Ajmer Singh Grewal

Updates on Aldose Reductase Inhibitors for Management of Diabetic Complications and Non-diabetic Diseases

Diabetes mellitus occurrence has been associated to the modification of the physiological levels of glucose and is often accompanied by several long-term complications, namely neuropathy, nephropathy, retinopathy, cataract, and cardiovascular. Aldose reductase (AR) is an enzyme of aldoketo reductase super-family that catalyzes the conversion of glucose to sorbitol in the polyol pathway of glucose metabolism. In this context, aldose reductase inhibitors (ARIs) have received much attention worldwide. Decreased sorbitol flux through polyol pathway by ARIs could be an emerging target for the management of major complications of diabetes. The present review article describes a brief overview of the role of aldose reductase in the diabetic complications, advances achieved on ARIs and their potential use in the treatment and management of the major diabetic complications such as cataract, retinopathy, neuropathy, nephropathy and cardiovascular. The ARIs developed vary structurally, and representative structural classes of ARIs include i) carboxylic acid derivatives (such as Epalrestat, Alrestatin, Zopalrestat, Zenarestat, Ponalrestat, Lidorestat, and Tolrestat), ii) spirohydantoins and related cyclic amides (such as Sorbinil, Minalrestat, and Fidarestat), and iii) phenolic derivatives (related to Benzopyran-4-one and Chalcone). Among these inhibitors, Epalrestat is the only commercially available inhibitor till date. In addition, some other ARIs such as Sorbinil and Ranirestat had been advanced into late stage of clinical trials and found to be safe for human use. The role of various natural ARIs in management of diabetic complications will be discussed. Adapting ARIs could prevent sepsis complications, prevent angiogenesis, ameliorate mild or asymptomatic diabetic cardiovascular autonomic neuropathy and appear to be a promising strategy for the treatment of endotoxemia and other ROS-induced inflammatory diseases. The role of ARIs in non-diabetic diseases will also be discussed.

Recent Updates on Glucokinase Activators for the Treatment of Type 2 Diabetes Mellitus

Glucose-phosphorylating enzyme, glucokinase (GK) plays a major role in glucose homeostasis primarily through its regulatory actions in pancreatic β-cells and liver hepatocytes. Conversion of glucose to glucose-6-phosphate by GK promotes glycogen synthesis in liver hepatocytes, and insulin release in the pancreatic β-cells. Small molecules called glucokinase activators (GKAs) which bind to an allosteric activator site of the GK enzyme have indeed been discovered and developed, and thus hold great promise as new, effective and safe antidiabetic agents. GKAs enhance the catalytic activity of GK and promising clinical trials in humans demonstrated that they are highly useful in the treatment of type 2 diabetes mellitus. Most of the reported GKAs include amide derivatives like benzamides, acrylamides, carboxamides, acetamides and acrylamides. Examples include Piragliatin, AZD1656, AZD6370, R1440 GKA2, GKA 50, YH GKA, PSN 010, and LY2121260. Recent findings on GKAs including lead compounds and overview of current hypothesis on mechanism of GK activation along with summary of the recently published patents as well as the GKAs of natural origin are reported in the present review.

Recent Updates on Development of Drug Molecules for Human African Trypanosomiasis

Human African trypanosomiasis (HAT, better called as sleeping sickness), caused by two morphologically identicalprotozoan parasite Trypanosoma bruceiis transmitted by the bite of tsetse flies of Glossinagenus, mainly in the rural areas of the sub-Saharan Africa. HAT is one of the neglected tropical diseases and is characterized by sleep disturbance as the main symptom, hence is called as sleeping sickness. As it is epidemic in the poorest population of Africa, there is limited availability of safe and cost-effective tools for controlling the disease. Trypanosoma bruceigambiense causes sleeping sickness in Western and Central Africa, whereas Trypanosoma bruceirhodesiense is the reason for prevalence of sleeping sickness in Eastern and Southern Africa. For the treatment of sleeping sickness, only five drugs have been approved suramin, pentamidine, melarsoprol, eflornithine and nifurtimox. Various small molecules of diverse chemical nature have been synthesized for targeting HAT and many of them are in the clinical trialsincluding fexinidazole (phase I completed) and SCYX-7158 (advanced in phase I). The present work has been planned to review various types of small molecules developed in the last 10 years having potent antitrypanosoma activity likely to be beneficial in sleeping sickness along with different natural anti-HAT agents.

Recent Updates on Peroxisome Proliferator-Activated Receptor δ Agonists for the Treatment of Metabolic Syndrome

Metabolic syndrome is a disorder described by reduced insulin sensitivity, overweight, hyperlipidaemia, high blood pressure and myocardial disorders, mainly due to high fat diet and lack of physical activity. The peroxisome proliferator activated receptors (PPARs) are type II nuclear hormone receptors that regulate a number of processes in living systems, such as metabolism of carbohydrates and fatty acids, growth and differentiation of cell, and inflammatory reactions. Alpha, gamma and delta are the three distinct isoforms of PPAR. The stimulation of PPARδ alters bodys energy fuel preference from glucose to fat. The PPARδ isoform is expressed ubiquitously in all tissues, especially in those tissues which involved in metabolism of lipids like adipose tissue, liver, kidney, and muscle. Currently, PPARδ is an emerging therapeutic target for the pharmacological therapy of disorders associated with metabolic syndrome. Several PPARδ selective agonists had been reported in last ten years, many of them had been advanced into the late phase of clinical trials such as Endurobol (GW501516). However, no PPARδ agonists are yet approved for human use. The present work had been planned to cover wide variety of PPARδ agonists reported till now along with their potential role to tackle various metabolic disorders. The present review has been planned to focus mainly the most popular PPARδ agonists.

Pesticide Residues in Food Grains, Vegetables and Fruits: A Hazard to Human Health

Pesticides are widely used in agriculture mainly to increase crop yields to cater huge supply of food products for increasing world population as well as to protect crops from pests and control insect-borne diseases. Increased use of pesticides results in contamination of the environment and the excess accumulation of pesticide residues in food products, which has always been a matter of serious concern. Pesticide residues in food and crops aredirectly related to the irrational application of pesticides to the growing crops. Accumulated pesticide residues in food products have been associated with a broad variety of human health hazards, ranging from short-term effects to longterm toxic effects. The preventive measures for pesticide residues in the developing countries are limited due to a shortage of funds and lack of defined government regulations. The impact of pesticide residues can be minimized by taking certain measures such as the rational use of pesticides, promoting organic farming, exploit natural and bio pesticides, and proper implementation and amendment of pesticide-related laws. The present article has been planned to review various aspects of pesticide residues including their accumulation in food products, impact on human health, and the preventive measures to counter their toxic effects.

Synthesis, Antimicrobial Activity and QSAR Studies of Some New Sparfloxacin Derivatives

The increasing global health problem of bacterial resistance to the major classes of antibiotics is driving scientists to search for newer antimicrobial agents. The present work was designed to synthesize and evaluate the antimicrobial activities of a new series of sparfloxacin derivatives. Aseries of 22 new sparfloxacin derivatives (1 – 22) were synthesized followed by their spectral characterization and antimicrobial evaluation using serial dilution method. QSAR studies were performed to relate their antimicrobial activity and structure. The results of antimicrobial activity testing against all the three selected bacterial strains (Bacillus subtilis, Staphylococcus aureus, and Escherichia coli) indicated that compounds 21 and 22 exhibited maximum antibacterial potential among all the synthesized sparfloxacin derivatives. Compounds 6, 17, and 22 exhibited maximum antifungal potential against two fungal strains (Candida albicans and Aspergillus niger). The results of QSAR studies revealed the fact that topological parameters, particularly the valence third-order molecular connectivity index, are the major factor in influencing the antibacterial potential of the synthesized molecules. These new derivatives can offer new avenues in the design of better antimicrobial molecules active against drug-resistant bacterial and fungal strains.

Synthesis, Anti-inflammatory Activity and Docking Studies of Some Newer 1,3-Thiazolidine-2,4-dione Derivatives as Dual Inhibitors of PDE4 and PDE7

BACKGROUND Phosphodiesterase 4 (PDE4) and phosphodiesterase 7 (PDE7), PDE superfamily members, increase inflammatory processes in immunomodulatory as well as pro-inflammatory cells via breakdown of cyclic adenosine monophosphate. Dual inhibitors of PDE4 and PDE7 are a novel class of drug candidates which can regulate pro-inflammatory as well as T-cell function and can be particularly advantageous in the treatment of a wide-ranging disorders associated with the immune system as well as inflammatory diseases with fewer unwanted adverse effects. OBJECTIVE The current research work was planned to design and synthesize some newer substituted 1,3- thiazolidine-2,4-dione derivatives as dual inhibitors of PDE4 and PDE7 followed by evaluation of their anti-inflammatory activity and in silico docking studies. METHODS A new series of substituted 1,3-thiazolidine-2,4-dione derivatives was synthesized followed by evaluation of their anti-inflammatory activity in animal models. In silico docking studies were performed for the evaluation of the binding pattern of synthesized derivatives in the binding site of both PDE4 and PDE7 proteins. RESULTS Amongst the newly synthesized derivatives, compounds 5 and 12 showed higher antiinflammatory activity in the animal model. The results of in vivo animal studies were found to be in concordance with the results of molecular docking studies. CONCLUSION These newly synthesized derivatives can act as the lead molecules for the design of safe and therapeutically effective agents for various inflammatory diseases acting via inhibition of both PDE4 and PDE7.

Design, synthesis and biological evaluation of novel thiazol-2-yl benzamide derivatives as glucokinase activators

Glucokinase (GK) is the main enzyme which controls the blood glucose levels in a safe and narrow physiological range in humans. GK activators are the novel type of therapeutic agents which act on GK enzyme and show their anti-diabetic potential. The present work was planned to synthesize and evaluate the antidiabetic potential of a new series of thiazole-2-yl benzamide derivatives as potential GK activators. A series of thiazole-2-yl benzamide derivatives were synthesized from benzoic acid and evaluated by in vitro enzymatic assay for GK activation. In silico docking studies were carried out to determine the binding interactions for the best fit conformations in the allosteric site of GK enzyme. Based on the results of in vitro enzyme assay and in silico studies, the selected molecules were tested for their antidiabetic activity in the oral glucose tolerance test (OGTT). The results of the in vitro enzymatic assay were found to be in accordance to that of in silico studies. Amongst the synthesized molecules, compounds 1, 2, 5 and 8 displayed good in vitro GK activation (activation fold between 1.48 and 1.83). Compounds 2 and 8 exhibited highest antidiabetic activity in OGTT studies. The results of the in vivo antidiabetic studies were found to be in parallel to that of docking and in vitro studies. These newly synthesized thiazol-2-yl benzamide derivatives thus can be treated as the initial hits for the development of new, safe, effective and orally bioavailable GK activators as therapeutic agents for the treatment of type 2 diabetes.

Targeting matrix metalloproteinases with novel diazepine substituted cinnamic acid derivatives: design, synthesis, in vitro and in silico studies

Lung cancer is the notable cause of cancer associated deaths worldwide. Recent studies revealed that the expression of matrix metalloproteinases (MMPs) is extremely high in lung tumors compared with non-malignant lung tissue. MMPs (-2 and -9) play an important part in tumor development and angiogenesis, which suggests that creating potent MMP-2 and -9 inhibitors, should be an important goal in lung cancer therapy. In the present study, an effort has been made to develop new anti-metastatic and anti-invasive agents, wherein a series of novel diazepine substituted cinnamic acid derivatives were designed, synthesized and assayed for their inhibitory activities on MMP-2 and MMP-9. These derivatives were prepared via microwave assisted reaction of tert-butyl (3-cinnamamidopropyl)carbamate derivatives mixed with 2,3-dibromopropanoic acid and potassium carbonate was added to obtain 4-(tert-butoxycarbonyl)-1-cinnamoyl-1,4-diazepane-2-carboxylic acid derivatives. The newly synthesized compounds were characterized by IR, NMR and mass spectroscopy. All the tested compounds showed good to excellent cytotoxic potential against A549 human lung cancer cells. The active compounds displaying good activity were further examined for the inhibitory activity against MMPs (-2 and -9). In addition, the structure and anticancer activity relationship were further supported by in silico docking studies of the active compounds against MMP-2 and MMP-9.

N-Pyridin-2-yl Benzamide Analogues as Allosteric Activators of Glucokinase: Design, Synthesis, In Vitro, In Silico and In Vivo Evaluation

Glucokinase (GK) is the key enzyme controlling levels of blood glucose under normal physiological range, and GK activators are emerging class of drug candidates with promising hypoglycaemic activity. The current study was planned to design, synthesize and evaluate novel N‐pyridin‐2‐yl benzamide analogues as allosteric activators of GK. A novel series of N‐pyridin‐2‐yl benzamide analogues were synthesized starting from 3‐nitrobenzoic acid and evaluated in vitro for GK activation followed by in silico studies to predict the binding interactions of the designed molecules with GK protein. The selected synthesized molecules (compounds 5b, 5c, 5e, 5g, 5h and 6d) which displayed excellent GK activity (GK fold activation around 2) in GK assay and appreciable binding interaction with GK in docking studies were further evaluated for their antihyperglycaemic potential using oral glucose tolerance test (OGTT) in rats. Amongst the compounds tested in vivo (OGTT assay) for antihyperglycaemic potential, compounds 5c, 5e and 5g displayed significant reduction in blood glucose levels. Compound 5e displayed most significant antidiabetic activity and comparable to that of standard drug in animal studies. The N‐pyridin‐2‐yl benzamide analogues discovered in the current study can provide some lead molecules for the development of potent oral GK activators with minimum side‐effects for the management of type 2 diabetes.