In Silico Drug Discovery Strategies Identified ADMET Properties of Decoquinate RMB041 and Its Potential Drug Targets against Mycobacterium tuberculosis.

The highly adaptive cellular response of Mycobacterium tuberculosis to various antibiotics and the high costs for clinical trials, hampers the development of novel antimicrobial agents with improved efficacy and safety. Subsequently, in silico drug screening methods are more commonly being used for the discovery and development of drugs, and have been proven useful for predicting the pharmacokinetics, toxicities, and targets, of prospective new antimicrobial agents. In this investigation we used a reversed target fishing approach to determine potential hit targets and their possible interactions between M. tuberculosis and decoquinate RMB041, a propitious new antituberculosis compound. Two of the 13 identified targets, Cyp130 and BlaI, were strongly proposed as optimal drug-targets for dormant M. tuberculosis, of which the first showed the highest comparative binding affinity to decoquinate RMB041. The metabolic pathways associated with the selected target proteins were compared to previously published molecular mechanisms of decoquinate RMB041 against M. tuberculosis, whereby we confirmed disrupted metabolism of proteins, cell wall components, and DNA. We also described the steps within these pathways that are inhibited and elaborated on decoquinate RMB041's activity against dormant M. tuberculosis. This compound has previously showed promising in vitro safety and good oral bioavailability, which were both supported by this in silico study. The pharmacokinetic properties and toxicity of this compound were predicted and investigated using the online tools pkCSM and SwissADME, and Discovery Studio software, which furthermore supports previous safety and bioavailability characteristics of decoquinate RMB041 for use as an antimycobacterial medication. IMPORTANCE This article elaborates on the mechanism of action of a novel antibiotic compound against both, active and dormant Mycobacterium tuberculosis and describes its pharmacokinetics (including oral bioavailability and toxicity). Information provided in this article serves useful during the search for drugs that shorten the treatment regimen for Tuberculosis and cause minimal adverse effects.

Topical Delivery of Artemisone, Clofazimine and Decoquinate Encapsulated in Vesicles and Their In vitro Efficacy Against Mycobacterium tuberculosis.

Vesicles are widely investigated as carrier systems for active pharmaceutical ingredients (APIs). For topical delivery, they are especially effective since they create a "depot-effect" thereby concentrating the APIs in the skin. Artemisone, clofazimine and decoquinate were selected as a combination therapy for the topical treatment of cutaneous tuberculosis. Delivering APIs into the skin presents various challenges. However, utilising niosomes, liposomes and transferosomes as carrier systems may circumvent these challenges. Vesicles containing 1% of each of the three selected APIs were prepared using the thin-film hydration method. Isothermal calorimetry, differential scanning calorimetry and hot-stage microscopy indicated no to minimal incompatibility between the APIs and the vesicle components. Encapsulation efficiency was higher than 85% for all vesicle dispersions. Vesicle stability decreased and size increased with an increase in API concentration; and ultimately, niosomes were found the least stable of the different vesicle types. Skin diffusion studies were subsequently conducted for 12 h on black human female skin utilising vertical Franz diffusion cells. Transferosomes and niosomes delivered the highest average concentrations of clofazimine and decoquinate into the skin, whereas artemisone was not detected and no APIs were present in the receptor phase. Finally, efficacy against tuberculosis was tested against the Mycobacterium tuberculosis H37Rv laboratory strain. All the dispersions depicted some activity, surprisingly even the blank vesicles portrayed activity. However, the highest percentage inhibition (52%) against TB was obtained with niosomes containing 1% clofazimine.

Deposition and depletion of decoquinate in eggs after administration of cross-contaminated feed.

Decoquinate, a chemical coccidiostat used as a feed additive, can occur in eggs due to cross-contamination of feedstuffs for laying hens. An experiment was designed to assess the transfer of decoquinate to hen eggs and its distribution between egg yolk and egg white. Hens were given the feed containing decoquinate at a cross-contamination level (0.34 mg kg(-1)) and collected eggs were analysed using an LC-MS/MS method. The plateau level was reached on the eighth day of the experiment and averaged 8.91 µg kg(-1), which is far below the maximum level established at 20 µg kg(-1) for whole eggs. Decoquinate was deposited mostly in egg yolks (26.2 µg kg(-1)) and did not deplete completely during 14 days of administration of decoquinate-free feed. The results confirmed that administration of cross-contaminated feed is associated with very low risk of non-compliant residue levels of decoquinate in eggs.

Metabolism of decoquinate in chickens and Japanese quail.

Thirty mature chicken hens and 40 mature Japanese quail hens were used in an experiment to compare pathways of decoquinate (DQ) excretion. Labelled DQ was injected into chickens (.5 microCi via wing vein puncture) and quail (.25 microCi via cardiac puncture) on Day 0. Blood was sampled at 0, 1.5, 3, 6, 9, 12, 24, and 48 h postinjection. Eggs and excreta of chickens and quail were collected for 28 and 14 days, respectively, and analyzed for 14C. Six chickens and eight quail were sacrificed prior to 14C-DQ injection and also on Days 1, 7, 14, and 34 or 32 postinjection. Samples of liver, heart, kidney, bile, skin, fat, and muscle were analyzed for 14C. Blood rapidly cleared 14C in both species, and the half-time of 14C excretion via excreta was more rapid in quail (.37 day) than in chickens (.92 day). Little 14C was found in the eggs of quail (.32% of dose) and chickens (.17% of dose). Quail appeared to excrete peak amounts of detectable 14C 1 day earlier (Day 4) than chickens (Day 5). Liver contained the greatest concentration of 14C on Day 1 in both species. By the end of the experiment, less than 1% of the dose remained in liver or other organs. Results indicate that chickens and quail metabolize 14C-DQ at comparable rates and by similar pathways.

Glucose phosphate isomerase isozymes as genetic markers for lines of Eimeria tenella.

Two strains of Eimeria tenella with different decoquinate sensitivity and different glucose phosphate isomerase (GPI) isozymes were used in genetic recombination experiments: a line derived from a laboratory strain (NIAH) was decoquinate-resistant (DR) and had the isozyme GPI-9, while a field isolate (Iwate strain) was decoquinate-sensitive (DS) and had GPI-1. Coccidia-free chickens were orally inoculated with mixed oocysts of the two strains and parasites of the F1 generation were recovered. The F1 progeny showed both forms of the isozyme. Next, oocysts of the F1 progeny were passaged through chickens given the decoquinate-containing diet. The F2 progeny also had GPI-1 and GPI-9, indicating cross-fertilization between the two strains. Six single oocysts were isolated from F2 progeny; 1 showed both phenotypes of GPI, 1 had GPI-1 and the remaining 4 lines had GPI-9. Analysis of the amount of GPI in recombinant oocysts suggested that the proliferation rate of the DR strain was slower than that of the DS strain. We concluded that GPI isozymes in E. tenella can serve as useful markers in experiments on chicken coccidia.

Comparative metabolism of 14C-decoquinate in chickens, quail and sheep.

Removal of pulse doses of 14C-decoquinate from blood was studied in chicken hens, quail hens, and ewe lambs. Estimated clearance before the first post-injection sample at 1 1/2 hr was 96% for sheep, 99% for chickens and over 99% for quail. Half-times for removal of the remaining radioactivity from the blood were 26.8 hr for sheep, 144.7 hr for chickens and 27.2 hr for quail. Treating the chicken data as biphasic yielded a 3.4 hr half-time for an initial fast phase and 210 hr for a later slow phase. Radioactivity disappeared from sheep blood between 2 and 7 d, from chicken blood between 7 and 14 d, and from quail blood between 1 and 2 d. Urine accounted for 35% of the radioactivity administered to sheep. It did not contain detectable activity after the third day.