Novel Triazole-Containing "Dipeptides": Synthesis, Molecular Docking and Analgesic Activity Studies.

Dipeptides of a new structure based on ß-triazolalanines and (L)-α-amino acids were synthesized and optimal conditions were developed that ensure both chemical and optical purity of the final products. Molecular docking was carried out and possible intermolecular interactions of dipeptides with potential targets were established. Based on these studies, the analgesic property of chosen dipeptides was studied and it was found that some compounds possess revealed antinociceptive activity in the tail-flick test.

Hydroxytakakiamide and Other Constituents from a Marine Sponge-Associated Fungus Aspergillus fischeri MMERU23, and Antinociceptive Activity of Ergosterol Acetate, Acetylaszonalenin and Helvolic Acid.

An unreported prenylated indole derivative hydroxytakakiamide (4) was isolated, together with the previously described ergosterol (1), ergosterol acetate (2), and (3R)-3-(1H-indol-3-ylmethyl)-3, 4-dihydro-1H-1,4-benzodiazepine-2,5-dione (3), from the column fractions of the crude ethyl acetate extract of the culture of a marine sponge-associated fungus, Aspergillus fischeri MMERU 23. The structure of 4 was elucidated by the interpretation of 1D and 2D NMR spectral data and high-resolution mass spectrum. The absolute configuration of the stereogenic carbon in 3 was proposed to be the same as those of the co-occurring congeners on the basis of their biogenetic consideration and was supported by the comparison of its sign of optical rotation with those of its steroisomers. The crude ethyl acetate extract and 2 were evaluated, together with acetylaszonalenin (5) and helvolic acid (6), which were previously isolated from the same extract, for the in vivo antinociceptive activity in the mice model. The crude ethyl acetate extract exhibited antinociceptive activity in the acetic acid-induced writhing and formalin tests, while 2, 5, and 6 displayed the effects in the late phase of the formalin test. On the other hand, neither the crude ethyl acetate extract nor 2, 5, and 6 affected the motor performance of mice in both open-field and rotarod tests. Additionally, docking studies of 2, 5, and 6 were performed with 5-lipoxygenase (5-LOX) and phosphodiesterase (PDE) enzymes, PDE4 and PDE7, which are directly related to pain and inflammatory processes. Molecular docking showed that 6 has low affinity energy to PDE4 and PDE7 targets while retaining high affinity to 5-LOX. On the other hand, while 2 did not display any hydrogen bond interactions in any of its complexes, it achieved overall better energy values than 6 on the three antinociceptive targets. On the other hand, 5 has the best energy profile of all the docked compounds and was able to reproduce the crystallographic interactions of the 5-LOX complex.

Three new antinociceptive diterpenoids from the fruits of Rhododendron molle.

Investigation of the fruits of Rhododendron molle G. Don led to the isolation of three new grayanane-type diterpenoids, rhodomolleins LIV-LVI (1-3). The structures and absolute configurations of new compounds were fully elucidated by spectroscopic analysis and single-crystal X-ray diffraction, including HRESIMS, 1 D and 2 D NMR data. Compounds 1-3 were evaluated for analgesic activities utilizing an acetic acid-induced writhing test in mice. Compound 1 showed a significant antinociceptive effect with writhe inhibition rates of 72.9% and 100% at doses of 6 mg/kg and 20 mg/kg in mice, respectively. The binding mode of 1 to N-ethylmaleimide-sensitive factor (NSF, PDB: 6IP2) was explored by molecular docking, indicating the presence of hydrogen bond interactions which account for its analgesic activity.

Antinociceptive iridoid glycosides from the aerial parts of Paederia foetida.

Two previously undescribed iridoid glycosides, 6'-O-trans-feruloyl-(4S,6R)-3,4-dihydro-3ß-ethoxypaederoside (1) and 6'-O-trans-caffeoyl-(4S,6R)-3,4-dihydro-2'-O-3α-paederoside (2), were isolated from the 90% EtOH extract of the air dried aerial parts of Paederia Foetida. Structural elucidation of all the compounds was performed by spectral methods such as 1D and 2D (1H-1H COSY, HMQC, and HMBC) NMR spectroscopy. The two isolated iridoid glycosides were tested in vivo for their antinociceptive properties. As a result, 2 showed potent antinociceptive effect and its ID50 value (53.4 µmol/kg) was 2-fold less than those of the positive control drugs aspirin and acetaminophen.

New N- and C-modified RGD-hemorphins as potential biomedical application on Ti-surface materials: synthesis, characterization and antinociceptive activity.

This manuscript presented the synthesis and characterization of two new N- and C-modified analogues of VV-hemorphin-7 containing RGD (Arg-Gly-Asp) residues as potential nociceptive agents and bioactive materials. It has been shown that the addition of one or two RGD sequences to natural VV-hemorphin-7 increases its effect on acute nociception, but the reduction of the inflammatory phase depends on the concentration of the peptide. The structure-property relationship of the new peptide derivatives was highlighted by electrochemical and FT-IR methods of analysis. Because of the proven bone-structural bonds of hydroxyapatite, the simultaneous deposition of peptide/hydroxyapatite on the surface of a titanium surface was investigated. The deposition was performed in a medium of gelatin solution containing dissolved amounts of peptide and hydroxyapatite using ultrasound. SEM-EDS analyzes confirmed the presence of a layer of the studied system.

Antinociceptive diterpenoid alkaloids from the roots of Aconitum austroyunnanense.

A phytochemical investigation on the roots of Aconitum austroyunnanense afforded three undescribed aconitine-type C19-diterpenoid alkaloids, austroyunnanines A-C (1-3). Structural elucidation of all the compounds were performed by spectral methods such as 1 D and 2 D (1H-1H COSY, HMQC, and HMBC) NMR spectroscopy. The isolated alkaloids were tested in vivo for their antinociceptive properties. Consequently, austroyunnanine B (2) exhibited significant antinociceptive effect and its ID50 value (48.0 µmol/kg) was 2-fold less than those of the positive control drugs aspirin and acetaminophen.

Antinociceptive C19-diterpenoid alkaloids from the roots of Aconitum nagarum.

Three new C19-diterpenoid alkaloids, nagarumines A-C (1-3), together two known alkaloids, deoxyaconitine (4) and N-deethyldeoxyaconitine (5), were isolated from the roots of Aconitum nagarum. The structures of the new compounds were elucidated by spectral methods such as 1D and 2D (1H-1H COSY, HMQC, and HMBC) NMR spectroscopy, as well as high resolution mass spectrometry. The in vivo pharmacological studies revealed that nagarumine C (3) possessed comparable antinociceptive activity (ED50 = 76.0 µmol/kg) with the positive control drugs aspirin and acetaminophen.

ß-Lactam TRPM8 Antagonists Derived from Phe-Phenylalaninol Conjugates: Structure-Activity Relationships and Antiallodynic Activity.

The protein transient receptor potential melastatin type 8 (TRPM8), a non-selective, calcium (Ca2+)-permeable ion channel is implicated in several pathological conditions, including neuropathic pain states. In our previous research endeavors, we have identified ß-lactam derivatives with high hydrophobic character that exhibit potent and selective TRPM8 antagonist activity. This work describes the synthesis of novel derivatives featuring C-terminal amides and diversely substituted N'-terminal monobenzyl groups in an attempt to increase the total polar surface area (TPSA) in this family of compounds. The primary goal was to assess the influence of these substituents on the inhibition of menthol-induced cellular Ca2+ entry, thereby establishing critical structure-activity relationships. While the substitution of the tert-butyl ester by isobutyl amide moieties improved the antagonist activity, none of the N'-monobencyl derivatives, regardless of the substituent on the phenyl ring, achieved the activity of the model dibenzyl compound. The antagonist potency of the most effective compounds was subsequently verified using Patch-Clamp electrophysiology experiments. Furthermore, we evaluated the selectivity of one of these compounds against other members of the transient receptor potential (TRP) ion channel family and some receptors connected to peripheral pain pathways. This compound demonstrated specificity for TRPM8 channels. To better comprehend the potential mode of interaction, we conducted docking experiments to uncover plausible binding sites on the functionally active tetrameric protein. While the four main populated poses are located by the pore zone, a similar location to that described for the N-(3-aminopropyl)-2-[(3-methylphenyl)methoxy]-N-(2-thienylmethyl)-benzamide (AMTB) antagonist cannot be discarded. Finally, in vivo experiments, involving a couple of selected compounds, revealed significant antinociceptive activity within a mice model of cold allodynia induced by oxaliplatin (OXA).

Phenolic Composition, Wound Healing, Antinociceptive, and Anticancer Effects of Caralluma europaea Extracts.

Caralluma europaea (Guss.) is an important medicinal plant widely used in Morocco for various traditional purposes. Our work aimed to evaluate the phenolic composition, wound healing, antinociceptive, and anticancer activities of C. europaea extracts. Moreover, this study assessed the beneficial effect of C. europaea phytocompounds on the TRADD, cyclooxegenase-2, Wnt/ß-catenin, and tyrosine kinase signaling pathways. The wound healing effect of C. europaea formulations against skin burn was evaluated for 21 days. The cytotoxic effect of the C. europaea extracts was evaluated against human leukemic (K562 and HL60) and liver cancer cell lines (Huh-7) using the MTT test. All the phytoconstituents identified by UHPLC in the polyphenols were docked for their inhibitory power on protein casein kinase-1, glycogen synthase kinase-3-ß, cyclooxegenase-2, tyrosine kinase, and TRADD. Luteolin and kaempferol are the main compounds identified in C. europaea polyphenols. The group treated with polyphenols showed the greatest wound contractions and all tested extracts presented a significant antinociceptive effect. Polyphenols showed a remarkable antitumoral activity against the K562, HL60 and Huh-7 cell lines. Saponins exerted an important cytotoxic effect against the Huh-7 cell line, whereas no cytotoxicity was observed for the hydroethanolic and flavonoids extracts. Hesperetin and trimethoxyflavone presented the highest docking G-score on tyrosine kinase and cyclooxygenase, respectively.

Discovery of a Potent Highly Biased MOR Partial Agonist among Diastereomeric C9-Hydroxyalkyl-5-phenylmorphans.

All possible diastereomeric C9-hydroxymethyl-, hydroxyethyl-, and hydroxypropyl-substituted 5-phenylmorphans were synthesized to explore the three-dimensional space around the C9 substituent in our search for potent MOR partial agonists. These compounds were designed to lessen the lipophilicity observed with their C9-alkenyl substituted relatives. Many of the 12 diastereomers that were obtained were found to have nanomolar or subnanomolar potency in the forskolin-induced cAMP accumulation assay. Almost all these potent compounds were fully efficacious, and three of those chosen for in vivo evaluation, 15, 21, and 36, were all extremely G-protein biased; none of the three compounds recruited beta-arrestin2. Only one of the 12 diastereomers, 21 (3-((1S,5R,9R)-9-(2-hydroxyethyl)-2-phenethyl-2-azabicyclo[3.3.1]nonan-5-yl)phenol), was a MOR partial agonist with good, but not full, efficacy (Emax = 85%) and subnanomolar potency (EC50 = 0.91 nM) in the cAMP assay. It did not have any KOR agonist activity. This compound was unlike morphine in that it had a limited ventilatory effect in vivo. The activity of 21 could be related to one or more of three well-known theories that attempt to predict a dissociation of the desired analgesia from the undesirable opioid-like side-effects associated with clinically used opioids. In accordance with the theories, 21 was a potent MOR partial agonist, it was highly G-protein biased and did not attract beta-arrestin2, and it was found to have both MOR and DOR agonist activity. All the other diastereomers that were synthesized were either much less potent than 21 or had either too little or too much efficacy for our purposes. It was also noted that a C9-methoxymethyl compound with 1R,5S,9R stereochemistry (41) was more potent than the comparable C9-hydroxymethyl compound 11 (EC50 = 0.65 nM for 41 vs. 2.05 nM for 11). Both 41 and 11 were fully efficacious.

Design, synthesis, and biological evaluation of new 2-(4-(methylsulfonyl)phenyl)-N-phenylimidazo[1,2-a]pyridin-3-amine as selective COX-2 inhibitors.

Cyclooxygenase (COX), which plays a role in converting arachidonic acid to inflammatory mediators, could be inhibited by non-steroidal anti-inflammatory drugs (NSAIDs). Although potent NSAIDs are available for the treatment of pain, fever, and inflammation, some side effects, such as gastrointestinal ulcers, limit the use of these medications. In recent years, selective COX-2 inhibitors with a lower incidence of adverse effects attained an important position in medicinal chemistry. In order to introduce some new potent COX-2 inhibitors, a new series of 2-(4-(methylsulfonyl)phenyl)-N-phenylimidazo[1,2-a]pyridin-3-amines was designed, synthesized, and evaluated. The docking studies performed by AutoDock Vina demonstrated that docked molecules were positioned as well as a crystallographic ligand in the COX-2 active site, and SO2Me pharmacophore was inserted into the secondary pocket of COX-2 and formed hydrogen bonds with the active site. The designed compounds were synthesized through two-step reactions. In the first step, different 1-(4-(methylsulfonyl)phenyl)-2-(phenylamino)ethan-1-one derivatives were obtained by the reaction of aniline derivatives and α-bromo-4-(methylsulfonyl)acetophenone. Then, condensation of intermediates with different 2-aminopyridines gave final compounds. Enzyme inhibition assay and formalin test were performed to evaluate the activity of these compounds. Among these compounds, 8-methyl-2-(4-(methylsulfonyl)phenyl)-N-(p-tolyl)imidazo[1,2-a]pyridin-3-amine (5n) exhibited the highest potency (IC50 = 0.07 µM) and selectivity (selectivity index = 508.6) against COX-2 enzyme (selectivity index: COX-1 IC50/COX-2 IC50). The antinociceptive activity assessment via the formalin test showed that nine derivatives (5a, 5d, 5h, 5i, 5k, 5q, 5r, 5s, and 5t) possessed significant activity compared with the control group with a p value less than 0.05.

Preclinical Pharmacokinetic and Pharmacodynamic Investigation of 5'-Methoxynobiletin from Ageratum conyzoides: In vivo and In silico Approaches.

PURPOSE: 5'-methoxynobiletin (5'-MeONB), a polymethoxyflavone isolated from A. conyzoides, has shown anti-inflammatory property. Nevertheless, the antinociceptive activity and pre-clinical pharmacokinetics (PK) characteristics of 5'-MeONB remain unknown. Considering the anti-inflammatory potential of the 5'-MeONB, this study aimed to investigate the pre-clinical PK behavior of 5'-MeONB, as well as its time course antinociceptive activity. METHODS: 5'-MeONB plasma concentrations were determined in Wistar rats after intravenous (i.v.) (10 mg/kg) and oral (50 mg/kg) administration, and in Swiss mice after oral administration (100 mg/kg). Plasma samples were deproteinization and 5'-MeONB quantified by a validated UPLC-MS method. Additionally, the antinociceptive activity of 5'-MeONB was evaluated after 15, 30, 60, 180 and 360 min following oral administration on the acute nocifensive behavior of mice induced by formalin. RESULTS: 5'-MeONB rats and mice plasma concentration-time profiles were best one-compartment model. After i.v. administration to rats, a short half-life, a high clearance and moderate volume of distribution at steady state were observed. Similar results were obtained after oral administration. The oral bioavailability ranged from 8 to 11%. Additionally, 5'-MeONB exhibited antinociceptive activity in both formalin phases, especially in the inflammatory phase of the model, inhibiting 68% and 91% of neurogenic and inflammatory responses, respectively, after 30 min of oral administration. CONCLUSIONS: The results described here provide novel insights on 5'-MeONB pharmacokinetics and pharmacodynamic effect, serving as support for future studies to confirm this compound as anti-nociceptive and anti-inflammatory effective agent.

Synthesis and antinociceptive activity of four 1H-isoindolo-1,3(2H)-diones.

The present study aimed to design and synthesize a series of 2-hydroxy-3-(4-aryl-1-piperazinyl)propyl phthalimide derivatives, which are analogs of 1H-pyrrolo[3,4-c]pyridine-1,3(2H)-dione derivatives with proven analgesic effect. In accordance with the basic principle proposed by Lipinski's rule, the probable bioavailabilities of the F1-F4 phthalimides were assessed. The obtained values indicate good absorption after oral administration and the ability to cross the blood-brain barrier. The four compounds F1-F4 differing in the type of pharmacophore in the phenyl group of the 2-hydroxy-3-(4-aryl-1-piperazinyl)propyl on the imide nitrogen atom (R, F1-F3) and the 4-benzhydryl analog (F4) were selected for in vitro and in vivo studies. Based on the in vitro studies, the effects of compounds F1-F4 on cell viability/proliferation and COX-2 levels were evaluated. Moreover, using in vivo methods, the compounds were tested for antinociceptive activity in models of acute pain (the writhing and the hot-plate tests) in mice. Their influence on the motor coordination effect and locomotor activity was also tested. The obtained results revealed that the compounds F1-F4 strongly suppress the pain of peripheral origin and to a lesser extent (F1-F3) pain of central/supraspinal origin. In the in vitro studies, F1-F4 reduced the COX-2 level in lipopolysaccharide-activated RAW 264.7 cells, which suggests their anti-inflammatory activity.

Five new Erythrina alkaloids from the stems of Erythrina corallodendron.

Five new Erythrina alkaloids and five known E. alkaloids were isolated from a 95% ethanol extract of the stems of Erythrina corallodendron L. Their chemical structures were elucidated by UV, IR, HRESIMS, NMR and X-ray. Furthermore, the analgesic activities of E. alkaloids 1, 2 and 6 were evaluated by using an acetic acid-induced writhing test in mice, and their writhing inhibition rates were 67.9%, 64.6% and 70.3% at doses of 20 mg/kg, respectively.

Antinociceptive C19-diterpenoid alkaloids from the root of Aconitum episcopale.

A chemical investigation on the roots of Aconitum episcopale afforded three undescribed aconitine-type C19-diterpenoid alkaloids, episcopalines A-C (1-3). The structures of the new compounds were elucidated by spectroscopic analysis (NMR, IR, UV, and MS). The isolated alkaloids were tested in vivo for their antinociceptive properties. As a result, episcopaline B (2) showed potent antinociceptive effect and its ID50 value (55.0 µmol/kg) was 2-fold less than those of the positive control drugs aspirin and acetaminophen.

New lignans and diterpenoid glycosides from the fruits of Xanthium italicum Moretti.

A pair of new lignans [(+)- 1 and (-)- 1] and three new compounds (2-4), together with a known compound 5, were isolated from the fruits of Xanthium italicum Moretti. The structures of these compounds were determined on the basis of spectroscopic analysis, particularly HR-ESI-MS and 1 D and 2 D NMR. Compounds 2 and 3 showed antinociceptive effects in an acetic acid-induced writhing test in mice with the writhe inhibition rates of 80.50% and 67.89% at the dose of 20 mg/kg, respectively.

Oral administration of essential oil from Psidium glaziovianum Kiaersk leaves alleviates pain and inflammation in mice.

Plants of the genus Psidium have been employed in "in natura" consumption and agroindustry, and owing to the diversity of phytochemicals, the development of new pharmaceutical forms has received remarkable research interest. In this study, the essential oil obtained from Psidium glaziovianum (PgEO) leaves were evaluated antinociceptive and anti-inflammatory activities were evaluated in mouse models. Initially, PgEO was characterized by gas chromatography-mass spectrometry and gas chromatography with flame ionization detection, and the profile was dominated by sesquiterpene compounds. In the evaluation of acute antinociceptive activity (abdominal contortions induced by acetic acid, formalin, tail immersion, and hot plate tests), PgEO promoted a reduction in nociception in the chemical and thermal models. Additionally, the potential underlying mechanism was investigated using pain pathway blockers, and the results revealed a combined action of opioidergic and muscarinic pathways. The anti-inflammatory potential was confirmed by anti-edematogenic action, reduced cell migration, pro-inflammatory cytokine production, and granuloma formation in chronic processes. This study provides evidence that PgEO can be effective for the treatment of pain and acute and chronic inflammation.

Design, synthesis, and preliminary evaluation of a potential synthetic opioid rescue agent.

BACKGROUND: One of the most prominent opioid analgesics in the United States is the high potency agonist fentanyl. It is used in the treatment of acute and chronic pain and as an anesthetic adjuvant. When used inappropriately, however, ingestion of just a few milligrams of fentanyl or other synthetic opioid can cause opioid-induced respiratory depression (OIRD), often leading to death. Currently, the treatment of choice for OIRD is the opioid receptor antagonist naloxone. Recent reports, however, suggest that higher doses or repeated dosing of naloxone (due to recurrence of respiratory depression) may be required to reverse fully fentanyl-induced respiratory depression, rendering this treatment inadequate. To combat this synthetic opioid overdose crisis, this research aims at identifying a novel opioid reversal agent with enhanced efficacy towards fentanyl and other synthetic opioids. METHODS: A series of naltrexone analogues were characterized for their ability to antagonize the effects of fentanyl in vitro utilizing a modified forskolin-induced cAMP accumulation assay. Lead analogue 29 was chosen to undergo further PK studies, followed by in vivo pharmacological analysis to determine its ability to antagonize opioid-induced antinociception in the hot plate assay. RESULTS: A series of potent MOR antagonists were identified, including the highly potent analogue 29 (IC50 = 2.06 nM). Follow-up PK studies revealed 29 to possess near 100% bioavailability following IP administration. Brain concentrations of 29 surpassed plasma concentrations, with an apparent terminal half-life of ~ 80 min in mice. In the hot plate assay, 29 dose-dependently (0.01-0.1 mg/kg; IP) and fully antagonized the antinociception induced by oxycodone (5.6 mg/kg; IP). Furthermore, the dose of 29 that is fully effective in preventing oxycodone-induced antinociception (0.1 mg/kg) was ineffective against locomotor deficits caused by the KOR agonist U50,488. CONCLUSIONS: Methods have been developed that have utility to identify enhanced rescue agents for the treatment of OIRD. Analogue 29, possessing potent MOR antagonist activity in vitro and in vivo, provides a promising lead in our search for an enhanced synthetic opioid rescue agent.

Synthetic efforts toward the bicyclo[3.2.1]octane fragment of rhodojaponin III.

Rhodojaponin III is a grayanane-type diterpenoid natural product with a novel chemical scaffold. It shows potent antinociceptive activity and may represent a new class of natural non-opioid analgesics with a novel mode of action. We explored the Au(I)-catalyzed Conia-ene cyclization and the Mn(III)-mediated radical cyclization of alkynyl ketones for the synthesis of the bicyclo[3.2.1]octane fragment of rhodojaponin III. These strategies will be applicable in the synthesis of rhodojaponin III and analogs for future biological studies.

Antinociceptive and sedative activity of Vernonia patula and predictive interactions of its phenolic compounds with the cannabinoid type 1 receptor.

When tested in the acetic acid-induced writhing and formalin-induced paw-licking tests, the ethanol extract of Vernonia patula (VP) aerial parts showed significant antinociceptive activity. In neuropharmacological tests, it also significantly delayed the onset of sleep, increased the duration of sleeping time, and significantly reduced the locomotor activity and exploratory behaviour of mice. Five phenolic compounds, namely gallic acid, vanillic acid, caffeic acid, quercetin and kaempferol, were detected in VP following HPLC-DAD analysis. The presence of these phenolic compounds in VP provides some support for the observed antinociceptive and sedative effects. A computational study was performed to predict the binding affinity of gallic acid, vanillic acid, caffeic acid, quercetin and kaempferol towards the cannabinoid type 1 (CB1) receptor. Caffeic and vanillic acid showed the highest probable ligand efficiency indices towards the CB1 target. Vanillic acid displayed the best blood-brain barrier penetration prediction score. These findings provide some evidence for the traditional use of VP to treat pain.