Synthesis and evaluation of febrifugine derivatives as anticoccidial agents

A series of new febrifugine derivatives with a 4(3H)-quinazolinone scaffold were synthesized and evaluated for their anticoccidial activity both in vitro and in vivo. The targets' in vitro activity against Eimeria tenella was studied using quantitative real-time reverse transcription polymerase chain reaction and Madin-Darby bovine kidney cells. Most of these compounds demonstrated anticoccidial efficacy, with inhibition ratios ranging from 3.3% to 85.7%. Specifically, compounds 33 and 34 showed significant inhibitory effects on the proliferation of E. tenella and exhibited lower cytotoxicity compared to febrifugine. The IC50 values of compounds 33 and 34 were 3.48 and 1.79 μM, respectively, while the CC50 values were >100 μM for both compounds. Furthermore, in a study involving 14-day-old chickens infected with 5 × 104 sporulated oocysts, treatment with five selected compounds (22, 24, 28, 33, and 34), which exhibited in vitro inhibition rate of over 50% at 100 μM, at a dose of 40 mg/kg in daily feed for 8 consecutive days showed that compound 34 possessed moderate in vivo activity against coccidiosis, with an anticoccidial index of 164. Structure-activity relationship studies suggested that spirocyclic piperidine may be a preferable substructure to maintain high effectiveness in inhibiting Eimeria spp., when the side chain 1-(3-hydroxypiperidin-2-yl)propan-2-one was replaced.

Response Surface Optimization of Dispersive Solid-Phase Extraction Combined with HPLC for the Rapid Analysis of Multiple Coccidiostats in Feed

Since antimicrobials were banned as feed additives, coccidiostats with favorable anticoccidial action and growth promotion have been widely used in the breeding industry. The monitoring of coccidiostats in feed is necessary, while the current methods based on mass-spectrometer analysis have limited applicability and matrix effects could interfere with the results. Accordingly, in the present paper, a rapid analytical strategy for the simultaneous determination of six synthetic coccidiostats in feed using high-performance liquid chromatography coupled with diode-array detection was developed. Coccidiostats in chicken feeds were extracted with the trichloroacetic acid-acetonitrile solution. The cleanup was performed by dispersive solid-phase extraction after the optimization of the response surface methodology. The method exhibited good linearity for target coccidiostats within the range of 0.05~20 µg/mL. Recoveries for six compounds in fortified feed samples were from 67.2% to 107.2% with relative standard deviations less than 9.6%. The limit of detection was 0.2~0.3 mg/kg. The successful application of the method in commercial feed verified that it is effective and sensitive for the rapid determination of multiple coccidiostats in chicken feeds.

Evaluation of ursolic acid derivatives with potential anti-Toxoplasma gondii activity

Toxoplasma gondii is an important pathogen that causes serious public health problems. Currently, therapeutic drugs for toxoplasmosis cause serious side effects, and more effective and novel substances with relatively low toxicity are urgently needed. Ursolic acid (UA) has many properties that can be beneficial to healthcare. In this study, we synthesized eight series of UA derivatives bearing a tetrazole moiety and evaluated their anti-T. gondii activity in vitro using spiramycin as a positive control. Most of the synthesized derivatives exhibited better anti-T. gondii activity in vitro than UA, among which compound 12a exhibited the most potent anti-T. gondii activity. Furthermore, the results of biochemical parameter determination indicated that 12a effectively restored the normal body weight of mice infected with T. gondii, reduced hepatotoxicity, and exerted significant anti-oxidative effects compared with the findings for spiramycin. Additionally, our molecular docking study indicated that the synthesized compounds could act as potential inhibitors of T. gondii calcium-dependent protein kinase 1 (TgCDPK1), with 12a possessing strong affinity for TgCDPK1 via binding to the key amino acids GLU129 and TYR131.

Pharmacokinetics, Activity, and Residue Elimination of R- and S-Diclazuril in Broiler Chickens

Diclazuril (DIC) is widely used as a racemic mixture to prevent and treat coccidiosis in farm animals, while the pharmacokinetics, bioactivity, and toxicity of DIC enantiomers are not known at all. This study first established a simple, sensitive, and reliable liquid chromatography tandem mass spectrometry method for separation of R-DIC and S-DIC and their analyses. Then, it was applied to investigate the stereoselective pharmacokinetics and residual elimination of individual enantiomers, and their anticoccidial activity was also evaluated in broiler chickens. The results indicated that the area under the concentration-time curve (AUC) and elimination half-life (t_1/2β) were significantly different (p < 0.05) for two enantiomers in chicken plasma. The AUC and t_1/2β of S-DIC were approximately 2 and 1.4 times those of R-DIC, respectively. The residual elimination of DIC enantiomers in chicken tissues was also stereoselective. The concentrations of S-DIC in chicken muscle and liver were greater than those of R-DIC, and it is the opposite in the kidney. There was no significant difference (p > 0.05) in the anticoccidial activity of racemate and enantiomers when a single enantiomer in feed was added above 0.5 mg kg^-1. However, the anticoccidial activity of R-DIC (0.25 mg kg^-1) was significantly higher (p < 0.05) than that of S-DIC (0.25 mg kg^-1) in the diet. It should be mentioned that in chicken small intestine and cecum, the enantiomerization rate of each enantiomer in the infection group was faster than that in the uninfected group.

Anticoccidial effects of Khaya senegalensis aqueous stem bark extract on broiler chickens experimentally infected with Eimeria species

Graded concentrations (200, 400 and 800 mg/kg) of the aqueous stem bark extract of Khaya senegalensis was evaluated for its therapeutic efficacy against experimentally induced coccidiosis in broiler chicken. The phytochemical analysis shows the presence of tannins, saponins, cardiac glycosides and steroids. There was significant reduction in oocyst count across the groups in a graded dose manner with 800 mg/kg being the most efficacious dose. There was also weight gain across the treatment groups with immuno-modulatory and erythropoetic activities observed. Also, a significant (p < 0.05) graded dose-dependent reduction in the oocyst count in the treatment groups. A significant (p < 0.05) increase in mean weight gain was also recorded across the experimental groups except the negative control. The haematology also showed a dose-dependent increase in red blood cells, haemoglobin and packed cell volume of the treatment groups. The extract had no significant difference (p > 0.05) on the white blood cells, but a slight decrease in the white blood cells and heterophil counts was observed at 400 mg/kg. Furthermore, the aspartate amino transaminase level showed a significant difference (p < 0.05). Fluctuating levels of other serum biochemical parameters such as total protein, albumin and potassium were observed. No significant difference (p > 0.05) in the sodium concentration was observed. In addition, oxidative stress biomarkers such as catalase significantly increased (p < 0.05) in all the experimental groups in addition to the concomitant increase in reduced gluthathione (GSH) and superoxide dismutase (SOD) levels. Conclusively, the aqueous extract of K. senegalensis was effective in the management of coccidiosis thus supporting its folkloric use.

Detection of p-Nitroaniline Released from Degradation of 4,4'-Dinitrocarbanilide in Chicken Breast during Thermal Processing

The diphenylurea 4,4'-dinitrocarbanilide (DNC) is the residue of concern left in edible tissues of broilers fed diets containing the anticoccidial nicarbazin. When chicken meat is submitted to thermal processing, p-nitroaniline (p-NA) is expected from DNC degradation. This work aimed at evaluating whether thermal processing of DNC-containing chicken meat induces p-NA appearance. First, a hydrolysis assay was performed in aqueous solutions at 100 °C in different pH, confirming that DNC cleavage yields p-NA. Then a novel LC-MS/MS method was used to detect traces of this aromatic amine in DNC-containing chicken breast fillets subjected to cooking methods. Our evidence showed p-NA occurrence in such chicken meat samples, which corroborated results from hydrolysis assay. The p-NA appearance in fillets was rather discrete during boiling treatment, but its concentration became pronounced over time for grilling, frying, and roasting, achieving respectively 326.3, 640.0, and 456.9 μg/kg. As far as we are concerned, no other research identified degradation products from DNC residue in heat-processed chicken fillets. Therefore, this study leads to additional approaches to assess impacts on food safety.

THE EFFICACY OF THREE MEDICINAL PLANTS: GARLIC, GINGER AND MIRAZID AND A CHEMICAL DRUG METRONIDAZOLE AGAINST CRYPTOSPORIDIUM PARVUM. I-IMMUNOLOGICAL RESPONSE

Cryptosporidisis parvum is a zoonotic protozoan parasite infects intestinal epithelial cells causing a major health problem for man and animals. Experimentally the immunologic mediated elimination of C. parvum requires CD4+ T cells and IFN-gamma. But, the innate immune responses also have a significant protective role in both man and animals. the mucosal immune response to C. parvum in C57BL/6 neonatal and GKO mice shows a concomitant Thl and Th2 cytokine mRNA expression, with a crucial role for IFN-gamma in the resolution of the infection. NK cells and IFN-gamma have been shown to be important components in immunity in T and B cell-deficient mice, but IFN-gamma-dependent resistance is demonstrated in alymphocytic mice. Epithelial cells may play a vital role in immunity as once infected these cells have increased expression of inflammatory chemokines and cytokines and demonstrate anti-infection killing mechanisms. C. parvum immunological response was used to evaluate the efficacy of anti-cryptosporidisis agents of Garlic, Ginger, Mirazid and Metronidazole in experimentally infected mice.

Reduction of Toxoplasma gondii Development Due to Inhibition of Parasite Antioxidant Enzymes by a Dinuclear Iron(III) Compound

Toxoplasma gondii, the causative agent of toxoplasmosis, is an obligate intracellular protozoan that can infect a wide range of vertebrate cells. Here, we describe the cytotoxic effects of the dinuclear iron compound [Fe(HPCINOL)(SO4)]2-μ-oxo, in which HPCINOL is the ligand 1-(bis-pyridin-2-ylmethyl-amino)-3-chloropropan-2-ol, on T. gondii infecting LLC-MK2 host cells. This compound was not toxic to LLC-MK2 cells at concentrations of up to 200 μM but was very active against the parasite, with a 50% inhibitory concentration (IC50) of 3.6 μM after 48 h of treatment. Cyst formation was observed after treatment, as indicated by the appearance of a cyst wall, Dolichos biflorus lectin staining, and scanning and transmission electron microscopy characteristics. Ultrastructural changes were also seen in T. gondii, including membrane blebs and clefts in the cytoplasm, with inclusions similar to amylopectin granules, which are typically found in bradyzoites. An analysis of the cell death pathways in the parasite revealed that the compound caused a combination of apoptosis and autophagy. Fluorescence assays demonstrated that the redox environment in the LLC-MK2 cells becomes oxidant in the presence of the iron compound. Furthermore, a reduction in superoxide dismutase and catalase activities in the treated parasites and the presence of reactive oxygen species within the parasitophorous vacuoles were observed, indicating an impaired protozoan response against these radicals. These findings suggest that this compound disturbs the redox equilibrium of T. gondii, inducing cystogenesis and parasite death.

Biodegradation and speciation of roxarsone in an anaerobic granular sludge system and its impacts

Roxarsone (3-nitro-4-hydroxy benzene arsenic acid) is an organoarsenic feed additive and has been widely used in the poultry industry to prevent coccidiosis and improve feed efficiency. The presence of roxarsone and its degradation products results in the instability of the anaerobic methanogenic process. This study investigated the degradation and speciation of roxarsone in an anaerobic granular sludge (AGS) system and the impacts of roxarsone and its degradation products on the structure of AGS. Roxarsone inhibited methane production, and the added roxarsone was rapidly degraded into 3-amino-4-hydroxyphenylarsonic acid (HAPA). After 240 days of incubation, the distribution of arsenic differed between the aqueous solution and the AGS in the assays of 20 and 350mg/L roxarsone. Species analysis indicated that HAPA was completely degraded in all of the assays with roxarsone addition after 240 days of incubation. Species distribution was affected by the phases and the initial concentration of roxarsone added. The concentration of As(III) was higher than that of As(V) in both the aqueous solution and the AGS in all assays with roxarsone addition. The toxicity of roxarsone and its degradation products resulted in changes in the structure and the microorganism species in the AGS.

Evaluation of anti-coccidial effects of 1-[4-(4-nitrophenoxy)phenyl]propane-1-one and identification of its potential target proteins in Toxoplasma gondii

Coccidiosis affects many vertebrates worldwide, but treatment with known anti-coccidial drugs causes several adverse side effects. There is a critical need for the development and evaluation of new drugs. The anti-coccidial effect of 1-[4-(4-nitrophenoxy)phenyl]propane-1-one (NPPP), a synthetic compound, was studied in vitro and in vivo. Treatment with NPPP showed anti-Toxoplasma activity in vitro with a lower EC50 value than pyrimethamine. In ICR mice infected with Toxoplasma gondii, oral administration of NPPP for 4 days showed statistically significant anti-Toxoplasma activity with lower numbers of tachyzoite than those of the negative control (p < 0.01). NPPP also exhibited strong anti-Eimeria activity in Eimeria tenella-infected chickens when treated for 4 days with orally administered NPPP at a dose of 100 mg/kg. Potential target proteins of NPPP were analyzed by proteomic profiles of T. gondii tachyzoites. Two hypothetical proteins were identified as possible targets of NPPP, a putative ortholog of vacuolar ATP synthase subunit C and a class I S-adenosylmethionine-dependent methyltransferase. Our data show that the NPPP might be an anti-coccidial drug candidate for clinical application against coccidial infections. Future investigations will focus on identifying the function of proteins regulated by NPPP.

Occurrence of arsenic impurities in organoarsenics and animal feeds

Organoarsenics are widely used as excellent feed additives in animal production in the world. Roxarsone (ROX) and arsanilic acid (ASA) are two organoarsenics permitted to be used in China. We collected 146 animal feed samples to investigate the appearance of ROX, ASA, and potential metabolites, including 3-amino-4-hydroxyphenylarsonic acid (3-A-HPA), 4-hydroxyphenylarsonic acid (4-HPA), As(V), As(III), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) in feeds. The stability of ROX in both ROX additives and animal feeds was also examined. The results show that 25.4% of the 146 animal feeds contained organoarsenics, with average contents of ROX and ASA as 7.0 and 21.2 mg of As/kg, respectively. Unexpectedly, As(III) and MMA frequently occurred as As impurities in feeds bearing organoarsenics, with higher contents than organoarsenics in some samples. 3-A-HPA, 4-HPA, and DMA were not detected in all samples. ROX and As impurities in both ROX additives and feeds stayed unchanged in the shelf life. It suggests that As impurities in animal feeds bearing organoarsenics should generate from the use of organoarsenics containing As impurities. This constitutes the first report of As impurities in organoarsenics.

Development of Toxoplasma gondii calcium-dependent protein kinase 1 (TgCDPK1) inhibitors with potent anti-toxoplasma activity

Toxoplasmosis is a disease of prominent health concern that is caused by the protozoan parasite Toxoplasma gondii. Proliferation of T. gondii is dependent on its ability to invade host cells, which is mediated in part by calcium-dependent protein kinase 1 (CDPK1). We have developed ATP competitive inhibitors of TgCDPK1 that block invasion of parasites into host cells, preventing their proliferation. The presence of a unique glycine gatekeeper residue in TgCDPK1 permits selective inhibition of the parasite enzyme over human kinases. These potent TgCDPK1 inhibitors do not inhibit the growth of human cell lines and represent promising candidates as toxoplasmosis therapeutics.

A new approach to the analysis of nicarbazin and ionophores in eggs by HPLC/MS/MS

An HPLC/MS/MS method has been developed and validated for the quantification and confirmation of nicarbazin and ionophores (lasalocid, monensin, salinomycin, and narasin) in eggs. Nicarbazin is determined in the negative electrospray mode with a basic mobile phase that supports creation of negative ions. Consequently, our ability to maintain instrument sensitivity over time has significantly improved. The analysis of the ionophores is done in the positive electrospray mode using ammonium buffer for HPLC separation. Monitoring ammonium adduct parent ions resulted in enhanced sensitivity and better reproducibility of the ionophore analysis. The validation of this improved HPLC/MS/MS method for the detection of nicarbazin and the ionophores demonstrated excellent precision of below 10% RSD and lower LOD values (microg/kg) for nicarbazin (0.018), lasalocid (0.015), monensin (0.015), salinomycin (0.033), and narasin (0.039).

Anti-coccidial effect of Commiphora molmol in the domestic rabbit (Oryctolagus cuniculus domesticus L.)

This study investigated the effect of oleo-gum-resin of Commiphora monlmol Engler (Family: Burceraceae) known as Myrrh and the commercial extract known as Mirazid as a treatment against hepatic coccidiosis induced by the parasite Eimeria stiedae in domestic rabbits. Rabbits were infected with 1000 parasite sporulated oocysts and subjected to two treatment regimens, using crude myrrh suspension and the oleo-resin extract, mirazid, each administered at 500 mg/kg rabbit body weight. Treatments of infected rabbits resulted in significant reduction of the mean oocyst numbers in rabbit faeces by 52.38% in the crude-treated rabbits and by 90.90% mirazid-treated rabbits, compared to the untreated infected rabbits at day 21 post-infection (pi). At day 28 pi no oocysts parasite were observed in the faeces of rabbits. Both treatments resulted in significant recovery of infected rabbits from all symptoms of infection compared to the untreated infected group and healthy control groups. Histopathological examination of liver showed remarkable improvement in all histopathological parameters in G5 and G8 compared with the infected untreated G2. These included an almost complete healing of the hemorrhagic tissue and partial healing of the endothelial lining and hepatocytes encircling the central vein, the hepatocytes laminate regained their original radial shape and disappearance of fat vacuoles from the tissue and remarkable reduction in lymphocytes infiltration, decreased hyperplasia of the epithelial cells with significant decreasing of the parasite stage numbers. Results also indicate that mirazid was more effective than crude myrrh, probably due to higher content of purified active ingredients.

Fate and antibacterial potency of anticoccidial drugs and their main abiotic degradation products

The antibacterial potency of eight anticoccidial drugs was tested in a soil bacteria bioassay (pour plate method), EC(50)-values between 2.4 and 19.6 microM were obtained; however, one compound, nicarbazin exhibited an EC(50)-value above the maximum tested concentration (21 microM, 9.1 mg L(-1)). The potency of mixtures of two of the compounds, narasin and nicarbazin, was synergistic (more than additive) with 10-fold greater antibacterial potency of the mixture than can be explained by their individual EC(50)-values. The influence of pH, temperature, oxygen concentration and light on the transformation of robenidine and salinomycin was investigated. Robenidine was transformed by photolysis (DT(50) of 4.1 days) and was unstable at low pH (DT(50) of approximately 4 days); salinomycin was merely transformed at low pH, the latter into an unknown number of products. The antibacterial potency of the mixtures of transformation products of robenidine after photolysis and at low pH was comparable with that of the parent compound. Finally five photo-transformation products of robenidine were structural elucidated by accurate mass measurements, i-FIT values (isotopic pattern fit) and MS/MS fragmentation patterns.

Effect of micelle interface on the binding of anticoccidial PW2 peptide

PW2 is an anticoccidial peptide active against Eimeria acervulina and Eimeria tenella. We determined the structure of PW2 in dodecylphosphocholine micelles. The structure showed two distinct regions: an amphipathic N-terminal 3(10) helix and an aromatic region containing WWR interface-binding motif. The aromatic region acted as a scaffold of the protein in the interface and shared the same structure in both DPC and SDS micelles. N-terminal helix interacted with DPC but not with SDS interface. Chemical shift change was slow when SDS was added to PW2 in DPC and fast when DPC was added to PW2 in SDS, indicating that interaction with DPC micelles was kinetically more stable than with SDS micelles. Also, DPC interface was able to accommodate PW2, but it maintained the conformational arrangement in the aromatic region observed for SDS micelles. This behavior, which is different from that observed for other antimicrobial peptides with WWR motif, may be associated with the absence of PW2 antibacterial activity and its selectivity for Eimeria parasites.

Isolation, structure, and coccidiostat activity of coccidiostatin A

Coccidiosis is one of the more common and costly diseases in poultry that is caused by various Eimeria species. In our quest to discover coccidiostats from natural products, we discovered a microbial fermentation extract that exhibited in vivo anticoccidial activity. Fractionation of this extract led to the discovery of two potent antiprotozoals, emecorrugatin A (1) and coccidiostatin A (2). The former compound exhibited only in vitro activity, whereas the latter new compound exhibited in vivo activity against Eimeria species in chickens at 150 ppm dosed in chicken feed. The isolation, structure elucidation, relative configuration, and activity of coccidiostatin A (2) are described.

Use of antigen mimics to produce specific antibodies to anti-coccidial drugs

A range of polyclonal antibodies was successfully produced to the coccidiostatic drugs diclazuril and robenidine. Initial attempts to make immunogenic complexes of both drugs were ineffective due to difficulties encountered while trying to couple the compounds to large carrier proteins. Structural mimics, which could act as haptens for each drug, were sought and identified. The compounds identified were more open to chemical manipulation and were conjugated to carrier proteins to produce effective immunogens. The most sensitive antisera produced displayed IC50s of 1.5 ng/ml and 13 ng/ml for diclazuril and robenidine respectively. The antibody for diclazuril was shown to be specific, cross-reacting only with clazuril by 15%. The robenidine antibody displayed a low cross-reactivity of 1.2% to the compound used to produce the antibody.

Synthesis and biological activity of imidazopyridine anticoccidial agents: part I

Coccidiosis is the major cause of morbidity and mortality in the poultry industry. Protozoan parasites of the genus Eimeria invade the intestinal lining of the avian host causing tissue pathology, poor weight gain, and in some cases mortality. Resistance to current anticoccidials has prompted the search for new therapeutic agents with potent in vitro and in vivo activity against Eimeria. Antiparasitic activity is due to inhibition of a parasite specific cGMP-dependent protein kinase (PKG). In this study, we present the synthesis and biological activity of imidazo[1,2-a]pyridine anticoccidial agents. From this series, several compounds showed subnanomolar in vitro activity and commercial levels of in vivo activity. However, the potential genotoxicity of these compounds precludes them from further development.

Synthesis and SAR Studies of diarylpyrrole anticoccidial agents

2-(4-Fluorophenyl)-3-(4-pyridinyl)-5-substituted pyrroles were prepared and evaluated as anticoccidial agents in both in vitro and in vivo assays. Among the compounds evaluated, the dimethylamine-substituted pyrrole 19a is the most potent inhibitor of Eimeria tenella PKG (cGMP-dependent protein kinase). Further SAR studies on the side chain of the 2-pyrrolidine nitrogen did not enhance in vivo anticoccidial activity.

Hydroxylated N-alkyl-4-piperidinyl-2,3-diarylpyrrole derivatives as potent broad-spectrum anticoccidial agents

Diaryl-(4-piperidinyl)-pyrrole derivatives bearing hydroxylated N-alkyl substituents have been synthesized and evaluated as anticoccidial agents. High potency in Et-PKG inhibition and broad-spectrum anticoccidial activities have been observed on compounds, such as 4b and 5h, which are fully efficacious in vivo at 50 ppm in feed.

Anticoccidial Efficacy of Drinking Water Soluble Diclazuril on Experimental and Field Coccidiosis in Broiler Chickens

Prophylactic and curative capacity of water soluble formulation of Diclazuril (Diclosol 1%) and feed additive form (Clinacox, 0.5%) were tested against Eimeria infection in broiler chickens. Such testing was performed both experimentally and in the field. Toltrazuril (Baycox, 2.5%) was used as reference control drug. Water soluble formulation of Diclazuril induced a marked inhibitory effect on the different stages of the parasite life cycle in experimentally infected treated birds especially when applied on the day when blood first appeared in the faeces [fifth day post-infection (d.p.i.)] as well as on the second day of blood dropping (6 d.p.i.). Both tested dosage levels of Diclazuril water soluble formulation in drinking water (5 and 10 ppm) showed the same effect in controlling coccidial infection and reducing the total oocyst numbers, lesion and faecal scores. Moreover, there was no significant difference in the efficacy of water soluble form of Diclazuril and the reference control drug (Toltrazuril, 25 ppm). In addition, testing the water soluble formulation (5 ppm) in naturally infected poultry farm (20,000 birds), showed the same anticoccidial effect observed when using Toltrazuril, as a treatment for coccidiosis. In conclusion, addition of Diclazuril at the dose of 5 ppm in the drinking water of naturally coccidia infected bird induced the same effect as 25 ppm of Toltrazuril as a treatment for coccidiosis in chickens.

Simple stochastic fingerprints towards mathematical modelling in biology and medicine. 1. The treatment of coccidiosis

We have developed a classification function that is capable of discriminating between anticoccidial and nonanticoccidial compounds with different structural patterns. For this purpose, we calculated the Markovian electron delocalization negentropies of several compounds. These molecular descriptors, which act as molecular fingerprints, are derived from an electronegativity-weighted stochastic matrix (1Pi). The method attempts to describe the delocalization of electrons with time during the process of molecule formation by considering the 3D environment of the atoms. Accordingly, the entropies of this random process are used as molecular descriptors. The present study involves a stochastic generalization of the original idea described by Kier, which concerned the use of molecular negentropies in QSAR. Linear discriminant analysis allowed us to fit the discriminant function. This function has given rise to a good classification of 82.35% (28 anticoccidials out of 34) and 91.8% of inactive compounds (56/61) in training series. An overall classification of 88.42% (84/95) was achieved. Validation of the model was carried out by means of an external predicting series and this gave a global predictability of 93.1%. Finally, we report the experimental assay (more than 95% of lesion control) of two compounds selected from a large data set through virtual screening. We conclude that the approach described here seems to be a promising 3D-QSAR tool based on the mathematical theory of stochastic processes.

Synthesis, biological activity and molecular modeling of 6-benzylthioinosine analogues as subversive substrates of Toxoplasma gondii adenosine kinase

Toxoplasma gondii is the most common cause of secondary CNS infections in immunocompromised persons such as AIDS patients. The major route of adenosine metabolism in T. gondii is direct phosphorylation to adenosine 5'-monophosphate (AMP) catalyzed by the enzyme adenosine kinase (EC 2.7.1.20). Adenosine kinase in T. gondii is significantly more active than any other purine salvage enzyme in this parasite and has been established as a potential chemotherapeutic target for the treatment of toxoplasmosis. Subversive substrates of T. gondii,but not the human, adenosine kinase are preferentially metabolized to their monophosphorylated forms and become selectively toxic to the parasites but not their host. 6-Benzylthioinosine (BTI) was identified as an excellent subversive substrate of T. gondii adenosine kinase. Herein, we report the synthesis of new analogues of BTI as subversive substrates for T. gondii adenosine kinase. These new subversive substrates were synthesized starting from tribenzoyl protected d-ribose. To accomplish the lead optimization process, a divergent and focused combinatorial library was synthesized using a polymer-supported trityl group at the 5'-position. The combinatorial library of 20 compounds gave several compounds more active than BTI. Structure-activity relationship studies showed that substitution at the para position plays a crucial role. To investigate the reasons for this discrimination, substrates with different substituents at the para position were studied by molecular modeling using Monte Carlo Conformational Search followed by energy minimization of the enzyme-ligand complex.

The production and characterisation of an antibody to detect the coccidiostat toltrazuril and its metabolite ponazuril

The production of an antibody to detect toltrazuril or its metabolite ponazuril is complicated due to structural constraints of conjugating these coccidiostats to a carrier protein. Therefore a search was carried out for a compound that shared a common substructure to use as an antigen mimic. The chosen compound, trifluoraminoether, was conjugated to two carrier proteins (HSA and BTG) and used in the immunisation of six rabbits. Two immunogen doses (1 mg and 0.1 mg) were also used. All six rabbits produced an immunological response to the hapten regardless of the carrier protein or immunogen dose used. The most sensitive polyclonal antibody produced, designated R609, was subsequently characterised. This antiserum exhibited an IC50 of 18 ng ml(-1) using a competitive ELISA format. Cross reactivity studies show that this serum is specific for toltrazuril and its metabolites (toltrazuril sulfoxide and toltrazuril sulfone) but does not cross-react with other coccidiostats such as halofuginone, nitroimidazoles or nicarbazin. This is the first reported production of an antibody capable of specifically binding toltrazuril and ponazuril.

Photodegradation of roxarsone in poultry litter leachates

Arsenic compounds have been used extensively in agriculture in the US for applications ranging from cotton herbicides to animal feed supplements. Roxarsone (3-nitro-4-hydroxyphenylarsonic acid), in particular, is used widely in poultry production to control coccidial intestinal parasites. It is excreted unchanged in the manure and introduced into the environment when litter is applied to farmland as fertilizer. Although the toxicity of roxarsone is less than that of inorganic arsenic, roxarsone can degrade, biotically and abiotically, to produce more toxic inorganic forms of arsenic, such as arsenite and arsenate. Experiments were conducted on aqueous litter leachates to test the stability of roxarsone under different conditions. Laboratory experiments have shown that arsenite can be cleaved photolytically from the roxarsone moiety at pH 4-8 and that the degradation rate increases with increasing pH. Furthermore, the rate of photodegradation increases with nitrate and natural organic matter concentration, reactants that are commonly found in poultry-litter-water leachates. Additional photochemical reactions rapidly oxidize the cleaved arsenite to arsenate. The formation of arsenate is not entirely undesirable, because it is less mobile in soil systems and less toxic than arsenite. A possible mechanism for the degradation of roxarsone in poultry litter leachates is proposed. The results suggest that poultry litter storage and field application practices could affect the degradation of roxarsone and subsequent mobilization of inorganic arsenic species.

Fragmentation studies on lasalocid acid by accurate mass electrospray mass spectrometry

Lasalocid acid is an important polyether ionophore veterinary drug. Polyether ionophores have been the subject of MS study for many years, but this is the first rigorous study of the complex fragmentation processes occurring in ESI MS/MS for lasalocid, underpinned by high-resolution accurate-mass measurement. Initial low-resolution analyses were performed on an ion-trap instrument. High-resolution analyses were performed on a Fourier-transform ion cyclotron resonance mass spectrometer. The MS/MS analysis of the pseudo-molecular ion shows that fragment ions are produced either by beta-elimination or by neutral losses of water. Additional ions were observed in the source dissociation analysis, indicating that additional fragmentation reactions occur in the source region. Some of these ions can then undergo additional ion-ion or ion-molecule reactions before being extracted from the source. The study of both the protonated and sodiated sodium salts shows the same fragmentation pathways, with fragment ions containing two sodiums at low intensity. A fragmentation pathway of the lasalocid acid protonated sodium salt [(M-H+Na)+H]+ (m/z 613) and sodiated sodium salt [(M-H+Na)+Na]+ (m/z 635) is presented. The increased understanding afforded by this study will help in the development of unequivocal analytical methods for lasalocid and related polyether ionophore veterinary drugs.

Synthesis of the proposed structure of fudecalone, an anticoccidial drimane terpenoid

[formula: see text] The proposed structure of fudecalone (1), an anticoccidial drimane sesquiterpene, was synthesized as a racemate in six steps starting from a known phthalide (5). Interestingly, our synthetic 1 showed conformation 1b, while the natural one was reported as 1a, and the NMR spectral data were not identical.

8-aminoquinolines as anticoccidials - Part III

Analogues of the antimalarial pentaquine, 1, in which the nature of the side-chain on the 8-amino position was varied, were prepared and evaluated for anticoccidial activity both in vitro and in vivo. Specifically, both the inter-nitrogen distance and the nature of the terminal amino group were investigated. Novel analogues of equal or improved efficacy in vitro and in vivo to pentaquine were discovered.

Coprophilin: an anticoccidial agent produced by a dung inhabiting fungus

Coprophilin, a decalin pentanedienoic acid methyl ester, was isolated from an unidentified fungus by bioassay guided separation. It inhibited (MIC = 1.5 microM) the growth of Eimeria tenella in an in vitro assay. The isolation, structure elucidation, absolute stereochemistry and biology are described.

Monensin carry-over into unmedicated broiler feeds

European Union Member States are now required to monitor poultry meat for the presence of coccidiostat residues. Among other factors contributing to the production of residue-free food is the ability of animal feed manufacturers to produce medication-free feedstuffs, ensuring the proper observance of withdrawal periods prior to slaughter. Carry-over of medication was investigated in a local poultry feed mill that was using monensin as its principal coccidiostat for broilers. Monensin, at levels in excess of 5% of the therapeutic dose (approximately 110 mg kg-1), was present in 22.5% of 40 withdrawal feeds. Subsequent studies in the mill indicated that most of the contamination occurred during the processing of feeds after the mixing stage. The mill altered its manufacturing process as a result of this study. The consequence of this was that the incidence of monensin withdrawal feeds, at levels greater than 5% of the therapeutic dose, fell from 22.5 to 2.5%. This collaborative study has helped the feed compounder to produce more effective withdrawal feeds, thereby reducing the potential exposure of consumers to unwanted residues of monensin in poultry meat.

8-Aminoquinolines as anticoccidials--II

During a chemistry program aimed at finding a novel analogue of pentaquine with improved in vivo activity, a number of hypotheses concerning the way this drug acts in the chicken were investigated. Consideration of the products of monoamine oxidase metabolism of pentaquine suggested that pentaquine aldehyde is the likely active metabolite. Although isolation of this unstable compound was not possible, oxime and cyclic acetal and ketal derivatives were obtained and shown to possess in vitro anticoccidial activity.

The effect of narasin on apparent nitrogen digestibility and large intestine volatile fatty acid concentrations in finishing swine

The effect of narasin on apparent nitrogen and dry matter digestibilities and large intestine VFA concentrations in finishing swine was investigated. The study used 21 crossbred barrows averaging 72 kg. Seven blocks were formed on the basis of pretreatment dry matter digestibility, and barrows were randomly assigned to three treatments in each block. Treatments consisted of a control (C) and narasin (N15 and N30) applied at 15 and 30 ppm, respectively. Fecal and urine samples were collected. Upon the completion of the digestibility work, intestinal samples were taken from three locations, and VFA concentrations for each animal were measured. Weight gains for the N15 and N30 treatments were increased 3.0 and 6.0% (not significant), respectively, over control. Fecal nitrogen was decreased (P < .05) in the narasin-fed barrows, and apparent nitrogen digestibility was increased (P < .05). Neither nitrogen retention nor urinary nitrogen excretion was altered (P > .05) due to narasin. There were no increases (P > .05) in apparent dry matter digestibility due to narasin. Analysis of pooled colon samples showed an increase (P < .05) in the concentration of propionic acid in relation to acetic and butyric in the narasin-fed barrows. Butyric acid was reduced (P < .05) in the transverse colon of narasin-fed barrows. In summary, narasin administration to finishing barrows resulted in improved apparent nitrogen digestibility, thus decreasing fecal nitrogen, and increased relative concentrations of propionic acid in the large intestine.

Microbiological method for determining macrolides in animal feeds in the presence of other drugs by thin-layer chromatography detection

A method was developed to separate, detect, and quantitate erythromycin (ERY) and tylosin (TYL) in animal feeds in the presence of 11 other drugs: 3 nitrofurans, 2 tetracycline antibiotics, 3 sulfonamides, 2 coccidiostats, and 1 antibacterial growth promoter. ERY and TYL were separated from coexisting drugs, detected by thin-layer chromatography, and quantitated microbiologically by an agar diffusion method. Analysis of 125 experimental animal feed samples fortified at 5 levels (7.5-400 ppm) with ERY and TYL and at 1 level (50 ppm) with the rest of the drugs gave limits of quantitation of 2 and 5 ppm, recoveries of 90.3 and 92.4%, and relative standard deviations of 4.3-7.3% and 3.6-6.1%, respectively.

Synthesis and biological activities of some new 4,5-dihydro-1H-1,2,4-triazol-5-ones

The reactions of 3-alkyl(aryl)-4-phenylamino-4,5-dihydro-1H-1,2,4-triazol-5-ones with appropriate alkyl halides via sodio derivatives were studied and the corresponding 1-alkyl-3-alkyl(aryl)-4-phenylamino-4,5-dihydro-1H-1,2,4-traizol-5 -ones were synthesized. Next, the new compounds were tested for their in vitro antimicrobial activities.

Xanthoquinodin B3, a new anticoccidial agent produced by Humicola sp. FO-888

Xanthoquinodin B3, a new component of anticoccidial xanthoquinodins, which was detected in the culture broth of Humicola sp. FO-888, was isolated by heat treatment of the xanthoquinodins complex. Structural elucidation indicated that xanthoquinodin B3 has the same heterodimer of xanthone- and anthraquinone-derived monomers as other xanthoquinodins. Schizont formation of monensin-resistant Eimeria tenella in BHK-21 cells was inhibited by xanthoquinodin B3 at concentrations greater than 0.035 microM.

A 3D-QSAR study of anticoccidial triazines using molecular shape analysis

A set of 54 anticoccidial triazine analogs were analyzed in terms of molecular shape analysis, MSA, with the goal of constructing a three-dimensional quantitative structure-activity relationship (3D-QSAR). This same dataset was previously investigated using alternate QSAR methods including comparative molecular field analysis (CoMFA). A complete 3D-QSAR was realized using MSA which included (a) identification of the active conformation of each individual analog, (b) the relative intramolecular stability of each analog in its active conformation, (c) general intramolecular stability requirements for activity, (d) a statistically significant correlation equation, and (e) mapping of the receptor space explored by the analogs. The MSA-3D-QSAR indicates that the steric shape and dipole moment of each analog governs its activity. The MSA-3D-QSAR correlation equations are more predictive than other QSARs as measured by cross-validation correlation coefficients.

Cytosaminomycins, new anticoccidial agents produced by Streptomyces sp. KO-8119. II. Structure elucidation of cytosaminomycins A, B, C and D

Structures of novel anticoccidial antibiotics, cytosaminomycins A, B, C and D, were elucidated by NMR studies. Cytosaminomycins were shown to be nucleoside antibiotics related to oxyplicacetin. Their carboxylic acid moieties bonded to the cytosine residue were different from that of oxyplicacetin. The carboxylic acids contained in cytosaminomycins A, B, C and D were (E)-3-(methylthio)acrylic acid, 4-methylaminobenzoic acid, 3-methylcrotonic acid, and tiglic acid, respectively.

Arohynapenes A and B, new anticoccidial agents produced by Penicillium sp. Taxonomy, fermentation, and structure elucidation

Penicillium sp. FO-2295, a water isolate, was found to produce a series of new anticoccidial compounds. Two active compounds, designated arohynapenes A and B, were isolated from the fermentation broth of the producing strain by solvent extration and preparative HPLC. Arohynapene A was deduced to be (2E,4E)-5-(5-hydroxy-2,6,8-trimethyl-5,6,7,8-tetrahydronaphtale ne)-2,4- pentadienoic acid, and arohynapene B was (2E,4E)-5-(2-hydroxymethyl-6,8-dimethyl-5,6,7,8-tetrahydronapht alene)-2,4- pentadienoic acid. Arohynapenes inhibited the growth of Eimeria tenella in an in vitro assay using BHK-21 cells as a host. No schizont in the cells was observed at concentrations ranging above 35.0 microM and 7.0 microM for arohynapenes A and B, respectively.

Hynapenes A, B and C, new anticoccidial agents produced by Penicillium sp. I. Production, isolation and physico-chemical and biological properties

Penicillium sp. FO-1611, a soil isolate, was found to produce a series of new anticoccidial compounds. Three active compounds, designated hynapenes A, B and C, were isolated from the fermentation broth of the producing strain by solvent extraction, silica gel column chromatography, gel filtration on Sephadex LH-20 and preparative HPLC. Hynapenes inhibited the growth of Eimeria tenella in an in vitro assay using BHK-21 cells as a host. No schizont in the cells was observed at concentrations ranging above 123 microM, 34.7 microM and 34.7 microM for hynapenes A, B and C, respectively.

Hynapenes A, B and C, new anticoccidial agents produced by Penicillium sp. II. Structure elucidation

The structures of hynapenes A, B and C, novel anticoccidial agents, were determined by spectroscopic analyses. Hynapenes A, B and C were deduced to be (2E,4E)-5-(1,3,4-trihydroxy-2,6,8-trimethyldecalin)-2,4-p entadienoic acid, (2E,4E)-5-(1-ene-3-oxo-2,6,8-trimethyldecalin)-2,4-pentad ienoic acid and (2E,4E)-5-(3-ene-1-oxo-2,6,8-trimethyldecalin)-2,2,4-pent adienoic acid, respectively.

Diolmycins, new anticoccidial agents produced by Streptomyces sp. II. Structure elucidation of diolmycins A1, A2, B1 and B2, and synthesis of diolmycin A1

The structures of diolmycins A1, A2, B1 and B2, novel anticoccidial agents, were determined by spectroscopic analyses. Diolmycins A1 and A2 are stereoisomers with the structure of 1-(3-indolyl)-4-(p-hydroxyphenyl)-2,3-butanediol. From the chemical synthesis of the erythro-isomer, the relative configurations of diolmycins A1 and A2 were determined to be the erythro- and threo-isomers, respectively. The stereoisomers, diolmycins B1 and B2, were also deduced to be erythro- and threo-1,4-di-(p-hydroxyphenyl)-2,3-butanediol, respectively.

Diolmycins, new anticoccidial agents produced by Streptomyces sp. I. Production, isolation and physico-chemical and biological properties

Streptomyces sp. WK-2955, a soil isolate, was found to produce a series of new anticoccidial compounds. Four active compounds, designated diolmycins A1, A2, B1 and B2, were isolated from the fermentation broth of the producing strain by solvent extraction, silica gel column chromatography, gel filtration on Sephadex LH-20, and preparative HPLC. Diolmycins inhibited the growth of Eimeria tenella in an in vitro assay system using BHK-21 cells as a host. No schizont in the cells was observed at concentrations of 0.02-2.0 micrograms/ml for diolmycin A1, at 0.2-2.0 micrograms/ml for diolmycin A2, and at 20 micrograms/ml for diolmycins B1 and B2.

Xanthoquinodins, new anticoccidial agents produced by Humicola sp. Production, isolation and physico-chemical and biological properties

Humicola sp. FO-888, a soil isolate, was found to produce a series of new anticoccidial compounds. Five active compounds, designated xanthoquinodins A1, A2, A3, B1 and B2 were isolated from the fermentation broth of the producing strain by solvent extraction and HPLC. Xanthoquinodins inhibited the growth of Eimeria tenella in an in vitro assay system using BHK-21 cells as a host. No schizont in the cells was observed at concentrations of 0.02-0.2 micrograms/ml for xanthoquinodins A1, A3, B1 and B2 and at 0.02 micrograms/ml for xanthoquinodin A2.

Anticoccidial activities of 7-bromo-N-(2-imidazolidinylidene)-1H-indazol-6-amine and other alpha 2 adrenergic agonists

Activity against the coccidial pathogen Eimeria tenella in chickens has been discovered among alpha 2 adrenergic agonists. The clonidine analog 7-bromo-N-(2-imidazolidinylidene)-1H-indazol-6-amine was active in feed at 7.5 ppm, a concentration similar to the use levels of potent commercial agents, e.g., maduramicin. Additional alpha 2 agonists were also found to have anticoccidial activity, for example, the catecholamine nordefrin, which is chemically unrelated to clonidine. However, alpha 1 agonists and alpha antagonists were inactive. These observations imply that anticoccidial effects reflect involvement of a receptor with the characteristics of the vertebrate alpha 2 adrenoceptor. alpha 2 agonists that permeate the blood-brain barrier (like clonidine) inhibit feed intake at efficacious levels, whereas those that are restricted to the peripheral compartment (such as catecholamines) do not inhibit feed intake as much. Hence, anticoccidial efficacy may be a peripheral adrenergic effect whereas depression of feed intake is likely centrally mediated.