p.o.) showed antinociceptive effects with similar activity than 100mg/kg naproxen. In the hot plate test, HPE at 100mg/kg (17%) and 200mg/kg (25%) showed moderate antinociceptive effects. HPE could be a good source of antinociceptive agents because of its good activity and low toxicity.