Licarin A, a neolignan isolated from Nectandra oppositifolia Nees & Mart. (Lauraceae), exhibited moderate preclinical efficacy against Schistosoma mansoni infection

Lignans Isolated from Piper truncatum Act as New Potent Antitrypanosomal Compounds

The hexane extract from twigs of Piper truncatum Vell (Piperaceae) displayed activity against Trypanosoma cruzi and was subjected to chromatographic steps to afford six dibenzylbutyrolactolic lignans, being four knowns: cubebin (1), (-)-9α-O-methylcubebin (2), (+)-9β-O-methylcubebinin (3) and 3,4-dimethoxy-3,4-demethylenedioxycubebin (4) as well as two new, named truncatin A (5) and B (6). Initially, in vitro activity against trypomastigotes was evaluated and compounds 1, 4 and 6 exhibited EC50 values of 41.6, 21.0 and 39.6 μM, respectively. However, when tested against amastigotes, the relevant clinical form in the chronic phase of Chagas disease, compounds 1-6 displayed activities with EC50 values ranging from 1.6 to 13.7 μM. In addition, the mammalian cytotoxicity of compounds 1-6 was evaluated against murine fibroblasts (NCTC). Compounds 2, 3 and 4 exhibited reduced toxicity against NCTC cells (CC50>200 μM), resulting in SI values of>21.9,>14.5 and>121.9, respectively. Compound 4 showed the highest potency with an SI value twice superior to that determined by the standard drug benznidazole (SI>54.6) against the intracellular amastigotes. These data suggest that lignan 4 can be considered a possible scaffold for designing a new drug candidate for Chagas disease.

Anti-allodynic and anti-hyperalgesic activity of (±)-licarin A in neuropathic rats via NO-cyclic-GMP-ATP-sensitive K+ channel pathway

The study aimed to examine the effect of intraperitoneal and intrathecal (±)-licarin A in neuropathic pain induced by L5 and L6 spinal nerve ligation (SNL) in male Wistar rats and the possible involvement of the NO-cGMP-ATP-sensitive K+ channel pathway. Neuropathic pain signs (allodynia and hyperalgesia) were evaluated on postoperative Day 14 using von Frey filaments. Single intraperitoneal (0.01, 0.1, 1, and 10 mg/kg) and intrathecal (0.01, 0.1, 1, and 10 µg/rat) administration of (±)-licarin A improved allodynia and hyperalgesia. The (±)-licarin A-induced anti-allodynic and anti-hyperalgesic activity was prevented by the intrathecal injection of  l-NAME (100 µg/rat; nonselective nitric oxide synthase inhibitor), ODQ (10 µg/rat; guanylate cyclase inhibitor), and glibenclamide (50 µg/rat; adenosine triphosphate (ATP)-sensitive K+ channel blocker). The data suggest that (±)-licarin A exerts its anti-allodynic and anti-hyperalgesic activity by activating the NO-cGMP-ATP-sensitive K+ channel pathway.

Targeting the Schistosoma mansoni nutritional mechanisms to design new antischistosomal compounds

The chemical classes of semicarbazones, thiosemicarbazones, and hydrazones are present in various compounds, each demonstrating diverse biological activities. Extensive studies have revealed their potential as schistosomicidal agents. Thiosemicarbazones, in particular, have shown inhibitory effects on Schistosoma mansoni's cathepsin B1 enzyme (SmCB1), which plays a crucial role in hemoglobin degradation within the worm's gut and its nutrition processes. Consequently, SmCB1 has emerged as a promising target for novel schistosomiasis therapies. Moreover, chloroquinoline exhibits characteristics in its aromatic structure that hold promise for developing SmCB1 inhibitors, along with its interaction with hemoglobin's heme group, potentially synergizing against the parasite's gut. In this context, we report the synthesis of 22 hybrid analogs combining hydrazones and quinolines, evaluated against S. mansoni. Five of these hybrids demonstrated schistosomicidal activity in vitro, with GPQF-8Q10 being the most effective, causing worm mortality within 24 h at a concentration of 25 µM. GPQF-8Q8 proved to be the most promising in vivo, significantly reducing egg presence in feces (by 52.8%) and immature eggs in intestines (by 45.8%). These compounds exhibited low cytotoxicity in Vero cells and an in in vivo animal model (Caenorhabditis elegans), indicating a favorable selectivity index. This suggests their potential for the development of new schistosomiasis therapies. Further studies are needed to uncover specific target mechanisms, but these findings offer a promising starting point.

Artificial intelligence-guided approach for efficient virtual screening of hits against Schistosoma mansoni

Background: The impact of schistosomiasis, which affects over 230 million people, emphasizes the urgency of developing new antischistosomal drugs. Artificial intelligence is vital in accelerating the drug discovery process. Methodology & results: We developed classification and regression machine learning models to predict the schistosomicidal activity of compounds not experimentally tested. The prioritized compounds were tested on schistosomula and adult stages of Schistosoma mansoni. Four compounds demonstrated significant activity against schistosomula, with 50% effective concentration values ranging from 9.8 to 32.5 μM, while exhibiting no toxicity in animal and human cell lines. Conclusion: These findings represent a significant step forward in the discovery of antischistosomal drugs. Further optimization of these active compounds can pave the way for their progression into preclinical studies.

Evaluating the Antischistosomal Activity of Dehydrodieugenol B and Its Methyl Ether Isolated from Nectandra leucantha-A Preclinical Study against Schistosoma mansoni Infection

Schistosomiasis, a parasitic disease affecting nearly 250 million individuals globally, poses a significant health challenge. With praziquantel being the sole available treatment and its limited efficacy in early stage infections, the identification of novel bioactive compounds becomes imperative. This study examines the potential of dehydrodieugenol B (1) and its methyl ether (2), derived from the leaves of the Brazilian Nectandra leucantha plant (Lauraceae), in combatting Schistosoma mansoni infections through a preclinical approach. Initially, compound 1 displayed noteworthy in vitro antiparasitic activity with an EC50 of 31.9 μM, showcasing low toxicity in mammalian cells and an in vivo animal model (Caenorhabditis elegans). Conversely, compound 2 exhibited no activity. In silico predictions pointed to favorable oral bioavailability and the absence of PAINS similarities. Subsequently, a single oral dose of 400 mg/kg of compound 1 or praziquantel was administered to mice infected with adult (patent infection) or immature parasites (prepatent infection). Remarkably, in prepatent infections, 1 resulted in a significant reduction (approximately 50%) in both worm and egg burden, while praziquantel reduced worm and egg numbers by 30%. The superior efficacy of dehydrodieugenol B (1) compared to praziquantel in premature infections holds the potential to advance the development of new molecular prototypes for schistosomiasis treatment.

The Existing Drug Nifuroxazide as an Antischistosomal Agent: In Vitro, In Vivo, and In Silico Studies of Macromolecular Targets

Schistosomiasis is a parasitic disease that afflicts approximately 250 million people worldwide. There is an urgent demand for new antiparasitic agents because praziquantel, the only drug available for the treatment of schistosomiasis, is not universally effective and may derail current progress toward the WHO goal of eliminating this disease as a public health problem by 2030. Nifuroxazide (NFZ), an oral nitrofuran antibiotic, has recently been explored to be repurposed for parasitic diseases. Here, in vitro, in vivo, and in silico studies were conducted to evaluate the activity of NFZ on Schistosoma mansoni. The in vitro study showed significant antiparasitic activity, with 50% effective concentration (EC50) and 90% effective concentration (EC90) values of 8.2 to 10.8 and 13.7 to 19.3 μM, respectively. NFZ also affected worm pairing and egg production and induced severe damage to the tegument of schistosomes. In vivo, a single oral dose of NFZ (400 mg/kg of body weight) to mice harboring either prepatent or patent S. mansoni infection significantly reduced the total worm burden (~40%). In patent infection, NFZ achieved a high reduction in the number of eggs (~80%), but the drug caused a low reduction in the egg burden of animals with prepatent infection. Finally, results from in silico target fishing methods predicted that serine/threonine kinases could be one of the potential targets for NFZ in S. mansoni. Overall, the present study revealed that NFZ possesses antischistosomal properties, mainly in terms of egg burden reduction in animals with patent S. mansoni infection. IMPORTANCE The increasing recognition of the burden imposed by helminthiasis, associated with the limited therapeutic arsenal, has led to initiatives and strategies to research and develop new drugs for the treatment of schistosomiasis. One of these strategies is drug repurposing, which considers low-risk compounds with potentially reduced costs and shorter time for development. In this study, nifuroxazide (NFZ) was evaluated for its anti-Schistosoma mansoni potential through in vitro, in vivo, and in silico studies. In vitro, NFZ affected worm pairing and egg production and induced severe damage to the tegument of schistosomes. In vivo, a single oral dose of NFZ (400 mg/kg) to mice harboring either prepatent or patent S. mansoni infection significantly reduced the total worm burden and egg production. In silico investigations have identified serine/threonine kinases as a molecular target for NFZ. Collectively, these results implied that NFZ might be a potential therapeutic candidate for the treatment of schistosomiasis.

Antischistosomal effects of green and chemically synthesized silver nanoparticles: in vitro and in vivo murine model

Schistosomiasis is one of the most important neglected tropical diseases in Africa, caused by blood fluke, Schistosoma sp. The use of nanotechnology in the treatment of this type of disease is urgently important to avoid the unwanted side effects of chemotherapy. The present study aimed to evaluate the efficacy of green silver nanoparticles (G-AgNPs), fabricated by (Calotropis procera), comparing with both chemically prepared silver ones (C-AgNPs) and Praziquantel (PZQ) treatments. The study included in vitro and in vivo evaluations. In in vitro study, 4 groups of schistosome worms were exposed to treatments as follows: the first one with a dose of PZQ (0.2 µg/ml), the 2^nd and 3^rd groups with different concentrations of G-AgNPs and C-AgNPs, respectively and the last one act as a negative control group. In in vivo study, six groups of mice were infected and then treated as follows: the first one with a dose of PZQ, the second with G-AgNPs, the third with C-AgNPs, the fourth with G-AgNPs plus a half dose of PZQ, the fifth with C-AgNPs accompanied by a half dose of PZQ, and the last group acted as a positive control group. The parasitological (worm burden, egg count & oogram) and histopathological parameters (hepatic granuloma profile) were used to evaluate antischistosomal activities in experimental groups. Additionally, the subsequent ultrastructural alterations were observed in adult worms using scanning electron microscopy (SEM). Transmission electron microscopy analysis showed that G-AgNPs and C-AgNPs have 8-25 and 8-11 nm in diameter, respectively, besides, fourier transform infrared analysis (FTIR) revealed the presence of organic compounds (aromatic ring groups) which act as capping agents around the surfaces of biogenic silver nanoparticles. In in vitro experiment, adult worms incubated either with G-AgNPs or C-AgNPs at concentrations higher than 100 µg/ml or 80 µg/ml, respectively, showed full mortality of parasites after 24 h. In the infected treated groups (with G-AgNPs plus PZQ & C-AgNPs plus PZQ) showed the most significant reduction in the total worm burdens (92.17% & 90.52%, respectively). Combined treatment with C-AgNPs and PZQ showed the highest value of dead eggs (93,6%), followed by G-AgNPs plus PZQ-treated one (91%). This study showed that mice treated with G-AgNPs plus PZQ significantly has the highest percentage of reduction in granuloma size and count (64.59%, 70.14%, respectively). Both G-AgNPs plus PZQ-treated & C-AgNPs plus PZQ treated groups showed the highest similar values of reduction percentage of total ova count in tissues (98.90% & 98.62%, respectively). Concerning SEM, G-AgNPs-treated worms showed more variability in ultrastructural alterations than G-AgNPs plus PZQ-treated one, besides, worms treated with C-AgNPs plus PZQ exhibited the maximum level of contractions or (shrinkage) as a major impact.

Antiparasitic properties of 4-nerolidylcatechol from Pothomorphe umbellata (L.) Miq. (Piperaceae) in vitro and in mice models with either prepatent or patent Schistosoma mansoni infections

ETHNOPHARMACOLOGICAL RELEVANCE

Roots of Pothomorphe umbellata (L.) Miq. are used in traditional medicine of Africa and South America for the treatment of malaria and helminthiasis. However, neither P. umbellata nor its isolated compounds have been evaluated against Schistosoma species.

AIMS OF THIS STUDY

To investigate the antischistosomal effects of P. umbellata root extracts and the isolated compound 4-nerolidylcatechol (4-NC) against Schistosoma mansoni ex vivo and in murine models of schistosomiasis.

MATERIALS AND METHODS

The crude hydroalcoholic (PuE) and hexane (PuH) extracts of P. umbellata roots were prepared and initially submitted to an ex vivo phenotypic screening against adult S. mansoni. PuH was analyzed by HPLC-DAD, characterized by UHPLC-HRMS/MS, and submitted to chromatographic fractionation, leading to the isolation of 4-NC. The anthelmintic properties of 4-NC were assayed ex vivo against adult schistosomes and in murine models of schistosomiasis for both patent and prepatent S. mansoni infections. Praziquantel (PZQ) was used as a reference compound.

RESULTS

PuE (EC₅₀: 18.7 μg/mL) and PuH (EC₅₀: 9.2 μg/mL) kill adult schistosomes ex vivo. The UHPLC-HRMS/MS analysis of PuH, the most active extract, revealed the presence of 4-NC, peltatol A, and peltatol B or C. After isolation from PuH, 4-NC presented remarkable in vitro schistosomicidal activity with EC₅₀ of 2.9 μM (0.91 μg/mL) and a selectivity index higher than 68 against Vero mammalian cells, without affecting viability of nematode Caenorhabditis elegans. In patent S. mansoni infection, the oral treatment with 4-NC decreased worm burden and egg production in 52.1% and 52.3%, respectively, also reducing splenomegaly and hepatomegaly. 4-NC, unlike PZQ, showed in vivo efficacy against juvenile S. mansoni, decreasing worm burden in 52.4%.

CONCLUSIONS

This study demonstrates that P. umbellata roots possess antischistosomal activity, giving support for the medicinal use of this plant against parasites. 4-NC was identified from P. umbellata roots as one of the effective in vitro and in vivo antischistosomal compound and as a potential lead for the development of novel anthelmintics.

Enhancing the antischistosomal activity of carvacryl acetate using nanoemulsion

Aim: To formulate a carvacryl acetate nanoemulsion (CANE) and test its antischistosomal activity. Materials & methods: CANE was prepared and tested in vitro on Schistosoma mansoni adult worms and both human and animal cell lines. Next, CANE was administered orally to mice infected with either a prepatent infection or a patent infection of S. mansoni. Results: CANE was stable during 90 days of analysis. CANE showed in vitro anthelmintic activity, and no cytotoxic effects were observed. In vivo, CANE was more effective than the free compounds in reducing worm burden and egg production. Treatment with CANE was more effective for prepatent infections than praziquantel. Conclusion: CANE improves antiparasitic properties and may be a promising delivery system for schistosomiasis treatment.

Toward anthelmintic drug candidates for toxocariasis: Challenges and recent developments

Infections caused by parasitic helminths rank among the most prevalent infections of humans and animals. Toxocariasis, caused by nematodes of the genus Toxocara, is one of the most widespread and economically important zoonotic parasitic infections that humans share with dogs and cats. Despite the completion of the Toxocara canis draft genome project, which has been an important step towards advancing the understanding of this parasite and the search for drug targets, the treatment of toxocariasis has been dependent on a limited set of drugs, necessitating the search for novel anthelmintic agents, specially against Toxocara larvae in tissues. Given that research, development, and innovation are crucial to finding appropriate solutions in the fight against helminthiasis, this paper reviews the progress made in the discovery of anthelmintic drug candidates for toxocariasis. The main compounds reported in the recent years regards on analogues of albendazole, reactive quinone derivatives and natural produts and its analogues. Nanoparticles and formulations were also reviewed. The in vitro and/or in vivo anthelmintic properties of such alternatives are herein discussed as well as the opportunities and challenges for treatment of human toxocariasis. The performed review clarify that the scarcity of validated molecular targets and limited chemical space explored are the main bottlenecks for advancing in the field of anti-Toxocara agents.

Lethal action of Licarin A derivatives in Leishmania (L.) infantum: Imbalance of calcium and bioenergetic metabolism

Natural metabolites present an extraordinary chemo-diversity and have been used as the inspiration for new drugs. Considering the need for new treatments against the neglected parasitic disease leishmaniasis, three semi-synthetic derivatives of natural neolignane licarin A were prepared: O-acetyl (1a), O-allyl (1b), and 5-allyl (1c). Using an ex vivo assay, compounds 1a, 1b, and 1c showed activity against the intracellular amastigotes of Leishmania (L.) infantum, with IC₅₀ values of 9, 13, and 10 μM, respectively. Despite no induction of hemolytic activity, only compound 1b resulted in mammalian cytotoxicity (CC₅₀ = 64 μM). The most potent compounds (1a and 1c) resulted in selectivity indexes >18. The mechanism of action of compound 1c was evaluated by fluorescent/luminescent based techniques and MALDI-TOF/MS. After a short incubation period, increased levels of the cytosolic calcium were observed in the parasites, with alkalinization of the acidocalcisomes. Compound 1c also induced mitochondrial hyperpolarization, resulting in decreased levels of ATP without altering the reactive oxygen species (ROS). Neither plasma membrane damages nor DNA fragmentation were observed after the treatment, but a reduction in the cellular proliferation was detected. Using MALDI-TOF/MS, mass spectral alterations of promastigote proteins were observed when compared to untreated and miltefosine-treated groups. This chemically modified neolignan induced lethal alterations of the bioenergetic and protein metabolism of Leishmania. Future PKPD and animal efficacy studies are needed to optimize this promising natural-derived compound.

Neolignans isolated from Saururus cernuus L. (Saururaceae) exhibit efficacy against Schistosoma mansoni

Schistosomiasis, a parasitic disease caused by the blood fluke of the genus Schistosoma, affects over 230 million people, especially in developing countries. Despite the significant economic and public health consequences, only one drug is currently available for treatment of schistosomiasis, praziquantel. Thus, there is an urgent demand for new anthelmintic agents. Based on our continuous studies involving the chemical prospection of floristic biodiversity aiming to discover new bioactive compounds, this work reports the in vitro antiparasitic activity against Schistosoma mansoni adult worms of neolignans threo-austrobailignan-6 and verrucosin, both isolated from Saururus cernuus L. (Saururaceae). These neolignans showed a significant in vitro schistosomicidal activity, with EC₅₀ values of 12.6-28.1 µM. Further analysis revealed a pronounced reduction in the number of S. mansoni eggs. Scanning electron microscopy analysis revealed morphological alterations when schistosomes were exposed to either threo-austrobailignan-6 or verrucosin. These relevant antischistosomal properties were accompanied by low cytotoxicity potential against the animal (Vero) and human (HaCaT) cell lines, resulting in a high selectivity index. Considering the promising chemical and biological properties of threo-austrobailignan-6 and verrucosin, this research should be of interest to those in the area of neglected diseases and in particular antischistosomal drug discovery.

Synthesis and Biological Activities of Dehydrodiisoeugenol: A Review

Dehydrodiisoeugenol (DHIE) is a neolignan found in more than 17 plant species, including herbs, fruit, and root. DHIE was, for the first time, isolated from Myristica fragrans bark in 1973. Since then, many methodologies have been used for the obtention of DHIE, including classical chemistry synthesis using metal catalysts and biocatalytic synthesis; employing horseradish peroxidase; peroxidase from Cocos nucifera; laccase; culture cells of plants; and microorganisms. Increasing evidence has indicated that DHIE has a wide range of biological activities: anti-inflammatory, anti-oxidant, anti-cancerogenic, and anti-microbial properties. However, evidence in vivo and in human beings is still lacking to support the usefulness potential of DHIE as a therapeutic agent. This study's review was created by searching for relevant DHIE material on websites such as Google Scholar, PubMed, SciFinder, Scholar, Science Direct, and others. This reviews the current state of knowledge regarding the different synthetical routes and biological applications of DHIE.

N-(4-Methoxyphenyl)Pentanamide, a Simplified Derivative of Albendazole, Displays Anthelmintic Properties against the Nematode Toxocara canis

Infections caused by parasitic helminths have enormous health, social, and economic impacts worldwide. The treatment and control of these diseases have been dependent on a limited set of drugs, many of which have become less effective, necessitating the search for novel anthelmintic agents. In this study, a simplified compound, N-(4-methoxyphenyl)pentanamide (N4MP), based on the structure of the most widely used anthelmintic (albendazole), was chemically prepared using 4-anisidine and pentanoic acid. N-(4-Methoxyphenyl)pentanamide was evaluated in vitro against the nematode Toxocara canis, an ascarid roundworm of animals that can infect humans. Similar to albendazole, bioassays showed that N-(4-methoxyphenyl)pentanamide affected the viability of parasites in a time- and concentration-dependent manner. Interestingly, N-(4-methoxyphenyl)pentanamide showed a profile of lower cytotoxicity to human and animal cell lines than albendazole. Pharmacokinetic, drug-likeness, and medicinal chemistry friendliness studies demonstrated an excellent drug-likeness profile for N-(4-methoxyphenyl)pentanamide as well as an adherence to major pharmaceutical companies’ filters. Collectively, the results of this study demonstrate that the molecular simplification of albendazole to give N-(4-methoxyphenyl)pentanamide may be an important pipeline in the discovery of novel anthelmintic agents.

IMPORTANCE Infections caused by parasitic helminths have enormous health, social, and economic impacts worldwide. The treatment and control of these diseases have been dependent on a limited set of drugs, many of which have become less effective, necessitating the search for novel anthelmintic agents. Considering this scenario, the present study reports the preparation of N-(4-methoxyphenyl)pentanamide (N4MP), a simplified molecule based on the structure of the most widely used anthelmintic (albendazole). N4MP was evaluated in vitro against the nematode Toxocara canis, a common ascarid roundworm of domestic animals that can infect humans. Similar to albendazole, bioassays showed that N4MP affected the viability of parasites in a time- and concentration-dependent manner but displayed a profile of lower cytotoxicity to human and animal cell lines than albendazole. Therefore, this study demonstrates that the molecular simplification of albendazole to give N4MP may be an important pipeline in the discovery of novel anthelmintic agents.

Therapeutic Efficacy of Carvacrol-Loaded Nanoemulsion in a Mouse Model of Schistosomiasis

Since praziquantel is the only drug available to treat schistosomiasis, a neglected parasitic disease that affects more than 240 million people worldwide, there is an urgent demand for new antischistosomal agents. Natural compound-loaded nanoparticles have recently emerged as a promising alternative for the treatment of schistosomiasis. Carvacrol is an antimicrobial monoterpene present in the essential oil extracted from several plants, especially oregano (Origanum vulgare). In this study, a carvacrol nanoemulsion (CVNE) was prepared, characterized, and administered orally (200 mg/kg) in a mouse infected with either immature (prepatent infection) or adult (patent infection) Schistosoma mansoni. For comparison, data obtained with an unloaded nanoemulsion (blank formulation), free carvacrol, and the drug of reference praziquantel are also presented. CVNE was more effective than free carvacrol in reducing the worm burden and egg production in both patent and prepatent infections. Favorably, CVNE had a high effect in terms of reducing the number of worms and eggs (85%–90%) compared with praziquantel (∼30%) in prepatent infection. In tandem, carvacrol-loaded nanoemulsion markedly improved antischistosomal activity, showing efficiency in reducing worm and egg burden, and thus it may be a promising delivery system for the treatment of schistosomiasis.

Recent trends in praziquantel nanoformulations for helminthiasis treatment

INTRODUCTION

Infections caused by parasitic flatworms impose a considerable worldwide health burden. Recently, World Health Organization launched its roadmap for neglected diseases for the period 2021 to 2030 and oral treatment with praziquantel (PZQ) in tablet form is the main drug therapy for combating these diseases, but its use is limited by many drawbacks, including the high therapeutic dose due to the drug's low solubility and bioavailability. Among the strategies to improve PZQ performance, the use of drug nanocarriers has been cited as an interesting approach to overcome these pharmacological issues.

AREAS COVERED

This review focuses on the various types of nanomaterials (polymeric, lipidic, inorganic nanoparticles, and nanocrystals) which have been recently used to improve PZQ therapy. In addition, recent advances in PZQ nanoformulations, developed to overcome the barriers of the conventional drug are described.

EXPERT OPINION

Considering the poor rate of discovery in the anthelmintic segment observed in recent decades, the effective management of existing drugs has become essential. The application of new strategies based on nanotechnology can extend the useful life of PZQ in new and more effective formulations. Pharmaceutical nanotechnology can solve the pharmacokinetic challenges characteristic of PZQ and improve its solubility and bioavailability.

Pyrazoline derivatives as promising novel antischistosomal agents

Praziquantel is the only available drug to treat schistosomiasis, a parasitic disease that currently infects more than 240 million people globally. Due to increasing concerns about resistance and inadequate efficacy there is a need for new therapeutics. In this study, a series of 17 pyrazolines (15–31) and three pyrazoles (32–34) were synthesized and evaluated for their antiparasitic properties against ex vivo adult Schistosoma mansoni worms. Of the 20 compounds tested, six had a 50% effective concentration (EC₅₀) below 30 μM. Our best hit, pyrazoline 22, showed promising activity against adult schistosomes, with an EC₅₀ < 10 µM. Additionally, compound 22 had low cytotoxicity, with selectivity index of 21.6 and 32.2 for monkey and human cell lines, respectively. All active pyrazolines demonstrated a negative effect on schistosome fecundity, with a marked reduction in the number of eggs. Structure–activity relationship analysis showed that the presence of the non-aromatic heterocycle and N-substitution are fundamental to the antischistosomal properties. Pharmacokinetics, drug-likeness and medicinal chemistry friendliness studies were performed, and predicted values demonstrated an excellent drug-likeness profile for pyrazolines as well as an adherence to major pharmaceutical companies’ filters. Collectively, this study demonstrates that pyrazoline derivatives are promising scaffolds in the discovery of novel antischistosomal agents.

Evaluation of Gibbilimbol B, Isolated from Piper malacophyllum (Piperaceae), as an Antischistosomal Agent

Infections caused by parasitic worms impose a considerable worldwide health burden. One of the most impactful is schistosomiasis, a disease caused by blood-dwelling of the genus Schistosoma that affects more than 230 million people worldwide. Since praziquantel has also been extensively used to treat schistosomiasis and other parasitic flatworm infections, there is an urgent need to identify novel anthelmintic compounds, mainly from natural sources. In this study, the hexane extract from roots of Piper malacophyllum (Piperaceae) showed to be mainly composed for gibbilimbol B by HPLC/ESI-HRMS. Based on this result, this compound was isolated by chromatographic steps and its structure was confirmed by NMR. In vitro bioassays showed that gibbilimbol B was more active than praziquantel against larval stage of S. mansoni, with effective concentrations of 50 % (EC₅₀ ) and 90 % (EC₉₀ ) values of 2.6 and 3.4 μM, respectively. Importantly, gibbilimbol B showed no cytotoxicity to mammalian cells at a concentration 190 times greater than the antiparasitic effect, giving support for the anthelmintic potential of gibbilimbol B as lead compound for novel antischistosomal agents.

Antiparasitic Properties of Cardiovascular Agents against Human Intravascular Parasite Schistosoma mansoni

The intravascular parasitic worm Schistosoma mansoni is a causative agent of schistosomiasis, a disease of great global public health significance. Praziquantel is the only drug available to treat schistosomiasis and there is an urgent demand for new anthelmintic agents. Adopting a phenotypic drug screening strategy, here, we evaluated the antiparasitic properties of 46 commercially available cardiovascular drugs against S. mansoni. From these screenings, we found that amiodarone, telmisartan, propafenone, methyldopa, and doxazosin affected the viability of schistosomes in vitro, with effective concentrations of 50% (EC₅₀) and 90% (EC₉₀) values ranging from 8 to 50 µM. These results were further supported by scanning electron microscopy analysis. Subsequently, the most effective drug (amiodarone) was further tested in a murine model of schistosomiasis for both early and chronic S. mansoni infections using a single oral dose of 400 mg/kg or 100 mg/kg daily for five consecutive days. Amiodarone had a low efficacy in chronic infection, with the worm and egg burden reduction ranging from 10 to 30%. In contrast, amiodarone caused a significant reduction in worm and egg burden in early infection (>50%). Comparatively, treatment with amiodarone is more effective in early infection than praziquantel, demonstrating the potential role of this cardiovascular drug as an antischistosomal agent.