Aryl-oxadiazole Schiff bases: Synthesis, α-glucosidase in vitro inhibitory activity and their in silico studies

Effective α-glycosidase inhibitors based on polyphenolic benzothiazole heterocycles

α-Glycosidase inhibition is one of the main approaches to treat Diabetes mellitus. Polyphenolic moieties are known to be responsible for yielding exhibit potent α-glycosidase inhibitory effects. In addition, compounds containing benzothiazole and Schiff base functionalities were previously reported to show α-glycosidase inhibition. In this paper, the synthesis of seven new phloroglucinol-containing benzothiazole Schiff base derivatives through the reaction of 6-substituted-2-aminobenzothiazole compounds with 2,4,6-trihydroxybenzaldehyde using acetic acid as a catalyst was reported. The synthesized compounds were characterized using spectroscopic methods such as FT-IR, 1H NMR, 13C NMR, and elemental analysis. The synthesized compounds were evaluated for their inhibitory effects on α-glycosidase, compounds 3f and 3g were found to show significant inhibitory properties when compared to the positive control. The IC50 values of 3f and 3g were calculated as 24.05 ± 2.28 and 18.51 ± 1.19 µM, respectively. Kinetic studies revealed that compounds 3f and 3g exhibited uncompetitive mode of inhibition against α-glycosidase. Molecular modeling predicted druglikeness for the title compounds and underpinned the importance of phloroglucinol hydroxyls for interacting with the key residues of α-glycosidase.

Synthesis,Antidiabetic and Antitubercular Evaluation of Quinoline-pyrazolopyrimidine hybrids and Quinoline-4-Arylamines

Two libraries of quinoline-based hybrids 1-(7-chloroquinolin-4-yl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine and 7-chloro-N-phenylquinolin-4-amine were synthesized and evaluated for their α-glucosidase inhibitory and antioxidant properties. Compounds with 4-methylpiperidine and para-trifluoromethoxy groups, respectively, showed the most promising α-glucosidase inhibition activity with IC50 =46.70 and 40.84 μM, compared to the reference inhibitor, acarbose (IC50 =51.73 μM). Structure-activity relationship analysis suggested that the cyclic secondary amine pendants and para-phenyl substituents account for the variable enzyme inhibition. Antioxidant profiling further revealed that compounds with an N-methylpiperazine and N-ethylpiperazine ring, respectively, have good DPPH scavenging abilities with IC50 =0.18, 0.58 and 0.93 mM, as compared to ascorbic acid (IC50 =0.05 mM), while the best DPPH scavenger is NO2 -substituted compound (IC50 =0.08 mM). Also, compound with N-(2-hydroxyethyl)piperazine moiety emerged as the best NO radical scavenger with IC50 =0.28 mM. Molecular docking studies showed that the present compounds are orthosteric inhibitors with their quinoline, pyrimidine, and 4-amino units as crucial pharmacophores furnishing α-glucosidase binding at the catalytic site. Taken together, these compounds exhibit dual potentials; i. e., potent α-glucosidase inhibitors and excellent free radical scavengers. Hence, they may serve as structural templates in the search for agents to manage Type 2 diabetes mellitus. Finally, in preliminary assays investigating the anti-tubercular potential of these compounds, two pyrazolopyrimidine series compounds and a 7-chloro-N-phenylquinolin-4-amine hybrid showed sub-10 μM whole-cell activities against Mycobacterium tuberculosis.

Polyhydroquinoline derivatives for diabetic management: synthesis, in vitro and in silico approaches

Background: Medication used to treat Type 2 diabetes by decreasing the absorption of carbohydrates in the intestine consists of α-glucosidase inhibitors. Polyhydroquinoline derivatives have attracted interest as excellent antidiabetic agents. Methods: Polyhydroquinoline derivatives (1-17) were synthesized and tested for in vitro α-glucosidase inhibitory activity. Results: All the synthesized compounds exhibited excellent to good inhibitory activity, having IC50 values from 1.23 ± 0.03 to 73.85 ± 0.61 μM, compared with the standard drug, acarbose. The binding mechanism of these derivatives with α-glucosidase was deduced by docking studies and indicated that a slight variation in the orientation of compounds, affects their binding capability. Conclusion: In order to find new antidiabetic drugs, this study has discovered prospective lead candidates.

Multitargeted inhibition of key enzymes associated with diabetes and Alzheimer's disease by 1,3,4-oxadiazole derivatives: Synthesis, in vitro screening, and computational studies

A library of 22 derivatives of 1,3,4-oxadiazole-2-thiol was synthesized, structurally characterized, and assessed for its potential to inhibit α-amylase, α-glucosidase, acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and antioxidant activities. Most of the tested compounds demonstrated good to moderate inhibition potential; however, their activity was lower than that of the standard acarbose. Significantly, compound 3f exhibited the highest inhibition potential against α-glucosidase and α-amylase enzymes, with IC50 values of 18.52 ± 0.09 and 20.25 ± 1.05 µM, respectively, in comparison to the standard acarbose (12.29 ± 0.26; 15.98 ± 0.14 µM). Compounds also demonstrated varying degrees of inhibitory potential against AChE (IC50  = 9.25 ± 0.19 to 36.15 ± 0.12 µM) and BChE (IC50  = 10.06 ± 0.43 to 35.13 ± 0.12 µM) enzymes compared to the standard donepezil (IC50  = 2.01 ± 0.12; 3.12 ± 0.06 µM), as well as DPPH (IC50  = 20.98 ± 0.06 to 52.83 ± 0.12 µM) and ABTS radical scavenging activities (IC50  = 22.29 ± 0.18 to 47.98 ± 0.03 µM) in comparison to the standard ascorbic acid (IC50  = 18.12 ± 0.15; 19.19 ± 0.72). The kinetic investigations have demonstrated that the compounds exhibit competitive-type inhibition for α-amylase, noncompetitive-type inhibition for α-glucosidase and AChE, and mixed-type inhibition for BChE. Additionally, a molecular docking study was performed on all synthetic oxadiazoles to explore the interaction details of these compounds with the active sites of the enzymes.

Synthesis, molecular structure and urease inhibitory activity of novel bis-Schiff bases of benzyl phenyl ketone: A combined theoretical and experimental approach

Background

Urease belongs to the family of amid hydrolases with two nickel atoms in their core structure. On the basis of literature survey, this research work is mainly focused on the study of bis-Schiff base derivatives of benzyl phenyl ketone nucleus.

Objective

Synthesis of benzyl phenyl ketone based bis-Schiff bases in search of potent urease inhibitors.

Method

In the current work, bis-Schiff bases were synthesized through two steps reaction by reacting benzyl phenyl ketone with excess of hydrazine hydrate in ethanol solvent in the first step to get the desired hydrazone. In last, different substituted aromatic aldehydes were refluxed in catalytic amount of acetic acid with the desired hydrazone to obtain bis-Schiff base derivatives in tremendous yields. Using various spectroscopic techniques including FTIR, HR-ESI-MS, and ¹H NMR spectroscopy were used to clarify the structures of the created bis-Schiff base derivatives.

Results

The prepared compounds were finally screened for their in-vitro urease inhibition activity. All the synthesized derivatives (3-9) showed excellent to less inhibitory activity when compared with standard thiourea (IC₅₀ = 21.15 ± 0.32 µM). Compounds 3 (IC₅₀ = 22.21 ± 0.42 µM), 4 (IC₅₀ = 26.11 ± 0.22 µM) and 6 (IC₅₀ = 28.11 ± 0.22 µM) were found the most active urease inhibitors near to standard thiourea among the synthesized series. Similarly, compound 5 having IC₅₀ value of 34.32 ± 0.65 µM showed significant inhibitory activity against urease enzyme. Furthermore, three compounds 7, 8, and 9 exhibited less activity with IC₅₀ values of 45.91 ± 0.14, 47.91 ± 0.14, and 48.33 ± 0.72 µM respectively. DFT used to calculate frontier molecular orbitals including; HOMO and LUMO to indicate the charge transfer from molecule to biological transfer, and MEP map to indicate the chemically reactive zone suitable for drug action. The electron localization function (ELF), non-bonding orbitals, AIM charges are also calculated. The docking study contributed to the analysis of urease protein binding.

Synthetic α-glucosidase inhibitors as promising anti-diabetic agents: Recent developments and future challenges

Diabetes mellitus is one of the biggest challenges for the scientific community in the 21st century. It is a well-recognized multifactorial health problem contributes significantly to high mortality rates by causing serious health complications mainly related to cardiovascular diseases, kidney damage and neuropathy. The inhibition of α-glucosidase (enzyme that catalyses starch hydrolysis in the intestine) is an effective therapeutic approach for controlling hyperglycemia associated with type-2 diabetes. However, the presently approved drugs/inhibitors such as acarbose, miglitol and voglibose have several undesirable gastrointestinal side effects impeding their applications. Therefore, search for novel and more effective inhibitors with reduced side effects and less cost remains a fascinating area of research. In this context, a large variety of α-glucosidase inhibitors have been identified in recent years that demands attention from drug development community. This review is therefore an effort to summarize and highlight the promising α-glucosidase inhibitors especially those which are primarily based on aromatic heterocyclic scaffolds such as coumarin, imidazole, isatin, pyrimidine, quinazoline, triazine, thiazole etc, having improved safety and pharmacological profiles.

Research progress on the synthesis and pharmacology of 1,3,4-oxadiazole and 1,2,4-oxadiazole derivatives: a mini review

Oxadiazole is a five-membered heterocyclic compound containing two nitrogen atoms and one oxygen atom. The 1,3,4-oxadiazole and 1,2,4-oxadiazole have favourable physical, chemical, and pharmacokinetic properties, which significantly increase their pharmacological activity via hydrogen bond interactions with biomacromolecules. In recent years, oxadiazole has been demonstrated to be the biologically active unit in a number of compounds. Oxadiazole derivatives exhibit antibacterial, anti-inflammatory, anti-tuberculous, anti-fungal, anti-diabetic and anticancer activities. In this paper, we report a series of compounds containing oxadiazole rings that have been published in the last three years only (2020-2022) as there was no report or their activities described in any article in 2019, which will be useful to scientists in research fields of organic synthesis, medicinal chemistry, and pharmacology.

Benzimidazole Bearing Thiosemicarbazone Derivatives Act as Potent α-Amylase and α-Glucosidase Inhibitors; Synthesis, Bioactivity Screening and Molecular Docking Study

Diabetes mellitus is one of the most chronic metabolic diseases. In the past few years, our research group has synthesized and evaluated libraries of heterocyclic analogs against α-glucosidase and α-amylase enzymes and found encouraging results. The current study comprises the evaluation of benzimidazole-bearing thiosemicarbazone as antidiabetic agents. A library of fifteen derivatives (7-21) was synthesized, characterized via different spectroscopic techniques such as HREI-MS, NMR, and screened against α-glucosidase and α-amylase enzymes. All derivatives exhibited excellent to good biological inhibitory potentials. Derivatives 19 (IC₅₀ = 1.30 ± 0.20 µM and 1.20 ± 0.20 µM) and 20 (IC₅₀ = 1.60 ± 0.20 µM and 1.10 ± 0.01 µM) were found to be the most potent among the series when compared with standard drug acarbose (IC₅₀ = 11.29 ± 0.07 and 11.12 ± 0.15 µM, respectively). These derivatives may potentially serve as the lead candidates for the development of new therapeutic representatives. The structure-activity relationship was carried out for all molecules which are mainly based upon the pattern of substituent/s on phenyl rings. Moreover, in silico docking studies were carried out to investigate the active binding mode of selected derivatives with the target enzymes.

Antidiabetic, antioxidant, and anti-obesity effects of phenylthio-ethyl benzoate derivatives, and molecular docking study regarding α-amylase enzyme

In addition to their wide therapeutic application, benzoates and benzoic acid derivatives are the most commonly utilized food preservatives. The purpose of this study was to estimate the antioxidant, anti-diabetic, and anti-obesity activities of four 2-(phenylthio)-ethyl benzoate derivatives utilizing standard biomedical assays. The results revealed that the 2a compound has potent antidiabetic activity through the inhibition of α-amylase and α-glycosidase with IC₅₀ doses of 3.57 ± 1.08 and 10.09 ± 0.70 µg/ml, respectively, compared with the positive control acarbose (IC₅₀ = 6.47 and 44.79 µg/ml), respectively. In addition, by utilizing the β-carotene linoleic acid and DPPH methods, the 2a compound showed the highest antioxidant activity compared with positive controls. Moreover, the 2a compound showed potential anti-lipase activity with an IC₅₀ dose of 107.95 ± 1.88 µg/ml compared to orlistat (IC₅₀ = 25.01 ± 0.78 µg/ml). A molecular docking study was used to understand the interactions between four derivatives of (2-(phenylthio)-ethyl benzoate with α-amylase binding pocket. The present study concludes that the 2a compound could be exploited for further antidiabetic, antioxidant, and anti-obesity preclinical and clinical tests and design suitable pharmaceutical forms to treat these global health problems.

Induction of anxiolytic, antidepressant and analgesic effects by Shiff base of (E)-3-(1H-imidazol-4-yl)-2-((2-oxoindolin-3-ylidene)amino)propanoic acid derivatives in diabetic rats

Diabetes mellitus is a metabolic disorder with several psychological problems such as anxiety, depression, and pain sense. This study aimed to evaluate the effect of Schiff base on the modulation of anxiety, depression, and pain behaviors in diabetic rats. Anxiety, depression, and pain behaviors were evaluated by elevated plus maze (EPM), forced swim test (FST), and hot-plate test, respectively. The results indicated that induction of diabetes decreased time spent in open arms (OAT) in the EPM whereas injection of insulin (1 ml/kg), glibenclamide (5 mg/kg), and Schiff base II (100 mg/kg) increased OAT in the EPM. So, induction of diabetes in rats caused an anxiogenic effect that this effect reversed by drug treatment. Interestingly, co-treatment of insulin and glibenclamide along with an ineffective dose of Schiff base II potentiated anxiolytic behavior in diabetic rats. Furthermore, induction of diabetes increased immobility time in the FST but administration of insulin (1 ml/kg), glibenclamide (5 mg/kg), and Schiff base II (25, 50, and 100 mg/kg) decreased immobility time in the FST which indicated depressant effect in diabetic rats without drug-treatment and antidepressant effect in diabetic rats with drug-treatment. Additionally, induction of diabetes decreased latency in the hot-plate test while injection of insulin (1 ml/kg), glibenclamide (5 mg/kg), Schiff base I (50 mg/kg), and Schiff base II (25, 50, and 100 mg/kg) enhanced latency in the hot-plate test which revealed hyperalgesic effect in diabetic rats without drug-treatment and analgesic effect in diabetic rats with drug-treatment. Consequently, induction of diabetes-induced anxiogenic, depressant, and hyperalgesia effects that administration of insulin, glibenclamide, Schiff bases I, and II reversed these effects.