Investigation of anthelmintic activity of the acetone extract and constituents of Typha capensis against animal parasitic Haemonchus contortus and free-living Caenorhabditis elegans

Bioactive compounds from the parasitic plant Arceuthobium vaginatum inhibit Haemonchus contortus egg hatching

The aim of this study was to assess the in vitro ovicidal activity of an ethyl acetate extract from Arceuthobium vaginatum (EtOAc-E) and their subfractions (AvR5-AvR14) against Haemonchus contortus using the egg hatching inhibition (EHI) test. The EtOAc-E and subfractions were tested at 0.12-2.00 and at 0.015-2.0 mg/mL, respectively. Distilled water and methanol (2%) were used as negative controls and Thiabendazole (0.10 mg/mL) as a positive control. Treatments with a dependent effect on concentration were subjected to regression analysis to determine the effective concentrations (EC50 and EC90). The major secondary compounds present in the extract and subfractions were identified by high performance liquid chromatography (HPLC). The EtOAc-E and AvR9 exhibited the best ovicidal effect recording 97.5 and 100% of EHI at 0.25 mg/mL, respectively. The EtOAc-E and AvR9 displayed an EC50= 0.12 and 0.08 mg/mL, respectively. The HPLC analysis in the EtOAc-E and bioactive fractions indicated the presence of a polyphenol, glycosylated flavanones, quercetin glucoside, cinnamates, coumarin, cinnamic acid derivative, ferulic acid, coumarate, naringenin, protocatechuic acid and naringin. Results demonstrated that A. vaginatum extract and fraction is able to inhibit the egg hatch process of H. contortus and could be a viable option for the control of small ruminant haemonchosis.

Model nematodes as a practical innovation to promote high throughput screening of natural products for anthelmintics discovery in South Asia: Current challenges, proposed practical and conceptual solutions

With the increasing prevalence of anthelmintic resistance in animals recorded globally, and the threat of resistance in human helminths, the need for novel anthelmintic drugs is greater than ever. Most research aimed at discovering novel anthelmintic leads relies on high throughput screening (HTS) of large libraries of synthetic small molecules in industrial and academic settings in developed countries, even though it is the tropical countries that are most plagued by helminth infections. Tropical countries, however, have the advantage of possessing a rich flora that may yield natural products (NP) with promising anthelmintic activity. Focusing on South Asia, which produces one of the world's highest research outputs in NP and NP-based anthelmintic discovery, we find that limited basic research and funding, a lack of awareness of the utility of model organisms, poor industry-academia partnerships and lack of technological innovations greatly limit anthelmintics research in the region. Here we propose that utilizing model organisms including the free-living nematode Caenorhabditis elegans, that can potentially allow rapid target identification of novel anthelmintics, and Oscheius tipulae, a closely related, free-living nematode which is found abundantly in soil in hotter temperatures, could be a much-needed innovation that can enable cost-effective and efficient HTS of NPs for discovering compounds with anthelmintic/antiparasitic potential in South Asia and other tropical regions that historically have devoted limited funding for such research. Additionally, increased collaborations at the national, regional and international level between parasitologists and pharmacologists/ethnobotanists, setting up government-industry-academia partnerships to fund academic research, creating a centralized, regional collection of plant extracts or purified NPs as a dereplication strategy and HTS library, and holding regional C. elegans/O. tipulae-based anthelmintics workshops and conferences to share knowledge and resources regarding model organisms may collectively promote and foster a NP-based anthelmintics landscape in South Asia and beyond.

Ivermectin-induced gene expression changes in adult Parascaris univalens and Caenorhabditis elegans: a comparative approach to study anthelminthic metabolism and resistance in vitro

Background

The nematode Parascaris univalens is one of the most prevalent parasitic pathogens infecting horses but anthelmintic resistance undermines treatment approaches. The molecular mechanisms underlying drug activity and resistance remain poorly understood in this parasite since experimental in vitro models are lacking. The aim of this study was to evaluate the use of Caenorhabditis elegans as a model for P. univalens drug metabolism/resistance studies by a comparative gene expression approach after in vitro exposure to the anthelmintic drug ivermectin (IVM).

Methods

Twelve adult P. univalens worms in groups of three were exposed to ivermectin (IVM, 10^–13 M, 10^–11 M, 10^–9 M) or left unexposed for 24 h at 37 °C, and total RNA, extracted from the anterior end of the worms, was sequenced using Illumina NovaSeq. Differentially expressed genes (DEGs) involved in metabolism, transportation, or gene expression with annotated Caernorhabditis elegans orthologues were identified as candidate genes to be involved in IVM metabolism/resistance. Similarly, groups of 300 adult C. elegans worms were exposed to IVM (10^–9 M, 10^–8 M and 10^–7 M) or left unexposed for 4 h at 20 °C. Quantitative RT-PCR of RNA extracted from the C. elegans worm pools was used to compare against the expression of selected P. univalens candidate genes after drug treatment.

Results

After IVM exposure, 1085 DEGs were found in adult P. univalens worms but the relative gene expression changes were small and large variabilities were found between different worms. Fifteen of the DEGs were chosen for further characterization in C. elegans after comparative bioinformatics analyses. Candidate genes, including the putative drug target lgc-37, responded to IVM in P. univalens, but marginal to no responses were observed in C. elegans despite dose-dependent behavioral effects observed in C. elegans after IVM exposure. Thus, the overlap in IVM-induced gene expression in this small set of genes was minor in adult worms of the two nematode species.

Conclusion

This is the first time to our knowledge that a comparative gene expression approach has evaluated C. elegans as a model to understand IVM metabolism/resistance in P. univalens. Genes in P. univalens adults that responded to IVM treatment were identified. However, identifying conserved genes in P. univalens and C. elegans involved in IVM metabolism/resistance by comparing gene expression of candidate genes proved challenging. The approach appears promising but was limited by the number of genes studied (n = 15). Future studies comparing a larger number of genes between the two species may result in identification of additional candidate genes involved in drug metabolism and/or resistance.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05260-4.