Antinociceptive effect of Nidularium procerum: a Bromeliaceae from the Brazilian coastal rain forest.

Nidularium procerum, a common plant of the Brazilian flora, has not yet been studied for its pharmacological properties. We report here that extracts of N. procerum show both analgesic and anti-inflammatory properties. Oral (p.o.) or intraperitoneal (i.p.) administration of an aqueous crude extract from leaves of N. procerum (LAE) inhibited the writhing reaction induced by acetic acid (ED50 value = 0.2 mg/kg body weight, i.p.) in a dose-dependent manner. This analgesic property was confirmed in rats using two different models of bradykinin-induced hyperalgesia; there was 75% inhibition of pain in the modified Hargreaves assay, and 100% inhibition in the classical Hargreaves assay. This potent analgesic effect was not blocked by naloxone, nor was it observed in the hot plate model, indicating that the analgesic effect is not associated with the activation of opioid receptors in the central nervous system. By contrast, we found that LAE (0.02 microg/ml) selectively inhibited prostaglandin E2 production by cyclooxygenase (COX)-2, but not COX-1, which is a plausible mechanism for the analgesic effect. A crude methanol extract from the leaves also showed similar analgesic activity. An identical extract from the roots of N. procerum did not, however, block acetic acid-induced writhes, indicating that the analgesic compounds are concentrated in the leaves. Finally, we found that LAE inhibited an inflammatory reaction induced by lipopolysaccharide in the pleural cavity of mice.

Inhibition of the hyperalgesic activity of Bothrops jararaca venom by an antibothropic fraction isolated from opossum (Didelphis marsupialis) serum.

The antibothropic fraction (ABF) already isolated from Didelphis marsupialis serum, inhibits the haemorrhagic, oedematogenic, myonecrotic and lethal activities of Bothrops jararaca venom (Bjv). The aim of this work was to verify the capability of ABF to inhibit the hyperalgesic activity of Bjv. Intraplantar injection of Bjv induced hyperalgesia in a time- and dose-dependent manner and ABF administered in situ concomitantly with Bjv or i.v. 30 min before venom injection reduced the induced hyperalgesia. This same effect was observed when ABF was intravenously injected at 5 and 15 min after Bjv. Our results show that ABF inhibits also the hyperalgesia induced by Bjv.

Analgesic and anti-ulcerogenic effects of a polar extract from leaves of Vernonia condensata.

An aqueous crude extract and a polar fraction derived from this extract were prepared from leaves of Vernonia condensata Baker and assessed in standard rodent models of algesia and ulcerogenesis. Oral pretreatment with the lyophilized crude extract (200 mg/kg) significantly reduced mouse writhing counts caused by the i.p. injection of increasing concentrations (0.6-1.2%) of acetic acid (0.1 ml/10 g). In doses ranging from 50 to 400 mg/kg, the crude extract inhibited dose-dependently mouse writhing induced by acetic acid (0.6%) (ED50 = 241 mg/kg) and also markedly increased the sleeping time induced by thiopental. The polar fraction, prepared by washing out the crude extract with chloroform, did not alter sleeping time but kept the analgesic activity (ED50 = 154 mg/kg), indicating that these effects are indeed dissociated. In contrast, the tail flick response in the immersion test was not modified by the crude extract or the polar fraction. The relative potency with which polar fraction and non-steroidal anti-inflammatory drugs inhibited mouse writhing caused by acetic acid in mice was indomethacin >> dypirone > polar fraction > aspirin. Furthermore, the combined polar fraction/aspirin or polar fraction/indomethacin treatments presented a marked synergistic effect, in contrast to what was observed when submaximal doses of indomethacin and aspirin were coadministered, suggesting that polar fraction and aspirin like drugs may have complementary analgesic actions. Finally, despite being able to potentiate the analgesic effect of indomethacin in mouse writhing caused by acetic acid, the pretreatment with the polar fraction (200 mg/kg, oral) significantly prevented indomethacin-induced ulcers in rats.(ABSTRACT TRUNCATED AT 250 WORDS)