Arun K. Rawat

Aza-annulation on the 16-dehydropregnenolone, via tandem intermolecular aldol process and intramolecular Michael addition.

16-Dehydropregnenolone undergoes a smooth annulation with propan-1-amine and aromatic aldehydes. Several amine derivatives of 16- dehydropregnenolone were synthesized and evaluated as inhibitors of DPP-IV. The structures of compounds were confirmed by (1)H, (13)C, NMR and mass spectral analysis. Among 17 compounds evaluated only five compounds 1, 9, 13, 15 and 16 demonstrated significant inhibition of DPP. This study suggest that introduction of appropriate substituents in the 16-dehydropregnenolone plays an important role in DPP-IV inhibitory activity.

Synthesis and antidyslipidemic activity of chalcone fibrates

A series of chalcone based PPAR-α agonists were synthesized and evaluated for their antidyslipidemic activity in high fructose high fat fed dyslipidemic Syrian golden hamsters. Most of the compounds exhibited antidyslipidemic activity. The compounds 4c and 4f have been identified as most potent antidyslipidemics. A definite structure-activity relationship was observed while varying the nature as well as the position of the substituent.

Identification of novel PTP1B inhibitors by pharmacophore based virtual screening, scaffold hopping and docking.

Design and synthesis of protein tyrosine phosphatases-1B (PTP1B) inhibitors are important for the drugs targeted to treat diabetes and obesity. The pharmacophore modeling, docking and scaffold hopping techniques have been applied to discover the novel PTP1B inhibitors. The ten prioritized compounds (115-119, 120-121, 127, 130-131) from the library of 86 compounds were synthesized and found positive in the micro molar range for PTP1B in-vitro inhibitory assays as compared to Suramin (IC50 9.5 μM). Among these five active compounds (115-119) were tested in STZ-s induced diabetic rat model and the most active compound 115 in this test, was further tested in C57BL/KsJ-db/db mice where it significantly improved OGTT along with the fasting and random blood glucose level. The treatment by the compound 115 significantly improved the insulin resistance and insulin signaling by restoring the insulin level and normalizing the serum lipid profile. Compound 115 also augmented the insulin action by modulating the expression of genes involved in insulin signaling like IRS 1-2, PI3K, PTPN1, Akt2, AMPK and PPAR-α. Western blot analysis of both skeletal muscle and liver demonstrated that proteins and intermediate enzymes of insulin signaling were also increased as compared to control group. The compound 115 was also investigated for anti-adipogenic effect on 3T3L-1 cells. The compound 115 inhibited MDI induced lipid accumulation in a dose-dependent manner. The oral bioavailability of compound 115 was ∼10.29% after 30 mg/kg oral dosing assessed in rat.

Design, Synthesis, Biological Screening, and Molecular Docking Studies of Piperazine-Derived Constrained Inhibitors of DPP-IV for the Treatment of Type 2 Diabetes

Novel piperazine‐derived conformationally constrained compounds were designed, synthesized, and evaluated for in vitro Dipeptidyl peptidase‐IV (DPP‐IV) inhibitory activities. From a library of compounds synthesized, 1‐(2‐(4‐(7‐Chloro‐4‐quinolyl)piperazin‐1‐yl)acetyl)pyrrolidine (2g) was identified as a potential DPP‐IV inhibitor exhibiting better inhibitory activity than P32/98, reference inhibitor. The in vivo studies carried out in STZ and db/db mice models indicated that the compound 2g showed moderate antihyperglycemic activity as compared to the marketed drug Sitagliptin. A two‐week repeated dose study in db/db mice revealed that compound 2g significantly declined blood glucose levels with no evidence of hypoglycemia risk. Furthermore, it showed improvement in insulin resistance reversal and antidyslipidemic properties. Molecular docking studies established good binding affinity of compound 2g at the DPP‐IV active site and are in favor of the observed biological data. These data collectively suggest that compound 2g is a good lead molecule for further optimization studies.

Design, synthesis and molecular modelling studies of novel 3-acetamido-4-methyl benzoic acid derivatives as inhibitors of protein tyrosine phosphatase 1B.

A novel series of 3-acetamido-4-methyl benzoic acid derivatives designed on the basis of vHTS hit ZINC02765569 were synthesized and screened for PTP1B inhibitory activity. The most potent compounds 3-(1-(5-methoxy-1H-benzo[d]imidazol-2-ylthio)acetamido)-4-methyl benzoic acid (10c, IC₅₀ 8.2 μM) and 3-(2-(benzo[d]thiazol-2-ylthio)acetamido)-4-methyl benzoic acid (10e, IC₅₀ 8.3 μM) showed maximum PTP1B inhibitory activity. Docking studies were also performed to understand the nature of interactions governing the binding mode of the designed molecules within the active site of the PTP1B enzyme.

Bioactivity-guided chemical analysis of Melia azedarach L. (Meliaceae), displaying antidiabetic activity.

One new Euphane-type triterpenoid 3β-hydroxytirucalla-5, 24-dien-21-oic acid (1), and ten known compounds (2-11) were isolated from Melia azedarach L. through bioassay-guided chemical analysis. The structures of the isolated compounds were established by means of 1D and 2D NMR spectroscopic ((1)H, (13)C, DEPT, COSY, HSQC and HMBC) and MS spectral analyses. All the fractions and isolated pure compounds were evaluated for antidiabetic activity by determining their inhibitory effects on PTP-1B enzyme as well as glucose uptake stimulation in C2Cl2 myoblasts cells. Compounds 4 and 7 showed significant in vitro PTP-1B inhibitory activity with 69.2 and 66.8% inhibition at 10 μg/ml concentrations respectively.

4-Hydroxyisoleucine improves insulin resistance by promoting mitochondrial biogenesis and act through AMPK and Akt dependent pathway.

4-Hydroxyisoleucine (4-HIL) is an unusual amino acid isolated from fenugreek seeds (Trigonella foenum graecum L). Various studies have shown that it acts as an antidiabetic agent yet its mechanism of action is not clear. We therefore investigated the effect 4-HIL on the high fructose diet fed streptozotocin induced diabetic rats and L6 myotubes. 4-HIL (50 mg/kg) has improved blood lipid profile, glucose tolerance and insulin sensitivity in a diabetic rat model. It has increased the glucose uptake in L6 myotubes in AMPK-dependent manner and upregulated the expression of genes (PGC-1α, PGC-1β, CPT 1 and CPT 2), which have role in mitochondrial biogenesis and energy metabolism in the liver, skeletal muscles as well as in L6 myotubes. Interestingly, it also increased the AMPK and Akt expression along with their phosphorylated forms in the liver and muscle tissues of treated animals. Altogether we concluded that 4-HIL acts to improve insulin resistance by promoting mitochondrial biogenesis in high fructose diet fed STZ induced diabetic rats.

Design and synthesis of lupeol analogues and their in vitro PTP-1B inhibitory activity

Synthetic analogues of the naturally occurring triterpenoid, lupeol by modification of A-ring and isopropylene moiety with different carboxylic acid functionalities and their biological activity were investigated. The analogues were designed by considering the incorporation of ester and amide linkages in the parent molecule. They were assayed for protein tyrosine phosphatase-1B (PTP-1B) inhibitory activity. Among them, compounds 9a, 9b, 14a, 14b and 14c showed significant dose-dependant inhibition at 10 μM concentration. Our report is marked by readily accessible synthesis, excellent yield and significant PTP-1B inhibitory effect.Graphical abstractA synthetic approach and in vitro PTP-1B inhibition of novel analogues of lupeol are described. Compounds 9a, 9b, 14a, 14b and 14a represent a new class of PTP-1B inhibitors in type 2 diabetes

Design, synthesis and biological evaluation of novel arylidine-malononitrile derivatives as non-carboxylic inhibitors of protein tyrosine phosphatase 1B

In this study, we describe the design, synthesis, biological evaluation and molecular modelling studies of novel non-carboxylic arylidine malononitrile-based molecules as Protein Tyrosine Phosphatase 1B (PTP1B) inhibitors. The synthesized derivatives were evaluated in vitro for glucose reuptake using L6 muscle cell lines and enzymatic assay against PTP1B. The biological activity results showed that the 2-methoxy substituted (14b) compound exhibited significant activity in both the assays. The unsubstituted compound (14a) also possessed comparable activity on glucose reuptake in L6 muscle cell lines and better inhibitory activity on PTP1B enzyme assays. Docking analysis was performed on the most potent compound of the series to understand the nature of interactions governing the binding of the designed molecule with the PTP1B enzyme.

Identification of novel urea derivatives as PTP1B inhibitors: synthesis, biological evaluation and structure–activity relationships

The protein tyrosine phosphatase 1B (PTP1B) is an attractive target for the treatment of type 2 diabetes. A series of substituted 1,3-benzyl urea has been synthesized and evaluated for PTP1B inhibitory, antidiabetic and antidyslipidemic activities. The most active compound of the series 5b showed 79.4% PTP1B inhibition and 20.7% blood glucose lowering in the STZ model. It also lowered the serum cholesterol level by 16.3% and significantly increased the serum HDL-cholesterol by 46.8%. The high activity of compound 5b has been explained by docking studies.