Suat Sari

Coumarin or benzoxazinone based novel carbonic anhydrase inhibitors: synthesis, molecular docking and anticonvulsant studies

Abstract Among many others, coumarin derivatives are known to show human carbonic anhydrase (hCA) inhibitory activity. Since hCA inhibition is one of the underlying mechanisms that account for the activities of some antiepileptic drugs (AEDs), hCA inhibitors are expected to have anti-seizure properties. There are also several studies reporting compounds with an imidazole and/or benzimidazole moiety which exert these pharmacological properties. In this study, we prepared fifteen novel coumarin-bearing imidazolium and benzimidazolium chloride, nine novel benzoxazinone-bearing imidazolium and benzimidazolium chloride derivatives and evaluated their hCA inhibitory activities and along with fourteen previously synthesized derivatives we scanned their anticonvulsant effects. As all compounds inhibited purified hCA isoforms I and II, some of them also proved protective against Maximal electroshock seizure (MES) and ScMet induced seizures in mice. Molecular docking studies with selected coumarin derivatives have revealed that these compounds bind to the active pocket of the enzyme in a similar fashion to that previously described for coumarin derivatives.

α-Glucosidase inhibitory effect of Potentilla astracanica and some isoflavones: Inhibition kinetics and mechanistic insights through in vitro and in silico studies

α-Glucosidase enzyme inhibitors are clinically used for the treatment of Type 2 diabetes mellitus. We tested α-glucosidase inhibitory effects of Potentilla astracanica Jacq. extracts (1, 2), two compounds isolated from these extracts, prunetin 5-O-β-glucopyranoside (3) and genistein 5-O-β-glucopyranoside (4), and their aglycon forms (5 and 6). All the tested materials possessed remarkable α-glucosidase inhibitor activity compared to the positive control, acarbose. Genistein (6) showed the highest activity with an IC50 value of 1.47 (±0.11) μg/ml. An enzyme kinetics analysis revealed that 3 and 6 were uncompetitive, 5 was noncompetitive, and 4 was competitive inhibitors. Using molecular modeling techniques we tried to provide insight into molecular mechanisms of their activity and how allosteric binding of 6 affected binding interactions between the agonist (maltose) and the enzyme.

New (arylalkyl)azole derivatives showing anticonvulsant effects could have VGSC and/or GABAAR affinity according to molecular modeling studies.

(Arylalkyl)azoles (AAAs) emerged as a novel class of antiepileptic agents with the invention of nafimidone and denzimol. Several AAA derivatives with potent anticonvulsant activities have been reported so far, however neurotoxicity was usually an issue. We prepared a set of ester derivatives of 1-(2-naphthyl)-2-(1H-1,2,4-triazol-1-yl)ethanone oxime and evaluated their anticonvulsant and neurotoxic effects in mice. Most of our compounds were protective against maximal electroshock (MES)- and/or subcutaneous metrazol (s.c. MET)-induced seizures whereas none of them showed neurotoxicity. Nafimidone and denzimol have an activity profile similar to that of phenytoin or carbamazepine, both of which are known to inhibit voltage-gated sodium channels (VGSCs) as well as to enhance γ-aminobutiric acid (GABA)-mediated response. In order to get insights into the effects of our compounds on VGSCs and A-type GABA receptors (GABAARs) we performed docking studies using homology model of Na+ channel inner pore and GABAAR as docking scaffolds. We found that our compounds bind VGSCs in similar ways as phenytoin, carbamazepine, and lamotrigine. They showed strong affinity to benzodiazepine (BZD) binding site and their binding interactions were mainly complied with the experimental data and the reported BZD binding model.

Potential of Potentilla inclinata and its polyphenolic compounds in α-glucosidase inhibition: Kinetics and interaction mechanism merged with docking simulations

In the present study we aimed to identify the α-glucosidase enzyme inhibitory potential of Potentilla inclinata Vill. MeOH and n-BuOH extracts which possessed remarkable α-glucosidase enzyme inhibitory effects with IC50 values of 1.06±0.02 and 0.93±0.01μg/ml respectively, compared to that of acarbose (IC50 31.92±0.17). Thus, BuOH extract was chosen for further phytochemical investigations. A phenolic acid, six flavonol glycosides, and two hydrolysable tannins were isolated from the most active n-BuOH extract of the title plant. Structures of the isolated compounds were elucidated by 1D- and 2D-NMR experiments. All the compounds exhibited remarkable α-glucosidase inhibitory activity compared to the positive control, acarbose. Rutin (2) showed the highest activity with an IC50 value of 26.31±0.02μg/ml. An enzyme kinetics analysis revealed that compounds 5 and 7 were competitive, 4 and 6 noncompetitive, and 3 was uncompetitive inhibitors of α-glucosidase enzyme. Molecular docking studies were performed to get insights into inhibition mechanisms of the isolates considering their inhibition type using various binding sites of the enzyme model we previously reported.

Discovery of potent α-glucosidase inhibitor flavonols: Insights into mechanism of action through inhibition kinetics and docking simulations

Beside other pharmaceutical benefits, flavonoids are known for their potent α-glucosidase inhibition. In the present study, we investigated α-glucosidase inhibitory effects of structurally related 11 flavonols, among which quercetin-3-O-(3″-O-galloyl)-β-galactopyranoside (8) and quercetin 3-O-(6″-O-galloyl)-β-glucopyranoside (9) showed significant inhibition compared to the positive control, acarbose, with IC50 values of 0.97 ± 0.02 and 1.35 ± 0.06 µM, respectively. It was found that while sugar substitution to C3-OH of C ring reduced the α-glucosidase inhibitory effect, galloyl substitution to these sugar units increased it. An enzyme kinetics analysis revealed that 7 was competitive, whereas 1, 2, 8, and 9 were uncompetitive inhibitors. In the light of these findings, we performed molecular docking studies to predict their inhibition mechanisms at atomic level.

New Anti‐Seizure (Arylalkyl)azole Derivatives: Synthesis, In Vivo and In Silico Studies

(Arylalkyl)azoles are a class of antiepileptic compounds including nafimidone, denzimol, and loreclezole (LRZ). Nafimidone and denzimol are thought to inhibit voltage‐gated sodium channels (VGSCs) and enhance γ‐aminobutyric acid (GABA)‐mediated response. LRZ, a positive allosteric modulator of A‐type GABA receptors (GABAARs), was reported to be sensitive to Asn265 of the β2/β3 subunit. Here, we report new N‐[1‐(4‐chlorophenyl)‐2‐(1H‐imidazol‐1‐yl)ethylidene]hydroxylamine esters showing anticonvulsant activity in animal models, including the 6‐Hz psychomotor seizure test, a model for therapy‐resistant partial seizure. We performed molecular docking studies for our active compounds using GABAAR and VGSC homology models. They predicted high affinity to the benzodiazepine binding site of GABAAR in line with the experimental results. Also, the binding mode and interactions of LRZ in its putative allosteric binding site of GABAAR is elucidated.

GPCR Modulation of Thieno[2,3-b]pyridine Anti-Proliferative Agents

A panel of docking scaffolds was developed for the known molecular targets of the anticancer agents, thieno[2,3-b]pyridines, in order to glean insight into their mechanism of action. The reported targets are the copper-trafficking antioxidant 1 protein, tyrosyl DNA phosphodiesterase 1, the colchicine binding site in tubulin, adenosine A2A receptor, and, finally, phospholipase C-δ1. According to the panel, the A2A receptor showed the strongest binding, inferring it to be the most plausible target, closely followed by tubulin. To investigate whether the thieno[2,3-b]pyridines modulate G protein-coupled receptors (GPCRs) other than A2A, a screen against 168 GPCRs was conducted. According to the results, ligand 1 modulates five receptors in the low µM region, four as an antagonist; CRL-RAMP3 (IC50—11.9 µM), NPSR1B (IC50—1.0 µM), PRLHR (IC50—9.3 µM), and CXCR4 (IC50—6.9 µM). Finally, one agonist, GPRR35, was found (EC50 of 7.5 µM). Molecular modelling showed good binding to all of the receptors investigated; however, none of these surpass the A2A receptor. Furthermore, the newly-identified receptors are relatively modestly expressed in the cancer cell lines most affected by the thieno[2,3-b]pyridines, making them less likely to be the main targets of the mechanism of action for this compound class. Nevertheless, new modulators against GPCRs are of an interest as potential hits for further drug development.

Synthesis and anticonvulsant screening of 1,2,4-triazole derivatives

BACKGROUND Currently available antiepileptic drugs offer limited symptomatic treatment and fail to cure more than 30% of the epileptic seizures. (Arylalkyl)azoles are a class of anticonvulsants including nafimidone and loreclezole. Here, we report the design and synthesis of new (arylalkyl)azoles in N-[1-(4-chlorophenyl)-2-(1H-1,2,4-triazol-1-yl)ethylidene]hydroxylamine ester structure, their anticonvulsant screening and in silico prediction studies of their pharmacokinetic properties. METHODS The title compounds were synthesized according to the Steglich esterification of N-[1-(4-chlorophenyl)-2-(1H-1,2,4-triazol-1-yl)ethylidene]hydroxylamine with various carboxylic acids. Anticonvulsant identification and quantification tests were performed in mice by the Epilepsy Therapy Screening Program (ETSP) of the National Institutes of Health (NIH) using 6Hz psychomotor, maximal electroshock (MES), and rotorod tests. Their physicochemical and pharmacokinetic properties were calculated using QikProp. RESULTS Most of the compounds showed protection against 6Hz- and/or MES-induced seizures. 4a, 4b, and 4g were active at 100mg/kg, 4g was active in both tests without neurotoxicity. According to the QikProp calculations the title compounds were druglike and had some favourable properties such as high membrane permeability and oral absorptivity. CONCLUSION Anticonvulsant screening of a set N-[1-(4-chlorophenyl)-2-(1H-1,2,4-triazol-1-yl)ethylidene]hydroxylamine esters yielded some active derivatives in 6Hz and MES test. Especially, 4g emerged as a promising compound with activity at 100mg/kg and no toxicity. The compounds were predicted to be drug like and have good pharmacokinetic properties except hERG inhibition, which needs to be addressed in further optimization studies.

Synthesis, anticonvulsant activity, and molecular modeling studies of novel 1-phenyl/1-(4-chlorophenyl)-2-(1H-triazol-1-yl)ethanol ester derivatives

A series of new ester derivatives were synthesized by the reaction of various acids with 1-phenyl/1-(4-chlorophenyl)-2-(1H-triazol-1-yl)ethanol and in vivo screened for their anticonvulsant activity. The title compounds were screened against MES and ScM seizure tests according to a modified version of the Epilepsy Therapy Screening Program (ETSP) protocol of the National Institutes of Health (NIH). Their neurotoxic effects were evaluated by the rotarod test. All the compounds showed protection against MES and/or ScM-induced seizures at 30 mg/kg without neurotoxicity. More compounds were found active in the ScM test and at lower dose than the MES test. Physicochemical and pharmacokinetic profiles of the compounds were predicted by QikProp. Using molecular docking approach we tried to get insights into their possible anticonvulsant mechanisms.

Tyrosinase inhibition by some flavonoids: Inhibitory activity, mechanism by in vitro and in silico studies

Flavonoids are main polyphenolic groups widely distributed to fruits, vegetables and beverages we consumed daily. They exhibit many biological effects. We tested tyrosinase inhibitor potential of structurally related (1-9) flavonoids and found that all the tested materials possessed tyrosinase inhibitory effect compared to the positive control, kojic acid. 2 exhibited the strongest tyrosinase inhibitory effect with an IC50 value of 40.94 ± 0.78 µM in a competitive manner. According to kinetic analysis 1, 4 and 7 were found to be competitive inhibitors, 3, 5, and 6 noncompetitive inhibitors of tyrosinase. According to the docking studies, A and C ring of the flavonoid structure, hydroxyl substituent at the 7th position, and hydroxyl substituents at para or para and meta position of ring B play key role for competitive inhibition of the enzyme.