Current Enzyme Inhibition - Volume 14, Issue 2, 2018

Introduction: 3-(3-thioxo-3H-1,2-dithiol-5-yl)phenyl 4-[(1E)-3-oxo-3-phenylprop-1-en-1- yl]benzoate and their analogues were synthesized on the basis of Claisen-Schmidt condensation reaction wherein chalcone intermediates were synthesized by the reaction of substituted aldehydes and acetophenones. Final products were synthesized by reacting chalcone intermediates with 5-(4- hydroxyphenyl)-3H-1,2-dithiole-3-thione. Conclusion: The compounds were characterized by IR, 1H NMR, 13C NMR and elemental analysis. In in-vitro Phosphodiesterase 5 inhibitory activity, compounds G4 and G8 exhibited a significant inhibitory effect against human platelet Phosphodiesterase 5 (PDE 5) while compound G3 exhibited a significant inhibitory effect on both human platelet PDE 5 and bovine recombinant Phosphodiesterase 5A (PDE 5A). This work will be highly fruitful to design novel compounds for dealing with problems associated with vasculature.

Background: In this study, we investigate the inhibitory effects of phenolic and saponins extracts of Cupressus sempervirens cones and seeds. Objective: The ethyl acetate and butanolic extracts of Cupressus sempervirens (L) cones and seeds, collected from Laghouat (Algeria) were analyzed for their saponins and phenolic content. We also studied the in vitro antidiabetic activity of C. sempervirens using α-amylase digestion enzyme. Methods: The amount of total phenolics and saponins in the samples was determined with the Folin- Ciocalteu reagent and with vanillin, respectively. To identify cones and seeds extracts with inhibitory capacities, we have studied the effects of ours extracts on the kinetics catalyzed of α-amylase an enzymes belonging to the class of hydrolase responsible for the digestion and we have subjected our extracts to inhibition assay to determine the inhibition percentage for each extract. Results: The fruits and seeds contained total free phenolic content of 1.96 mg/gGAE and 2.25 mg/gGAE, respectively. The saponin content determined with vanillin reagent shows a good yeild of 119.85 and 131.46 mg/gDE in ethyl acetate and butanolic extracts, respectively. In addition, phenolic and saponins extracts were found to inhibit enzymatic activity of α-amylase under in vitro starch digestion bioassay and the values of the IC50 constants have been determined for both seeds and cones extracts. The values ranged from 0.49 to 1.12 mg/ml. This paper is the first report on antidiabetic activity of saponins and phenolic extracts of cones and seeds from Cupressus sempervirens (L).

Background: There has been a great interest in the discovery of alternative medicines from medicinal herbs for type 2 diabetes, specifically screening for phytochemicals which are able to inhibit or delay glucose absorption. Introduction: The aim of this study was to evaluate the inhibition of crude extract and rosmarinic acid rich fractions from Orthosiphon stamineus on α-amylase and α-glucosidase activities. Methods: The plant crude extract was prepared by a reflux method using 70 %v/v ethanol, followed by fractionation using column chromatography to obtain rosmarinc acid rich fractions. Results: The crude extract and its rosmarinic acid rich fractions showed a dose dependent manner to inhibit the saccharide hydrolysing enzymes. Fr. A (100 % rosmarinic acid) was found to have comparable performance with standard rosmarinic acid as an inhibitor for both enzymes. Approximately, 62.50 mg/mL and 5 mg/mL of Fr. A were sufficient to achieve almost 100 % inhibition against α- amylase and α-glucosidase, respectively. Rosmarinic acid in Fr. A (IC50 0.34 mg/mL) was found to be 5 times more active than the anti-diabetic drug acarbose (IC50 1.66 mg/mL) in the inhibition of α- glucosidase. Fr. B with 50 % rosmarinic acid (IC50 1.48 mg/mL) had an inhibitory power comparable to that of acarbose. Kinetic studies revealed that Fr. A inhibited α-amylase competitively, but displayed non-competitive inhibition towards α-glucosidase. Rosmarinic acid had higher affinity towards α-glucosidase with lower Michaelis-Menten constant (Km), 1.42 mM. Conclusion: The findings suggest that rosmarinic acid rich fractions of O. stamineus could be a potential drug to regulate and manage type 2 diabetes mellitus.

Background: Inhibition of aromatase enzyme presents the key in Breast cancer treatment actually an important number of synthetics and natural inhibitors of this enzyme were studied. However, steroidal synthetic inhibitors were identified as the most efficient ones, indeed, the most commercialized treatment of breast cancer is steroidal. On the other hand, natural inhibitors have also provided good activities via the aromatase enzyme (Gingerol, Capsaïcine, Rhizome). Methods: In this work, we present a comparative, theoretical study of aromatase enzyme inhibitors by steroidal and natural inhibitors by means of molecular docking and conceptual DFT (Density functional theory) approaches. Theoretical calculations were done using the MOE programme for molecular docking and Gaussian 09 package for DFT calculation using B3lyp/6-31g* level of theory. Results: The DFT study was done for the best natural and synthetic inhibitors (deducted from the docking best scores for Lig5 and Lig 9, and lowest score for Lig ref). The relative global reactivity of these systems is rationalized by means of the global softness index. The present study shows that the Docking trends of the relative activities of these inhibitors are correlated with their predicted softness indexes. Conclusion: The obtained Docking and DFT results lead to the same conclusion and predict that exemestane is the best inhibitor which is synthetic and natural.

Background: Obesity is an important risk factor for nonalcoholic fatty liver disease which varies from hepatic steatosis to liver cirrhosis. Interventions in weight and metabolic control are important in reducing steatosis risk. Aims: The aim of the present study was to investigate the role of celecoxib in hepatic triacylglycerol deposition in non-alcoholic fatty liver disease exploring the signaling involved in obese mice lipogenesis. Methods: Males FVB/N mice were allocated into three groups and were fed with experimental diets: standard, a high-fat diet or a high-fat diet along with Cox-2 inhibitor treatment (Celecoxib; 100mg/kg of body weight). The body weight, food intake, blood parameters and liver histology were analyzed. Expression of liver lipogenesis-related genes (ACC, PPAR-γ, FAS, SREBP-1c) was evaluated by quantitative real-time PCR. Results: The main findings showed that celecoxib treatment resulted in body weight loss in obese animals, reduced food consumption and decreased triglycerides. ACC, FAS and SREBP1-c mRNA expression was significantly suppressed in HFD+ICOX-2 fed mice. Conclusion: Celecoxib improved lipid metabolism and decreased fat deposition in the liver of obese mice by reducing lipogenesis, which may be a promising therapeutic target for liver disorders, obesity and its comorbidities.

Introduction: Peptidoglycan, key constituent of bacterial cell wall, presents a novel target for broad spectrum antibiotics and extensive research is being conducted to synthesize inhibitors of its biosynthesis. A majority of bacteria need either lysine, or meso-DAP, as component of peptidoglycan. Background: Present compound has been designed as per structure activity relationship (SAR) of reported analogues and enzyme active site studies. The compounds have been subjected to in silico studies by PASS which confirm them to act as inhibitors of dapB, dapF, dapA and ddh. In this work, we have successfully synthesized various analogues of meso-DAP as per SAR requirement. The carboxyl groups in DAP were effectively replaced with five membered heterocyclic moieties and central carbon atom was replaced with sulfur. Compounds 4 and 5 were tested for antibacterial activity as per the inferences of predicted hypothesis to inhibit DAP enzymes. Methods: Antibacterial evaluation was performed on gram-positive and gram-negative bacteria. Two selectively protected tetrazole and imidazole analogues of DAP viz., compounds 4 and 5 were synthesized by condensation of NBS as brominating agent and later on, N-Trityl protected five member heterocycles obtained showed expected mono-bromide 17 and 11. This further allowed reaction of these heterocycles with thiol group of cystiene, thus making them susceptible to oxidation in the presence of K2CO3 to yield N-Trityl protected analogues 18 and 12. The separation and hydrolytic deprotection of 18 and 12 shows sterically hindered pure 5 and 4. Protein-ligand interaction was investigated for hydrophobic/ hydrophilic properties of these complexes and docking was carried out by VLife MDS 4.2 based on scoring functions. Results: A computational ligand-target docking approach was used to analyze structural complexes of dapF (target) with 4, 5 and LL-DAP (ligand) in order to understand the structural basis of this protein target specificity. The energy of interaction of compounds 4 and 5 with the dapF is assigned “grid point.” At each step of the simulation, the energy of interaction of ligand and protein was evaluated using atomic affinity potentials computed on a grid. The minimum binding energy indicated that dapF was successfully docked with compounds 4 and 5 showing good affinities. Both analogs showed relatively greater binding affinity as compared to natural substrate LL-DAP which showed minimum binding energy. Conclusion: In the present research, the compounds 4 and 5 have been designed such that they would be acting as inhibitors of enzymes involved in lysine pathway. Also, the results of antibacterial activity have revealed that these compounds can serve as good drug candidates against bacterial infections.

Background: Based on the sequences of their catalytic domains, the astacins can be grouped into several major subfamilies such as digestive and hatching enzymes, meprin cluster and BMP1/ Tolloid like Proteases (BTP). Ethylene Diamine Tetra-Acetate (EDTA) was used to dock into the active site cleft of the astacins to know the interaction network and to identify the important residues for binding. Introduction: Comparative analysis of the binding interactions helps to reveal the binding affinity of the ligand to the astacins. Virtual alanine screening helps to identify the hotspot residues on the protease which act as potential contributors to protein-ligand stability. Pharmacophore analysis generates common features among all three clusters of the astacin family which helps in significant interactions between the astacins and EDTA. Methods: Comparative homology modeling and docking study were performed by MODELLER 9.10 and LibDock respectively. To know the importance of interacting residues, in silico alanine scanning was done. Pharmacophore modeling was elaborated by using the information obtained from receptorligand complexes. Results: Homology model explained the structure and function of the unknown astacins. It was observed that several interactions such as hydrogen bonding, pi-sigma, electrostatic and van der Waal's were involved in EDTA binding. The important pharmacophoric features such as hydrogen bond acceptor, positive ionisable and negative ionisable are involved in significant interactions between astacins and EDTA. Conclusion: Understanding the inhibitor selectivity of astacins via the contribution of specific residues could help in the design of better therapeutics targeting astacins with high binding affinity.

Introduction: Pseudomonas aeruginosa is an opportunistic pathogen leading to severe, acute and chronic infections in burn patients. In the process of wound healing, a significant delay in the closure of excisional wound sites is due to the bacterial skin infection, so anti-infection is important in wound healing. Objective: Abuse of antibiotics leads to the development of multi drug resistance of P. aeruginosa strains which requires a rapid intervention to find a solution focusing on new natural antibacterial pathways. Punica granatum (pomegranate) has emerged as a medicinal plant with potential antimicrobial activity. The present study was planned to evaluate this activity against P. aeruginosa collected from burn wound cultures. Methods: Aqueous extract of sweet pomegranate peels from Safita, a mountainous region west of Syria was prepared. Minimum inhibitory concentration (MIC) and antivirulence efficacy were determined for the -prepared extract. Results: MIC was 1.4 mg/ml and bacterial gelatinase and lecithinase activities were reduced by 40.28±2.35% and 53.84±4.89%, respectively. Conclusion: The extracts from pomegranate fruit peel possess strong antimicrobial and antivirulence activities against P. aeruginosa. Therefore, this plant could be an important source of new antimicrobial compounds.

Background: It has been considered that Helicobacter pylori, a bacterium associated with a number of important upper gastrointestinal conditions cannot always effectively eradicated by the traditional approaches; however, there some alternative therapies have been presented. Honey has been used as a medicine since ancient times in many countries for its elevated antioxidant activity, as well as expressive antimicrobial activity. Objective: the objective of this study was to investigate the effecting degree of H. pylori with different type of honey samples from Syria. Methods: micro-dilution method and agar-well diffusion assay were carried out on H. pylori isolated from gastric biopsy. Inhibition of H. pylori urease was also tested. Results: all honey samples inhibited the growth of H. pylori with a MIC ranging from 30-50%. Both Black seed honey and Coastal Mountain honeys at 50% (v/v%) showed a growth inhibition zone of 16 and 15 mm, respectively; being similar to the growth inhibition zone of Amoxicillin (15 mm) and Levofloxacin (14 mm). 65% of H. pylori urease activity was inhibited using Black seed honey and Coastal Mountain at 50% (v/v%). Conclusion: These results indicate that Black seed and Coastal Mountain honey samples may be appropriate agents to treat H. pylori.

Background: Serine/threonine protein kinase CK2 is involved in the regulation of a number of cellular functions such as cell growth, proliferation, differentiation and apoptosis. Increased activity of CK2 is associated with the development of different types of cancer, inflammatory response, pain and virus infections. Therefore, protein kinase CK2 is an attractive molecular target for the development of small-molecular inhibitors which can be important compounds for pharmaceutical application. Objective: The main aim of this research is to identify novel chemical class of CK2 inhibitors with good lead-like properties. Methods: In order to find novel CK2 inhibitors, virtual screening experiments were performed using Autodock software. Best-scored compounds were tested in vitro using P32 radioactive kinase assay. Results: Small-molecular inhibitors of protein kinase CK2 were identified among the derivatives of 1,3-thiazole-5-carboxylic acid. The most active compound inhibited CK2 with IC50 value of 0.4 μM. Ligand efficiency for studied derivatives of 1,3-thiazole-5-carboxylic acid was in the range from 0.45 to 0.56 kcal/mol/non-hydrogen atom. Conclusion: Considering the fact that the lower limit for ligand efficiency parameter is 0.3, the identified CK2 inhibitors among the derivatives of 1,3-thiazole-5-carboxylic acid are excellent candidates for further lead optimization.