In vitro anti-Onchocerca ochengi activities of extracts and chromatographic fractions of Craterispermum laurinum and Morinda lucida

In vitro nematocidal potential of hydro-ethanolic and aqueous extracts of Calotropis procera (Aiton) W.T. Aiton, 1811 (Apocynaceae) and Faidherbia albida (Delile) A. Chev., 1934 (Fabacae) against Onchocerca ochengi and Caenorhabditiselegans

Onchocerciasis caused by Onchocerca volvulus Leuckart, 1893 is the second-world infection responsible for human blindness. Except Ivermectin which has as targets the microfilariae of that parasite, specific treatment for this disease does not exist and in developing countries, medicinal plants seem to remedy that health problem. For that, aqueous and hydro-ethanolic leaf, bark, and root extracts of Calotropis procera and Faidherbia albida were evaluated in vitro, against the most popular bovine model, Onchocerca ochengi and the free-resistant nematode Caenorhabditis elegans. O. ochengi microfilariae and adults extracted from the bovine nodules and skins as well as the free strains of C. elegans were exposed to the various concentrations of the plant parts extracts and Ivermectin. In results, all the plant parts extracts were rich in tannins, saponins, alkaloids, flavonoids, phenols, coumarins, and glycosides. Phenols (175.45 ± 0.01 mg EGA/g DM), flavonoids (158.98 ± 0.05 mg EC/g DM), and tannins (89.98 ± 2.56 mg ETA/g DM) contents were high in the bark hydro-ethanolic extract of F. albida. The leaf hydro-ethanolic extract of F. albida induced high activity against O. ochengi microfilariae (CL₅₀ = 0.13 mg/mL). The bark hydro-ethanolic extract of F. albida was also the most effective on O. ochengi adults and particularly on female adults (CL₅₀ = 0.18 mg/mL). Against the parasite strain resistant to Ivermectin, F. albida leaf hydro-ethanolic extract appeared more active with CL₅₀ = 0.13 mg/mL. Similarly, the bark hydro-ethanolic extract of F. albida was the most potent on the wild strain of C. elegans. Thus, this study validates the use of these plants by traditional healers in the management of onchocerciasis and suggests a new source of isolation of the potential plant compounds against Onchocerca.

Anti-Onchocercal Properties of Extracts of Scoparia dulcis and Cylicodiscus gabunensis

Introduction. The elimination of onchocerciasis is hampered by the absence of suitable drugs that are effective against adult filariae. This study is aimed at assessing the anti-onchocercal effects of extracts of Scoparia dulcis and Cylicodiscus gabunensis that could serve as drug leads against onchocerciasis. Methods. Different parts of the plants (Scoparia dulcis and Cylicodiscus gabunensis) were extracted with hexane, methylene chloride, and methanol. The extracts were tested in vitro against the bovine model parasite, Onchocerca ochengi. Adult female worm viability was determined biochemically by MTT/formazan colorimetry, while the adult male and microfilariae viability were determined by microscopy based on % inhibition of worm motility score. Cytotoxicity and acute toxicity of active extracts were tested on monkey kidney epithelial cells (LLC-MK2) and Balb/C mice, respectively. Results. The hexane extract of Scoparia dulcis recorded the highest activity, with IC50s of 50.78 μg/ml on both adult male and female worms and 3.91 μg/ml on microfilariae. For Cylicodiscus gabunensis extract, the highest activity was seen with the methylene chloride extract, with IC50s of 50.78 μg/ml, 62.50 μg/ml, and 16.28 μg/ml on, respectively, adult male, female, and microfilariae. The 50% cytotoxic concentration on the LLC-MK2 cells was 31.25 μg/ml for the most active extracts. No acute toxicity was recorded for the extracts. Phytochemical analysis of the extracts revealed the presence of alkaloids, flavonoids, sterols, saponins, phenols, and glycosides. Conclusion. This study validates the traditional use of these plants in treating onchocerciasis and suggests S. dulcis and C. gabunensis as new potential sources for the isolation of anti-onchocerca lead compounds.

Antifilarial Activity of the Methanolic Extract of Indigofera tinctoria (Fabaceae) on Bovine Parasites (Onchocerca ochengi)

Onchocerciasis is a major public health problem caused by Onchocerca volvulus parasite and transmitted to humans via black flies (simulium) bites. The control of onchocerciasis relies much on the use of the chemical drug ivermectin, which is only effective against microfilariae and has led to drug resistance. This study was carried out to assess the in vitro antifilarial activity of methanolic extract of Indigofera tinctoria and its most active fractions on adult male O. ochengi worm, the closest model to O. volvulus, after 48 h and 72 h of treatment. Worms' viability was determined biochemically by MTT/formazan colorimetry assay. The promising plant extract's acute and subacute oral toxicity were evaluated on both mice and rats. The result revealed a highest antifilarial activity of the methanolic extract (LC50 = 12.28 μg/mL) compared to ivermectin (LC50 = 26.50 μg/mL) after 72 h of treatment. Out of the eight (08), chromatographic fractions screened, only three (03) fractions (C, F, and G) revealed the highest anti-Onchocerca activity after 72 h of treatment. An oral administration of the plant extract at a single dose of 2000 mg/kg did not produce any toxicity in mice. After repeated daily administration of methanolic extract of I. tinctoria (250 mg/kg, 500 mg/kg, and 1000 mg/kg) for 28 days, no significant changes in body weight, biochemical, and haematological parameters was observed. Histopathological examination of organs did not reveal any sign of alteration. The phytochemical analysis of the methanolic extract of I. tinctoria revealed the presence of various phenolic compounds. Therefore, this study demonstrated the potential antifilarial activity of Indigofera tinctoria and offered an alternative to treating onchocerciasis. Moreover, further studies could be developed in promising new antifilarial sources of the isolated compound and in vivo antifilarial activity of Indigofera tinctoria in the animal model needs to be studied.

Drug development for onchocerciasis-the past, the present and the future

Onchocerciasis affects predominantly rural communities in Africa, and with small foci in South America and the Yemen. The disease is a major cause of blindness and other significant morbidity and mortality. Control programs have achieved a major impact on the incidence and prevalence of onchocerciasis by interrupting transmission with vector control programs, and treatment with mass drug administration using the microfilaricide ivermectin. Over the last few decades, several microfilaricides have been developed. This initially included diethylcarbamazine, which had significant side effects and is no longer used as such. Ivermectin which is a safe and highly effective microfilaricide and moxidectin which is a longer acting microfilaricide are presently recognized therapies. Suramin was the first effective macrofilaricide but was prohibitively toxic. Certain antibiotics including doxycycline can help eliminate adult worms by targeting its endosymbiont bacteria, Wolbachia pipientis. However, the dosing regimens may make this difficult to use as part of a mass disease control program in endemic areas. It is now widely recognized that treatments that are able to kill or permanently sterilize adult filarial worms should help achieve the elimination of this disease. We summarize in detail the historic drug development in onchocerciasis, including prospective future candidate drugs.

Molecular Docking Simulation Studies Identifies Potential Natural Product Derived-Antiwolbachial Compounds as Filaricides against Onchocerciasis

Onchocerciasis is the leading cause of blindness and severe skin lesions which remain a major public health problem, especially in tropical areas. The widespread use of antibiotics and the long duration required for effective treatment continues to add to the increasing global menace of multi-resistant pathogens. Onchocerca volvulus harbors the endosymbiont bacteria Wolbachia, essential for the normal development of embryos, larvae and long-term survival of the adult worm, O. volvulus. We report here results of using structure-based drug design (SBDD) approach aimed at identifying potential novel Wolbachia inhibitors from natural products against the Wolbachia surface protein (WSP). The protein sequence of the WSP with UniProtKB identifier Q0RAI4 was used to model the three-dimensional (3D) structure via homology modelling techniques using three different structure-building algorithms implemented in Modeller, I-TASSER and Robetta. Out of the 15 generated models of WSP, one was selected as the most reasonable quality model which had 82, 15.5, 1.9 and 0.5% of the amino acid residues in the most favored regions, additionally allowed regions, generously allowed regions and disallowed regions, respectively, based on the Ramachandran plot. High throughput virtual screening was performed via Autodock Vina with a library comprising 42,883 natural products from African and Chinese databases, including 23 identified anti-Onchocerca inhibitors. The top six compounds comprising ZINC000095913861, ZINC000095486235, ZINC000035941652, NANPDB4566, acetylaleuritolic acid and rhemannic acid had binding energies of −12.7, −11.1, −11.0, −11, −10.3 and −9.5 kcal/mol, respectively. Molecular dynamics simulations including molecular mechanics Poisson-Boltzmann (MMPBSA) calculations reinforced the stability of the ligand-WSP complexes and plausible binding mechanisms. The residues Arg45, Tyr135, Tyr148 and Phe195 were predicted as potential novel critical residues required for ligand binding in pocket 1. Acetylaleuritolic acid and rhemannic acid (lantedene A) have previously been shown to possess anti-onchocercal activity. This warrants the need to evaluate the anti-WSP activity of the identified molecules. The study suggests the exploitation of compounds which target both pockets 1 and 2, by investigating their potential for effective depletion of Wolbachia. These compounds were predicted to possess reasonably good pharmacological profiles with insignificant toxicity and as drug-like. The compounds were computed to possess biological activity including antibacterial, antiparasitic, anthelmintic and anti-rickettsials. The six natural products are potential novel antiwolbachial agents with insignificant toxicities which can be explored further as filaricides for onchocerciasis.

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

This study aimed to determine in vitro anthelmintic activity of plant extracts of eleven plant species used traditionally in South Africa to treat various disorders including symptoms related to nematode infections, and to isolate bioactive compounds from the most active plant extract. Crude plant extracts were tested on different life-cycle stages of Haemonchus contortus. The cytotoxicity of the most active extracts, fractions and compounds was evaluated on Vero cells and the most potent extract, fractions and compounds were tested for their ability to kill the parasitic H. contortus and the free-living nematode Caenorhabditis elegans. Typha capensis acetone extract had the strongest egg hatching inhibitory effect with an EC₅₀ of 184.94 μg/mL, and this extract also halted larval development of H. contortus with an EC₅₀ of 83.30 μg/mL compared to the positive control (albendazole) with an EC₅₀ of 2.66 μg/mL. Typha capensis crude extract and its butanol fraction had promising anthelmintic activity against both parasitic H. contortus and free-living C. elegans. Two compounds isolated from T. capensis, namely, isorhamnetin-3-O-β-D-glucoside and isorhamnetin 3-O-rutinoside, had antioxidant activity with IC₅₀ values of 3.16 μg/mL and 0.96 μg/mL respectively, and good anthelmintic activity against H. contortus with IC₅₀ values of 55.61 μg/mL and 145.17 μg/mL respectively. Identification of bioactive compounds from the T. capensis crude extract supports development of this extract as a complementary or alternative treatment against haemonchosis. However, further research is necessary to confirm the anthelmintic efficacy of the plant, including in vivo studies.

Filaricidal activity of Daniellia oliveri and Psorospermum febrifugum extracts

BACKGROUND

Drugs currently used for controlling onchocerciasis and lymphatic filariasis (LF) are mainly microfilaricidal, with minimal or no effect on the adult worms. For efficient management of these diseases, it is necessary to search for new drugs with macrofilaricidal activities that can be used singly or in combination with existing ones. Daniellia oliveri and Psorospermum febrifugum are two plants commonly used in the local management of these infections in Bambui, a township in the North West Region of Cameroon, but there is currently no documented scientific evidence to support their claimed anthelmintic efficacy and safety. The aim of this study was to provide evidence in support of the search for means to eliminate these diseases by screening extracts and chromatographic fractions isolated from these plants for efficacy against the parasitic roundworms Onchocerca ochengi and Brugia pahangi.

METHODS

The viability of O. ochengi adult worms was assessed using the MTT/formazan assay. Fully confluent monkey kidney epithelial cells (LLC-MK2) served as the feeder layer for the O. ochengi microfilariae (mfs) assays. Viability of the mfs was assessed by microscopic examination for mean motility scoring (relative to the negative control) every 24 h post addition of an extract. The Worminator system was used to test the effects of the extracts on adult B. pahangi motility, and mean motility units were determined for each worm. Cytotoxicity of the active extracts on N27 cells was assessed using the MTS assay.

RESULTS

Extracts from D. oliveri and P. febrifugum were effective against the adult roundworms O. ochengi and B. pahangi. Interestingly, extracts showing macrofilaricidal activities against O. ochengi also showed activity against O. ochengi mfs. The hexane stem bark extract of D. oliveri (DO_BHEX) was more selective for adult O. ochengi than for mfs, with a half maximal and 100% inhibitory concentration (IC₅₀ and IC₁₀₀, respectively) against adult O. ochengi of 13.9 and 31.3 μg/ml, respectively. The in vitro cytotoxicity of all active extracts on N27 cells showed selective toxicity for parasites (selectivity index > 1). Bioassay-guided fractionation of the extracts yielded fractions with activity against adult B. pahangi, thus confirming the presence of bioactive principles in the plant extracts.

CONCLUSIONS

Our study supports the use of D. oliveri and P. febrifugum in the traditional treatment of onchocerciasis and LF. The further purification of active extracts from these plants could yield lead compounds for filarial drug discovery and development.

Anticancer activity of Nigerian medicinal plants: a review

Background

Cancer is currently the leading cause of death globally and the number of deaths from cancer is on the rise daily. Medicinal plants have been in continuous use over the years for the management of cancer, particularly, in most developing countries of the world including Nigeria. The use of synthetic drugs for the treatment of cancer is often accompanied by toxic side effects. Thus, the alternative use of readily available and inexpensive medicinal plants is the panacea to the toxic side effects associated with synthetic drugs.

Main body

The present review summarized the anticancer activity of 51 medicinal plants that are widespread in all regions of Nigeria. Furthermore, the proposed anticancer pharmacological actions as well as the anticancer bioactive compounds, the type of cancer cell inhibited, the plant parts responsible for the anticancer activity, and the nature of the extracts used for the studies were discussed in this review. The 51 Nigerian medicinal plants were reported to exhibit anticancer activities of the prostate, cervices, lung, skin, colon, esophagus, blood, ovary, central nervous system/brain, breast, stomach, pancreas, larynx, and kidney. The major classes of bioactive compounds indicated to be responsible for the anticancer activity include the polyphenols, flavonoids, alkaloids, saponins, triterpenes, tannins, and quinones. The major anticancer pharmacological actions of these bioactive compounds were antiproliferative, cytotoxic, cytostatic, antimetastatic, apoptotic, and antioxidative as well as provoked cell cycle arrest, inhibition of angiogenesis and reduction of cancer cell viability.

Conclusion

The Nigerian medicinal plants can be harnessed to provide for readily available and inexpensive anticancer drugs in the future because the plants reported in this review showed promising anticancer activity.

The Functional Parasitic Worm Secretome: Mapping the Place of Onchocerca volvulus Excretory Secretory Products

Nematodes constitute a very successful phylum, especially in terms of parasitism. Inside their mammalian hosts, parasitic nematodes mainly dwell in the digestive tract (geohelminths) or in the vascular system (filariae). One of their main characteristics is their long sojourn inside the body where they are accessible to the immune system. Several strategies are used by parasites in order to counteract the immune attacks. One of them is the expression of molecules interfering with the function of the immune system. Excretory-secretory products (ESPs) pertain to this category. This is, however, not their only biological function, as they seem also involved in other mechanisms such as pathogenicity or parasitic cycle (molting, for example). We will mainly focus on filariae ESPs with an emphasis on data available regarding Onchocerca volvulus, but we will also refer to a few relevant/illustrative examples related to other worm categories when necessary (geohelminth nematodes, trematodes or cestodes). We first present Onchocerca volvulus, mainly focusing on the aspects of this organism that seem relevant when it comes to ESPs: life cycle, manifestations of the sickness, immunosuppression, diagnosis and treatment. We then elaborate on the function and use of ESPs in these aspects.

Diethylcarbamazine activates TRP channels including TRP-2 in filaria, Brugia malayi

Diethylcarbamazine is an important classic drug used for prevention and treatment of lymphatic filariasis and loiasis, diseases caused by filarial nematodes. Despite many studies, its site of action has not been established. Until now, the consensus has been that diethylcarbamazine works by activating host immune systems, not by a direct action on the parasites. Here we show that low concentrations of diethylcarbamazine have direct and rapid (<30 s) temporary spastic paralyzing effects on the parasites that lasts around 4 h, which is produced by diethylcarbamazine opening TRP channels in muscle of Brugia malayi involving TRP-2 (TRPC-like channel subunits). GON-2 and CED-11, TRPM-like channel subunits, also contributed to diethylcarbamazine responses. Opening of these TRP channels produces contraction and subsequent activation of calcium-dependent SLO-1K channels. Recovery from the temporary paralysis is consistent with inactivation of TRP channels. Our observations elucidate mechanisms for the rapid onset and short-lasting therapeutic actions of diethylcarbamazine.

Phytosterols and triterpenes from Morinda lucida Benth. exhibit binding tendency against class I HDAC and HDAC7 isoforms

The important role of histone deacetylases (HDACs) in the development of cancer has been demonstrated by various studies. Thus targeting HDACs with inhibitors is a major focus in anticancer drug research. Although few synthetic HDAC inhibitors (HDIs) have been approved for cancer treatment, they have significant undesirable side effects. Therefore emphases have been placed on natural HDIs as substitutes for the synthetic ones. In a bid to identify more HDIs, this study evaluated the binding tendency of compounds derived from Morinda lucida Benth. towards selected HDACs for the discovery of potent HDIs as potential candidates for anticancer therapeutics, based on the report of anticancer potentials of Morinda lucida-derived extracts and compounds. Givinostat and 49 Morinda-lucida derived compounds were docked against selected HDAC isoforms using AutodockVina, while binding interactions were viewed with Discovery Studio Visualizer, BIOVIA, 2016. Druglikeness and Absorption-Distribution-Metabolism-Excretion (ADME) parameters of the top 7 compounds were evaluated using the Swiss online ADME web tool. The results revealed that out of the 49 compounds, 3 phytosterols (campesterol, cycloartenol, and stigmasterol) and 2 triterpenes (oleanolic acid and ursolic acid) exhibited high HDAC inhibitory activity compared to givinostat. These 5 compounds also fulfill oral drugability of Lipinski rule of five. Morinda lucida-derived phytosterols and triterpenes show high binding tendency towards the selected HDACs and exhibited good drugability characteristics and are therefore good candidates for further studies in the search for therapies against abnormalities linked with over-activity of HDACs.

Brevipedicelones D and E, Two C-O-C Flavonoid Dimmers from the Leaves of Garcinia brevipedicellata and Anti-onchocercal Activity

A novel isoflavone-chromone flavonoid C-O-C dimmer, brevipedicelone D (1), along with one new C-O-C biflavonoid derivative, brevipedicelone E (2), were isolated from the ethyl acetate extract of the leaves of Garcinia brevipedicellata, a medicinal plant used in folk medicine in parts of Cameroon. Their structures were elucidated by extensive spectroscopic techniques, including 1D- and 2D- NMR, MS experiments, as well as comparing their spectral data with those of known analogues. Anti-onchocercal screening of 1 showed moderate inhibition of adult worm motility of Onchocerca ochengi by 60% at the highest concentration (20 µg/mL) and inhibited motility of both the juvenile worms of O. ochengi and Loa loa by 90% at this same concentration.

Review on medicinal plants and natural compounds as anti-Onchocerca agents

Onchocerciasis is a filarial vector borne disease which affects several million people mostly in Africa. The therapeutic approach of its control was based on a succession of drugs which always showed limits. The last one: ivermectin is not the least. It was shown to be only microfilaricidal and induced resistance to the human parasite Onchocerca volvulus. The approach using medicinal plants used in traditional medicine is a possible alternative method to cure onchocerciasis. Onchocerca ochengi and Onchocerca gutturosa are the parasite models used to assess anthelmintic activity of potentially anthelmintic plants. Numerous studies assessed the in vitro and/or in vivo anthelmintic activity of medicinal plants. Online electronic databases were consulted to gather publications on in vitro and in vivo studies of anti-Onchocerca activity of plants from 1990 to 2017. Globally, 13 plant families were investigated for anti-Onchocerca activity in 13 studies. The most active species were Anacardium occidentale, Euphorbia hirta and Acacia nilotica each with an LC₅₀ value of 2.76, 6.25 and 1.2 μg/mL, respectively. Polycarpol, voacamine, voacangine, ellagic acid, gallic acid, gentisic acid, 3-O-acetyl aleuritolic acid and (-)-epigallocatechin 3-O-gallate were the isolated plant compounds with anti-Onchocerca activity. Most of the assessed extract/compounds showed a good safety after in vivo acute toxicity assays and/or in vitro cytotoxicity test. The exception was the ethanol extract of Trichilia emetica, which killed completely and drastically mice at a dose of 3000 mg/kg. Several plant groups of compounds were shown active against Onchocerca sp. such as tannins, alkaloids, triterpenoids and essential oils. Nevertheless, none of the active compounds was subjected to clinical trial, to assessment of its diffusibility through nodular wall or its capability to induce genetic resistance of Onchocerca sp.

Filaricidal properties of Lantana camara and Tamarindus indica extracts, and Lantadene A from L. camara against Onchocerca ochengi and Loa loa

BACKGROUND

Ivermectin is the only drug currently recommended for the treatment of onchocerciasis, the second leading infectious cause of blindness in the world. This drug kills only the first stage larvae-microfilariae (mf) of Onchocerca volvulus and is to be used cautiously in areas where Loa loa is prevalent because of severe adverse events observed with coinfected patients.

METHODOLOGY/PRINCIPAL FINDINGS

This study investigated the anti-filarial activities of two Cameroonian medicinal plants, Lantana camara and Tamarindus indica locally used to treat onchocerciasis. Twelve (12) extracts were prepared and tested in vitro on the bovine model parasite, O. ochengi as well as L. loa mf. Both mf and adult male worm viabilities were assessed by motility scoring, while adult female worm viability was determined biochemically by standard MTT/formazan colorimetry. Cytotoxicity and acute toxicity were determined respectively, in monkey kidney epithelial cells and in BALB/c mice. Pure compounds were isolated by LC/MS using a bio-assay guided strategy. All the extracts showed 100% activity at 500 μg/mL against O. ochengi adult worms and mf. The highest activity against O. ochengi was observed with the hexane extract of L. camara leaves (LCLhex), with IC50 of 35.1 μg/mL for adult females and 3.8 μg/mL for the mf. Interestingly, this extract was more active against O. ochengi mf than L. loa mf. Further studies on the extracts led to the isolation of lantadene A from the methylene chloride extract of L. camara leaves, with IC50s of 7.85 μg/mL for adult males, 10.38 μg/mL for adult females, 10.84 μg/mL for O. ochengi mf and 20.13 μg/mL for L. loa mf.

CONCLUSIONS/SIGNIFICANCE

We report for the first time the anti-onchocercal activities of these locally consumed medicinal plants and lantadene A, a potential lead for further development as an onchocerciasis cure.

Phytochemical analysis and in vitro anthelmintic activity of Lophira lanceolata (Ochnaceae) on the bovine parasite Onchocerca ochengi and on drug resistant strains of the free-living nematode Caenorhabditis elegans

Background

Onchocerciasis is one of the tropical neglected diseases (NTDs) caused by the nematode Onchocerca volvulus. Control strategies currently in use rely on mass administration of ivermectin, which has marked activity against microfilariae. Furthermore, the development of resistance to ivermectin was observed. Since vaccine and safe macrofilaricidal treatment against onchocerciasis are still lacking, there is an urgent need to discover novel drugs. This study was undertaken to investigate the anthelmintic activity of Lophira lanceolata on the cattle parasite Onchocerca ochengi and the anthelmintic drug resistant strains of the free living nematode Caenorhabditis elegans and to determine the phytochemical profiles of the extracts and fractions of the plants.

Methods

Plant was extracted in ethanol or methanol-methylene chloride. O. ochengi, C. elegans wild-type and C. elegans drug resistant strains were cultured in RPMI-1640 and NGM-agar respectively. Drugs diluted in dimethylsulphoxide/RPMI or M9-Buffer were added in assays and monitored at 48 h and 72 h. Worm viability was determined by using the MTT/formazan colorimetric method. Polyphenol, tannin and flavonoid contents were determined by dosage of gallic acid and rutin. Acute oral toxicity was evaluated using Swiss albino mice.

Results

Ethanolic and methanolic-methylene chloride extracts killed O. ochengi with LC₅₀ values of 9.76, 8.05, 6.39 μg/mL and 9.45, 7.95, 6.39 μg/mL respectively for leaves, trunk bark and root bark after 72 h. The lowest concentrations required to kill 50% of the wild-type of C. elegans were 1200 and 1890 μg/mL with ethanolic crude extract, 1000 and 2030 μg/mL with MeOH-CH₂Cl₂ for root bark and trunk bark of L. lanceolata, respectively after 72 h. Leave extracts of L. lanceolata are lethal to albendazole and ivermectin resistant strains of C. elegans after 72 h. Methanol/methylene chloride extracted more metabolites. Additionally, extracts could be considered relatively safe.

Conclusion

Ethanolic and methanolic-methylene chloride crude extracts and fractions of L. lanceolata showed in vitro anthelmintic activity. The extracts and fractions contained polyphenols, tannins, flavonoids and saponins. The mechanism of action of this plant could be different from that of albendazole and ivermectin. These results confirm the use of L. lanceolata by traditional healers for the treatment of worm infections.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-017-1904-z) contains supplementary material, which is available to authorized users.

Anti-Onchocerca and Anti-Caenorhabditis Activity of a Hydro-Alcoholic Extract from the Fruits of Acacia nilotica and Some Proanthocyanidin Derivatives

Acacia nilotica fruits with high tannin content are used in the northern parts of Cameroon as anti-filarial remedies by traditional healers. In this study, the hydro-alcoholic fruit extract (crude extract (CE)) and, one of the main constituents in its most active fractions, (+)-catechin-3-O-gallate (CG), as well as four related proanthocyanidins, (−)-epicatechin-3-O-gallate (ECG), (+)-gallocatechin (GC), (−)-epigallocatechin (EGC) and (−)-epigallocatechin-3-O-gallate (EGCG), were assessed for their potential in vitro anthelmintic properties against the free-living model organism Caenorhabditis elegans and against the cattle filarial parasite Onchocerca ochengi. Worms were incubated in the presence of different concentrations of fruit extract, fractions and pure compounds. The effects on mortality were monitored after 48 h. The plant extract and all of the pure tested compounds were active against O. ochengi (LC₅₀ ranging from 1.2 to 11.5 µg/mL on males) and C. elegans (LC₅₀ ranging from 33.8 to 350 µg/mL on wild type). While high LC₅₀ were required for the effects of the compounds on C. elegans, very low LC₅₀ were required against O. ochengi. Importantly, tests for acute oral toxicity (lowest dose: 10 mg/kg) in Wistar rats demonstrated that crude extract and pure compounds were non-toxic and safe to use. Additionally, the results of cytotoxicity tests with the Caco-2 cell line (CC₅₀ ranging from 47.1 to 93.2 µg/mL) confirmed the absence of significant toxicity of the crude extract and pure compounds. These results are in good accordance with the use of A. nilotica against nematode infections by traditional healers, herdsmen and pastoralists in Cameroon.

Filaricidal activities on Onchocerca ochengi and Loa loa, toxicity and phytochemical screening of extracts of Tragia benthami and Piper umbellatum

BACKGROUND

Onchocerciasis is the world's second leading infectious cause of blindness. Its control is currently hampered by the lack of a macrofilaricidal drug and by severe adverse events observed when the lone recommended microfilaricide, ivermectin is administered to individuals co-infected with Loa loa. Therefore, there is the need for a safe and effective macrofilaricidal drug that will be able to cure the infection and break transmission cycles, or at least, an alternative microfilaricide that does not kill L. loa microfilariae (mf).

METHODS

Fourteen extracts from two medicinal plants, Tragia benthami and Piper umbellatum were screened in vitro against Onchocerca ochengi parasite and L. loa mf. Activities of extracts on male worms and microfilariae were assessed by motility reduction, while MTT/Formazan assay was used to assess biochemically the death of female worms. Cytotoxicity and acute toxicity of active extracts were tested on monkey kidney cells and Balb/c mice, respectively.

RESULTS

At 500 μg/mL, all extracts showed 100 % activity on Onchocerca ochengi males and microfilariae, while 9 showed 100 % activity on female worms. The methylene chloride extract of Piper umbellatum leaves was the most active on adult male and female worms (IC50s: 16.63 μg/mL and 35.65 μg/mL, respectively). The three most active extracts on Onchocerca ochengi females were also highly active on Loa loa microfilariae, with IC50s of 35.12 - 13.9 μg/mL. Active extracts were generally more toxic to the worms than to cells and showed no acute toxicity to Balb/c mice. Phytochemical screening revealed the presence of saponins, steroids, tannins and flavanoids in the promising extracts.

CONCLUSIONS

These results unfold potential sources of novel anti-Onchocerca lead compounds and validate the traditional use of the plants in onchocerciasis treatment.

Development and validation of an Onchocerca ochengi microfilarial hamster model for onchocerciasis drug screens

Background

Onchocerciasis, caused by the parasitic nematode, Onchocerca volvulus afflicts some 37 million people worldwide, and is the second leading infectious cause of blindness globally. The only currently recommended drug for treatment of the disease, ivermectin, is only microfilaricidal and has serious adverse effects in individuals co-infected with high loads of Loa loa microfilariae (mf), prompting the search for new and better drugs. Onchocerciasis drug discovery studies have so far been based on in vivo models using Onchocerca species which are not the closest to O. volvulus, and which may therefore, not adequately mimic the natural infection in humans. Therefore, this study was carried out to develop a better drug screening model for onchocerciasis, based on the use of cow-derived O. ochengi, the closest known relative of O. volvulus.

Methods

Mf of O. ochengi were injected subcutaneously at the nape of Syrian hamsters (Mesocricetus auratus) and BALB/c mice. The skin, and especially the earlobes of the animals were examined for mf 15–31 days after infection. For selected model validation, the hamsters were treated with ivermectin at 150 or 600 μg/kg body weight and examined 30 days after infection for mf. For L. loa studies in hamsters, isolated mf were injected intraperitoneally and animal organs were examined on day 26 for mf.

Results

The Syrian hamsters were found to be the more permissive to O. ochengi mf as fully viable mf were recovered from them on day 30, compared to BALB/c mice where such mf were recovered on day 15, but not 30. However, both animals were not permissive to L. loa mf even by day 15. Interestingly, more than 50 % of the total O. ochengi mf recovered were from the earlobes. The number of mf injected was directly proportional to the number recovered. Ivermectin at both concentrations tested completely eliminated the O. ochengi mf from the hamsters.

Conclusion

This study reveals the Syrian hamster as an appropriate small animal model for screening of novel compounds against O. ochengi, the closest known relative of O. volvulus.

Ethnomedical and ethnobotanical investigations on the response capacities of Guinean traditional health practioners in the management of outbreaks of infectious diseases: The case of the Ebola virus epidemic

ETHNOPHARMACOLOGICAL RELEVANCE

The recent outbreak of Ebola virus infections has mostly remained confined to the West African countries Guinea-Conakry, Sierra-Leone and Liberia. Due to intense national and international mobilizations, a significant reduction in Ebola virus transmission has been recorded. While international efforts focus on new vaccines, medicines and diagnostics, no coherent national or international approach exists to integrate the potential of the traditional health practitioners (THPs) in the management of infectious diseases epidemics. Nevertheless, the first contact of most of the Ebola infected patients is with the THPs since the symptoms are similar to those of common traditionally treated diseases or symptoms such as malaria, hemorrhagic syndrome, typhoid or other gastrointestinal diseases, fever and vomiting.

MATERIALS AND METHODS

In an ethnomedical survey conducted in the 4 main Guinean regions contacts were established with a total of 113 THPs. The socio-demographic characteristics, the professional status and the traditional perception of Ebola Virus Disease (EVD) were recorded.

RESULTS

The traditional treatment of the main symptoms was based on 47 vegetal recipes which were focused on the treatment of diarrhea (22 recipes), fever (22 recipes), vomiting (2 recipes), external antiseptic (2 recipes), hemorrhagic syndrome (2 recipes), convulsion and dysentery (one recipe each). An ethnobotanical survey led to the collection of 54 plant species from which 44 identified belonging to 26 families. The most represented families were Euphorbiaceae, Caesalpiniaceae and Rubiaceae. Literature data on the twelve most cited plant species tends to corroborate their traditional use and to highlight their pharmacological potential.

CONCLUSIONS

It is worth to document all available knowledge on the traditional management of EVD-like symptoms in order to evaluate systematically the anti-Ebola potential of Guinean plant species.