Present-day anthelmintics and perspectives on future new targets

Unveiling Drimenol: A Phytochemical with Multifaceted Bioactivities

Drimenol, a phytochemical with a distinct odor is found in edible aromatic plants, such as Polygonum minus (known as kesum in Malaysia) and Drimys winteri. Recently, drimenol has received increasing attention owing to its diverse biological activities. This review offers the first extensive overview of drimenol, covering its sources, bioactivities, and derivatives. Notably, drimenol possesses a wide spectrum of biological activities, including antifungal, antibacterial, anti-insect, antiparasitic, cytotoxic, anticancer, and antioxidant effects. Moreover, some mechanisms of its activities, such as its antifungal effects against human mycoses and anticancer activities, have been investigated. However, there are still several crucial issues in the research on drimenol, such as the lack of experimental understanding of its pharmacokinetics, bioavailability, and toxicity. By synthesizing current research findings, this review aims to present a holistic understanding of drimenol, paving the way for future studies and its potential utilization in diverse fields.

OPTICAL COHERENCE TOMOGRAPHY FINDINGS IN PRESUMED VETERINARY ANTHELMINTIC DRUG-INDUCED RETINAL TOXICITY: A Glimpse into Underlying Mechanism

PURPOSE

To report optical coherence tomography findings of presumed veterinary anthelmintic drugs (VADs)-induced retinal toxicity that may aid in understanding potential pathogenic mechanisms.

METHODS

This is a retrospective observational case series analysis of patients with vision abnormalities following the accidental or intentional consumption of veterinary anthelmintic drugs. All cases underwent a thorough ophthalmological examination. Moreover, medical records, as well as the initial and follow-up optical coherence tomography images, were thoroughly scrutinized.

RESULTS

Four patients were identified (3 men; mean [range] age, 36.5 [22-52] years). Each patient overdosed on one or two of the following VADs: closantel, triclabendazole, praziquantel, pyrantel pamoate, and niclofolan. The most characteristic optical coherence tomography finding was diffuse, granular, hyperreflective lesions throughout the outer retina, which were initially identified in the ellipsoid zone in two cases. At follow-up, optical coherence tomography exhibited regression of hyperreflective lesions and extensive loss of the outer retinal elements in two patients. In addition, the subfoveal outer retinal layers may be partially preserved.

CONCLUSION

Some veterinary anthelmintic drugs could be detrimental to the human retina if overdosed, resulting in visual disturbances. Optical coherence tomography revealed the mitochondria-enriched ellipsoid zone where outer retinal damage first appeared on, implying that these medications may harm the retina by inhibiting mitochondrial energy metabolism, as they do to eliminate parasites.

Antiparasitic activity of the steroid-rich extract of Schima wallichii against poultry cestode

Background and Aim

Schima wallichii Korth., commonly known as the needlewood tree (family Theaceae) has therapeutic uses in traditional Mizo medicine for human helminthiasis and serves as a balm against ectoparasites in animals. Although the medicinal properties have been studied experimentally, its use as a traditional anthelmintic remains unexplored. This study aimed to analyze the chemical components and antiparasitic activity of S. wallichii.

Materials and Methods

The chemical analysis of S. wallichi bark extracts was conducted focusing on the secondary metabolites using petroleum ether, chloroform, and methanol. Gas chromatography-mass spectrometry (GC-MS) was used to identify the specific compounds. An anthelmintic susceptibility test was carried out against Raillietina tetragona, intestinal cestode parasite of fowl.

Results

The methanol extract yielded the highest concentrations of alkaloids, carbohydrates, glycosides, sterols, saponins, and tannins among all the extracts. Sterols were the most abundant compounds in all extracts, with flavonoids being absent. Secondary metabolites were largely absent in the petroleum ether and chloroform extracts. The GC-MS data identified cholest-22-ene-21-ol as the major steroid component. The cestode parasite was inhibited in a concentration-dependent manner by the plant extract. The plant extract's anthelmintic activity was evident through observable damage to the parasite's outer structure.

Conclusion

Phytosterols in S. wallichii bark are responsible for its anthelmintic properties. The mechanism and pharmaceutical properties of the anthelmintic molecule require further exploration.

Anti-inflammatory and immunomodulatory effects of mesenchymal stem cell therapy on parasitic drug resistance

INTRODUCTION

The emergence of antiparasitic drug resistance poses a concerning threat to animals and humans. Mesenchymal Stem Cells (MSCs) have been widely used to treat infections in humans, pets, and livestock. Although this is an emerging field of study, the current review outlines possible mechanisms and examines potential synergism in combination therapies and the possible harmful effects of such an approach.

AREAS COVERED

The present study delved into the latest pre-clinical research on utilizing MSCs to treat parasitic infections. As per investigations, the introduction of MSCs to patients grappling with parasitic diseases like schistosomiasis, malaria, cystic echinococcosis, toxoplasmosis, leishmaniasis, and trypanosomiasis has shown a reduction in parasite prevalence. This intervention also alters the levels of both pro- and anti-inflammatory cytokines. Furthermore, the combined administration of MSCs and antiparasitic drugs has demonstrated enhanced efficacy in combating parasites and modulating the immune response.

EXPERT OPINION

Mesenchymal stem cells are a potential solution for addressing parasitic drug resistance. This is mainly because of their remarkable immunomodulatory abilities, which can potentially help combat parasites' resistance to drugs.

Anthelmintics in the environment: Their occurrence, fate, and toxicity to non-target organisms

Anthelmintics are drugs used for the treatment and prevention of diseases caused by parasitic worms (helminths). While the importance of anthelmintics in human as well as in veterinary medicine is evident, they represent emerging contaminants of the environment. Human anthelmintics are mainly used in tropical and sub-tropical regions, while veterinary anthelmintics have become frequently-occurring environmental pollutants worldwide due to intensive agri- and aquaculture production. In the environment, anthelmintics are distributed in water and soil in relation to their structure and physicochemical properties. Consequently, they enter various organisms directly (e.g. plants, soil invertebrates, water animals) or indirectly through food-chain. Several anthelmintics elicit toxic effects in non-target species. Although new information has been made available, anthelmintics in ecosystems should be more thoroughly investigated to obtain complex knowledge on their impact in various environments. This review summarizes available information about the occurrence, behavior, and toxic effect of anthelmintics in environment. Several reasons why anthelmintics are dangerous contaminants are highlighted along with options to reduce contamination. Negative effects are also outlined.

Preliminary Phytochemical Composition and In Vitro Anthelmintic Activity of Aqueous and Ethanol Extracts of Olea africana against Mixed Gastrointestinal Worms in Dogs

Olea africana is used by some indigenous communities in Kenya to control gastrointestinal worms in animals. Plant-based anthelmintics are gaining popularity globally in the control of gastrointestinal worms in animals. The egg hatch inhibition assay was used to assess the in vitro anthelmintic efficacy of aqueous and ethanol leaf extracts of O. africana against the eggs of mixed gastrointestinal helminths in dogs. Probit regression was used to calculate the concentration of extracts that inhibited egg hatching by 50% (IC50). Albendazole was used as a control. Standard techniques were used to quantify the phytochemicals in the extracts. The aqueous extract had an IC50 of 1.85 mg/mL (1.64-2.10), and the ethanol extract had an IC50 of 0.25 mg/mL (0.23-0.26). Quantitative phytochemical analysis revealed that aqueous and ethanol extracts of O. africana contained alkaloids (19.40 and 61.60%), saponins (24.00 and 6.00%), phenols (0.95 and 1.28 mg/g gallic acid equivalents (GAE)), flavonoids (8.71 and 12.26 mg/g catechin equivalents (CE)), and tannins (67.30 and 76.30 mg/g of tannic acid equivalent (TAE)), respectively. O. africana has dose-dependent anthelmintic effects against mixed gastrointestinal worms in dogs. These findings support the traditional use of Olea africana as a treatment option for gastrointestinal worms in dogs.

Filarial nematode phenotypic screening cascade to identify compounds with anti-parasitic activity for drug discovery optimization

Filarial diseases, including lymphatic filariasis and onchocerciasis, are considered among the most devastating of all tropical diseases, affecting over 86 million people worldwide. To control and more rapidly eliminate onchocerciasis requires treatments that target the adult stage of the parasite. Drug discovery efforts are challenged by the lack of preclinical animal models using the human-pathogenic filariae, requiring the use of surrogate parasites for Onchocerca volvulus for both ex vivo and in vivo evaluation. Herein, we describe a platform utilizing phenotypic ex vivo assays consisting of the free-living nematode Caenorhabditis elegans, microfilariae and adult filariae of the bovine filariae Onchocerca lienalis and Onchocerca gutturosa, respectively, as well as microfilariae and adult filariae of the feline filariae Brugia pahangi, the rodent filariae Litomosoides sigmodontis and the human-pathogenic filariae Brugia malayi to assess activity across various surrogate parasites. Utilization of those surrogate nematodes for phenotypic ex vivo assays in order to assess activity across various parasites led to the successful establishment of a screening cascade and identification of multiple compounds with potential macrofilaricidal activity and desirable physicochemical, MW = 200-400 and low lipophilicity, logP <4, and pharmacokinetic properties, rat and human liver S9 stability of ≥70% remaining at 60 min, and AUC exposures above 3 μM h. This platform demonstrated the successful establishment of a screening cascade which resulted in the discovery of potential novel macrofilaricidal compounds for futher drug discovery lead optimization efforts. This screening cascade identified two distinct chemical series wherein one compound produced a significant 68% reduction of adult Litomosoides sigmodontis in the mouse model. Successful demonstration of efficacy prompted lead optimization medicinal chemistry efforts for this novel series.

Using newly optimized genetic tools to probe Strongyloides sensory behaviors

The oft-neglected human-parasitic threadworm, Strongyloides stercoralis, infects roughly eight percent of the global population, placing disproportionate medical and economic burden upon marginalized communities. While current chemotherapies treat strongyloidiasis, disease recrudescence and the looming threat of anthelminthic resistance necessitate novel strategies for nematode control. Throughout its life cycle, S. stercoralis relies upon sensory cues to aid in environmental navigation and coordinate developmental progression. Odorants, tastants, gases, and temperature have been shown to shape parasite behaviors that drive host seeking and infectivity; however, many of these sensory behaviors remain poorly understood, and their underlying molecular and neural mechanisms are largely uncharacterized. Disruption of sensory circuits essential to parasitism presents a promising strategy for future interventions. In this review, we describe our current understanding of sensory behaviors - namely olfactory, gustatory, gas sensing, and thermosensory behaviors - in Strongyloides spp. We also highlight the ever-growing cache of genetic tools optimized for use in Strongyloides that have facilitated these findings, including transgenesis, CRISPR/Cas9-mediated mutagenesis, RNAi, chemogenetic neuronal silencing, and the use of fluorescent biosensors to measure neuronal activity. Bolstered by these tools, we are poised to enter an era of rapid discovery in Strongyloides sensory neurobiology, which has the potential to shape pioneering advances in the prevention and treatment of strongyloidiasis.

Environmental circulation of the anthelmintic drug albendazole affects expression and activity of resistance-related genes in the parasitic nematode Haemonchus contortus

Veterinary anthelmintics excreted from treated animals pass to soil, subsequently to plants and then to their consumers. This circulation might have various consequences, including drug-resistance promotion in helminths. The present study was designed to follow the effect of the environmental circulation of the common anthelmintic drug albendazole (ABZ) in real farm conditions on the parasitic nematode Haemonchus contortus in vivo. Two fields with fodder plants (clover and alfalfa) were fertilized, the first with dung from ABZ-treated sheep (at the recommended dosage), the second with dung from non-treated sheep (controls). After a 10-week growth period, the fresh fodder from both fields was used to feed two groups of sheep, which were infected with H. contortus. Eggs and adult nematodes from the animals of both groups were isolated, and various parameters were compared. No significant changes in the eggs' sensitivity to ABZ and thiabendazole were observed. However, significantly increased expression of several cytochromes P450 and UDP-glycosyl transferases as well as increased oxidation and glycosylation of ABZ and ABZ-sulfoxide (ABZ-SO) was found in the exposed nematodes. These results show that ABZ environmental circulation improves the ability of the helminths to deactivate ABZ.

The Current Directions of Searching for Antiparasitic Drugs

Parasitic diseases are still a huge problem for mankind. They are becoming the main cause of chronic diseases in the world. Migration of the population, pollution of the natural environment, and climate changes cause the rapid spread of diseases. Additionally, a growing resistance of parasites to drugs is observed. Many research groups are looking for effective antiparasitic drugs with low side effects. In this work, we present the current trends in the search for antiparasitic drugs. We report known drugs used in other disease entities with proven antiparasitic activity and research on new chemical structures that may be potential drugs in parasitic diseases. The described investigations of antiparasitic compounds can be helpful for further drug development.

Sertraline as a new potential anthelmintic against Haemonchus contortus: toxicity, efficacy, and biotransformation

Haemonchus contortus is a parasitic nematode of ruminants which causes significant losses to many farmers worldwide. Since the drugs currently in use for the treatment of haemonchosis are losing their effectiveness due to the drug-resistance of this nematode, a new or repurposed drug is highly needed. As the antipsychotic drug sertraline (SRT) has been shown to be effective against the parasitic nematodes Trichuris muris, Ancylostoma caninum and Schistosoma mansoni, the aim of the present study was to evaluate the possible effect of SRT on H. contortus. The potential hepatotoxicity of SRT was tested in sheep, a common H. contortus host. In addition, the main metabolic pathways of SRT in H. contortus and the ovine liver were identified. While no effect of SRT on H. contortus egg hatching was observed, SRT was found to significantly decrease the viability of H. contortus adults in drug-sensitive and resistant strains, with its effect comparable to the commonly used anthelmintics levamisole and monepantel. Moreover, SRT in anthelmintically active concentrations showed no toxicity to the ovine liver. Biotransformation of SRT in H. contortus was weak, with most of the drug remaining unmetabolized. Production of the main metabolite hydroxy-SRT did not differ significantly between strains. Other minor metabolites such as SRT-O-glucoside, dihydroxy-SRT, and SRT-ketone were also identified in H. contorts adults. Compared to H. contortus, the ovine liver metabolized SRT more extensively, mainly via desmethylation and glucuronidation. In conclusion, the potency of SRT against H. contortus was proven, and it should be tested further toward possible repurposing.

Proof of the environmental circulation of veterinary drug albendazole in real farm conditions

Anthelmintics, drugs against parasitic worms, are frequently used in livestock and might act as danger environmental microcontaminants. The present study was designed to monitor the possible circulation of common anthelmintic drug albendazole (ABZ) and its metabolites in the real agriculture conditions. The sheep were treated with the recommended dose of ABZ. Collected faeces were used for the fertilization of a field with fodder plants (alfalfa and clover) which served as feed for sheep from a different farm. The selective ultrasensitive mass spectrometry revealed surprisingly high concentrations of active ABZ metabolite (ABZ-sulphoxide) in all samples (dung, plants, ovine plasma, rumen content and faeces). Our results prove for the first time an undesirable permeation of ABZ metabolites from sheep excrement into plants (used as fodder) and subsequently to other sheep in real agricultural conditions. This circulation causes the permanent exposition of the ecosystems and food-chain to the drug and can promote the development of drug resistance in helminths.

In vitro effects of tropisetron and granisetron against Echinococcus granulosus (s.s.) protoscoleces by involvement of calcineurin and calmodulin

Background

Cystic echinococcosis (CE) is a disease caused by the larval stage of Echinococcus granulosus sensu lato  (s.l.). The treatment of CE mainly relies on the use of benzimidazoles, which can commonly cause adverse side effects. Therefore, more efficient treatment options are needed. Drug repurposing is a useful approach for advancing drug development. We have evaluated the in vitro protoscolicidal effects of tropisetron and granisetron in E. granulosus sensu stricto (s.s.) and assessed the expression of the calcineurin (CaN) and calmodulin (CaM) genes, both of which have been linked to cellular signaling activities and thus are potentially promising targets for the development of drugs.

Methods

Protoscoleces (PSC) of E. granulosus (s.s.) (genotype G1) obtained from sheep hepatic hydatid cysts were exposed to tropisetron and granisetron at concentrations of 50, 150 and 250 µM for various periods of time up to 10 days. Cyclosporine A (CsA) and albendazole sulfoxide were used for comparison. Changes in the morphology of PSC were investigated by light microscopy and scanning electron microscopy. Gene expression was assessed using real-time PCR at the mRNA level for E. granulosus calcineurin subunit A (Eg-CaN-A), calcineurin subunit B (Eg-CaN-B) and calmodulin (Eg-CaM) after a 24-h exposure at 50 and 250 µM, respectively.

Results

At 150 and 250 µM, tropisetron had the highest protoscolicidal effect, whereas CsA was most effective at 50 µM. Granisetron, however, was less effective than tropisetron at all three concentrations. Examination of morphological alterations revealed that the rate at which PSC were killed increased with increasing rate of PSC evagination, as observed in PSC exposed to tropisetron. Gene expression analysis revealed that tropisetron at 50 μM significantly upregulated Eg-CaN-B and Eg-CaM expression while at 250 μM it significantly downregulated both Eg-CaN-B and Eg-CaM expressions; in comparison, granisetron decreased the expression of all three genes at both concentrations.

Conclusions

Tropisetron exhibited a higher efficacy than granisetron against E. granulosus (s.s.) PSC, which is probably due to the different mechanisms of action of the two drugs. The concentration-dependent effect of tropisetron on calcineurin gene expression might reflect its dual functions, which should stimulate future research into its mechanism of action and evaluation of its potential therapeutical effect in the treatment of CE.

Graphic Abstract

Dehydroabietylamine, A Diterpene from Carthamus tinctorious L. Showing Antibacterial and Anthelmintic Effects with Computational Evidence

BACKGROUND

Plant-based drugs provide an outstanding contribution to modern therapeutics, and it is well known that the presence of different phytochemicals is responsible for such pharmacological effects. Carthamus tinctorius L. is one such medicinally important plant whose different solvent extracts have been reported with several pharmacological effects like antibacterial, hepatoprotective, and wound healing. The exploration of phytoconstituents from such a medicinally important plant for different pharmacological effects could produce new and effective drugs to treat human diseases.

OBJECTIVE

The present study attempts to explore the antibacterial and anthelmintic properties of dehydroabietylamine, a diterpene isolated from Carthamus tinctorius L. followed by the in silico elucidation of its probable mode of action.

METHODS

The minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) of dehydroabietylamine were assessed against Staphylococcus aureus and Pseudomonas aeruginosa, using micro- broth dilution method. The anthelmintic activity of was determined to assess the time taken for paralysis and death of Pheretima Posthuma at different concentrations. Additionally, molecular docking study was conducted to understand the interaction between dehydroabietylamine with target proteins identified for both antibacterial and anthelmintic activity viz., glucosamine-6-phosphate synthase and β-Tubulin, respectively.

RESULTS

The dehydroabietylamine showed the significant MIC for S. aureus (12.5 μg/ml) and P. aeruginosa (6.25μg/ml), respectively. The result of anthelmintics effect of dehydroabietylamine was found to be dosedependent and compared to the standard drug, albendazole.

CONCLUSION

The interactions of dehydroabietylamine with the two target proteins with high binding affinity indicated the probable inhibition of target proteins, which could be the cause for prominent antibacterial and antihelminthic effects.

Sertaconazole induced toxicity in HeLa cells through mitotic arrest and inhibition of microtubule assembly

Econazole, miconazole, and sertaconazole, the structurally related azoles with imidazole moiety, were evaluated for their cytotoxicity and their ability to bind to mammalian tubulin. Our results indicated that sertaconazole and econazole bound to goat brain tubulin with a dissociation constant of 9 and 19 μM respectively, while miconazole did not bind to goat brain tubulin. Econazole, miconazole, and sertaconazole inhibited the proliferation of HeLa cells with an IC₅₀ of 28, 98, and 38 μM respectively with sertaconazole alone inducing a mitotic block in the treated cells. Since sertaconazole bound to goat brain tubulin with higher affinity and blocked the cells at mitosis, we hypothesized that its cytotoxic mechanism might involve inhibition of tubulin and econazole which did not block the cells at mitosis may have additional targets than tubulin. Sertaconazole inhibited the polymerization of tubulin in HeLa cells and the in vitro assembled goat brain tubulin. Competitive tubulin-binding assay using colchicine and computational simulation studies showed that sertaconazole bound closer to the colchicine site and induced the tubulin dimer to adopt a "bent" conformation which is incompetent for the polymerization. Results from RT-PCR analysis of the A549 cells treated with sertaconazole indicated activation of apoptosis. Sertaconazole significantly inhibited the migration of HeLa cells and showed synergistic antiproliferative potential with vinblastine. Collectively, the results suggest that sertaconazole which is already in clinical practice could be useful as a topical chemotherapy agent for the treatment of skin cancers in combination with other systemic anticancer agents.

Inhibition of miR-99a-5p prevents allergen-driven airway exacerbations without compromising type-2 memory responses in the intestine following helminth infection

Acute exacerbations (AE) of asthma, remain one of the biggest concerns for patients living with asthma. As such, identifying the causes, the molecular mechanisms involved and new therapeutic interventions to prevent AE is a high priority. Immunity to intestinal helminths involves the reactivation of type-2 immune responses leading to smooth muscle contraction and mucus hypersecretion-physiological processes very similar to acute exacerbations in the airways following allergen exposure. In this study, we employed a murine model of intestinal helminth infection, using Heligmosomoides polygyrus, to identify miRNAs during active expulsion, as a system for the identification of miRNAs that may contribute to AE in the airways. Concomitant with type-2 immunity and expulsion of H. polygyrus, we identified miR-99a-5p, miR-148a-3p and miR-155-5p that were differentially regulated. Systemic inhibition of these miRNAs, alone or in combination, had minimal impact on expulsion of H. polygyrus, but inhibition of miR-99a-5p or miR-155-5p significantly reduced house dust mite (HDM)-driven acute inflammation, modelling human acute exacerbations. Immunological, pathological and transcriptional analysis identified that miR-155-5p or miR-99a-5p contribute significantly to HDM-driven AE and that transient inhibition of these miRNAs may provide relief from allergen-driven AE, without compromising anti-helminth immunity in the gut.

Combating Parasitic Nematode Infections, Newly Discovered Antinematode Compounds from Marine Epiphytic Bacteria

Parasitic nematode infections cause debilitating diseases and impede economic productivity. Antinematode chemotherapies are fundamental to modern medicine and are also important for industries including agriculture, aquaculture and animal health. However, the lack of suitable treatments for some diseases and the rise of nematode resistance to many available therapies necessitates the discovery and development of new drugs. Here, marine epiphytic bacteria represent a promising repository of newly discovered antinematode compounds. Epiphytic bacteria are ubiquitous on marine surfaces where they are under constant pressure of grazing by bacterivorous predators (e.g., protozoans and nematodes). Studies have shown that these bacteria have developed defense strategies to prevent grazers by producing toxic bioactive compounds. Although several active metabolites against nematodes have been identified from marine bacteria, drug discovery from marine microorganisms remains underexplored. In this review, we aim to provide further insight into the need and potential for marine epiphytic bacteria to become a new source of antinematode drugs. We discuss current and emerging strategies, including culture-independent high throughput screening and the utilization of Caenorhabditis elegans as a model target organism, which will be required to advance antinematode drug discovery and development from marine microbial sources.

Chemical composition and broad-spectrum anthelmintic activity of a cultivar of toothache plant, Acmella oleracea, from Mizoram, India

Context: A variety of Acmella oleracea (L.) R.K. Jansen (Asteraceae) is used by the Mizo people of India and Myanmar for intestinal helminthiasis.Objective: To perform a chemical analysis of the plant extract using gas chromatography-mass spectrometry (GC-MS) and test the anthelmintic activity on intestinal parasites.Materials and methods: An extract of the aerial parts was prepared in hexane and analysed using GC-MS. Survival test was performed in vitro on the cestode, Taenia tetragona, and the nematode, Ascaridia perspicillum. Concentrations of 1.25, 2.5, 5, 10 and 20 mg/mL, prepared in phosphate-buffered saline (PBS) with 1% dimethylsulphoxide (DMSO), were tested. Negative control was maintained in PBS with DMSO, and albendazole was used as a reference drug. Each treatment consisted of six worms and was done until death was confirmed. Scanning electron microscopy was used to describe the structural changes.Results: Nineteen compounds were detected. The major compounds were fatty alcohols such as 3,7,11,15-tetramethylhexadec-2-en-1-ol and (9Z)-9-hexadecen-1-ol. Important bioactive compounds including an alkylamide, N-isobutyl-(2E,4Z,8Z,10E)-dodecatetraenamide, and a triterpenoid, lupeol, were also confirmed. The lethal concentration (LC₅₀) of the plant extract was 5128.61 ppm on T. tetragona and 8921.50 ppm on A. perspicillum. Tegumental shrinkage, erosion of microtriches, and distortion of the suckers were observed on the cestode. The nematode showed collapse of the lips and shrunk cuticle.Conclusions: Acmella oleracea contains important bioactive compounds, which are responsible for the broad-spectrum anthelmintic activity. Further study on the pharmacology of the compounds is warranted.

Phytochemical analysis and in vitro anthelmintic activity of Imperata cylindrica underground parts

Background

Imperata cylindrica is considered as an agricultural weed, but it is a valuable plant in the traditional medicines of Southeast Asia. In the Mizo traditional medicine of India and Myanmar, the rhizomes and roots are used as a remedy for bacterial, fungal and intestinal helminth infections.

Methods

An extract of the whole underground parts was prepared in Soxhlet apparatus using chloroform as a solvent. After concentrating in a vacuum rotary evaporator, the extract was analysed using gas chromatography-mass spectrometry. Anthelmintic activity was tested in vitro against the tapeworm Raillietina tetragona and the roundworm Ascaridia galli. Scanning electron microscopy was used to examine the structural changes on the helminths after treatment with the plant extract.

Results

Twenty-two compounds were identified from the plant extract out of which fatty acids were the predominant compounds. Palmitic acid was the most abundant. Bioactive phytosterols such as campesterol and stigmasterol were also detected. The plant extract was significantly effective on both the helminths and showed dose-dependent anthelmintic activity as that of albendazole. The tapeworm treated with the plant extract showed deformities on the suckers, clumping of the spines, tegumental folds and erosion of microtriches. Extensive damage was also seen on the roundworm including cuticular shrinkage, collapse of the lips, and formation of warty surface throughout the body.

Conclusion

I. cylindrica extract effectively killed and caused detrimental effects on parasitic tapeworm and roundworm. The study therefore validates the traditional usage among the Mizo people, and guarantees further investigation on the exact compound(s) and mechanism of action.

Direct label-free methods for identification of target proteins in agrochemicals

Green agrochemicals are important guarantee for food production and security, and target protein identification is the most important basis for development of novel agrochemicals. Affinity chromatography methods for immobilization of agrochemicals have been widely used to identify and confirm new targets. However, this method often requires modification of the active molecules which can affect or damage its biological activity, and biomacromolecules, particularly most natural products, are hard to be modified either. In order to overcome the shortcomings of molecular modification, label-free technology has been developed based on evaluating responses to thermal or proteolytic treatments. Combined with the chemical biology technology and molecular biology technology, it has been used in the development of drugs and agrochemicals. Herein, common methods of label-free technology for identification of direct target of agrochemicals are reviewed, including the principle, advantages, limitations and applications in the research of agrochemicals in the last decade. And the methods for validation of candidate targets obtained by the label-free methods are also reviewed, which are important to obtain the accurate and reliable targets. Combined application of these methods will greatly reduce the experimental costs and shorten the period for the new target identification and validation by improving its accuracy, which will provide a systematic solution for new ecological agrochemicals research and development.

Natural Compounds from the Marine Brown Alga Caulocystis cephalornithos with Potent In Vitro-Activity against the Parasitic Nematode Haemonchus contortus

Eight secondary metabolites (1 to 8) were isolated from a marine sponge, a marine alga and three terrestrial plants collected in Australia and subsequently chemically characterised. Here, these natural product-derived compounds were screened for in vitro-anthelmintic activity against the larvae and adult stages of Haemonchus contortus (barber's pole worm)-a highly pathogenic parasitic nematode of ruminants. Using an optimised, whole-organism screening system, compounds were tested on exsheathed third-stage larvae (xL3s) and fourth-stage larvae (L4s). Anthelmintic activity was initially evaluated on these stages based on the inhibition of motility, development and/or changes in morphology (phenotype). We identified two compounds, 6-undecylsalicylic acid (3) and 6-tridecylsalicylic acid (4) isolated from the marine brown alga, Caulocystis cephalornithos, with inhibitory effects on xL3 and L4 motility and larval development, and the induction of a "skinny-straight" phenotype. Subsequent testing showed that these two compounds had an acute nematocidal effect (within 1-12 h) on adult males and females of H. contortus. Ultrastructural analysis of adult worms treated with compound 4 revealed significant damage to subcuticular musculature and associated tissues and cellular organelles including mitochondria. In conclusion, the present study has discovered two algal compounds possessing acute anthelmintic effects and with potential for hit-to-lead progression. Future work should focus on undertaking a structure-activity relationship study and on elucidating the mode(s) of action of optimised compounds.

Intestinal cestodes of chicken are effectively killed by quinoline-rich extract of Spilanthes acmella

Background and Aim

Spilanthes acmella is used for the treatment of intestinal helminth infections in Mizo traditional medicine. In spite of a variety of drugs developed for helminthiases, an entirely safe and absolutely effective drug is still lacking, so much so that infections remain a major problem in human and animal welfare. In this study, we attempted to substantiate S. acmella as an anticestodal agent.

Materials and Methods

The aqueous extract of the aerial parts of S. acmella was prepared and from it a bioactive fraction was obtained using column chromatography. Chemical analyses were done using thin-layer chromatography (TLC) and gas chromatography-mass spectrometry (GC-MS). Helminth survival test was performed in vitro on an intestinal cestode, Raillietina tetragona. Structural effects on the cestode were examined under scanning electron microscopy.

Results

From the bioactive fraction of S. acmella extract, TLC indicated the presence of an aromatic quinone, which was identified using GC-MS as a quinoline derivative (2,2,4-trimethyl-1,2-dihydroquinoline having a retention time of 24.97 min and chemical formula of C₁₂H₁₅N). The quinoline-rich fraction showed concentration-dependent activity against R. tetragona as that of albendazole. Scanning electron microscopy of the treated cestode revealed classic anthelmintic effects such as tegumental shrinkage and damage of surface organs. The scolex was shrunk, suckers were degenerated with disintegrated spines, and rostellum was completely collapsed. There were severe damages on the tegument and formation of pit-like scars on the proglottids.

Conclusion

The efficacy of S. acmella extract and structural damages it caused on the cestode indicates that it is a potential source of anthelmintic agent and that 2,2,4-trimethyl-1,2-dihydroquinoline contributes to its antiparasitic activity.

Macrofilaricides: An Unmet Medical Need for Filarial Diseases

Neglected parasitic helminth diseases such as onchocerciasis and lymphatic filariasis affect an estimated 145 million people worldwide, creating a serious health burden in endemic areas such as sub-Saharan Africa and India. Although these diseases are not usually lethal, these filarial nematodes, transmitted by blood-feeding insect vectors, cause severe debilitation and cause chronic disability to infected individuals. The adult worms can reproduce from 5 to up to 14 years, releasing millions of microfilariae, juvenile worms, over an infected individual's lifetime. The current treatments for controlling human filarial infections is focused on killing microfilariae, the earliest larval stage. Currently, there is an unmet medical need for treatments consisting of a macrofilaricidal regimen, one that targets the adult stage of the parasite, to increase the rate of elimination, allow for safe use in coendemic regions of Onchocerca volvulus and Loa loa, and to provide a rapid method to resolve reinfections. Herein, recent approaches for targeting human filarial diseases are discussed, including direct acting agents to target parasitic nematodes and antibacterial approaches to target the endosymbiotic bacteria, Wolbachia.

Anthelmintics in the future: current trends in the discovery and development of new drugs against gastrointestinal nematodes

The control of gastrointestinal nematodes (GINs), the most abundant and serious parasites of livestock, has become difficult because of the limited number of available drugs and fast development of drug resistance. Thus, considerable efforts have been devoted to developing new anthelmintics that are efficient against nematodes, especially resistant species. Here, we summarize the most recent results using various approaches: target-based or high-throughput screening (HTS) of compound libraries; the synthesis of new derivatives or new combinations of current anthelmintics; the repurposing of drugs currently approved for other indications; and lastly, the identification of active plant products. We also evaluate the advantages and disadvantages of each of these approaches.

Probiotics and yogurt modulate oxidative stress and fibrosis in livers of Schistosoma mansoni-infected mice

Background

Considerable morbidity, mortality, and economic loss result from schistosomiasis infection. Deposition of Schistosoma eggs in the hepatic portal vein is considered as the main causative agent for the development of liver fibrosis and subsequent liver cirrhosis. Probiotics are exogenous and beneficial microorganisms to living hosts against the harmful effect of many parasites. Strong evidence suggests the importance of probiotics in the control strategy of helminth. The ultimate goal of this study is to evaluate the protective effect of probiotics and yogurt on Schistosoma mansoni-induced oxidative stress and hepatic fibrosis in mice.

Methods

Mice were infected by tail immersion of schistosomal cercariae followed by an oral treatment with either probiotics or yogurt for one week before infection and immediately post-infection. Mice were scarified on day 56 following infection with S. mansoni and liver sample were obtained.

Results

We showed that oral administration of probiotics or yogurt revealed a significant reduction in worm number, egg load, and granuloma size in liver tissue, which is mainly assigned to the decreased expression level of matrix metalloproteinases 9 (MMP-9) in liver tissue. A significant reduction in the oxidative stress markers-induced by S. mansoni infection including lipid peroxidation and nitrite/nitrate was also detected. The level of some antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase) and reduced glutathione was greatly enhanced. Furthermore, treatment with probiotics or yogurt inhibited apoptosis in hepatic tissue, which is mainly assigned to the decreased expression level of caspases-3 in liver tissue.

Conclusion

Our findings represent the promising anti-schistosomal activities of probiotics and yogurt.

Electronic supplementary material

The online version of this article (10.1186/s12906-018-2406-3) contains supplementary material, which is available to authorized users.

Menthol acts as a positive allosteric modulator on nematode levamisole sensitive nicotinic acetylcholine receptors

The ongoing and widespread emergence of resistance to the existing anti-nematodal pharmacopeia has made it imperative to develop new anthelminthic agents. Historically, plants have been important sources of therapeutic compounds and offer an alternative to synthetic drugs. Monoterpenoids are phytochemicals that have been shown to produce acute toxic effects in insects and nematodes. Previous studies have shown nicotinic acetylcholine receptors (nAChRs) to be possible targets for naturally occurring plant metabolites such as carvacrol and carveol. In this study we examined the effects of monoterpenoid compounds on a levamisole sensitive nAChR from Oesophagostomum dentatum and a nicotine sensitive nAChR from Ascaris suum. We expressed the receptors in Xenopus laevis oocytes and used two-electrode voltage-clamp to characterize the effect of various compounds on these cys-loop receptors. At 100 μM the majority of these compounds acted as antagonists. Interestingly, further experiments revealed that both 0.1 μM and 10 μM menthol potentiated acetylcholine and levamisole responses in the levamisole sensitive receptor but not the nicotine sensitive receptor. We also investigated the effects of 0.1 μM menthol on the contractility of A. suum somatic muscle strips. Menthol produced significant potentiation of peak contractions at each concentration of acetylcholine. The positive allosteric modulatory effects of menthol in both in vivo and in vitro experiments suggests menthol as a promising candidate for combination therapy with cholinergic anthelmintics.

•

We screened 12 monoterpenoid compounds to search for a potential anthelmintic.

•

Menthol acted as a PAM on levamisole sensitive nematode nAChRs in vitro & in vivo.

•

Carvacrol produced antagonism on both levamisole and nicotine sensitive nAChRs.

•

Monoterpenoid compounds can be used as an adjunct with cholinergic anthelmintics.

Bioassay-guided isolation of active substances from Semen Torreyae identifies two new anthelmintic compounds with novel mechanism of action

ETHNOPHARMACOLOGICAL RELEVANCE

Semen Torreyae, the seeds of Torreya grandis Fortune ex Lindley (Cephalotaxaceae) is a well-known traditional Chinese medicinal plant recorded in the Chinese Pharmacopeia (2010 version). It is widely used for treating intestinal parasites in China, owing to its desirable efficacy and safety. However, the anthelmintic compounds in Semen Torreyae have not yet been identified.

AIM OF THE STUDY

This study aims to identify the compounds active against helminths from Semen Torreyae. In addition, we tested whether C. elegans strains resistant to currently-used anthelmintic drugs showed cross-resistance to these compounds.

METHODS

A bioassay-guided isolation of anthelmintic compounds from Semen Torreyae was performed using a Caenorhabditis elegans (C. elegans) testing model. The structures of active compounds were elucidated by a combination of GC-MS, high resolution MS, and NMR. The median-effect method was employed to generate a combination index (CI) to evaluate the synergistic effect of the anthelmintic compounds. A panel of C. elegans mutant strains resistant against the major anthelmintic drug classes was used to study the cross-resistance to currently-used anthelmintic drugs. A panel of transient receptor potential (TRP) channel mutant strains was also tested to explore the possible mechanisms of action of the anthelmintic compounds.

RESULTS

The bioassay-guided isolation led to two active compounds, i.e. galangal acetate (IC₅₀: 58.5 ± 8.9 μM) and miogadial (IC₅₀: 25.1 ± 5.4 μM). The combination of galangal acetate and miogadial resulted in a synergistic effect at IC₅₀, IC₇₀, and IC₉₀ levels (CIs < 1). Galangal acetate and miogadial demonstrated similar activity against drug-resistant C. elegans strains compared to the wild-type strain. In addition, none of the TRP mutants was significantly resistant to galangal acetate or miogadial compared to wild type worms.

CONCLUSIONS

We identified the bioactive compounds from Semen Torreyae responsible for its anthelmintic activity: galangal acetate and miogadial. The two anthelmintic compounds demonstrated a synergistic effect against C. elegans. Galangal acetate and miogadial are unlikely to act on the targets of currently-used anthelmintics (ivermectin, levamisole, benomyl and aldicarb), and an action on TRP channels appears to be ruled out as well. In summary, galangal acetate and miogadial are promising anthelmintic hits worth further investigation.

Bioassay-guided isolation of three anthelmintic compounds from Warburgia ugandensis Sprague subspecies ugandensis, and the mechanism of action of polygodial

Parasitic helminths continue to pose problems in human and veterinary medicine, as well as in agriculture. Resistance to current anthelmintics has prompted the search for new drugs. Anthelmintic metabolites from medicinal plants could be good anthelmintic drug candidates. However, the compounds active against nematodes have not been identified in most medicinal plants with anthelmintic activity. In this study, we aimed to identify the active compounds against helminths in Warburgia ugandensis Sprague subspecies ugandensis (Canellaceae) and study the underlying mechanism of action. A bioassay-guided isolation of anthelmintic compounds from the plant was performed using a Caenorhabditis elegans (C. elegans) test model with a WMicrotracker instrument to monitor motility. Three active compounds were purified and identified by nuclear magnetic resonance and high resolution MS: warburganal (IC₅₀: 28.2 ± 8.6 μM), polygodial (IC₅₀: 13.1 ± 5.3 μM) and alpha-linolenic acid (ALA, IC₅₀: 70.1 ± 17.5 μM). A checkerboard assay for warburganal and ALA as well as polygodial and ALA showed a fractional inhibitory concentration index of 0.41 and 0.37, respectively, suggesting that polygodial and ALA, as well as warburganal and ALA, have a synergistic effect against nematodes. A preliminary structure-activity relationship study for polygodial showed that the α,β-unsaturated 1,4-dialdehyde structural motif is essential for the potent activity. None of a panel of C. elegans mutant strains, resistant against major anthelmintic drug classes, showed significant resistance to polygodial, implying that polygodial may block C. elegans motility through a mechanism which differs from that of currently marketed drugs. Further measurements showed that polygodial inhibits mitochondrial ATP synthesis of C. elegans in a dose-dependent manner (IC₅₀: 1.8 ± 1.0 μM). Therefore, we believe that the underlying mechanism of action of polygodial is probably inhibition of mitochondrial ATP synthesis. In conclusion, polygodial could be a promising anthelmintic drug candidate worth considering for further development.

Metabolism of albendazole, ricobendazole and flubendazole in Haemonchus contortus adults: Sex differences, resistance-related differences and the identification of new metabolites

Haemonchus contortus (family Trichostrongylidae, Nematoda), a hematophagous gastrointestinal parasite found in small ruminants, has a great ability to develop resistance to anthelmintic drugs. We studied the biotransformation of the three benzimidazole anthelmintics: albendazole (ABZ), ricobendazole (albendazole S-oxide; RCB) and flubendazole (FLU) in females and males of H. contortus in both a susceptible ISE strain and resistant IRE strain. The ex vivo cultivation of living nematodes in culture medium with or without the anthelmintics was used. Ultrasensitive UHPLC/MS/MS analysis revealed 9, 7 and 12 metabolites of ABZ, RCB and FLU, respectively, with most of these metabolites now described in the present study for the first time in H. contortus. The structure of certain metabolites shows the presence of biotransformation reactions not previously reported in nematodes. There were significant qualitative and semi-quantitative differences in the metabolites formed by male and female worms. In most cases, females metabolized drugs more extensively than males. Adults of the IRE strain were able to form many more metabolites of all the drugs than adults of the ISE strain. Some metabolites were even found only in adults of the IRE strain. These findings suggest that increased drug metabolism may play a role in resistance to benzimidazole drugs in H. contortus.

MicroRNA-mediated regulation of immune responses to intestinal helminth infections

Intestinal helminth infections are highly prevalent in the developing world, often resulting in chronic infection and inflicting high host morbidity. With the emergence of drug-resistant parasites, a limited number of chemotherapeutic drugs available and stalling vaccine efforts, an increased understanding of antihelminth immunity is essential to provide new avenues to therapeutic intervention. MicroRNAs are a class of small, nonprotein coding RNAs which negatively regulate mRNA translation, thus providing finite control over gene expression in a plethora of biological settings. The miRNA-mediated coordinated control of gene expression has been shown to be essential in infection and immunity, in promoting and fine-tuning the appropriate immune response. This review gathers together and discusses observations of miRNA-mediated effects on the immune system and the subsequent impact on our understanding of antihelminth immunity.

Diastereoselective synthesis of fluoroisosteric analogues of antiparasitic pyrrolobenzoxazine alkaloids from tryptophan by successive fluorination–cyclization and a Meisenheimer-type rearrangement

Fluoroisosteric analogues of an antiparasitic pyrrolobenzoxazine alkaloid CJ-12663 were designed and diastereoselectively synthesized.

[Clinical approach to imported eosinophilia]

Eosinophilia is a common finding in international travelers and immigrants, being an helmintic infection its main etiology. The positive predictive value of eosinophilia for an helmintosis is low in travellers. Eosinophilia may be an incidental finding, or symptomatic, and it represents a clinical challenge due to the low sensitivity and specificity of direct and indirect parasitological diagnostic tests, respectively. It requires a structured approach based on geographical areas, environmental exposures and behavioral risks, and associated symptoms. The initial assessment should include a comprehensive and tailored anamnesis and physical examination, basic laboratory tests, a complete parasitological examination of stool samples and a Strongyloides stercoralis serology, supplemented with other explorations guided by epidemiological and clinical suspicion. Empiric treatment with albendazole and/or ivermectin (plus praziquantel if risk of schistosomiasis) is an option for unidentified persistent eosinophilia after study, and in persons in whom a proper assessment or follow-up can not be assured. In patients at risk for estrongiloidosis who are candidates for immunosuppressive therapies, it is indicated a prior screening and treatment to prevent a future hyperinfestation syndrome.

Benzimidazole resistance in helminths: From problem to diagnosis

Helminth parasites cause significant morbidity and mortality in endemic countries. Given the severity of symptoms that helminths may elicit in the host, intervention with prophylactic and therapeutic measures is imperative. Treatment with benzimidazoles is the most widely used means of combatting these parasites. However, widespread use of these drugs can select for drug-resistant parasite strains. In this review, we approach the problem of benzimidazole resistance in helminths in both humans and animals, focusing on the properties of the drug, the molecular mechanisms of drug resistance and how resistance is diagnosed.

Microfluidic platform for electrophysiological recordings from host-stage hookworm and Ascaris suum larvae: A new tool for anthelmintic research

The screening of candidate compounds and natural products for anthelmintic activity is important for discovering new drugs against human and animal parasites. We previously validated in Caenorhabditis elegans a microfluidic device (‘chip’) that records non-invasively the tiny electrophysiological signals generated by rhythmic contraction (pumping) of the worm's pharynx. These electropharyngeograms (EPGs) are recorded simultaneously from multiple worms per chip, providing a medium-throughput readout of muscular and neural activity that is especially useful for compounds targeting neurotransmitter receptors and ion channels. Microfluidic technologies have transformed C. elegans research and the goal of the current study was to validate hookworm and Ascaris suum host-stage larvae in the microfluidic EPG platform. Ancylostoma ceylanicum and A. caninum infective L3s (iL3s) that had been activated in vitro generally produced erratic EPG activity under the conditions tested. In contrast, A. ceylanicum L4s recovered from hamsters exhibited robust, sustained EPG activity, consisting of three waveforms: (1) conventional pumps as seen in other nematodes; (2) rapid voltage deflections, associated with irregular contractions of the esophagus and openings of the esophogeal-intestinal valve (termed a ‘flutter’); and (3) hybrid waveforms, which we classified as pumps. For data analysis, pumps and flutters were combined and termed EPG ‘events.’ EPG waveform identification and analysis were performed semi-automatically using custom-designed software. The neuromodulator serotonin (5-hydroxytryptamine; 5HT) increased EPG event frequency in A. ceylanicum L4s at an optimal concentration of 0.5 mM. The anthelmintic drug ivermectin (IVM) inhibited EPG activity in a concentration-dependent manner. EPGs from A. suum L3s recovered from pig lungs exhibited robust pharyngeal pumping in 1 mM 5HT, which was inhibited by IVM. These experiments validate the use of A. ceylanicum L4s and A. suum L3s with the microfluidic EPG platform, providing a new tool for screening anthelmintic candidates or investigating parasitic nematode feeding behavior.

•

Pharyngeal pumping in nematodes generates an electropharyngeogram (EPG).

•

The EPG provides a readout of the electrical activity of neurons and muscles.

•

A microfluidic platform for recording EPGs was validated in parasitic nematodes.

•

EPG activity and drug responses were characterized in host-stage larvae.

•

Microfluidic EPG recordings provide a powerful new tool for anthelmintic research.

Discovery of Novel Antischistosomal Agents by Molecular Modeling Approaches

Schistosomiasis, a chronic neglected tropical disease caused by Schistosoma worms, is reported in nearly 80 countries. Although the disease affects approximately 260 million people, the treatment relies exclusively on praziquantel, a drug discovered in the mid-1970s that lacks efficacy against the larval stages of the parasite. In addition, the dependence on a single treatment has raised concerns about drug resistance, and reduced susceptibility has already been found in laboratory and field isolates. Therefore, novel therapies for schistosomiasis are needed, and several approaches have been used to that end. One of these strategies, molecular modeling, has been increasingly integrated with experimental techniques, resulting in the discovery of novel antischistosomal agents.

Pharmacological profile of Ascaris suum ACR-16, a new homomeric nicotinic acetylcholine receptor widely distributed in Ascaris tissues

Background and Purpose

Control of nematode parasite infections relies largely on anthelmintic drugs, several of which act on nicotinic ACh receptors (nAChRs), and there are concerns about the development of resistance. There is an urgent need for development of new compounds to overcome resistance and novel anthelmintic drug targets. We describe the functional expression and pharmacological characterization of a homomeric nAChR, ACR‐16, from a nematode parasite.

Experimental Approach

Using RT‐PCR, molecular cloning and two‐electrode voltage clamp electrophysiology, we localized acr‐16 mRNA in Ascaris suum (Asu) and then cloned and expressed acr‐16 cRNA in Xenopus oocytes. Sensitivity of these receptors to cholinergic anthelmintics and a range of nicotinic agonists was tested.

Key Results

Amino acid sequence comparison with vertebrate nAChR subunits revealed ACR‐16 to be most closely related to α7 receptors, but with some striking distinctions. acr‐16 mRNA was recovered from Asu somatic muscle, pharynx, ovijector, head and intestine. In electrophysiological experiments, the existing cholinergic anthelmintic agonists (morantel, levamisole, methyridine, thenium, bephenium, tribendimidine and pyrantel) did not activate Asu‐ACR‐16 (except for a small response to oxantel). Other nAChR agonists: nicotine, ACh, cytisine, 3‐bromocytisine and epibatidine, produced robust current responses which desensitized at a rate varying with the agonists. Unlike α7, Asu‐ACR‐16 was insensitive to α‐bungarotoxin and did not respond to genistein or other α7 positive allosteric modulators. Asu‐ACR‐16 had lower calcium permeability than α7 receptors.

Conclusions and Implications

We suggest that ACR‐16 has diverse tissue‐dependent functions in nematode parasites and is a suitable drug target for development of novel anthelmintic compounds.

Target-based molecular modeling strategies for schistosomiasis drug discovery

Schistosomiasis, a neglected tropical disease caused by worms from the class Trematoda (genus Schistosoma), is a serious chronic condition that has been reported in approximately 80 countries. Nearly 250 million people are affected worldwide, mostly in the sub-Saharan Africa. Praziquantel, the mainstay of treatment, has been used for 30 years, and cases of resistance have been reported. The purpose of this perspective is to discuss current target-based molecular modeling strategies in schistosomiasis drug discovery. Advances in the field and the role played by the integration between computational modeling and experimental validation are also discussed. Finally, recent cases of the contribution of modern approaches in computational medicinal chemistry to the field are explored.

Spotlight on the in vitro effect of artemisinin-naphthoquine phosphate on Schistosoma mansoni and its snail host Biomphalaria alexandrina

Malaria and schistosomiasis are the two most important parasitic diseases in the tropics and sub-tropics with geographic overlap. Efforts have been made for developing new schistosomicidal drugs, or testing existing drugs originally used for non-related diseases. The antimalarial artemisinin-naphthoquine phosphate combination (CO-ArNp) was recently reported to be a promising novel antischistosomal therapy with potent in vivo activity against Schistosoma mansoni. In this work, we report the in vitro dose- and time-response effect of CO-ArNp against the Egyptian strain of S. mansoni, and its snail host, Biomphalaria alexandrina. Incubation of adult S. mansoni with CO-ArNp at 40 or 20 μg/ml for 48 or 72 h killed all worms. Exposure of S. mansoni miracidia and cercariae to the molluscicidal LC50 of CO-ArNp (16.8 μg/ml) resulted in 100% mortality of the free larval stages within 90 and 15 min, respectively. Moreover, incubation of adult B. alexandrina snails with this drug combination killed all snails at 40 μg/ml within 24h. Scanning electron microscope revealed marked morphological and tegumental alterations on the different stages of the parasite and its snail soft tissue. Our study highlights the schistosomicidal and molluscicidal effects of artemisinin-naphthoquine phosphate. No doubt more studies are needed to clarify its potential value to control schistosomiasis.