The juice of fresh leaves of Boerhaavia diffusa L. (Nyctaginaceae) markedly reduces pain in mice

The decoction or juice of leaves of Boerhaavia diffusa L. (Nyctaginaceae) i s used in Martinican folk medicine for its analgesic and anti-inflammatory properties. In the present investigation we studied the acute oral (p.o.) t oxicity of a crude extract obtained from a lyophilized decoction (DE) and f rom the juice (JE) of fresh leaves. We observed no signs of toxicity up to the dose of 5000 mg/kg (p.o.) in mice. At the dose of 1000 mg/kg, neither e xtract altered sleeping time evoked by the administration of pentobarbital sodium (i.p.). The DE and JE of B. diffusa were assessed in standard rodent models of algesia and inflammation. We investigated the antinociceptive ef fect of DE and JE in chemical (acetic acid) and thermal (hot plate) models of hyperalgesia in mice. Dipyrone sodium (200 mg/kg), JE (1000 mg/kg) and D E at the same dose (p.o.), produced a significant inhibition of acetic acid -induced abdominal writhing in mice (100, 50 and 47% inhibition, respective ly) when compared with the negative control (P < 0.001). In the hot-plate t est in mice, morphine and JE produced a significant increase in latency dur ing the observation time. The DE, however, only raised the pain thresholds during the first period (30 min) of observation (P < 0.05). The extracts of B. diffusa were also investigated for their anti-edematogenic effect on ca rrageenan-induced edema in mice. However, neither extract inhibited the paw edema induced in mice (P > 0.05). In the acetic acid-induced abdominal wri thing in mice, pre-treatment of the animals with naloxone (5 mg/kg, i.p.) s ignificantly reversed the analgesic effect of morphine and JE but not that of DE. These data show that the active antinociceptive principle of B. diff usa is present mainly in the juice of fresh leaves and has a significant an tinociceptive effect when assessed in these pain models. The mechanism unde rlying this analgesic effect of fresh leaves of B. diffusa remains unknown, but seems to be related to interaction with the opioid system. (C) 2000 El sevier Science Ireland Ltd. All rights reserved.