Antiallodynic effect induced by [6]-gingerol in neuropathic rats is mediated by activation of the serotoninergic system and the nitric oxide-cyclic guanosine monophosphate-adenosine triphosphate-sensitive K+ channel pathway.

The present study evaluated the possible antiallodynic effect induced by [6]-gingerol in rats with L5-L6 spinal nerve ligation (SNL). Moreover, we determined the possible mechanism underlying the antiallodynic effect induced by [6]-gingerol in neuropathic rats. The animals underwent L5-L6 SNL for the purpose of developing tactile allodynia. Tactile allodynia was measured with von Frey filaments. Intrathecal administration of [6]-gingerol reversed SNL-induced tactile allodynia. The [6]-gingerol-induced antiallodynic effect was prevented by the intrathecal administration of methiothepin (30 µg per rat; nonselective 5-hydroxytryptamine [5-HT] antagonist), WAY-100635 (6 µg per rat; selective 5-HT1A receptor antagonist), SB-224289 (5 µg per rat; selective 5-HT1B receptor antagonist), BRL-15572 (4 µg per rat; selective 5-HT1D receptor antagonist), and SB-659551 (6 µg per rat; selective 5-HT5A receptor antagonist), but naloxone (50 µg per rat; nonselective opioid receptor antagonist) did not prevent the [6]-gingerol-induced antiallodynic effect. Moreover, intrathecal administration of Nω-nitro-l-arginine methyl ester (100 µg per rat; nonselective nitric oxide [NO] synthase inhibitor), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (10 µg per rat; inhibitor of guanylate cyclase), and glibenclamide (50 µg per rat; channel blocker of adenosine triphosphate [ATP]-sensitive K+ channels) prevented the [6]-gingerol-induced antiallodynic effect. These data suggest that the antiallodynic effect induced by [6]-gingerol is mediated by the serotoninergic system involving the activation of 5-HT1A/1B/1D/5A receptors, as well as the NO-cyclic guanosine monophosphate-ATP-sensitive K+ channel pathway but not by the opioidergic system.

Anti-allodynic effect of mangiferin in neuropathic rats: Involvement of nitric oxide-cyclic GMP-ATP sensitive K+ channels pathway and serotoninergic system.

The neurobiology of neuropathic pain is caused by injury in the central or peripheral nervous system. Recent evidence points out that mangiferin shows anti-nociceptive effect in inflammatory pain. However, its role in inflammatory and neuropathic pain and the possible mechanisms of action are not yet established. The purpose of this study was to determine the possible anti-allodynic effect of mangiferin in rats with spinal nerve ligation (SNL). Furthermore, we sought to investigate the possible mechanisms of action that contribute to these effects. Mechanical allodynia to stimulation with the von Frey filaments was measured by the up and down method. Intrathecal administration of mangiferin prevented, in a dose-dependent fashion, SNL-induced mechanical allodynia. Mangiferin-induced anti-allodynia was prevented by the intrathecal administration of L-NAME (100µg/rat, non-selective nitric oxide synthase inhibitor), ODQ (10µg/rat, inhibitor of guanylate-cyclase) and glibenclamide (50µg/rat, channel blocker of ATP-sensitive K+ channels). Moreover, methiothepin (30µg/rat, non-selective 5-HT receptor antagonist), WAY-100635 (6µg/rat, selective 5-HT1A receptor antagonist), SB-224289 (5µg/rat, selective 5-HT1B receptor antagonist), BRL-15572 (4µg/rat, selective 5-HT1D receptor antagonist) and SB-659551 (6µg/rat, selective 5-HT5A receptor antagonist), but not naloxone (50µg/rat, non-selective opioid receptor antagonist), were able to prevent mangiferin-induced anti-allodynic effect. These data suggest that the anti-allodynic effect induced by mangiferin is mediated at least in part by the serotoninergic system, involving the activation of 5-HT1A/1B/1D/5A receptors, as well as the nitric oxide-cyclic GMP-ATP-sensitive K+ channels pathway, but not by the opioidergic system, in the SNL model of neuropathic pain in rats.

Mechanisms underlying the antinociceptive effect of mangiferin in the formalin test.

The purpose of this study was to investigate the possible antinociceptive effect of mangiferin, a glucosylxanthone present in Mangifera indica L., in inflammatory pain. Furthermore, we sought to investigate the possible mechanisms action that contributes to these effects. The ipsilateral local peripheral (1-30 µg/paw), intrathecal (1-30 µg/rat) and oral (1-30 mg/kg) administration of mangiferin produced a dose-dependent reduction in formalin-induced nociception. The antinociceptive effect of this drug was similar to that induced by diclofenac after oral and local peripheral administration. Furthermore, mangiferin was also able to reduce 0.1% capsaicin- and serotonin-induced nociceptive behavior. The local peripheral antinociceptive effect of mangiferin in the formalin test was blocked by naloxone (50 µg/paw), naltrindole (1 µg/paw), 5-guanidinonaltrindole (5-GNTI, 1 µg/paw), N(G)-L-nitro-arginine methyl ester (L-NAME, 100 µg/paw), 1H-(1,2,4)-oxadiazolo [4,2-a]quinoxalin-1-one (ODQ, 50 µg/paw) and glibenclamide (50 µg/paw), but not by methiothepin (30 µg/paw). These results suggest that the antinociceptive effects induced by mangiferin are mediated by the peripheral opioidergic system involving the activation of δ, κ, and probably µ, receptors, but not serotonergic receptors. Data also suggests that mangiferin activates the NO-cyclic GMP-ATP-sensitive K(+) channels pathway in order to produce its local peripheral antinociceptive effect in the formalin test. Mangiferin may prove to be effective in treating inflammatory pain in humans.

Cyclic Systems Distribution Along Similarity Measures: Insights for an Application to Activity Landscape Modeling.

The emerging concept of the activity landscape has been widely applied for structureactivity relationships (SAR) characterization. Since chemical space representation plays a crucial role in activity landscape modeling, an adequate selection of similarity measures is desirable. Herein a set of 658 cyclooxygenase inhibitors were structurally analyzed using 12 molecular similarity representations and two levels of chemotype classification. Then, three uncorrelated similarity measures and mean similarity (obtained with data fusion) were combined with chemotype information using the herein proposed chemotypesimilarity graphs. Chemotype-similarity graphs showed the cumulative distribution of molecular pairs with the same and different chemotype along similarity values; leading to establish an interpretable, quantitative and activity independent threshold in similarity measures based on chemotype distributions. This approach gave additional information to similarity measures and can be considered as an interpretable criterion to define high and low similar compounds. The results were applied to model the activity landscape using StructureActivity Similarity (SAS)-like maps. Some examples of pairs in each region of the SAS-like maps were analyzed which showed valuable SAR information for cyclooxygenase inhibitors.

Synthesis, cytotoxic and antioxidant evaluations of amino derivatives from perezone.

A series of eight amino derivatives (3a-h) from perezone 1 were prepared by nucleophilic addition of bioactive amines v.gr. melatonin, acetyl tryptamine, tryptophan and other amino acids esters (valine, leucine and methionine). Their structures were elucidated by spectroscopy data. The cytotoxic evaluation against four human tumor cell lines PC-3, K-562, HCT-15 and SKLU-1 was performed as well as the TBARS assay for antioxidant activity. The results suggest that 1 and its isomer 4 were highly active against all cell lines, 4 was twice as potent than 1 against PC-3 and HCT-15. The derivative 3a (IC(50)=7.5 ± 0.3 µM) was more active than 1 against HCT-15 whereas 3h was selective against K-562 with IC(50)=4.5 ± 0.4 µM. The TBARS assay has shown that 3c with IC(50)=5.564 ± 0.24 µM is a potent antioxidant with superior effect comparing to α-tocopherol and moreover was more active than the precursor molecule 1.

CASE plots for the chemotype-based activity and selectivity analysis: a CASE study of cyclooxygenase inhibitors.

Structure-activity characterization of molecular databases plays a central role in drug discovery. However, the characterization of large databases containing structurally diverse molecules with several end-points represents a major challenge. For this purpose, the use of chemoinformatic methods plays an important role to elucidate structure-activity relationships. Herein, a general methodology, namely Chemotype Activity and Selectivity Enrichment plots, is presented. Chemotype Activity and Selectivity Enrichment plots provide graphical information concerning the activity and selectivity patterns of particular chemotypes contained in structurally diverse databases. As a case study, we analyzed a set of 658 compounds screened against cyclooxygenase-1 and cyclooxygenase-2. Chemotype Activity and Selectivity Enrichment plots analysis highlighted chemotypes enriched with active and selective molecules against cyclooxygenase-2; all this in a simple 2D graphical representation. Additionally, the most active and selective chemotypes detected in Chemotype Activity and Selectivity Enrichment plots were analyzed separately using the previously reported dual activity-difference maps. These findings indicate that Chemotype Activity and Selectivity Enrichment plots and dual activity-difference maps are complementary chemoinformatic tools to explore the structure-activity relationships of structurally diverse databases screened against two biological end-points.