Plant Occurring Flavonoids as Modulators of the Aryl Hydrocarbon Receptor.

The aryl hydrocarbon receptor (AhR) is a transcription factor deeply implicated in health and diseases. Historically identified as a sensor of xenobiotics and mainly toxic substances, AhR has recently become an emerging pharmacological target in cancer, immunology, inflammatory conditions, and aging. Multiple AhR ligands are recognized, with plant occurring flavonoids being the largest group of natural ligands of AhR in the human diet. The biological implications of the modulatory effects of flavonoids on AhR could be highlighted from a toxicological and environmental concern and for the possible pharmacological applicability. Overall, the possible AhR-mediated harmful and/or beneficial effects of flavonoids need to be further investigated, since in many cases they are contradictory. Similar to other AhR modulators, flavonoids commonly exhibit tissue, organ, and species-specific activities on AhR. Such cellular-context dependency could be probably beneficial in their pharmacotherapeutic use. Flavones, flavonols, flavanones, and isoflavones are the main subclasses of flavonoids reported as AhR modulators. Some of the structural features of these groups of flavonoids that could be influencing their AhR effects are herein summarized. However, limited generalizations, as well as few outright structure-activity relationships can be suggested on the AhR agonism and/or antagonism caused by flavonoids.

A Pharmacological Update of Ellagic Acid.

Ellagic acid is a common metabolite present in many medicinal plants and vegetables. It is present either in free form or as part of more complex molecules (ellagitannins), which can be metabolized to liberate ellagic acid and several of its metabolites, including urolithins. While ellagic acid's antioxidant properties are doubtless responsible for many of its pharmacological activities, other mechanisms have also been implicated in its various effects, including its ability to reduce the lipidemic profile and lipid metabolism, alter pro-inflammatory mediators (tumor necrosis factor-α, interleukin-1ß, interleukin-6), and decrease the activity of nuclear factor-κB while increasing nuclear factor erythroid 2-related factor 2 expression. These events play an important role in ellagic acid's anti-atherogenic, anti-inflammatory, and neuroprotective effects. Several of these activities, together with the effect of ellagic acid on insulin, glycogen, phosphatases, aldose reductase, sorbitol accumulation, advanced glycation end-product formation, and resistin secretion, may explain its effects on metabolic syndrome and diabetes. In addition, results from recent research have increased the interest in ellagic acid, both as a potential protective agent of the liver and skin and as a potential anticancer agent, due to the specific mechanisms affecting cell proliferation, apoptosis, DNA damage, and angiogenesis and its aforementioned anti-inflammatory properties. Taken together, these effects make ellagic acid a highly interesting compound that may contribute to different aspects of health; however, more studies are needed, especially on the compound's pharmacokinetic profile. In this review, we selected papers published from 2005 to the present.

Antioxidant Activity of Natural Hydroquinones.

Secondary metabolites derived from hydroquinone are quite rare in nature despite the original simplicity of its structure, especially when compared to other derivatives with which it shares biosynthetic pathways. However, its presence in a prenylated form is somewhat relevant, especially in the marine environment, where it is found in different algae and invertebrates. Sometimes, more complex molecules have also been identified, as in the case of polycyclic diterpenes, such as those possessing an abietane skeleton. In every case, the presence of the dihydroxy group in the para position gives them antioxidant capacity, through its transformation into para-quinones.This review focuses on natural hydroquinones with antioxidant properties referenced in the last fifteen years. This activity, which has been generally demonstrated in vitro, should lead to relevant pharmacological properties, through its interaction with enzymes, transcription factors and other proteins, which may be particularly relevant for the prevention of degenerative diseases of the central nervous system, or also in cancer and metabolic or immune diseases. As a conclusion, this review has updated the pharmacological potential of hydroquinone derivatives, despite the fact that only a small number of molecules are known as active principles in established medicinal plants. The highlights of the present review are as follows: (a) sesquiterpenoid zonarol and analogs, whose activity is based on the stimulation of the Nrf2/ARE pathway, have a neuroprotective effect; (b) the research on pestalotioquinol and analogs (aromatic ene-ynes) in the pharmacology of atherosclerosis is of great value, due to their agonistic interaction with LXRα; and (c) prenylhydroquinones with a selective effect on tyrosine nitration or protein carbonylation may be of interest in the control of post-translational protein modifications, which usually appear in chronic inflammatory diseases.

Phenolic substances from Phagnalon rupestre protect against 2,4,6-trinitrochlorobenzene-induced contact hypersensitivity.

2-isoprenylhydroquinone-1-glucoside (1), 3,5-dicaffeoylquinic acid (2), and 3,5-dicaffeoylquinic acid methyl ester (3), isolated from Phagnalon rupestre, improved the contact hypersensitivity response to 2,4,6-trinitrochlorobenzene in mice. These phenolics reduced ear swelling and IL-1ß content by 50% 24 h after challenge; in addition, 2 inhibited tumor necrosis factor-α by 53%. All three compounds also reduced interleukin-2 content by 50% 72 h after challenge. Both 2 and 3 inhibited metalloproteinase-9 levels in the skin lesions by 66% and 41%, respectively, and lowered cyclooxygenase-2 expression by 44% and 49%, respectively, at 24 h. Moreover, 2 was effective against atopic dermatitis induced by repeated application of 2,4,6-trinitrochlorobenzene; it attenuated edema by over 40% from day 7 and inhibited inflammatory cell infiltration by 44% at day 22. In addition, 1-3 reduced metalloproteinase-9 expression in a dose-dependent manner in macrophages RAW 264.7 stimulated with lipopolysaccharide. Thus, compounds 2 and 3 were found to exhibit a greater activity against contact hypersensitivity than 1.

Risks Associated with the Use of Garcinia as a Nutritional Complement to Lose Weight.

Nowadays, obesity is one of the great nutritional problems facing public health. The prevalence of this pathology has increased in a worrying way over recent years, currently reaching epidemic proportions. In this context, nutritional supplements are presented as a therapeutic alternative to which more and more people are turning to. Nutritional supplements to lose weight based on the Garcinia plant, specifically on Garcinia cambogia, are commonly used. The active principle of this plant to which these properties have been attributed, is hydroxycitric acid (HCA). The aim of the present review is to gather reported data concerning the effectiveness of nutritional supplements based on Garcinia extracts on weight loss and their possible negative effects. Contradictory results have been observed regarding the effectiveness of the supplements. While statistically significant weight loss was observed in some studies, no changes were found in others. Regarding safety, although Garcinia supplements have been revealed as safe in the vast majority of the studies carried out in animal models and humans, some cases of hepatotoxicity, serotonin toxicity and mania have been reported. In conclusion, the results suggest that Garcinia-based supplements could be effective in short-term weight loss, although the data are not conclusive. In addition, the safety of the complement should be further studied.

Inhibition of delayed-type hypersensitivity by Cucurbitacin R through the curbing of lymphocyte proliferation and cytokine expression by means of nuclear factor AT translocation to the nucleus.

Cucurbitacin R is known to exhibit an anti-inflammatory effect in different experimental models of inflammation. In this article, we outline the effect of cucurbitacin R on T lymphocyte proliferation, cytokine production, and nuclear factor activation, as well as its influence on various experimental models of delayed-type hypersensitivity (DTH) in mice. Cucurbitacin R reduced the proliferation of phytohemagglutinin A-stimulated human T lymphocytes (IC(50), 18 microM), modifying the cell cycle, as well as the production of cytokines [interleukin (IL)-2, IL-4, IL-10, and especially interferon-gamma] and the induction of the principal cyclins implicated in the cell cycle (A(1), B(1), D(2), and E). These effects are brought on by a novel, selective inhibition of nuclear factor AT (NFAT) by cucurbitacin R, with no concomitant effect on other transcription factors such as activator protein-1. In addition, we tested the in vivo effects of cucurbitacin R in three experimental models of DTH, as well as its effects on T lymphocyte proliferation, the cell cycle, cytokines, and cyclins. Although cucurbitacin R was found to reduce the inflammatory response brought on by both oxazolone and dinitrofluorobenzene, its activity was even more pronounced against sheep red blood cell-induced edema in mouse paws, with a clear reduction in the production of IL-1beta, IL-4, and tumor necrosis factor alpha in the inflamed paw. In conclusion, cucurbitacin R has the potential to be a new immunosuppressive agent with antiproliferative effects through the inhibition of the NFAT with anti-inflammatory activity in DTH reactions.

Discovery of 2-aryl and 2-pyridinylbenzothiazoles endowed with antimicrobial and aryl hydrocarbon receptor agonistic activities.

Benzothiazole is a privileged scaffold in medicinal chemistry present in diverse bioactive compounds with multiple pharmacological applications such as analgesic, anticonvulsant, antidiabetic, anti-inflammatory, anticancer and radioactive amyloidal imagining agents. We reported in this work the study of sixteen functionalized 2-aryl and 2-pyridinylbenzothiazoles as antimicrobial agents and as aryl hydrocarbon receptor (AhR) modulators. The antimicrobial activity against Gram-positive (S. aureus and M. luteus) and Gram-negative (P. aeruginosa, S. enterica and E. coli) pathogens yielded MIC ranging from 3.13 to 50 µg/mL and against the yeast C. albicans, the benzothiazoles displayed MIC from 12.5 to 100 µg/mL. All compounds showed promising antibiofilm activity against S. aureus and P. aeruginosa. The arylbenzothiazole 12 displayed the greatest biofilm eradication in S. aureus (74%) subsequently verified by fluorescence microscopy. The ability of benzothiazoles to modulate AhR expression was evaluated in a cell-based reporter gene assay. Six benzothiazoles (7, 8-10, 12, 13) induced a significant AhR-mediated transcription and interestingly compound 12 was also the strongest AhR-agonist identified. Structure-activity relationships are suggested herein for the AhR-agonism and antibiofilm activities. Furthermore, in silico predictions revealed a good ADMET profile and druglikeness for the arylbenzothiazole 12 as well as binding similarities to AhR compared with the endogenous agonist FICZ.

Predictive modeling of aryl hydrocarbon receptor (AhR) agonism.

The aryl hydrocarbon receptor (AhR) plays a key role in the regulation of gene expression in metabolic machinery and detoxification systems. In the recent years, this receptor has attracted interest as a therapeutic target for immunological, oncogenic and inflammatory conditions. In the present report, in silico and in vitro approaches were combined to study the activation of the AhR. To this end, a large database of chemical compounds with known AhR agonistic activity was employed to build 5 classifiers based on the Adaboost (AdB), Gradient Boosting (GB), Random Forest (RF), Multilayer Perceptron (MLP) and Support Vector Machine (SVM) algorithms, respectively. The built classifiers were examined, following a 10-fold external validation procedure, demonstrating adequate robustness and predictivity. These models were integrated into a majority vote based ensemble, subsequently used to screen an in-house library of compounds from which 40 compounds were selected for prospective in vitro experimental validation. The general correspondence between the ensemble predictions and the in vitro results suggests that the constructed ensemble may be useful in predicting the AhR agonistic activity, both in a toxicological and pharmacological context. A preliminary structure-activity analysis of the evaluated compounds revealed that all structures bearing a benzothiazole moiety induced AhR expression while diverse activity profiles were exhibited by phenolic derivatives.

Targeting the aryl hydrocarbon receptor with a novel set of triarylmethanes.

The aryl hydrocarbon receptor (AhR) is a chemical sensor upregulating the transcription of responsive genes associated with endocrine homeostasis, oxidative balance and diverse metabolic, immunological and inflammatory processes, which have raised the pharmacological interest on its modulation. Herein, a novel set of 32 unsymmetrical triarylmethane (TAM) class of structures has been synthesized, characterized and their AhR transcriptional activity evaluated using a cell-based assay. Eight of the assayed TAM compounds (14, 15, 18, 19, 21, 22, 25, 28) exhibited AhR agonism but none of them showed antagonist effects. TAMs bearing benzotrifluoride, naphthol or heteroaromatic (indole, quinoline or thiophene) rings seem to be prone to AhR activation unlike phenyl substituted or benzotriazole derivatives. A molecular docking analysis with the AhR ligand binding domain (LBD) showed similarities in the binding mode and in the interactions of the most potent TAM identified 4-(pyridin-2-yl (thiophen-2-yl)methyl)phenol (22) compared to the endogenous AhR agonist 5,11-dihydroindolo[3,2-b]carbazole-12-carbaldehyde (FICZ). Finally, in silico predictions of physicochemical and biopharmaceutical properties for the most potent agonistic compounds were performed and these exhibited acceptable druglikeness and good ADME profiles. To our knowledge, this is the first study assessing the AhR modulatory effects of unsymmetrical TAM class of compounds.

Anti-inflammatory activity of flavonoids from Cayaponia tayuya roots.

ETHNOPHARMACOLOGICAL RELEVANCE: Taiuiá or tayuya (Cayaponia tayuya, Cucurbitaceae) is a climbing, lignified plant with a large swollen root that has traditionally been used as an anti-inflammatory and anti-rheumatic agent in the folk medicine of Brazil, Peru, and Colombia. THE AIM OF THE STUDY: We have assayed the pharmacological properties of a flavonoid fraction obtained from the butanol extract of Cayaponia tayuya roots using two models of topical mouse ear oedema, paying special attention to its influence on the induction on pro-inflammatory enzymes and peptidic mediators. MATERIAL AND METHODS: The in vivo experiments involved both the acute oedema induced by a single application of TPA and the subchronic inflammation brought on by repeated applications of TPA. The effects on the induction of pro-inflammatory enzymes and peptidic mediators in RAW 264.7 macrophages were analyzed with the aid of Western blot analysis. RESULTS: The extract was identified as a mixture of flavonoids in which vicenin-2, spinosin, isovitexin, and a mixture of swertisin and isoswertisin were found. In acute TPA-induced oedema in mouse ears, the flavonoid-enriched fraction (at a dose of 0.5mg/ear) inhibited the oedema by 66% (4.2+/-0.6 mg vs. 12.3+/-1.4 mg, P<0.01) while in the subchronic model, the inhibition reached 37% at a dose of 0.5mg/ear x 7 applications (7.5+/-0.6 mg vs. 11.9+/-1.3mg, P<0.05). When assayed in vitro, the flavonoid showed no toxicity at 33.45 microg/mL on RAW 264.7 macrophages. Although the nitric oxide production in these cells was moderately reduced (42%) at 33.45 microg/mL, the flavonoid-enriched fraction had no effect on TNF-alpha production. In addition, at 22.30 microg/mL, the test sample inhibited both iNOS and COX-2 expression by 98% and 49%, respectively. CONCLUSION: These results indicate that the anti-inflammatory activity of flavonoids from tayuya roots most likely stems from their inhibition of the induction of the enzymes COX-2 and iNOS.

Interaction of dicaffeoylquinic derivatives with peroxynitrite and other reactive nitrogen species.

Plant phenolic antioxidants, among them catechins and hydroxycinnamoyl conjugates, constitute a well defined class of inhibitors of reactive nitrogen species (RNS). To gain deeper insight in this field, we examined the effects of 3,5-di-O-caffeoylquinic acid (DCA), its methyl ester (DCE) and epigallocatechin gallate (EGCG) in nitrative and oxidative processes. These compounds were found to be strong inhibitors of the nitration of tyrosine residues induced by ONOO- in bovine seroalbumin, with their IC50 values (10-40 microM) notably decreasing in the presence of bicarbonate. When studied on the intracellular protein tyrosine nitration induced by ONOO- in cultured murine fibroblasts as well as that induced by phorbol ester (PMA) in nitrite-supplemented human neutrophils, all three phenolics were also effective (100% and over 75% inhibition for fibroblasts and neutrophils, respectively, at 25 microM). This ability seems to be due to a direct interaction with ONOO- or with the species generated by leukocytes. The possible interference with the production of NO was also studied: both DCA and EGCG inhibited nitrite production in LPS-stimulated macrophages by 24% and 40%, respectively, and the expression of nitric oxide synthase-2 (NOS-2), as well. DCA and EGCG reduced by 52% and 59%, respectively, the NF-kappaB transcriptional activity. In contrast, DCE did not show any effect. The assayed phenolics exert varying degrees of protection against the chemical modifications induced by RNS depending not only on the hydroxyl pattern, but also on the presence of bicarbonate.

Extracellular Vesicles From the Helminth Fasciola hepatica Prevent DSS-Induced Acute Ulcerative Colitis in a T-Lymphocyte Independent Mode.

The complexity of the pathogenesis of inflammatory bowel disease (ulcerative colitis and Crohn's disease) has led to the quest of empirically drug therapies, combining immunosuppressant agents, biological therapy and modulators of the microbiota. Helminth parasites have been proposed as an alternative treatment of these diseases based on the hygiene hypothesis, but ethical and medical problems arise. Recent reports have proved the utility of parasite materials, mainly excretory/secretory products as therapeutic agents. The identification of extracellular vesicles on those secreted products opens a new field of investigation, since they exert potent immunomodulating effects. To assess the effect of extracellular vesicles produced by helminth parasites to treat ulcerative colitis, we have analyzed whether extracellular vesicles produced by the parasitic helminth Fasciola hepatica can prevent colitis induced by chemical agents in a mouse model. Adult parasites were cultured in vitro and secreted extracellular vesicles were purified and used for immunizing both wild type C57BL/6 and RAG1-/- mice. Control and immunized mice groups were treated with dextran sulfate sodium 7 days after last immunization to promote experimental colitis. The severity of colitis was assessed by disease activity index and histopathological scores. Mucosal cytokine expression was evaluated by ELISA. The activation of NF-kB, COX-2, and MAPK were evaluated by immunoblotting. Administration of extracellular vesicles from F. hepatica ameliorates the pathological symptoms reducing the amount of pro-inflammatory cytokines and interfering with both MAPK and NF-kB pathways. Interestingly, the observed effects do not seem to be mediated by T-cells. Our results indicate that extracellular vesicles from parasitic helminths can modulate immune responses in dextran sulfate sodium (DSS)-induced colitis, exerting a protective effect that should be mediated by other cells distinct from B- and T-lymphocytes.

Anti-Inflammatory Activity and Cheminformatics Analysis of New Poten t 2-Substituted 1-Methyl-5-Nitroindazolinones.

After the identification of the anti-inflammatory properties of VA5-13l (2-benzyl-1- methyl-5-nitroindazolinone) in previous investigations, some of its analogous compounds were designed, synthesized and evaluated in two anti-inflammatory methods: LPS-enhanced leukocyte migration assay in zebrafish; and 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced mouse ear edema. The products evaluated (3, 6, 8, 9 and 10) showed the lower values of relative leukocyte migration at 30 µM (0.14, 0.07, 0.10, 0.13 and 0.07, respectively), while in ear edema and myeloperoxidase activity methods, all the compounds reduced inflammation, only 4 and 16 yielded unsatisfactory results. The relationship linking structure and activity (SAR analysis) was determinate by using SARANEA software. The importance of the 5-Nitro group of the indazole ring for the activity was evident, and showed modest reduction when benzyl (Bn) is changed by alkyl group. A substituted Bn moiety at N2 (R) is the best substituent (5-10); nevertheless, if methylene group of Bn is deleted, the activity is affected. Also, introduction of halogen atoms mainly at positions 3 or 4 of the benzyl moiety (6 and 10) leads in general to strong activities. In fact, compounds 7 and 8 (R = 4-FBn or 4-ClBn, respectively) exhibit satisfactory results in in vivo tests and appear promising. The production of IL-6 at all doses assayed was significantly reduced, except with 16. Nonetheless, the production of TNF-α was significantly inhibited only by this chemical (16) at concentration of 50 µM. On the other hand, compound 2 was the one that mostly inhibited the expression of COX-2 and iNOS. From these results, it can be concluded that the inhibition in the release of cytokines can be one of the mechanisms of action responsible for the anti-inflammatory effect for 2-benzyl derivates while other 2-alkyl derivatives can inhibit production of NO. Therefore, nitroindazolinone chemical prototype could be an interesting structural group with anti-inflammatory purposes in the therapeutic.

New insight into the inhibition of the inflammatory response to experimental delayed-type hypersensitivity reactions in mice by scropolioside A.

Scropolioside A, an iridoid isolated from Scrophularia auriculata ssp. pseudoauriculata, showed anti-inflammatory properties against different experimental models of delayed-type hypersensitivity. This iridoid reduced the oedema induced by oxazolone by 79% (72 h) at 0.5 mg/ear while reducing that induced by sheep red blood cells by 47% (18 h), 45% (24 h) and 36% (48 h) at 10 mg/kg. In vivo it reduced both oedema formation and cell infiltration whereas in vitro it reduced the proliferation of activated T-lymphocytes (IC50 of 67.74 microM). Treatment with scropolioside A (100 microM) 18 and 24 h after phytohemagglutinin stimulation increased the number of cells arrested in the subG(0) phase whereas treatment 3 h after stimulation clearly increased the number of cells that passed to the S phase. Scropolioside A also inhibited the production of prostaglandin E2, leukotriene B4, nitric oxide, interleukin-1beta, interleukin-2, interleukin-4, tumour necrosis factor-alpha and interferon-gamma, but had no effect on the production of interleukin-10. Moreover, it modified the expression of both nitric oxide synthase-2 and cyclooxygenase-2, as well as the activation of nuclear factor-kappaB in RAW 264.7 macrophages.

Effects of naturally occurring dihydroflavonols from Inula viscosa on inflammation and enzymes involved in the arachidonic acid metabolism.

The anti-inflammatory properties of three flavanones isolated from Inula viscosa, sakuranetin, 7-O-methylaromadendrin, and 3-acetyl-7-O-methylaromadendrin, have been tested both in vitro and in vivo. Acute inflammation in vivo was induced by means of topical application of 12-O-tetradecanoylphorbol 13-acetate (TPA) to mouse ears or by subcutaneous injection of phospholipase A(2) (PLA(2)) into mouse paws. The test compounds were evaluated in vitro for their effect on both the metabolism of arachidonic acid and on the release and/or activity of enzymes involved in the inflammatory response such as elastase, myeloperoxidase (MPO), and protein kinase C (PKC). The most active compounds in vivo against PLA(2)-induced paw oedema were 7-O-methylaromadendrin (ED(50)=8 mg/kg) and sakuranetin (ED(50)=18 mg/kg). In contrast, the most potent compound against TPA-induced ear oedema was 3-acetyl-7-O-methylaromadendrin (ED(50)=185 microg/ear), followed by sakuranetin (ED(50)=205 microg/ear). In vitro, the latter compound was the most potent inhibitor of leukotriene (LT) B(4) production by peritoneal rat neutrophils (IC(50)=9 microM) and it was also the only compound that directly inhibited the activity of 5-lipoxygenase (5-LOX). 3-Acetyl-7-O-methylaromadendrin also inhibited LTB(4) production (IC(50)=15 microM), but had no effect on 5-LOX activity. The only flavanone that inhibited the secretory PLA(2) activity in vitro was 7-O-methylaromadendrin. This finding may partly explain the anti-inflammatory effect observed in vivo, although other mechanisms such as the inhibition of histamine release by mast cells may also be implicated. Sakuranetin at 100 microM was found to inhibit elastase release, although this result is partly due to direct inhibition of the enzyme itself. At the same concentration, 7-O-methylaromadendrin only affected the enzyme release. Finally, none of the flavanones exhibited any effect on MPO or PKC activities. Taken together, these findings indicate that sakuranetin may be a selective inhibitor of 5-LOX.

Inhibition of the pro-inflammatory mediators' production and anti-inflammatory effect of the iridoid scrovalentinoside.

We have studied scrovalentinoside, an iridoid with anti-inflammatory properties isolated from Scrophularia auriculata ssp. pseudoauriculata, as an anti-inflammatory agent in different experimental models of delayed-type hypersensitivity. We found that scrovalentinoside reduced the edema induced by oxazolone at 0.5 mg/ear and sheep red blood cells at 10 mg/kg. The observed effect occurred during the last phase or inflammatory response; during the earlier phase or induction of the delayed-type hypersensitivity reaction, no significant activity was noted. Thus, scrovalentinoside reduced both the edema and cell infiltration in vivo and reduced lymphocyte proliferation in vitro, affecting the cycle principally during the first 48 h. Whereas cells stimulated with phytohemagglutinin changed from the G(0)/G(1) phase to the S and G(2)/M phases, when these same cells were treated with scrovalentinoside (100 microM), they remained in the G(0)/G(1) phase. Finally, scrovalentinoside inhibited the production of the pro-inflammatory mediators' TNF-alpha, IFN-gamma, IL-1beta, IL-2, IL-4, LTB(4), and NO, but had no effect on the production of the anti-inflammatory cytokine IL-10.

Influence of Dimerization of Apocynin on Its Effects in Experimental Colitis.

Apocynin has been widely used as an inhibitor of the nicotinamide adenine dinucleotide phosphate oxidase (NADPH-oxidase) system and shows promise as an anti-inflammatory drug. Diapocynin, the dimeric product generated by the oxidation of apocynin in the presence of myeloperoxidase (MPO), is supposed to be its active form. In this study, diapocynin has been chemically synthesized and its activity on several inflammatory mediators in LPS-stimulated RAW 264.7 macrophages and its anti-inflammatory effect on ulcerative colitis induced by dextran sodium sulfate (DSS) in mice analyzed. We found that diapocynin showed higher inhibitory activity than apocynin. The dimer reduced ROS production, TNF-α, IL-6, and IL-1ß levels and inhibited iNOS and COX-2 expression as well as decreased NO and PGE2 production induced in LPS-stimulated RAW 264.7 cells. The anti-inflammatory molecular mechanism of diapocynin was associated with the suppression of NF-κB activation. However, these results were not paralleled by in vivo studies. Oral administration of apocynin and diapocynin (100 mg/kg) three times a week exhibited similar protections against experimental inflammatory bowel disease induced by DSS; therefore, apocynin should not be considered a prodrug. However, it should be taken into account that the dimer is more potent because its dose (0.3 mmol/kg) is half that of apocynin.

Fishing Anti-Inflammatories from Known Drugs: In Silico Repurposing, Design, Synthesis and Biological Evaluation of Bisacodyl Analogues.

Herein is described in silico repositioning, design, synthesis, biological evaluation and structure-activity relationship (SAR) of an original class of anti-inflammatory agents based on a polyaromatic pharmacophore structurally related to bisacodyl (BSL) drug used in therapeutic as laxative. We describe the potential of TOMOCOMD-CARDD methods to find out new anti-inflammatory drug-like agents from a diverse series of compounds using the total and local atom based bilinear indices as molecular descriptors. The models obtained were validated by biological studies, identifying BSL as the first anti-inflammatory lead-like using in silico repurposing from commercially available drugs. Several biological in vitro and in vivo assays were performed in order to understand its mechanism of action. A set of analogues of BSL was prepared using low-cost synthetic procedures and further biologically investigated in zebrafish models. Compound 5c and 7e exhibited the best antiinflammatory activities and represent new promising anti-inflammatory agents for further preclinical development.

A new dual inhibitor of arachidonate metabolism isolated from Helichrysum italicum.

Six acetophenones (1-6) and one gamma-pyrone (7), previously isolated from Helichrysum italicum, were tested for their ability to inhibit enzymatic and non-enzymatic lipid peroxidation, the stable 1,1-diphenyl-2-pycryl-hydrazyl free radical, superoxide scavenging and arachidonic acid metabolism. In addition, they were studied in different experimental models such as the chronic inflammation induced by 12-O-tetradecanoylphorbol 13-acetate (TPA), the phospholipase A(2)-induced mouse paw oedema test, the carrageenan-induced mouse paw oedema test, and the writhing induced by acetic acid in the mouse. Of the assayed compounds, only 1 inhibited enzymatic lipid peroxidation but had no effect on non-enzymatic lipid peroxidation. None of them scavenged the superoxide radical. Study of the inhibition of arachidonic acid metabolism demonstrated that 1 was an inhibitor of both cyclooxygenase and 5-lipoxygenase, whereas 2 was a selective inhibitor of 5-lipoxygenase. In the assay of phospholipase A(2)-induced mouse paw oedema, the gamma-pyrone derivative inhibited oedema formation, showing a similar profile to that obtained with cyproheptadine. The acetophenones were effective at 30 and 60 min. In the carrageenan test, acetophenone 1 gave the best results and had analgesic effects in the acetic acid writhing test. In conclusion acetophenone 1 (4-hydroxy-3-(3-methyl-2-butenyl)acetophenone) is a new dual inhibitor of arachidonate metabolism, and could be a useful tool for obtaining anti-inflammatory and analgesic drugs.

Assessment of the anti-inflammatory activity and free radical scavenger activity of tiliroside.

Three flavonoids, gnaphaliin, pinocembrin and tiliroside, isolated from Helichrysum italicum, were studied in vitro for their antioxidant and/or scavenger properties and in vivo in different models of inflammation. In vitro tests included lipid peroxidation in rat liver microsomes, superoxide radical generation in the xanthine/xanthine oxidase system and the reduction of the stable radical 1,1-diphenyl-2-pycryl-hydrazyl (DPPH). Acute inflammation was induced by application of 12-O-tetradecanoylphorbol 13-acetate (TPA) to the mouse ear or by subcutaneous injection of phospholipase A(2) or serotonin in the mouse paw. Eczema provoked on the mouse ear by repeated administration of TPA was selected as a model of chronic inflammation. The flavonoids were assayed against sheep red blood cell-induced mouse paw oedema as a model of delayed-type hypersensitivity reaction. The most active compound, both in vitro and in vivo, was tiliroside. It significantly inhibited enzymatic and non-enzymatic lipid peroxidation (IC(50)=12.6 and 28 microM, respectively). It had scavenger properties (IC(50)=21.3 microM) and very potent antioxidant activity in the DPPH test (IC(50)=6 microM). In vivo, tiliroside significantly inhibited the mouse paw oedema induced by phospholipase A(2)(ED(50)=35.6 mg/kg) and the mouse ear inflammation induced by TPA (ED(50)=357 microg/ear). Pinocembrin was the only flavonoid that exhibited anti-inflammatory activity in the sheep red blood cell-induced delayed-type hypersensitivity reaction. However, only tiliroside significantly reduced the oedema and leukocyte infiltration induced by TPA. As in the case of other flavonoids, the anti-inflammatory activity of tiliroside could be based on its antioxidant properties, although other mechanisms are probably involved.