Potential Anthelmintics Research Articles

Extracts and Terpenoids from Stevia Species as Potential Anthelmintics for Neglected Tropical Diseases Caused by Cestode Parasites.

Cestodes are etiological agents of neglected diseases such as echinococcosis and cysticercosis, which are major public health problems. Antiparasitic treatment relies on a small number of approved drugs, which are often only partially effective, poorly tolerated and require prolonged administration. Thus, the discovery of novel potential treatments is critical. The Stevia genus (Asteraceae) includes species that are recognized as a source of bioactive compounds, with many species associated with medicinal uses. In this study, the cestocidal activity of four South American Stevia species that previously showed antiprotozoal activity was analyzed using a motility assay on the laboratory cestode model, Mesocestoides vogae. The four Stevia extracts showed cestocidal activity, with S. alpina var. alpina as the most active. The sesquiterpene lactones estafietin and eupatoriopicrin were purified from S. alpina var. alpina and S. maimarensis, respectively, and tested on M. vogae. Estafietin showed cestocidal activity, inhibiting parasite viability in a dose-dependent manner, even from the first day of incubation. Consistent with the motility effects, the extract of S. alpina var. alpina and estafietin induced marked alterations in the morphology of the parasite. The results of this report show that Stevia species represent a source of new molecules with potential for the treatment of neglected tropical diseases caused by cestodes.

Identification of a family of species-selective complex I inhibitors as potential anthelmintics

Soil-transmitted helminths (STHs) are major pathogens infecting over a billion people. There are few classes of anthelmintics and there is an urgent need for new drugs. Many STHs use an unusual form of anaerobic metabolism to survive the hypoxic conditions of the host gut. This requires rhodoquinone (RQ), a quinone electron carrier. RQ is not made or used by vertebrate hosts making it an excellent therapeutic target. Here we screen 480 structural families of natural products to find compounds that kill Caenorhabditis elegans specifically when they require RQ-dependent metabolism. We identify several classes of compounds including a family of species-selective inhibitors of mitochondrial respiratory complex I. These identified complex I inhibitors have a benzimidazole core and we determine key structural requirements for activity by screening 1,280 related compounds. Finally, we show several of these compounds kill adult STHs. We suggest these species-selective complex I inhibitors are potential anthelmintics.

Genotoxicity of Beta-Sitosterol, Betulinic Acid, Biochanin A, and Ursolic Acid, Potential Anthelmintic Phyto-Compounds

Beta-sitosterol, betulinic acid, biochanin A and ursolic acid are known to possess anthelmintic properties. This study was undertaken to assess the genotoxic potentials of these phytocompounds in albino rats. Animals were orally administered with 1 and 10 mg/ml of the above phyto-compounds for a period of 14 days. All the animals were subjected to mitotic arrest before sacrifice and then bone marrow cells were collected from both the femurs and processed to observe the chromosomal aberrations. The results revealed that ursolic acid induced the maximum number of statistically significant abnormalities (p ≤ 0.05) followed by betulinic acid and biochanin A. Beta-sitosterol was found to be the safest of all the tested phytocompounds as far as chromosomal abnormalities in short term oral studies are concerned as it did not lead to major changes at genomic level. Although these phyto-compounds are considered potential anthelmintics, their long-term use may cause genotoxic effects to the users.

Black Cumin Seed Extract Decrease Motility and Shortening Mortality Time of Ascaridia galli Worm In Vitro

Ascaridiasis caused by roundworm Ascaridia galli is one of important diseases in poultry industry in Indonesia. This disease can affect economic losses in the form of death, growth retardation, reduced egg production as well as trigger for secondary viral or bacteria infections. Control of this nematode requires a good strategy to avoid the risk of anthelmintic resistance, one of which is the use of herbal medicine such as black cumin seed (Nigella sativa). This study was aimed to determine the level of motility and mortality time of A. galli after treated with black cumin seed extract in vitro. In this study, black cumin seed was extracted using ethanol 96%, and then diluted to 15% (P1), 25% (P2), and 45% (P3) concentration. Pyrantel pamoate preparation was used as positive control (C1), and carboxymethyl cellulose (CMC) solution as negative control (C0). Observations were carried out every 15 minutes until all the treatment worms died. The results revealed that the motility and mortality time of A. galli were significantly different in some treatment groups. The mortality time of group C0, C1 , P1, P2, and P3 were 2592, 801, 1557, 1350, and 612 minutes, respectively. 45% of black cumin seed extract had the ability to decrease worm motility, and it showed the shortest mortality time compared to other treatment groups. It can be concluded that ethanolic extract of black cumin seeds had potential anthelmintics property on A. galli worms.

Assessment of the anthelmintic activity and toxicity of metabolites of Dalea pogonathera (Fabaceae)

Dalea pogonathera A. Gray was collected as part of a project to determine if metabolites of the genus Dalea have potential for the treatment of human hookworm disease, based on earlier findings of very active materials in D. ornata . We report here the isolation, characterization, and results of ex vivo bioassays of a new chalcone pogonatheridin A ( 1 ), and three new prenylated flavanones ( 3 , 6 , and 12 ). The isolated known compounds, a chalcone ( 2 ), flavanones ( 4 , 5 , 7 - 11 , 13 , 14 ), and a flavan-3-ol ( 15 ), were also examined. Pogonatheridin A ( 1 ) reduced the survival of the adults of Ancylostoma ceylanicum hookworm by 12.5 % (50 μg/mL), while all other compounds showed very weak or no activity. The compounds were tested (50 μg/mL) for toxicity to healthy mammalian cells. Seven of them ( 2 - 8 ) showed > 98 % reduction in survival of splenocytes, while 1 was somewhat less toxic at 74.3 % reduction in survival. While metabolites of D. pogonathera did not show promise as potential anthelmintics for hookworm disease, the toxicity information is of interest, and the rich diversity of metabolites of Dalea spp. remains apparent. • A new chalcone ( 1 ) and three new prenylated flavanones ( 3 , 6 and 12 ) were isolated from Dalea pogonathera. • All compounds were assessed for their anthelmintic activity to the human pathogenic hookworm Ancylostoma ceylanicum . • Ten of the isolated compounds showed significant toxicity to mammalian splenocytes at 50 μg/mL using flow cytometry.

Flukicidal effects of abietane diterpenoid derived analogues against the food borne pathogen Fasciola hepatica.

Control of liver fluke infections remains a significant challenge in the livestock sector due to widespread distribution of drug resistant parasite populations. In particular, increasing prevalence and economic losses due to infection with Fasciola hepatica is a direct result of drug resistance to the gold standard flukicide, triclabendazole. Sustainable control of this significant zoonotic pathogen, therefore, urgently requires the identification of new anthelmintics. Plants represent a source of molecules with potential flukicidal effects and, amongst their secondary metabolites, the diterpenoid abietic acids can be isolated in large quantities. In this study, nineteen (19) chemically modified abietic acid analogues (MC_X) were first evaluated for their anthelmintic activities against F. hepatica newly excysted juveniles (NEJs, from the laboratory-derived Italian strain); from this, 6 analogues were secondly evaluated for their anthelmintic activities against adult wild strain flukes. One analogue, MC010, was progressed further against 8-week immature- and 12-week mature Italian strain flukes. Here, MC010 demonstrated moderate activity against both of these intra-mammalian fluke stages (with an adult fluke EC50 = 12.97 µM at 72 h post culture). Overt mammalian cell toxicity of MC010 was inferred from the Madin-Darby bovine kidney (MDBK) cell line (CC50 = 17.52 µM at 24 h post culture) and demonstrated that medicinal chemistry improvements are necessary before abietic acid analogues could be considered as potential anthelmintics against liver fluke pathogens

Structure-Based Bioisosterism Design, Synthesis, Biological Evaluation and In Silico Studies of Benzamide Analogs as Potential Anthelmintics

A recent screen of 67,012 compounds identified a new family of compounds with excellent nematicidal activity: the ortho-substituted benzamide families Wact-11 and Wact-12. These compounds are active against Caenorhabditis elegans and parasitic nematodes by selectively inhibiting nematode complex II, and they display low toxicity in mammalian cells and vertebrate organisms. Although a big number of benzamides were tested against C. elegans in high-throughput screens, bioisosteres of the amide moiety were not represented in the chemical space examined. We thus identified an opportunity for the design, synthesis and evaluation of novel compounds, using bioisosteric replacements of the amide group present in benzamides. The compound Wact-11 was used as the reference scaffold to prepare a set of bioisosteres to be evaluated against C. elegans. Eight types of amide replacement were selected, including ester, thioamide, selenoamide, sulfonamide, alkyl thio- and oxo-amides, urea and triazole. The results allowed us to perform a structure–activity relationship, highlighting the relevance of the amide group for nematicide activity. Experimental evidence was complemented with in silico structural studies over a C. elegans complex II model as a molecular target of benzamides. Importantly, compound Wact-11 was active against the flatworm Echinococcus granulosus, suggesting a previously unreported pan-anthelmintic potential for benzamides.

Emerging Anthelmintic Resistance in Poultry: Can Ethnopharmacological Approaches Offer a Solution?

Limited pharmacological studies have been conducted on plant species used against poultry helminths. The objective of this study was to provide a basis for plant based anthelmintics as possible alternatives against poultry anthelmintic resistance. The study justified the need for alternative anthelmintics. The study places emphasis on the increasing anthelmintic resistance, mechanism of resistance, and preparational protocols for plant anthelmintics and their associated mechanism of action. Pharmaceutical studies on plants as alternative therapies for the control of helminth parasites have not been fully explored especially in several developing countries. Plants from a broad range of species produce a wide variety of compounds that are potential anthelmintics candidates. Important phenolic acids have been found in Brassica rapa L. and Terminalia avicenniodes Guill. and Perri that affect the cell signaling pathways and gene expression. Benzo (c) phenanthridine and isoquinoline alkaloids are neurotoxic to helminths. Steroidal saponins (polyphyllin D and dioscin) interact with helminthic mitochondrial activity, alter cell membrane permeability, vacuolation and membrane damage. Benzyl isothiocyanate glucosinolates interfere with DNA replication and protein expression, while isoflavones from Acacia oxyphylla cause helminth flaccid paralysis, inhibit energy generation, and affect calcium utilization. Condensed tannins have been shown to cause the death of nematodes and paralysis leading to expulsion from the gastro-intestinal tract. Flavonoids from Chenopodium album L and Mangifera indica L act through the action of phosphodiesterase and Ca2+-ATPase, and flavonoids and tannins have been shown to act synergistically and are complementary to praziquantel. Artemisinins from Artemisia cina O. Berg are known to disrupt mitochondrial ATP production. Terpenoids from Cucurbita moschata L disrupt neurotransmission leading to paralysis as well as disruption of egg hatching. Yeast particle encapsulated terpenes are effective for the control of albendazole-resistant helminths.

Plant-Based Solutions to Global Livestock Anthelmintic Resistance

Anthelmintic resistance in livestock is increasing globally. Livestock intestinal parasites now develop resistance to synthetic anthelmintics within 2–10 years, collectively costing billions of dollars annually in lost revenue around the world. Over-reliance on commercial drugs and dips and changes in livestock management practices are key drivers of this trend. To date, current research has focused on identifying new anthelmintics from bacterial and fungal sources or even synthesizing new drugs that target parasite metabolism or reproduction. Plant-derived anthelmintics are a promising alternative, yet to date major research funders and scientists have overlooked this option. Until the mid-20th century, rural communities relied on plant-based methods of controlling livestock parasites. These methods include feeding livestock specific medicinal plants and trees, grazing livestock on herbal leys, and changing where livestock grazed based on ecological factors (e.g., flooding) that increased parasite burdens. Many historic texts and ethnological accounts record the ethnobotanical knowledge of rural communities and the plants they used to control livestock intestinal parasites. Some traditions persist today yet the farmers, graziers, and shepherds who hold this knowledge are rapidly disappearing and with them perhaps a potential long-term solution to anthelmintic resistance. This short perspective piece will cover recent research using ethnobotanical data as a means to identifying potential new anthelmintics; the morphological, physiological, and metabolic effect of plant secondary metabolites on parasites; and an overview of “best practices” which can reduce bias in assessments of plant bioactivity and increase reproducibility of test results. This will hopefully bring recent advances in ethnobiology, chemistry, and ecology to new audiences, and, potentially, spark new interest in using medicinal plants to improve livestock health.

Using C. elegans Forward and Reverse Genetics to Identify New Compounds with Anthelmintic Activity

BackgroundThe lack of new anthelmintic agents is of growing concern because it affects human health and our food supply, as both livestock and plants are affected. Two principal factors contribute to this problem. First, nematode resistance to anthelmintic drugs is increasing worldwide and second, many effective nematicides pose environmental hazards. In this paper we address this problem by deploying a high throughput screening platform for anthelmintic drug discovery using the nematode Caenorhabditis elegans as a surrogate for infectious nematodes. This method offers the possibility of identifying new anthelmintics in a cost-effective and timely manner.Methods/Principal findingsUsing our high throughput screening platform we have identified 14 new potential anthelmintics by screening more than 26,000 compounds from the Chembridge and Maybridge chemical libraries. Using phylogenetic profiling we identified a subset of the 14 compounds as potential anthelmintics based on the relative sensitivity of C. elegans when compared to yeast and mammalian cells in culture. We showed that a subset of these compounds might employ mechanisms distinct from currently used anthelmintics by testing diverse drug resistant strains of C. elegans. One of these newly identified compounds targets mitochondrial complex II, and we used structural analysis of the target to suggest how differential binding of this compound may account for its different effects in nematodes versus mammalian cells.Conclusions/SignificanceThe challenge of anthelmintic drug discovery is exacerbated by several factors; including, 1) the biochemical similarity between host and parasite genomes, 2) the geographic location of parasitic nematodes and 3) the rapid development of resistance. Accordingly, an approach that can screen large compound collections rapidly is required. C. elegans as a surrogate parasite offers the ability to screen compounds rapidly and, equally importantly, with specificity, thus reducing the potential toxicity of these compounds to the host and the environment. We believe this approach will help to replenish the pipeline of potential nematicides.

Comparative pharmacology of flatworm and roundworm glutamate-gated chloride channels: Implications for potential anthelmintics

Pharmacological targeting of glutamate-gated chloride channels (GluCls) is a potent anthelmintic strategy, evidenced by macrocyclic lactones that eliminate numerous roundworm infections by activating roundworm GluCls. Given the recent identification of flatworm GluCls and the urgent need for drugs against schistosomiasis, flatworm GluCls should be evaluated as potential anthelmintic targets. This study sought to identify agonists or modulators of one such GluCl, SmGluCl-2 from the parasitic flatworm Schistosoma mansoni. The effects of nine glutamate-like compounds and three monoterpenoid ion channel modulators were measured by electrophysiology at SmGluCl-2 recombinantly expressed in Xenopus laevis oocytes. For comparison with an established anthelmintic target, experiments were also performed on the AVR-14B GluCl from the parasitic roundworm Haemonchus contortus. l-Glutamate was the most potent agonist at both GluCls, but l-2-aminoadipate, d-glutamate and d-2-aminoadipate activated SmGluCl-2 (EC50 1.0±0.1mM, 2.4±0.4mM, 3.6±0.7mM, respectively) more potently than AVR-14B. Quisqualate activated only SmGluCl-2 whereas l-aspartate activated only AVR-14B GluCls. Regarding the monoterpenoids, both GluCls were inhibited by propofol, thymol and menthol, SmGluCl-2 most potently by thymol (IC50 484±85μM) and least potently by menthol (IC50>3mM). Computational docking suggested that agonist and inhibitor potency is attributable to particular interactions with extracellular or membrane-spanning amino acid residues. These results reveal that flatworm GluCls are pharmacologically susceptible to numerous agonists and modulators and indicate that changes to the glutamate γ-carboxyl or to the propofol 6-isopropyl group can alter the differential pharmacology at flatworm and roundworm GluCls. This should inform the development of more potent compounds and in turn lead to novel anthelmintics.

ChemInform Abstract: Synthesis and QSAR in 2,3,6,8-Substituted 1,3-Quinazolin-4(4H)-ones as Potential Anthelmintics.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Synthesis of Some 2-Heterocyclic 5-Nitrothiazoles as Potential Anthelmintics.

ChemInform Abstract: Synthesis of Some 2-Heterocyclic 5-Nitrothiazoles as Potential Anthelmintics.

<i>Curtisia dentata</i> (Cornaceae) leaf extracts and isolated compounds inhibit motility of parasitic and free-living nematodes

Haemonchus contortus and Trichostrongylus colubriformis are among the most important parasitic nematodes of small ruminants. Caenorhabditis elegans, a free-living nematode, is used as a model for evaluating anthelmintic activity of a variety of test substances. Extracts of several medicinal plants are useful in vitro and in vivo against nematode development. Extracts of Curtisia dentata, a South African medicinal plant, and compounds isolated from leaves of this plant were investigated for anthelmintic activity against T. colubriformis, H. contortus and C. elegans. The acetone and dichloromethane extracts were active against all nematodes at concentrations as low as 160 microg/ml. Betulinic acid and lupeol were active against the parasitic nematodes only at the high concentrations of 1000 and 200 microg/ml, respectively. All compounds were effective against C. elegans with active concentrations as low as 8 microg/ml. Betulinic acid was less active than lupeol and ursolic acid against C. elegans. The acetone and dichloromethane extracts were also active against C. elegans with a concentration of 0.31 mg/ml resulting in almost 80% inhibition of larval motility. The use of free-living nematodes may provide information on the activity of potential anthelmintics against parasitic nematodes. Extracts of various medicinal plant species may provide solutions to ill-health of small ruminants caused by parasitic nematodes in poor communities of southern Africa.

Potential anthelmintics: polyphenols from the tea plant Camellia sinensis L. are lethally toxic to Caenorhabditis elegans

A novel gallate of tannin, (-)-epigallocatechin-(2 beta-->O-->7',4 beta-->8')-epicatechin-3'-O-gallate (8), together with (-)-epicatechin-3-O-gallate (4), (-)-epigallocatechin (5), (-)-epigallocatechin-3-O-gallate (6), and (+)-gallocatechin-(4 alpha-->8')-epigallocatechin (7), were isolated from the tea plant Camellia sinensis (L.) O. Kuntze var. sinensis (cv., Yabukita). The structure of 8, including stereochemistry, was elucidated by spectroscopic methods and hydrolysis. The compounds, along with commercially available pyrogallol (1), (+)-catechin (2), and (-)-epicatechin (3), were examined for toxicity towards egg-bearing adults of Caenorhabditis elegans. The anthelmintic mebendazole (9) was used as a positive control. Neither 2 nor 3 were toxic but the other compounds were toxic in the descending order 8, 7 approximately 6, 9, 4, 5, 1. The LC(50) (96 h) values of 8 and 9 were evaluated as 49 and 334 micromol L(-1), respectively. These data show that many green tea polyphenols may be potential anthelmintics.

A rapid colorimetric assay for the quantitation of the viability of free-living larvae of nematodes in vitro

With increasing drug resistance in gastrointestinal parasites, identification of new anthelmintics is essential. The non-parasitic nematode Caenorhabditis elegans is used extensively as a model to identify drug targets and potential novel anthelmintics because it can be readily cultured in vitro. Traditionally, the assessment of worm viability has relied on labour-intensive developmental and behavioral assays. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide-formazan (MTT-formazan) colorimetric assay uses metabolic activity as a marker of viability in mammalian cell culture systems and has been applied for use with filarial nematodes. In the present study, this assay has been optimized and validated to rapidly assess the viability of C. elegans after drug treatment. Living, but not dead, C. elegans take up MTT and reduce it to the blue formazan, providing visual, qualitative, and quantitative assessment of viability. MTT at a concentration of 5 mg/ml with 3 h incubation was optimal for detecting changes in viability with drug treatment. We have applied this assay to quantitate the effects of ivermectin and short-chain alcohols on the viability of C. elegans. This assay is also applicable to first-stage larvae of the parasitic nematode Haemonchus contortus. The advantage of this assay is the rapid quantitation in screening drugs to identify potential anthelmintics.

Improved bioassay for estimation of inhibitory effects of ovine gastrointestinal mucus and anthelmintics on nematode larval migration

A bioassay based on the ability of substances present in ovine gastrointestinal mucus or anthelmintics to paralyse third stage larval (L3) nematodes and inhibit their passage through 20 μm nylon mesh sieves [larval migration inhibition (LMI) activity] is described. Factors influencing the reproducibility of the bioassay were examined using exsheathed L3 of the sheep gastrointestinal nematode parasite Trichostrongylus colubriformis. Levamisole, morantel tartrate and piperazine were shown to inhibit L3 migration in the bioassay. The bioassay was used to demonstrate that gastrointestinal mucus from nematode-resistant sheep possessed greater L3 inhibitory activity than mucus from nematode-susceptible sheep. LMI activity of mucus used in this bioassay was significantly correlated with LMI activities obtained using two previously described similar bioassays. The action of mucus components on nematode larvae was shown to be reversible in the bioassay. The modified assay has advantages over other bioassays as it avoided the use of temperature-dependent agar blocks, reduced the number of L3 required to a more manageable size, and the whole experiment could be performed on a 48-well culture plate. The reproducibility, high correlation with other bioassays, ease of performance, suitability for testing a large number of samples and low cost make this modified assay the method of choice for determining antiparasitic activity of gastrointestinal mucus components and as a screen for potential anthelmintics.

The effects of anthelmintics on ovine larval nematode parasite migration in vitro

The anthelmintics ivermectin, levamisole, morantel tartrate and thiabendazole all inhibited, in vitro, the motility of third stage larvae (L3) of Trichostrongylus colubriformis. The bioassay, based on the inhibition of L3 migration from agar gels, yielded sigmoid dose-response curves for ivermectin, levamisole and morantel tartrate, but not thiabendazole. The concentration of levamisole giving 50% inhibition of migration (EC50) was determined for Cooperia curticei, Haemonchus contortus, Nematodirus spathiger, Ostertagia circumcincta, Trichostrongylus axei, T. colubriformis and T. vitrinus. EC50s differed between species but within species the EC50s for ensheathed and exsheathed L3 were similar except for N. spathiger which showed significantly higher EC50 for the ensheathed L3. No difference between EC50s for levamisole-resistant and susceptible strains of T. colubriformis were found. Similarly, morantel-resistant and susceptible stains of T. colubriformis could not be differentiated in this bioassay. The inhibition of L3 motility by known anthelmintic compounds in this bioassay suggests that the bioassay could be used as a screen for potential new anthelmintics.

ChemInform Abstract: Piperazine Derivatives of Benzimidazole as Potential Anthelmintics. Part 1. Synthesis and Activity of Methyl‐5‐(4‐Substituted‐piperazin‐1‐yl)benzimidazole‐2‐carbamates.

AbstractThe piperazinylnitroanilines (III), prepared by coupling the piperazines (I) with the chloronitroaniline (II), are reduced and subsequently treated with the S‐methylisothiourea (IV) to produce the piperazinylbenzimidazoles (V).

ChemInform Abstract: Synthesis of Some 1,2,4‐Triazolo(3,4‐b)(1,3,4)thiadiazoles as Potential Anthelmintics.

AbstractThe title compounds (VIII), (IX), and (XI) are synthesized as shown in the reaction scheme.