New Insights into Anthelmintic Mechanisms of Action of a Synthetic Peptide: An Ultrastructural and Nanomechanical Approach

An alkaloidal fraction of Annona tomentosa possesses anthelmintic activity and induces surface modifications in Haemonchus contortus

The nematode Haemonchus contortus is, as a parasite, responsible for most mortality of small ruminants, causing significant economic losses. Numerous plant-derived compounds have exhibited promising anthelmintic activities against this nematode. Notably, the Annona genus stands out for demonstrated anthelmintic effects by extracts from several of its species against different nematodes. This study aimed to assess the effect of an Annona tomentosa fraction, rich in alkaloids, on H. contortus. This fraction, named Alk.F, is derived from the methanolic extract of the plant's stem bark. Chemical characterization of Alk.F was performed by liquid chromatography coupled with mass spectrometry. Among the nine predominant peaks obtained, seven alkaloids were identified: reticuline, reticuline N-oxide, reticuline N-oxide isomer, cyclanoline, asimilobine, tetrahydropalmatine and anonaine. Alk.F inhibited the larval development of H. contortus with an IC50 of 0.026 mg/mL, inhibited larval exsheathment with an IC50 of 0.38 mg/mL, and displayed low hemolytic activity towards sheep erythrocytes. Furthermore, atomic force microscopy revealed that Alk.F altered adhesive forces and the height profile on the surface of H. contortus larvae. In conclusion, A. tomentosa alkaloids alter the cuticle structure of H. contortus, inhibiting larval development and exsheathment, thus offering possibilities for contributing to the development of new anthelmintic drugs.

Methods for extraction, isolation and sequencing of cyclotides and others cyclic peptides with anti-helminthic activities: An overview

The mortality rate caused by parasitic worms on their hosts is of great concern and studies have been carried out to find molecules to reduce the prevalence, host-parasite interaction, and resistance of parasites to treatments. Existing drugs on the market are very often toxic and have many side effects, hence the need to find new, more active molecules. It has been demonstrated in several works that medicinal plants constitute a wide range of new molecules that can solve this problem. Several works have already been able to demonstrate that cyclic peptides of plant origin have shown good activity in the fight against different types of helminths. Therefore, this review aims to provide a general overview of the methods and techniques of extraction, isolation, activities and mechanisms of action of cyclotides and other cyclic peptides for application in the treatment of helminthic infections.

Potent anthelmintic activity of a colloidal nano-silver formulation (Silversol®) against the model worm Caenorhabditis elegans

OBJECTIVE

In the background of a very small number of effective anthelmintics available today with a narrow activity spectrum, and a rise in resistance against them among parasitic helminths, there is an urgent need for discovery of novel broad-spectrum anthelmintics displaying no or minimal toxicity towards the host. Silver being used since centuries for therapeutic purposes and considered safe for human consumption, we investigated anthelmintic activity of a colloidal nanosilver formulation Silversol®. Anthelmintic efficacy of the test formulation was assayed employing the nematode Caenorhabditis elegans as a model worm through a live-dead count.

RESULTS

Silversol® exerted anthelmintic action superior to one of the positive controls (Benzimidazole), and almost at par to another positive control (Ivermectin). At concentrations ≥ 2 ppm, it could kill all the worms present in the experimental well. Lower concentrations of silver were found to have a cuticle-damaging action on worms. Further investigation is warranted to assess whether Silversol® can exert similar potent activity against different species of parasitic helminths, and elucidate the underlying molecular mechanisms of action.

Bioactive Antimicrobial Peptides: A New Weapon to Counteract Zoonosis

Zoonoses have recently become the center of attention of the general population and scientific community. Notably, more than 30 new human pathogens have been identified in the last 30 years, 75% of which can be classified as zoonosis. The complete eradication of such types of infections is far out of reach, considering the limited understanding of animal determinants in zoonoses and their causes of emergence. Therefore, efforts must be doubled in examining the spread, persistence, and pathogenicity of zoonosis and studying possible clinical interventions and antimicrobial drug development. The search for antimicrobial bioactive compounds has assumed great emphasis, considering the emergence of multi-drug-resistant microorganisms. Among the biomolecules of emerging scientific interest are antimicrobial peptides (AMPs), potent biomolecules that can potentially act as important weapons against infectious diseases. Moreover, synthetic AMPs are easily tailored (bioinformatically) to target specific features of the pathogens to hijack, inducing no or very low resistance. Although very promising, previous studies on SAMPs’ efficacy are still at their early stages. Indeed, further studies and better characterization on their mechanism of action with in vitro and in vivo assays are needed so as to proceed to their clinical application on human beings.

Ethnopharmacology, phytochemistry and a new chemotaxonomic marker in Oldenlandia affinis (Roem. & Schult.) DC. Rubiaceae

The proper documentation of ethnopharmacological application of widely used indigenous plants and their phytochemical analysis has positively impacted the drug discovery pipeline. Medicinal plants with potential commercial value and prospects for clinical application need to be properly identified and authenticated to avoid confusion, adulteration and substitution. Oldenlandia affinis (OA) has continued to attract scientific attention following the discovery of extremely stable cyclotides (circular peptides) that are not expressed in many investigated members of the contentious genus, Oldenlandia (synonym – Hedyotis); yet there is a lack of an elaborate review covering some broader aspects of its traditional uses, ethnopharmacology and phytochemistry of the species. More importantly, the age long but lingering confusion and taxonomic inconsistencies common to the Oldenlandia–Hedyotis debate could foster species mismatching, increase cases of misidentification, promote adulteration of OA and thereby limit its proper clinical application. Here, we aim to reveal the extent of indigenous use of and research on OA from 1960 till date, unveil knowledge gaps, document hitherto unknown traditional applications, ethnopharmacological uses, pharmacological properties, and reported phytochemical profile. In addition, to encourage proper selection and utilization of genuine crude drug, the chemotaxonomically important phytoconstituents of OA have been presented and the modern approach of chemophenetic study of OA proposed to resolve the lack of consensus in the taxonomy of OA as well as the morphologically and anatomically close members of the taxon. The abundant cyclotide expression in OA represents a new chemotaxonomic marker for its unambiguous identification, utilization and reproducibility of research findings on the species.