Syntheses of 4,6-dihydroxypyrimidine diones, their urease inhibition, in vitro, in silico, and kinetic studies.

A library of 4,6-dihydroxypyrimidine diones (1-35) were synthesized and evaluated for their urease inhibitory activity. Structure-activity relationships, and mechanism of inhibition were also studied. All compounds were found to be active with IC50 values between 22.6±1.14-117.4±0.73µM, in comparison to standard, thiourea (IC50=21.2±1.3µM). Kinetics studies on the most active compounds 2-7, 16, 17, 28, and 33 were performed to investigate their modes of inhibition, and dissociation constants Ki. Compounds 2, 3, 7, 16, 28, and 33 were found to be mixed-type of inhibitors with Ki values in the range of 7.91±0.024-13.03±0.013µM, whereas, compounds 4-6, and 17 were found to be non-competitive inhibitors with Ki values in the range of 9.28±0.019-13.05±0.023µM. In silico study was also performed, and a good correlation was observed between experimental and docking studies. This study is continuation of our previously reported urease inhibitory activity of pyrimidine diones, representing potential leads for further research as possible treatment of diseases caused by ureolytic bacteria.

Dihydropyrimidine based hydrazine dihydrochloride derivatives as potent urease inhibitors.

Four series of heterocyclic compounds 4-dihydropyrimidine-2-thiones 7-12 (series A), N,S-dimethyl-dihydropyrimidines 13-18 (series B), hydrazine derivatives of dihydropyrimidine 19-24 (series C), and tetrazolo dihydropyrimidine derivatives 25-30 (series D), were synthesized and evaluated for in vitro urease inhibitory activity. The series B-D were first time examined for urease inhibition. Series A and C were found to be significantly active with IC50 values between 34.7-42.9 and 15.0-26.0 µM, respectively. The structure-activity relationship showed that the free S atom and hydrazine moiety are the key pharmacophores against urease enzyme. The kinetic studies of the active series A (7-12) and C (19-24) were carried out to determine their modes of inhibition and dissociation constants Ki. Compounds of series A (7-12) and series C (19-24) showed a mixed-type of inhibition with Ki values ranging between 15.76-25.66 and 14.63-29.42 µM, respectively. The molecular docking results showed that all the active compounds of both series have significant binding interactions with the active sites specially Ni-ion of the urease enzyme. Cytotoxicity of all series A-D was also evaluated against mammalian mouse fibroblast 3T3 cell lines, and no toxicity was observed in cellular model.

RNAi by Soaking Aedes aegypti Pupae in dsRNA.

RNA-interference (RNAi) is a standard technique for functional genomics in adult mosquitoes. However, RNAi in immature, aquatic mosquito stages has been challenging. Several studies have shown successful larval RNAi, usually in combination with a carrier molecule. Except for one study in malaria mosquito, Anopheles gambiae, none of the previous studies has explored RNAi in mosquito pupae. Even in the study that used RNAi in pupae, double stranded RNA (dsRNA) was introduced by microinjection. Here, we describe a successful method by soaking pupae in water containing dsRNA without any carrier or osmotic challenge. The knockdown persisted into adulthood. We expect that this simple procedure will be useful in the functional analysis of genes that highly express in pupae or newly emerged adults.

The sugar substitute erythritol shortens the lifespan of Aedes aegypti potentially by N-linked protein glycosylation.

Adult male and female mosquitoes consume sugar as floral and extrafloral nectar. Earlier work demonstrated that mosquito populations and their vector potential are dependent upon the availability of sugar sources. Thus, a novel method of vector control may involve targeting sugar-feeding mosquitoes. Multiple human-safe sugar substitutes are already approved by the U.S. Food and Drug Administration and are readily available. However, plant-based sugar substitutes such as stevia (erythritol) have been shown to affect lifespan in other flies. Therefore, the current study was carried out to test the potential of commercially available sugar substitutes to adversely affect the survival, fecundity, and metabolism of adult Aedes aegypti mosquitoes. Of the four sugar substitutes tested, erythritol (Stevia), sucralose (Splenda), aspartame (Equal), and saccharin (Sweet'N Low), only erythritol negatively affected mosquito longevity and fecundity. The effect on fecundity was probably due in part to a corresponding decrease in glycogen and lipid levels over time in mosquitoes fed on erythritol. Comparative mosquito head transcriptomes indicated upregulation of a gene in the mannose biosynthesis pathway in females fed on erythritol, suggesting that N-linked glycosylation might be responsible for the negative impact of erythritol feeding in mosquitoes. Mosquitoes preferred sucrose when a choice was given but were not averse to erythritol. Our results suggest the possibility of using erythritol alone or in combination with sucrose as a component of attractive toxic sugar baits for a human-safe approach for mosquito control.

Relating neural processing of reward and loss prospect to risky decision-making in individuals with and without Gambling Disorder.

Neuroimaging studies demonstrate alterations in fronto-striatal neurocircuitry in gambling disorder (GD) during anticipatory processing, which may influence decision-making impairments. However, to date little is known about fronto-striatal anticipatory processing and emotion-based decision-making. While undergoing neuroimaging, 28 GD and 28 healthy control (HC) participants performed the Monetary Incentive Delay Task (MIDT). Pearson correlation coefficients assessed out-of-scanner Iowa Gambling Task (IGT) performance with the neural activity during prospect (A1) processing on the MIDT across combined GD and HC groups. The HC and GD groups showed no significant difference in out-of-scanner IGT performance, although there was a trend for higher IGT scores in the HC group on the last two IGT trial blocks. Whole-brain correlations across combined HC and GD groups showed that MIDT BOLD signal in the ventral striatum/caudate/ventromedial prefrontal cortex and anterior cingulate regions during the prospect of winning positively correlated with total IGT scores. The GD group also contained a higher proportion of tobacco smokers, and correlations between neural activations in prospect on the MIDT may relate in part to gambling and/or smoking pathology. In this study, fronto-striatal activity during the prospect of reward and loss on the MIDT was related to decision-making on the IGT, with blunted activation linked to disadvantageous decision-making. The findings from this work are novel in linking brain activity during a prospect-of-reward phase with performance on a decision-making task in individuals with and without GD.

Synthesis and dynamics studies of barbituric acid derivatives as urease inhibitors.

BACKGROUND: Discovery of potent inhibitors of urease (jack bean) enzyme is the first step in the development of drugs against diseases caused by ureolytic enzyme. RESULTS: Thirty-two derivatives of barbituric acid as zwitterionic adducts of diethyl ammonium salts were synthesized. All synthesized compounds (4a-z and 5a-s) were screened for their in vitro inhibition potential against urease enzyme (jack bean urease). The compounds 4i (IC50 = 17.6 ± 0.23 µM) and 5l (IC50 = 17.2 ± 0.44 µM) were found to be the most active members of the series, and showed several fold more urease inhibition activity than the standard compound thiourea (IC50 = 21.2 ± 1.3 µM). Whereas, compounds 4a-b, 4d-e, 4g-h, 4j-4r, 4x, 4z, 5b, 5e, 5k, 5n-5q having IC50 values in the range of 22.7 ± 0.20 µM-43.8 ± 0.33 µM, were also found as potent urease inhibitors. Furthermore, Molecular Dynamics simulation and molecular docking studies were carried out to analyze the binding mode of barbituric acid derivatives using MOE. During MD simulation enol form is found to be more stable over its keto form due to their coordination with catalytic Nickel ion of Urease. Additionally, structural-activity relationship using automated docking method was applied where the compounds with high biological activity are deeply buried within the binding pocket of urease. As multiple hydrophilic crucial interactions with Ala169, KCX219, Asp362 and Ala366 stabilize the compound within the binding site, thus contributing greater activity. CONCLUSIONS: This research study is useful for the discovery of economically, efficient viable new drug against infectious diseases.Graphical abstract:STD. Thiourea (IC50 = 21.2 ± 1.3 µM).