Protective effect of apocynin in a mouse model of chemically-induced colitis.

Apocynin, a constituent of Picrorhiza kurroa, successfully inhibits NADPH oxidase and shows promise as an anti-inflammatory drug. Now, we report anti-inflammatory effects of apocynin in an experimental colitis model induced by dextran sulfate sodium as well as the effects on the mediators involved in this process. Apocynin reduced the colitis induced in mice by administration of 5 % dextran sulfate sodium during 7 days. Mice were fed a control diet or a diet supplemented with 2 % of apocynin or 2 % of rutin. Sulfasalazine (50 mg/kg, p. o.) was used as a positive control. Treatment with apocynin and rutin ameliorated the course of colonic inflammation with results similar to those of the reference drug, as could be seen by reductions in the disease activity index scores and colon length. NO and PGE2 production as well as the iNOS and COX-2 expression were reduced by apocynin and rutin. Moreover, the activation of NF-κB p65 as well as STAT3 in dextran sulfate sodium-treated colon tissues was significantly reduced by apocynin. These results are promising for further experimental studies on treating gastrointestinal diseases and on the potential protective effects of apocynin.

Beneficial effect of shikonin on experimental colitis induced by dextran sulfate sodium in BALB/c mice.

The naphthoquinone shikonin, a major component of the root of Lithospermum erythrorhizon, now is studied as an anti-inflammatory agent in the treatment of ulcerative colitis (UC). Acute UC was induced in Balb/C mice by oral administration of 5% dextran sodium sulfate (DSS). The disease activity index was evaluated, and a histologic study was carried out. Orally administered shikonin reduces induced UC in a dose-dependent manner, preventing the shortening of the colorectum and decreasing weight loss by 5% while improving the appearance of feces and preventing bloody stools. The disease activity index score was much lower in shikonin-treated mice than in the colitic group, as well as the myeloperoxidase activity. The expression of cyclooxygenase-2 was reduced by 75%, activation of NF-κB was reduced by 44%, and that of pSTAT-3 by 47%, as well as TNF-α, IL-1ß, and IL-6 production. Similar results were obtained in primary macrophages culture. This is the first report of shikonin's ability to attenuate acute UC induced by DSS. Shikonin acts by blocking the activation of two major targets: NF-κB and STAT-3, and thus constitutes a promising potential therapeutic agent for the management of the inflammatory bowel disease.

Anti-inflammatory and apoptotic activities of pomolic acid isolated from Cecropia pachystachya.

The dichloromethane extract and pomolic acid ( 5) obtained from leaves of Cecropia pachystachya both reduced carrageenan-induced paw oedema in mice. Interestingly, while the triterpenoid inhibited the in vivo production of interleukin-1beta by 39 %, it had no effect on tumour necrosis factor-alpha production. We also demonstrated that both the dichloromethane extract and 5 inhibited the viability of human polymorphonuclear (PMN) cells in a time- and dose-dependent fashion. The PMN membrane integrity was determined with the aid of flow cytometry by means of the exclusion of propidium iodide as assay. Although the cell membrane integrity was altered, neither the extract nor 5 produced cellular necrosis. Moreover, the development of hypodiploid nuclei and DNA fragmentation in the PMN cells were both dependent on dose and time. Finally, in the annexin V-FITC binding assay, compound 5 increased the total of apoptotic cells by 42 % at 100 microM and by 71 % at 200 microM with respect to the control group. In conclusion, both the dichloromethane extract of ambay and isolated compound 5 inhibit the viability of PMN cells through apoptosis. Since they can regulate human neutrophil functions in this way, it is likely that these substances can also limit inflammation.

Inhibition of pro-inflammatory enzymes by inuviscolide, a sesquiterpene lactone from Inula viscosa.

This work concerns the pharmacological activity of inuviscolide, a sesquiterpenoid from Inula viscosa. It exerts inhibitory effects on elastase, cyclooxygenase 1 and secretory phospholipase A(2). Furthermore, it reduces the skin leukocyte infiltration in a murine model of dermatitis induced by repeated application of 12-O-tetradecanoylphorbol 13-acetate.

Isoprenylhydroquinone glucoside: a new non-antioxidant inhibitor of peroxynitrite-mediated tyrosine nitration.

Three hydroquinone glucosides and four caffeoylquinic esters were examined for their effect on tyrosine nitration, as well as on the oxidation of dihydrorhodamine (DHR) 123 and cytochrome c(2+) induced by peroxynitrite. All these phenolics, which had previously been characterized as the active principles of the plant Phagnalon rupestre, were fairly active in preventing the oxidation of DHR 123, though inefficient in the cytochrome c test. While their antioxidant potency is associated with the presence of a caffeoyl moiety, not so an obvious chemical character was correlated to a greater activity against nitration of tyrosine. Here, the highest potency corresponded to 2-isoprenylhydroquinone-1-glucoside. On the basis of the fact that the susceptibility to nitration of given aromatic compound confers to it inhibitory activity of tyrosine nitration, the analysis of ultraviolet and nuclear magnetic resonance spectral shifts provides valuable information for explaining the ability of natural phenolics to interfere with that reaction.

Inhibition of xanthine oxidase by phenolic conjugates of methylated quinic acid.

The caffeoyl conjugates of prenylhydroquinone glucoside and of quinic acid, either in the carboxyl-free or carboxymethyl forms, isolated from Phagnalon rupestre (Asteraceae), showed inhibitory activity on lipid peroxidation induced by Fe 2+/ascorbate and by CCl4/NADPH in rat liver microsomes, with IC50 values ranging from 3 to 11 microM. After having demonstrated their effect on the xanthine oxidase-regulated superoxide production, the active compounds were tested for the direct inhibition of this enzyme. Methylated dicaffeoylquinic conjugates competitively inhibited the enzyme and the highest potency was obtained for the 4,5-diester, with an IC50 value of 3.6 microM, nearly ten times lower than that of the 3,5-analogue. In conclusion, the presence of the caffeoyl moiety is essential for both the antiperoxidative and radical scavenging activities, and the methylation of the quinic carboxyl group enhances the potency on xanthine oxidase inhibitory activity.

Effects of caffeoyl conjugates of isoprenyl-hydroquinone glucoside and quinic acid on leukocyte function.

The activity of three prenylhydroquinone glucosides (1-3) and four caffeoylquinic esters (4-7), obtained from Phagnalon rupestre, on elastase release, myeloperoxidase activity and superoxide and leukotriene B(4) production from polymorphonuclear leukocytes was determined. 4,5-Dicaffeoylquinic acid strongly inhibited elastase release with an IC(50) value of 4.8 microM. Methylated caffeoylquinic derivatives were the most potent inhibitors of myeloperoxidase (IC(50) near 60 microM), whereas both methylated and free carboxyl isomers inhibited superoxide production with similar potency (IC(50) between 27 and 42 microM). The monocaffeoyl conjugate of prenylhydroquinone glucoside (3), the most potent inhibitor of leukotriene B(4) production (IC(50) = 33 microM), possesses a mixed hydroquinone-caffeoyl character that could be considered as a potential anti-inflammatory entity.

Phagnalon rupestre as a source of compounds active on contact hypersensitivity.

The effect of Phagnalon rupestre MeOH extract on dinitrofluorobenzene- and sheep red blood cells-induced hypersensitivity was investigated. Eight compounds were identified: three dimethylallyl-hydroquinone glucosides (1 - 3), 3,5- and 4,5-di-O-caffeoylquinic acid methyl esters (4 and 5), their free carboxyl analogues (6 and 7), and luteolin 7-O-beta-glucoside (8). All were tested for dinitrofluorobenzene-induced contact hypersensitivity inhibitory activity. Flavonoid 8 was the most active (49 % and 79 % inhibition at 24 and 96 h, respectively). The hydroquinones 1, 2 and 3 were effective at 96 h after challenge (62 %, 73 % and 60 % inhibition, respectively), while some of the dicaffeoylquinic derivatives (4 and 7) produced slightly lower reduction of the inflammatory reaction.