Exploring the Molecular Structural Requirements of Flavonoids as Beta- Secretase-1 Inhibitors Using Molecular Modeling Studies.

BACKGROUND: BACE1 (beta-site amyloid precursor protein (APP) cleaving enzyme) is a key target for Alzheimer's disease research because it catalyses the rate-limiting step in the formation of amyloid protein (Aß). Natural dietary flavonoids have gained a lot of interest as potential Alzheimer's therapy candidates because of their anti-amyloidogenic, antioxidative, and anti-inflammatory properties. More research is needed, however, to learn more about the specific routes through which flavonoids may have neuroprotective benefits in Alzheimer's disease. OBJECTIVE: Here, we report an in silico molecular modeling study for natural compounds, particularly flavonoids, as BACE-1 inhibitors. METHODS: The interactions of flavonoids with the BACE-1 catalytic core were disclosed by demonstrating the predicted docking pose of flavonoids with BACE-1. The stability of flavonoids BACE-1 complex was analyzed by molecular dynamic simulation (standard dynamic cascade). RESULTS: Our findings imply that these flavonoids, which have methoxy group instead of hydroxy may be promising BACE1 inhibitors that could reduce Aß formation in Alzheimer's disease. The molecular docking study revealed that flavonoids e bind with the BACE1's wide active site along with the catalytic residues Asp32 and Asp228. Further molecular dynamic investigation revealed that the average RMSD for all complexes ranged from 2.05 to 2.32 Å, indicating that the molecules were relatively stable during MD simulation. The RMSD analyses demonstrate that the flavonoids were structurally stable during the MD simulation. The RMSF was utilised to study the time-dependent fluctuation of the complexes. The N-terminal (~2.5 Å) fluctuates less than the C-terminal (~6.5 Å). Rutin and Hesperidin were highly stable in the catalytic region as compared to other flavonoids like Rhoifolin, Hesperidin, Methylchalcone, Phlorizin and Naringin. CONCLUSION: We were able to justify the flavonoids' selectivity for BACE-1 and crossing BBB for the treatment of Alzheimer's disease by using a combination of molecular modelling tools.

Synthesis and Anticancer Activity of Thiadiazole Containing Thiourea, Benzothiazole and Imidazo[2,1-b][1,3,4]thiadiazole Scaffolds.

BACKGROUND: A great array of nitrogen-containing heterocyclic rings were being extensively explored for their functional versatility in the field of medicine, especially in anticancer research. 1,3,4- thiadiazole is one of such heterocyclic rings with promising anticancer activity against several cancer cell lines, inhibiting diverse biological targets. INTRODUCTION: The 1,3,4-thiadiazole, when equipped with other heterocyclic scaffolds, has displayed enhanced anticancer properties. The thiourea, benzothiazole, imidazo[2,1,b][1,3,4]-thiadiazoles are such potential scaffolds with promising anticancer activity. METHODS: A new series of 5-substituted-1,3,4-thiadiazoles linked with phenyl thiourea, benzothiazole and 2,6-disubstituted imidazo[2,1-b][1,3,4]thiadiazole derivatives were synthesized and tested for invitro anticancer activity on various cancer cell lines. RESULTS: The National Cancer Institute's preliminary anticancer screening results showed compounds 4b and 5b having potent antileukemic activity. Compound 4b selectively showed 32 percent lethality on Human Leukemia-60 cell line. The docking studies of the derivatives on aromatase enzyme (Protein Data Bank: 3S7S) have shown reversible interactions at the active site with good docking scores comparable to Letrozole and Exemestane. Furthermore, the selected derivatives were tested for anticancer activity on HeLa cell line based on the molecular docking studies. CONCLUSION: Compounds 4b and 5b showed effective inhibition equivalent to Letrozole. These preliminary biological screening studies have given positive anticancer activity for these new classes of derivatives. An additional research study like the mechanism of action of the anticancer activity of this new class of compounds is necessary. These groundwork studies illuminate a future pathway for research of this class of compounds enabling the discovery of potent antitumor agents.

A review of pharmacological and clinical studies on the application of Shenling Baizhu San in treatment of Ulcerative colitis.

ETHNOPHARMACOLOGICAL RELEVANCE: The prescription of Shenling Baizhu San (SLBZS) was derived from the Song Dynasty "Taiping Huimin Heji Ju Fang", which was a representative prescription for treating spleen asthenic diarrhea. The prescription comprised of 10 herbs for treating weak spleen and stomach. It describes symptoms like eating less, loose stools, cough, shortness of breath and tired limbs. SLBZS has been reported to be capable of eliminating discomfort when it is administered for treating irritable bowel syndrome and diarrhea. This traditional Chinese medicine (TCM) formula has been widely used for improving gastrointestinal dysfunction and modifying the immune response to inflammation. AIM OF THE STUDY: This review is aimed to provide the up-to-date information on the pharmacology and clinical research of SLBZS in the treatment of ulcerative colitis (UC), and to discuss the research findings and possible deficiencies, hoping to better guide the clinical application and scientific research of SLBZS in the treatment of UC. MATERIALS AND METHODS: Relevant studies from 2004 to 2018 on SLBZS in the treatment of UC mechanism and curative effect were collected from ancient books, pharmacopoeia, reports, thesis via library and Digital databases (PubMed, CNKI, Google Scholar, Web of Science, SciFinder, Springer, Elsevier, etc). RESULTS: SLBZS could regulate inflammatory factors and intestinal flora, and ERK/p38 MAPK signaling pathway may be one of its targets. In addition, clinical research results show that SLBZS has a good therapeutic effect on UC, and the adverse reactions are small. CONCLUSION: Although SLBZS has achieved some success in the treatment of UC, there are still some scientific gaps. There is a lack of uniform standards for constructing UC animal models, and some methods of modeling through environmental and dietary interventions are not reproducible, and there is a lack of uniform dosing regimen standards. SLBZS doses follow the tradition and lack toxicological validation. Therefore, more specific toxicological research models are essential. The clinical application of SLBZS requires reassessment and standardization. Although all clinical research reports randomly assigned patients to different groups, most did not describe a detailed method of randomization and no description of the analysis data. In addition, extensive in vitro studies and further in-depth molecular studies are essential for the determination of mechanisms that have been performed in all in vivo experiments on animal models and patients.

Chemical synthesis and in silico molecular modeling of novel pyrrolyl benzohydrazide derivatives: Their biological evaluation against enoyl ACP reductase (InhA) and Mycobacterium tuberculosis.

In efforts to develop new antitubercular agents, we report here the synthesis of a series of novel pyrrole hydrazine derivatives. The molecules were evaluated against inhibitors of InhA, which is one of the key enzymes involved in type II fatty acid biosynthetic pathway of the mycobacterial cell wall as well as inhibitors of Mycobacterium tuberculosis H37Rv. The binding mode of compounds at the active site of enoyl-ACP reductase was explored using the surflex-docking method. The model suggests one or two H-bonding interactions between the compounds and the InhA enzyme. Some compounds exhibited good activities against InhA in addition to promising activities against M. tuberculosis.

Graph theoretical analysis, insilico modeling, design, and synthesis of compounds containing benzimidazole skeleton as antidepressant agents.

In this study, drug target was identified using KEGG database and network analysis through Cytoscape software. Designed series of novel benzimidazoles were taken along with reference standard Flibanserin for insilico modeling. The novel 4-(1H-benzo[d]imidazol-2-yl)-N-(substituted phenyl)-4-oxobutanamide (3a-j) analogs were synthesized and evaluated for their antidepressant activity. Reaction of 4-(1H-benzo[d]imidazol-2-yl)-4-oxobutanoic acid (1) with 4-(1H-benzo [d] imidazol-2-yl)-4-oxobutanoyl chloride (2) furnished novel 4-(1H-benzo [d] imidazol-2-yl)-N-(substituted phenyl)-4-oxobutanamide (3a-j). All the newly synthesized compounds were characterized by IR, 1 H-NMR, and mass spectral analysis. The antidepressant activities of synthesized derivatives were compared with standard drug clomipramine at a dose level of 20 mg/kg. Among the derivatives tested, most of the compounds were found to have potent activity against depression. The high level of activity was shown by the compounds 3d, 3e, 3i, and it significantly reduced the duration of immobility time at the dose level of 50 mg/kg.

Synthesis, characterization and antitubercular activities of novel pyrrolyl hydrazones and their Cu-complexes.

Novel pyrrolyl hydrazones and their copper complexes have been synthesized and characterized using analytical and spectral techniques to show the tetrahedral geometry for Cu(II) complexes. Biological activities of hydrazones have been assessed to understand the role of metal ion on their biological activity and the effect of pyrrolyl hydrazones. In vitro antitubercular activity against Mycobacterium tuberculosis of the metal complexes (13b and 13r) exhibited the highest antitubercular activity that are quite close to rifampicin (0.4 µg/mL), giving a MIC of 0.8 µg/mL. All other compounds showed good activity with the MIC values ranging from 1.6 to 100 µg/mL. A comparative study of inhibition values of the ligands and their complexes showed higher antimicrobial activity of the complexes than the ligands. Some compounds have a good activity against InhA and in particular, compounds 12r, 13b and 13r exhibited more than 60% binding with the enzyme even at 5 µM (exhibited good IC50 upto 2.4 µM). Most of the active molecules have a very less cytotoxicity against the human lung cancer cell-line A549. The docking and 3D-QSAR studies have been carried out to provide some insights into the mechanism of action for this class of compounds.

Synthesis, evaluation and in silico molecular modeling of pyrroyl-1,3,4-thiadiazole inhibitors of InhA.

Enoyl acyl carrier protein reductase (ENR)is an essential type II fatty acid synthase (FAS-II) pathway enzyme that is an attractive target for designing novel antitubercular agents.Herein, we report sixty-eight novel pyrrolyl substituted aryloxy-1,3,4-thiadiazoles synthesized by three-step optimization processes. Three-dimensional quantitative structure-activity relationships (3D-QSAR) were established for pyrrolyl substituted aryloxy-1,3,4-thiadiazole series of InhA inhibitors using the comparative molecular field analysis (CoMFA).Docking analysis of the crystal structure of ENR performed by using Surflex-Dock in Sybyl-X 2.0 software indicates the occupation of pyrrolyl substituted aryloxy 1,3,4-thiadiazole into hydrophobic pocket of InhA enzyme. Based on docking and database alignment rules, two computational models were established to compare their statistical results. The analysis of 3D contour plots allowed us to investigate the effect of different substituent groups at different positions of the common scaffold. In vitro testing of ligands using biological assays substantiated the efficacy of ligands that were screened through in silico methods.

Discovery of target based novel pyrrolyl phenoxy derivatives as antimycobacterial agents: an in silico approach.

A new series of pyrrolyl phenoxy derivatives bearing alkoxy linker were synthesized and evaluated for anti-tubercular activity (anti-TB) against Mycobacterium tuberculosis. Molecular modeling, pharmacophore constructed using GALAHAD to produce an effective alignment of data set and evaluated by Pareto ranking. The pharmacophore features were filtered by Surflex-dock study using enoyl ACP reductase from M. tuberculosis, which is one of the key enzymes involved in type II fatty acid biosynthesis pathway of M. tuberculosis. Compound 6a27 showed the H-bond with NAD(+), whereas compound 6a26 showed H-bonds with Tyr158, Thr196, Met199 and NAD(+) that fitted well into the binding pocket of target InhA. The alkoxy linker bridge and acceptor groups with benzene ring were advantageous for anti-TB activity, which merit further investigation.

Multi-spectroscopic investigation of the binding interaction of fosfomycin with bovine serum albumin.

The interaction between fosfomycin (FOS) and bovine serum albumin (BSA) has been investigated effectively by multi-spectroscopic techniques under physiological pH 7.4. FOS quenched the intrinsic fluorescence of BSA via static quenching. The number of binding sites n and observed binding constant KA were measured by the fluorescence quenching method. The thermodynamic parameters ΔG0, ΔH0 and ΔS0 were calculated at different temperatures according to the van't Hoff equation. The site of binding of FOS in the protein was proposed to be Sudlow's site I based on displacement experiments using site markers viz. warfarin, ibuprofen and digitoxin. The distance r between the donor (BSA) and acceptor (FOS) molecules was obtained according to the Förster theory. The effect of FOS on the conformation of BSA was analyzed using synchronous fluorescence spectra (SFS), circular dichroism (CD) and 3D fluorescence spectra. A molecular modeling study further confirmed the binding mode obtained by the experimental studies.

Controlled release of therapeutics using interpenetrating polymeric networks.

INTRODUCTION: The ever-increasing developments in pharmaceutical formulations have led to the widespread use of biodegradable polymers in various forms and configurations. In particular, interpenetrating network (IPN) and semi-IPN polymer structures that are capable of releasing drugs in a controlled manner have gained much wider importance in recent years. AREAS COVERED: Recently, IPNs and semi-IPNs have emerged as innovative materials of choice in controlled release (CR) of drugs as the release from these systems depends on pH of the media and temperature in addition to the nature of the system. These networks can be prepared as smart hydrogels following chemical or physical crosslinking methods to show remarkable drug release patterns compared to single polymer systems. EXPERT OPINION: A large number of IPNs and semi-IPNs have been reported in the literature. The present review is focused on the preparation methods and their CR properties with reference to anticancer, anti-asthmatic, antibiotic, anti-inflammatory, anti-tuberculosis and antihypertensive drugs, as majority of these drugs have been reported to be the ideal choices for using IPNs and semi-IPNs.

Enoyl ACP reductase as effective target for the synthesized novel antitubercular drugs: a-state-of-the-art.

The emergence of drug resistant strains of important human pathogens has created an urgent necessity to find new targets and novel antitubercular agents. According to the literature survey, we noticed that enoyl ACP reductase is one of the most promising targets. This enzyme is the most important catalyst for the FAS II synthesis of mycolic acid, which is the most essential component of the mycobacterial cell wall. This review summarizes the progress made in the design of enoyl ACP reductase inhibitors and the role played by 3D-structure of the enzyme in drug design process.

Polysaccharide-based micro/nanohydrogels for delivering macromolecular therapeutics.

Increased interest in developing novel micro/nanohydrogel based formulations for delivering macromolecular therapeutics has led to multiple choices of biodegradable and biocompatible natural polymers. This interest is largely due to the availability of large number of highly pure recombinant proteins and peptides with tunable properties as well as RNA interference technology that are used in treating some of the deadly diseases that were difficult to be treated by the conventional approaches. The majority of marketed drugs that are now available are in the form of injectables that pose limited patient compliance and convenience. On the other hand, micro/nanotechnology based macromolecular delivery formulations offer many alternative routes of administration and advantages with improved patient compliance and efficient or targeted delivery of intracellular therapeutics to the site of action. This review outlines and critically evaluates the research findings on micro and nano-carrier polymeric hydrogels for the delivery of macromolecular therapeutics.

Guar gum as platform for the oral controlled release of therapeutics.

INTRODUCTION: The past decade of research has witnessed a huge advancement in research efforts on guar gum (GG)-based polymers as controlled release (CR) formulations for the delivery of therapeutics. AREAS COVERED: The unique structure and beneficial properties of GG makes it an attractive biomaterial in CR applications. Current status on GG-based polymers has been addressed as a CR formulation in the form of microspheres, nanoparticles, hydrogels and matrix tablets for the delivery of various types of therapeutics having a wide range of physicochemical properties. Majority of literature on GG as a platform technology has dealt with oral route of drug administration as it is the most convenient, patient-compliant and preferred approach. Recent reports on GG-based polymers are summarized and critically discussed to narrate their usefulness as oral delivery systems. EXPERT OPINION: The research on GG-based formulations has been focused on optimization of the therapy by designing CR dosage forms with a minimum number of excipients. In this context, GG-based polymers are quite attractive. The present review summarizes published reports on these systems and offers expert opinion relevant to oral delivery of therapeutics.

In vitro studies on the interaction between human serum albumin and fosfomycin disodium salt, an antibiotic drug by multi-spectroscopic and molecular docking methods.

The interaction between the human serum albumin (HSA) and drug, fosfomycin disodium salt (FOS) has been studied by different spectroscopic techniques. The experimental results showed a static quenching mechanism in the interaction of FOS with HSA. The number of binding sites, n and observed binding constant K a were measured by fluorescence quenching method. The thermodynamic parameters ΔG°, ΔH° and ΔS° were calculated according to van't Hoff equation. The calculated distance r between FOS and the protein is evaluated according to the theory of Förster energy transfer. A change in the secondary structure of the protein was evident from the circular dichroism measurements, synchronous fluorescence and three-dimensional fluorescence spectra.

Design, synthesis, molecular docking and 3D-QSAR studies of potent inhibitors of enoyl-acyl carrier protein reductase as potential antimycobacterial agents.

In order to develop a lead antimycobacterium tuberculosis compound, a series of 52, novel pyrrole hydrazine derivatives have been synthesized and screened which target the essential enoyl-ACP reductase. The binding mode of the compounds at the active site of enoyl-ACP reductase was explored using surflex-docking method. The binding model suggests one or two hydrogen bonding interactions between pyrrole hydrazones and InhA enzyme. Highly active compound 5r (MIC 0.2 µg/mL) showed hydrogen bonding interactions with Tyr158 and NAD(+) in the same manner as those of ligands PT70 and triclosan. The CoMFA and CoMSIA models generated with database alignment were the best in terms of overall statistics. The predictive ability of the CoMFA and CoMSIA models was determined using a test set of 13 compounds, which gave predictive correlation coefficients (r(pred)(2)) of 0.896 and 0.930, respectively.

Synthesis, biological evaluation and docking studies of 4-aryloxymethyl coumarins derived from substructures and degradation products of vancomycin.

Two series of 4-aryloxymethyl coumarins derived from the reaction of 4-bromomethyl coumarins with ethyl gallate and ethyl ester of N-Benzoyl tyrosine have been synthesized. Gallate ethers 3a-3g and tyrosine derivatives 4e-4j were most effective against Entercoccus faecalis. They were also found to be effective against Aspergillus niger and Candida albicans. Comparative docking studies with novobiocin have indicated better binding ability and higher 'C' score values than novobiocin.