Immobilization of fungal (Trametes versicolor) laccase onto Amberlite IR-120 H beads: Optimization and characterization

Laccase from Trametes versicolor was immobilized on Amberlite IR-120 H beads. Maximum immobilization obtained was 78.7% at pH = 4.5 and temperature T = 45 °C. Kinetic parameters, K_m and V_max values, were determined respectively as 0.051 mM and 2.77 × 10^?2 mM/s for free and 4.70 mM and 5.27 × 10^?3 mM/s for immobilized laccase. The Amberlite–laccase system showed a 30% residual activity after 7 cycles. On the other hand, the loss of activity for free laccase after 7 days of storage at 4 °C was 18.5% in comparison to Amberlite–laccase system with a loss of 1.4%, during the same period. Improved operational, thermal and storage stabilities of the immobilized laccase were obtained compared to the free counterpart. Therefore, the use of low-cost matrices, like Amberlite for enzyme immobilization represents a promising product for enzymatic industrial applications.     

Plasmepsin inhibitors: design, synthesis, inhibitory studies and crystal structure analysis.

Plasmepsin group of enzymes are key enzymes in the life cycle of malarial parasites. As inhibition of plasmepsins leads to the parasite's death, these enzymes can be utilized as potential drug targets. Although many drugs are available, it has been observed that Plasmodium falciparum, the species that causes most of the malarial infections and subsequent death, has developed resistance against most of the drugs. Based on the cleavage sites of hemglobin, the substrate for plasmepsins, we have designed two compounds (p-nitrobenzoyl-leucine-beta-alanine and p-nitrobenzoyl-leucine-isonipecotic acid), synthesized them, solved their crystal structures and studied their inhibitory effect using experimental and theoretical (docking) methods. In this paper, we discuss the synthesis, crystal structures and inhibitory nature of these two compounds which have a potential to inhibit plasmepsins.     

Design, synthesis and evaluation of potential inhibitors of HIV gp120-CD4 interactions

This paper describes an approach to prevent HIV-cell fusion by disrupting the interaction between HIV protein gp120 and CD4 receptor. The CD4 residues Phe43 and Arg59 make important interactions with gp120. Small molecule analogues were made to mimic the crucial features of these residues. The analogues were assayed using a cellular 'FIGS' assay to measure inhibition of cell fusion and caused some inhibition.     

Novel morpholinone-based D-Phe-Pro-Arg mimics as potential thrombin inhibitors: design, synthesis, and X-ray crystal structure of an enzyme inhibitor complex

A morpholinone structural motif derived from D(+)- and L(-)-malic acid has been used as a mimic of D-Phe-Pro in the thrombin inhibiting tripeptide D-Phe-Pro-Arg. In place of Arg the more rigid P1 truncated p-amidinobenzylamine (Pab) or 2-amino-5-aminomethyl-3-methyl-pyridine have been utilized. The synthetic strategy developed readily delivers these novel thrombin inhibitors used to probe the alpha-thrombin inhibitor binding site. The best candidate in this series of thrombin inhibitors exhibits an in vitro IC(50) of 720 nM. The X-ray crystal structure of this candidate co-crystallized with alpha-thrombin is discussed.     

Design and synthesis of Pfmrk inhibitors as potential antimalarial agents

The synthesis and inhibitory activities of 10 potential inhibitors of Pfmrk, a Plasmodium falciparum cyclin-dependent protein kinase, are described. The most potent inhibitor is a 3-phenyl-quinolinone compound with an IC(50) value of 18 microM. It is the first compound reported to inhibit Pfmrk at the micro molar range.     

Design, synthesis, and activity of caffeoyl pyrrolidine derivatives as potential gelatinase inhibitors

The synthesis and biological evaluation of caffonyl pyrrolidine derivatives as MMPs inhibitors are reported in this paper. Inhibiting activities of synthesized compounds on gelatinase (MMP-2 and -9) were tested by using succinylated gelatin as substrate. Structure-activity relationship results from these tested compounds demonstrated that longer and more flexible side chain linked to the pyrrolidine ring at C(4) produced higher activity at gelatinase. Furthermore, aromatic heterocycle and sulfamide in the same position could enhance the activities. Compounds with free phenol hydroxyl group showed higher activity compared to methylated derivatives (or counterparts), which confirms the importance of phenol hydroxyl functionality in the interaction with gelatinase. The anti-metastasis model of mice bearing H(22) tumor cell was used to evaluate their in vivo inhibiting activities. All tested compounds were orally administered at a dose of 50 or 100mg/kg, 6days/week for two weeks. The test results demonstrated that most of these inhibitors showed significant anti-cancer activities (inhibitory rate>35%) and were devoid of toxic effects. Compound 29 showed the highest inhibitory rate at 69.25%, indicating that it might be a promising lead compound.     

Design,synthesis and evaluation of novel HDAC inhibitors as potential antitumor agents

Phenyl imidazolidin-2-one was introduced as the linker for novel HDAC inhibitors. A focused library of 20 compounds was designed and synthesized, among which eight compounds showed equivalent or higher potencies against HDAC1 as compared to vorinostat. In vitro antitumor activity assays in HCT-116, PC-3 and HL-60 cancer cells revealed six compounds with potent antitumor activities, and compound 1o showed 6- to 9-fold higher potencies compared to vorinostat. In an HCT-116 nude mice xenograft model, compound 1o displayed significant antitumor activity in both continuous and intermittent dosing schedules.     

Construction and functionalization of pyranone ring fused with pyran moiety: Design and synthesis of novel pyrano[4,3-b]pyran-5(4H)-ones as potential inhibitors of sirtuins

Novel pyrano[4,3-b]pyran-5(4H)-one based small molecules were designed as potential inhibitors of sirtuins (i.e., yeast sir2, a homolog of human SIRT1). Elegant synthesis of these compounds was performed via a multi-step sequence consisting of MCR, Sandmeyer type iodination, Sonogashira type coupling followed by iodocyclization and then Pd-mediated various C–C bond forming reactions. The overall strategy involved the construction of a pyran ring followed by the fused pyranone moiety and subsequent functionalization at C-8 position of the resultant core pyrano[4,3-b]pyran-5(4H)-one framework. The crystal structure analysis of a representative iodolactonized product (6d) is presented. Some of the synthesized compounds showed promising inhibitory activities when tested against yeast sir2 in vitro. The compound 6g showed dose dependent inhibition (IC₅₀ = 78.05 μM) of yeast sir2 and good interactions with this protein in silico.     

Design,synthesis, and evaluation of curcumin analogues as potential inhibitors of bacterial sialidase

Sialidases are key virulence factors that remove sialic acid from the host cell surface glycan, unmasking receptors that facilitate bacterial adherence and colonisation. In this study, we developed potential agents for treating bacterial infections caused by Streptococcus pneumoniae Nan A that inhibit bacterial sialidase using Turmeric and curcumin analogues. Design, synthesis, and structure analysis relationship (SAR) studies have been also described. Evaluation of the synthesised derivatives demonstrated that compound 5e was the most potent inhibitor of S. pneumoniae sialidase (IC₅₀?=?0.2?±?0.1?µM). This compound exhibited a 3.0-fold improvement in inhibitory activity over that of curcumin and displayed competitive inhibition. These results warrant further studies confirming the antipneumococcal activity 5e and indicated that curcumin derivatives could be potentially used to treat sepsis by bacterial infections.     

Design,synthesis, and evaluation of guanylhydrazones as potential inhibitors or reactivators of acetylcholinesterase

Analogs of pralidoxime, which is a commercial antidote for intoxication from neurotoxic organophosphorus compounds, were designed, synthesized, characterized, and tested as potential inhibitors or reactivators of acetylcholinesterase (AChE) using the Ellman’s test, nuclear magnetic resonance, and molecular modeling. These analogs include 1-methylpyridine-2-carboxaldehyde hydrazone, 1-methylpyridine-2-carboxaldehyde guanylhydrazone, and six other guanylhydrazones obtained from different benzaldehydes. The results indicate that all compounds are weak AChE reactivators but relatively good AChE inhibitors. The most effective AChE inhibitor discovered was the guanylhydrazone derived from 2,4-dinitrobenzaldehyde and was compared with tacrine, displaying similar activity to this reference material. These results indicate that guanylhydrazones as well as future similar derivatives may function as drugs for the treatment of Alzheimer's disease.     

Design,synthesis and bioevaluation of novel umbelliferone analogues as potential mushroom tyrosinase inhibitors

Abstract

A series of umbelliferone analogues were synthesized and their inhibitory effects on the DPPH and mushroom tyrosinase were evaluated. The results showed that some of the synthesized compounds exhibited significant mushroom tyrosinase inhibitory activities. Especially, 2-oxo-2-[(2-oxo-2H-chromen-7-yl)oxy]ethyl-2,4-dihydroxybenzoate (4e) bearing 2,4-dihydroxy substituted phenyl ring exhibited the most potent tyrosinase inhibitory activity with IC₅₀ value 8.96?µM and IC₅₀ value of kojic acid is 16.69. The inhibition mechanism analyzed by Lineweaver–Burk plots revealed that the type of inhibition of compound 4e on tyrosinase was non-competitive. The docking study against tyrosinase enzyme was also performed to determine the binding affinity of the compounds. The compounds 4c and 4e showed the highest binding affinity with active binding site of tyrosinase. The initial structure activity relationships (SARs) analysis suggested that further development of such compounds might be of interest. The statistics of our results endorses that compounds 4c and 4e may serve as a structural template for the design and development of novel tyrosinase inhibitors.     

Design,synthesis and biological evaluation of new Myo-inositol derivatives as potential RAS inhibitors

Ras is a small family of GTPases that control numerous cellular functions like cell proliferation, growth, survival, gene expression, and is closely engaged in cancer pathogenesis. The ras-targeted methodology entails a holy grail in oncology. Nevertheless, there are no specific molecules reported targeting the same, although it is a known oncogene for more than three decades. In this study, we have designed and synthesized new phosphate derivatives of Myo-inositol to inhibit the oncogenic KRAS pathway in breast cancer cells, which has been validated by cellular and theoretical studies. The synthesized compound 1b (C2-O-phosphate derivative of Myo-inositol 1,3,5-orthobenzoate) inhibited the downstream signaling pathway of oncogenic KRAS, RAF/MEK/ERK. Furthermore, we also found that this compound induced necrosis/apoptosis and causes cell cycle arrest. This class of molecules may work as a potential inhibitor of breast cancer caused by a mutation in KRAS and its downstream proteins. Though the efficacy of the molecules is in the micromolar scale, they have not been explored previously for RAS inhibition. Impressive preliminary results are presented in this article which could be further explored for its detailed biological studies to get better candidates as RAS inhibitors.     

Design,synthesis and evaluation of newer 5,6-dihydropyrimidine-2(1H)-thiones as GABA-AT inhibitors for anticonvulsant potential

Several new 5,6-dihydropyrimidine-2(1H)-thione derivatives have been prepared and investigated for their potencies for anticonvulsant activity against maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) test in mice. The acute neurotoxicity was measured by rotarod test. Compounds 3c and 3l were found active in both of the animal models. Further, in vitro GABA-AT enzyme activity assay was carried out to investigate the possible mechanism of action through GABA-AT inhibition. The most potent compounds 3c and 3l showed inhibitory potency (IC₅₀) of 18.42 μM and 19.23 μM, respectively. The molecular modeling was performed for all the synthesized compounds. The docking results were found in concordant with the observed animal studies.     

Design,synthesis and docking study of novel coumarin ligands as potential selective acetylcholinesterase inhibitors

New coumaryl-thiazole derivatives with the acetamide moiety as a linker between the alkyl chains and/or the heterocycle nucleus were synthesized and in vitro tested as acetylcholinesterase (AChE) inhibitors. 2-(diethylamino)-N-(4-(2-oxo-2H-chromen-3-yl)thiazol-2-yl)acetamide (6c, IC₅₀ value of 43?nM) was the best AChE inhibitor with a selectivity index of 4151.16 over BuChE. Kinetic study of AChE inhibition revealed that 6c was a mixed-type inhibitor. Moreover, the result of H4IIE hepatoma cell toxicity assay for 6c showed negligible cell death. Molecular docking studies were also carried out to clarify the inhibition mode of the more active compounds. Best pose of compound 6c is positioned into the active site with the coumarin ring wedged between the residues of the CAS and catalytic triad of AChE. In addition, the coumarin ring is anchored into the gorge of the enzyme by H-bond with Tyr130.     

1,3,4-Oxadiazoline derivatives as novel potential inhibitors targeting chitin biosynthesis: Design,synthesis and biological evaluation

Two series of 1,3,4-oxadiazoline heterocycle derivatives were designed, synthesized and identified. Bioactivity assays showed that all synthesized compounds inhibited chitin synthesis in yeast, suggesting they might be a novel class of potential inhibitors against chitin biosynthesis. The structure–activity relationships (SAR) of these compounds are discussed.     

Design,synthesis and biological evaluation of novel carbamates as potential inhibitors of acetylcholinesterase and butyrylcholinesterase

Rivastigmine, a dual inhibitor of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), has been approved by U.S. Food and Drug Administration to treat Alzheimer’s disease (AD) and Parkinson’s disease (PD) dementia. In the current work, a bambuterol derivative lacking one of the carbamoyloxy groups on the benzene ring (BMC-1) and its analogues were synthesized using 1-(3-hydroxyphenyl) ethan-1-one and 1-(4-hydroxyphenyl) ethan-1-one as starting materials. In-vitro cholinesterase assay established that nine compounds were more potent to inhibit both electric eel AChE and equine serum BChE than rivastigmine under the same experimental conditions. Further study confirmed that among the nine carbamates, BMC-3 (IC_50(AChE) = 792 nM, IC_50(BChE) = 2.2 nM) and BMC-16 (IC_50(AChE) = 266 nM, IC_50(BChE) = 10.6 nM) were excellent cholinesterase inhibitors with potential of permeating through the blood-brain barrier. These carbamates could be used as potential dual inhibitors of AChE and BChE and to discover novel drugs for the treatment of AD and PD dementia.     

Design and synthesis of mimics of S-adenosyl-L-homocysteine as potential inhibitors of erythromycin methyltransferases

A series of indanotriazine C-ribosides were prepared as SAH mimics, and tested for their ability to inhibit erythromycin resistance methylases Erm AM and Erm C'. A carbocyclic analogue derived from quinic acid was also synthesized and tested.     

Amberlite IR-120 Modified with 8-Hydroxyquinoline as Efficient Adsorbent for Solid-Phase Extraction and Flame Atomic Absorption Determination of Trace Amounts of Some Metal Ions

In this study, a solid-phase extraction method combined with atomic absorption spectrometry for extraction, preconcentration, and determination of iron (Fe³⁺), copper (Cu²⁺), and lead (Pb²⁺) ions at trace levels in water samples has been reported. The influences of effective parameters such as flow rate, pH, eluent conditions (type, volume, and concentration), sample volumes, and interference of matrix ions on metal ions recoveries were studied. Under optimized conditions, the limits of detection were found in the range of 0.7–2.2 μg L⁻¹, while preconcentration factors for Fe³⁺, Cu²⁺, and Pb²⁺ ions were found to be 166, 200, and 250, respectively, and loading half time (t _1/2) values were less than 2 min for all analyte ions. The proposed procedure was applied for the determination of metal ions in different water samples with recovery of >94.4% and relative standard deviation less than 4.4% for N = 5.     

Design and synthesis of potential inhibitors of the ergosterol biosynthesis as antifungal agents

A series of azolylmethyloxolane derivatives with modified sterol side-chain structures, designed as potential dual functional inhibitors of cytochrome P450 14alpha-demethylase (14DM) and delta24-sterol methyltransferase (24-SMT) based on the common characteristic features of 24-aminosterols and azole antifungal agents, were synthesized and evaluated for their antifungal activities and inhibitory activities of 14DM and 24-SMT. Among these compounds, imidazolylmethyloxolane derivatives 28a and 28b showed potent in vitro antifungal activities comparable to those of itraconazole. However, the in vitro bioactivities have not been linearly translated into in vivo protection data for some unknown reasons.     

Novel thiobarbiturates as potent urease inhibitors with potential antibacterial activity: Design,synthesis, radiolabeling and biodistribution study

Urease enzyme is a virulence factor that helps in colonization and maintenance of highly pathogenic bacteria in human. Hence, the inhibition of urease enzymes is well-established to be a promising approach for preventing deleterious effects of ureolytic bacterial infections. In this work, novel thiobarbiturate derivatives were synthesized and evaluated for their urease inhibitory activity. All tested compounds effectively inhibited the activity of urease enzyme. Compounds 1, 2a, 2b, 4 and 9 displayed remarkable anti-urease activity (IC₅₀ = 8.21–16.95 μM) superior to that of thiourea reference standard (IC₅₀ = 20.04 μM). Moreover, compounds 3a, 3g, 5 and 8 were equipotent to thiourea. Among the tested compounds, morpholine derivative 4 (IC₅₀ = 8.21 µM) was the most potent one, showing 2.5 folds the activity of thiourea. In addition, the antibacterial activity of the synthesized compounds was estimated against both standard strains and clinical isolates of urease producing bacteria. Compound 4 explored the highest potency exceeding that of cephalexin reference drug. Moreover, biodistribution study using radiolabeling approach revealed a remarked uptake of ^99mTc-compound 4 into infection induced in mice. Furthermore, a molecular docking analysis revealed proper orientation of title compounds into the urease active site rationalizing their potent anti-urease activity.