Antinociceptive and anti-inflammatory activity of the siaresinolic acid, a triterpene isolated from the leaves of Sabicea grisea Cham. & Schltdl. var. grisea.

In the present study, siaresinolic acid (siaresinol, SA) was isolated from the leaves of Sabicea grisea and studied to evaluate its antinociceptive and anti-inflammatory activity. The antinociceptive effect of SA was investigated in mice using different animal models to study pain. In the acetic acid-induced writhing test, intraperitoneal (i.p.) injection of SA (0.1, 1, and 10 mg/kg, i.p.) 1 h before a pain stimulus significantly reduced the nociceptive response (by 42.3, 68.2, and 70.9 %, respectively). Pretreatment with glibenclamide, but not with yohimbine, metoclopramide, ketanserin, or naloxone, restored the antinociceptive effect induced by SA in the writhing test, suggesting that the K(+)ATP channel pathway might be involved in its mechanism of action. In the formalin test, SA (1 mg/kg, i.p.) decreased licking time in the second phase only, thereby indicating an anti-inflammatory effect. In the hot plate test, there was no significant difference in nociceptive behavior. In the rota-rod test, it was verified that a high dose of SA (10 mg/kg, i.p.) did not affect the locomotor activity of mice. In the pleurisy model, induced by carrageenan, treatment with SA inhibited important events involved in inflammatory responses, namely leukocyte influx, plasma leakage, and increased inflammatory mediators (TNF-α, IL-1ß, and chemokine CXCL1), in the pleural exudate. Additionally, SA itself was not cytotoxic when evaluated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in macrophages cultured for 24 h at concentrations ranging from 1 to 200 µg/mL. These results suggest, for the first time, that SA attenuates nociceptive behavior through mechanisms involving receptors for ATP-dependent potassium channels, in addition to suppressing acute inflammatory responses.

Isolation of a dihydrobenzofuran lignan, icariside E4, with an antinociceptive effect from Tabebuia roseo-alba (Ridley) Sandwith (Bignoniaceae) bark.

The antinociceptive activity of icariside E4, a dihydrobenzofuran-type lignan isolated from Tabebuia roseo-alba (Ridley) Sandwith (Bignoniaceae) bark, was evaluated in mice by using chemical and thermal models of nociception. Intraperitoneal (i.p.) administration of crude T. roseo-alba bark extract and its methanol fraction inhibited acetic acid-induced abdominal constriction in mice. Furthermore, i.p. administration of 0.1, 1, and 10 mg/kg of icariside E4 reduced the number of writhes evoked by acetic acid injection by 46.9, 82.3, and 66.6%, respectively. Icariside E4 administration had no effect in the first phase of the formalin test, but it reduced nociceptive behavior in the second phase as indicated by a reduction in the licking time. Icariside E4 did not modify thermal nociception in the hot-plate test model, suggesting that it had a peripheral antinociceptive action. The antinociceptive effect of icariside E4 in the writhing test was reversed by pre-administration of glibenclamide, but not of naloxone, atropine, yohimbine, or haloperidol. Together, these results indicated that the antinociceptive activity of icariside E4 from T. roseo-alba in models of chemical pain occurred through ATP-sensitive K(+) channel-dependent mechanisms.

A new iridoid from Guettarda grazielae M.R.V. Barbosa (Rubiaceae).

Chromatographic fractionation of the chloroform extracts from the stem bark and stems of Guettarda grazielae resulted in the isolation of a new iridoid (guettardodiol, 1) and the secoiridoid sarracenin (2), described for the first time in this genus. The structural elucidation of these compounds was based on spectroscopic analyses (IR, MS as well as 1-D and 2-D NMR experiments).

Determination of the phenolic content and antioxidant potential of crude extracts and isolated compounds from leaves of Cordia multispicata and Tournefortia bicolor.

In this work, the total phenolic content and antioxidant activity of extracts and four flavonoids isolated from leaves of two Boraginaceae species (Cordia multispicata Cham. and Tournefortia bicolor Sw.) were evaluated using Folin-Ciocalteu reagent, DPPH free radical scavenging and inhibition of peroxidation of linoleic acid by FTC method. For comparison, ascorbic acid, alpha-tocopherol and BHT were used. In general, extracts from T. bicolor (68.8 +/- 0.001 to > 1000 mg/g) showed higher phenolic content than C. multispicata (66.1 +/- 0.009 to 231 +/- 0.07 mg/g), and also scavenged radicals (IC(50) 12.8 +/- 2.5 to 437 +/- 3.5 mg/L) and inhibited lipid peroxide formation (IC(50) 51.2 +/- 2.29 to 89 +/- 0.59 mg/L). For these extracts a good correlation between the phenolic content and antioxidant activity was observed, suggesting that T. bicolor is richer in phenolic compounds and that it could serve as a new source of natural antioxidants or nutraceuticals with potential applications. Chromatographic procedures monitored by antioxidant assays afforded seven compounds, which were identified by spectral analyses (IR, MS and 1D and 2D NMR) and comparison with reported data as being trans-phytol (1), taraxerol (2), 3,7,4'-trimethoxyflavone (3), 5,3'-dihydroxy-3,7,4'-trimethoxyflavone (4), quercetin (5), tiliroside (6), and rutin (7). Compounds (4-7) were also evaluated and were effective as DPPH quenching (IC(50) 7.7 +/- 3.6 to 79.3 +/- 3.4 mg/L) and as inhibition of lipid peroxidation (IC(50) 80.1 +/- 0.98 to 88.7 +/- 3.62 mg/L). This is the first report on the total phenolic content, radical-scavenging and antioxidant activities of these species.