An Insight into the Discovery of Potent Antifilarial Leads Against Lymphatic Filariasis.

BACKGROUND AND OBJECTIVES: Lymphatic filariasis is a neglected tropical disease caused by infection with filarial worms that are transmitted through mosquito bites. Globally, 120 million people are infected, with nearly 40 million people disfigured and disabled by complications such as severe swelling of the legs (elephantiasis) or scrotum (hydrocele). Current treatments (ivermectin, diethylcarbamazine) have limited effects on adult parasites and produce side effects; therefore, there is an urgent to search for new antifilarial agents. Numerous studies on the antifilarial activity of pure molecules have been reported accross the recent literature. The present study describes the current standings of potent antifilarial compounds against lymphatic filariasis. METHODS: A literature search was conducted for naturally occurring and synthetic antifilarial compounds by referencing textbooks and scientific databases (SciFinder, PubMed, Science Direct, Wiley, ACS, SciELO, Google Scholar, and Springer, among others) from their inception until September 2019. RESULTS: Numerous compounds have been reported to exhibit antifilarial acitivity in adult and microfilariae forms of the parasites responsible for lymphatic filariasis. In silico studies of active antifilarial compounds (ligands) showed molecular interactions over the protein targets (trehalose-6-phosphate phosphatase, thymidylate synthase, among others) of lymphatic filariasis, and supported the in vitro results. CONCLUSION: With reference to in vitro antifilarial studies, there is evidence that natural and synthetic products can serve as basic scaffolds for the development of antifilarial agents. The optimization of the most potent antifilarial compounds can be further performed, followed by their in vivo studies.

In Vitro and In Vivo Antifilarial Activity of Standardized Extract of Calotropis procera Flowers against Brugia malayi.

BACKGROUND: Lymphatic filariasis (LF) is a parasitic disease that causes permanent disability (elephantiasis). Currently used antifilarial drugs are failing to control LF and there is resurgence in some areas. Looking for new antifilarial leads, we found that Calotropis procera plant parts have been used in traditional medicine for alleviating elephantiasis but the antifilarial activity is not known. OBJECTIVE: In the present study, the antifilarial activity of ethanolic extract (A001) and its hexane fraction (F001) of C. procera flowers was investigated using the human filarial parasite Brugia malayi. METHODS: A001 and F001 were tested for antifilarial activity using motility and 3-(4,5-dimethylthiazol-2- yl)-2,5 diphenyltetrazolium bromide (MTT) assays (in vitro) and in the rodent models B. malayi- Meriones unguiculatus and B. malayi-Mastomys coucha. In the rodent models, A001 and F001 were administered orally for 5 consecutive days, and the adult worm burden and course of microfilaraemia were determined. RESULTS: Both A001 and F001 showed microfilaricidal and macrofilaricidal activity in vitro. In animal models, A001 killed ~49-54% adult worms. In M. coucha model, F001 killed 12-60% adult worms in a dose (125-500 mg/kg) dependent manner; A001 and F001 suppressed microfilaraemia till days 91 and 35 post initiation of treatment, respectively. HPTLC revealed 0.61% lupeol, 0.50% ß-sitosterol and 1.50% triacontanol in F001. CONCLUSION: Flowers of C. procera have definite microfilaricidal and macrofilaricidal activities. Whether this activity is due to lupeol, ß-sitosterol and triacontanol found in the hexane fraction remains to be investigated. This is the first report on the antifilarial efficacy of flowers of the plant C. procera.

Polyphenol enriched ethanolic extract of Cajanus scarabaeoides (L.) Thouars exerts potential antifilarial activity by inducing oxidative stress and programmed cell death.

Development of antifilarial drug from the natural sources is considered as one of the most efficacious, safe, and affordable approaches. In this study, we report the antifilarial activity of a leguminous plant Cajanus scarabaeoides (L.) Thouars. The polyphenol-rich ethanolic extract obtained from the stem part of the plant C. scarabaeoides (EECs) was found to be efficient in killing the filarial nematode Setaria cervi in all the three developmental stages viz. oocytes, microfilariae (Mf) and adults with LD50 values of 2.5, 10 and 35 µg/ml, respectively. While studying the molecular mechanism of action, we found that induction of oxidative stress plays the key role in inducing the mortality in S. cervi. The redox imbalance finally results in activation of the nematode CED pathway that executes the death of the parasite. Intriguingly, EECs was found to be selectively active against the worm and absolutely non-toxic to the mammalian cells and tissues. Taken together, our experimental data demonstrate that C. scarabaeoides can be chosen as an affordable natural therapeutic for treating filarial infection in the future with high efficacy and less toxicity.

Exploration of antifilarial activity of gold nanoparticle against human and bovine filarial parasites: A nanomedicinal mechanistic approach.

The present work seeks to explore the antifilarial activity of biopolymer functionalized gold nanoparticles (AuNPs) against human filarial parasite (Wuchereria bancrofti) through Nrf2 signaling for the first time. A natural polymer, chitosan is used along with Terminalia chebula extract to synthesize AuNPs following the principles of green chemistry. The probable mode of action of AuNPs as filaricidal agent has been investigated in detail using model filarial parasite, Setaria cervi (bovine parasite). Biopolymers inspired AuNPs exhibit superior antifilarial activity against both human and bovine filarial parasites, and are able to induce oxidative stress and apoptotic cell death in filarial parasites mediated through mitochondria. AuNPs also alter the Nrf2 signaling. In addition, the synthesized nanomaterials appear to be nontoxic to mammalian system. Thus the present mechanistic study, targeting human filarial parasites, has the potential to increase the therapeutic prospects of AuNPs to control lymphatic filariasis in the upcoming days.

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.

Antifilarial activity of diterpenoids from Taxodium distichum.

BACKGROUND: Lymphatic filariasis caused by Wuchereria bancrofti, Brugia malayi and B. timori, is a debilitating disease with an adverse social and economic impact. The infection remains unabated in spite of treatment with existing antifilarial drugs diethylcarbamazine (DEC) and ivermectin which are chiefly microfilaricides. There is therefore, need for macrofilaricides, embryostatic agents and better microfilaricides. In the present study we explored the antifilarial potential of crude extract and its molecular fractions of the plant Taxodium distichum using in vitro assay systems and rodent models of B. malayi infection. METHODS: Ethanolic extract (A001) of aerial parts of T. distichum was solvent fractionated and sub-fractionated. Four molecules, 3-Acetoxylabda-8(20), 13-diene-15-oic acid (K001), Beta-sitosterol (K002), labda-8(20),13-diene-15-oic acid (K003) and Metasequoic acid A (K004) were isolated from the fractions and their structure determined by spectroscopic analysis. The extract, subfractions and molecules were evaluated for antifilarial activity against B. malayi by 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) reduction and motility assays in vitro and in two animal models, Meriones unguiculatus and Mastomys coucha, harbouring B. malayi infection. RESULTS: A001 was effective in killing microfilariae (mf) and adult worms in vitro. The diterpenoid K003 produced 100 % reduction in motility of both mf and adult worms and > 80 % inhibition in MTT reduction potential of adult female worms. In B. malayi-M. unguiculatus model, A001 killed all the adult worms in > 80 % of infected animals. K003 was embryostatic (> 95 %) in this model. In the B. malayi-M. coucha model, K003 killed ~54 % of adult worms (macrofilaricidal activity) and rendered > 36 % female worms sterile; it also stopped any further rise in microfilaraemia after day 42 post-initiation of treatment. CONCLUSION: Ethanolic extract of aerial parts of the plant T. distichum possesses potent antifilarial activity and the active principle was localised to K003 which showed significant macrofilaricidal activity and late suppression of peripheral microfilaraemia and some embryostatic activity. These findings indicate that labdane diterpenoid molecule(s) may provide valuable leads for design and development of new macrofilaricidal agent(s). To the best of our knowledge, this is the first report on antifilarial efficacy of products from the plant T. distichum.

Synthesis and biological evaluation of 4-oxycoumarin derivatives as a new class of antifilarial agents.

A series of 4-oxycoumarin derivatives was synthesized, characterized and evaluated in vitro and in vivo for antifilarial activity against the human lymphatic filarial parasite, Brugia malayi. A majority of the compounds studied showed potent in vitro activity with low IC50 values in the micro molar (µM) range (0.014-1.73 and 0.0056-0.43) against adult worms and microfilariae, respectively. Compounds 8 and 9 were identified to be the most promising antifilarial candidate molecules exhibiting activity in the nanomolar (nM) range. The IC50 values for compound 8 were 14 nM and 5.6 nM while for compound 9 were 94 nM and 13 nM, respectively, for adult worm and microfilaria. These two compounds also displayed promising adulticidal activity (74.9 ± 4.8% and 69.4 ± 2.8%, respectively) in the primary rodent (jird) screen. This study also serves as a starting point for investigating structure-activity relationship with different amino substituents.

Anti-Onchocerca activity and phytochemical analysis of an essential oil from Cyperus articulatus L.

BACKGROUND: The lack of a safe and effective adult worm drug and the emergence of resistant animal parasite strains to the only recommended drug, the microfilaricide, ivermectin put many at risk of the devastating effects of the onchocerciasis. The present study was undertaken to investigate the acclaimed anti-Onchocerca activity of the roots/rhizomes of Cyperus articulatus in the traditional treatment of onchocerciasis in North Western Cameroon and to assess the plant as a new source of potential filaricidal lead compounds. METHODS: Crude extracts were prepared from the dried plant parts using hexane, methylene chloride and methanol. The antifilarial activity was evaluated in vitro on microfilariae (Mfs) and adult worms of the bovine derived Onchocerca ochengi, a close relative of Onchocerca volvulus. The viabilities of microfilariae and adult male worms were determined based on motility reduction, while for the adult female worms the viability was based on the standard MTT/formazan assay. Cytotoxicity of the active extract was assessed on monkey kidney epithelial cells in vitro and the selectivity indices (SI) were determined. Acute toxicity of the promising extract was investigated in mice. Chemical composition of the active extract was unraveled by GC/MS analysis. RESULTS: Only the hexane extract, an essential oil exhibited anti-Onchocerca activity. The oil killed both the microfilariae and adult worms of O. ochengi in a dose manner dependently, with IC50s of 23.4 µg/ml on the Mfs, 23.4 µg/ml on adult male worms and 31.25 µg/ml on the adult female worms. Selectivity indices were 4, 4, and 2.99 for Mfs, adult males and adult females, respectively. At a single limit dose of 2000 mg/kg body weight, none of 6 mice that received the essential oil by gavage died. GC/MS analysis revealed the presence of terpenoids, hydrocarbons and fatty acids or fatty acid derivatives as components of the oil. CONCLUSIONS: The essential oil from the roots/rhizomes of Cyperus articulatus is active against O. ochengi microfilariae and adult worms in vitro in a dose dependent manner, hence may provide a source of new anti-filarial compounds. The results also support the traditional use of C. articulatus in the treatment of human onchocerciasis.

Antifilarial effect of ursolic acid from Nyctanthes arbortristis: molecular and biochemical evidences.

A bio-assay guided fractionation and purification approach was used to examine in vitro antifilarial activities of the crude methanolic extract of Nyctanthes arbortristis as well as fractions and isolated compound. From ethyl-acetate fraction we isolated and identified a triterpenoid compound which has been characterized as ursolic acid (UA) by HPLC and NMR data. We are reporting for the first time isolation and identification of UA from the leaves of N. arbortristis. The crude extract and UA showed significant micro- as well as macrofilaricidal activities against the oocyte, microfilaria and adult of Setaria cervi (S. cervi) by dye exclusion test and MTT reduction assay. Significant microfilaricidal activity of UA was further proved against mf of W. bancrofti by viability assay. The findings thus provide a new lead for development of a suitable filaricide from natural products. The molecular mechanism of UA was investigated by performing TUNEL, Hoechst staining, Annexin V-Cy3, flow cytometric analysis and DNA fragmentation assay. Differential expressions of pro- and anti-apoptotic genes were observed at the transcription and translational levels in a dose-dependent manner. Depletion in the worm GSH level and elevation in the parasite GST, SOD and super oxide anion indicated the generation of ROS. In this investigation we are reporting for the first time that UA acts its antifilarial effect through induction of apoptosis and by downregulating and altering the level of some key antioxidants like GSH, GST and SOD of S. cervi.

Virtual screening of traditional Chinese medicine (TCM) database: identification of fragment-like lead molecules for filariasis target asparaginyl-tRNA synthetase.

Lymphatic filariasis (LF) is a vector borne infectious disease caused by the nematode Wuchereria bancrofti, Brugia malayi, and Brugia timori. Over 120 million people are affected by LF in the world, of which two-thirds are in Asia. The infection restricts the normal flow of lymph from the infected area resulting in swelling of the extremities and causing permanent disability. As the available drugs for the treatment of LF are becoming ineffective due to the development of resistance, there is an urgent need to find new leads for drug development. In this study, asparaginyl-tRNA synthetase (AsnRS; PDB ID: 2XGT) essential for the protein bio-synthesis in the filarial nematode was used to carry out virtual screening (VS) of plant constituents from traditional Chinese medicine (TCM) database. Docking as well as E-pharmacophore based VS were carried out to identify the hits. The top scoring hits, Agri 1 (1,3,8-trihydroxy-4,5-dimethoxyxanthen-9-one-3-O-beta-D-glucopyranoside) and Agri 2 (5,7-dihydroxy-2-propylchromone 7-O-beta-D-glucopyranoside), constituents of Agrimonia pilosa, were selected for molecular dynamics (MD) simulation study for 10 ns. MD simulation showed that both the glycosides Agri 1 and Agri 2 were forming stable interactions with the target protein. Moreover, docking and MD simulation of the lead A (1,3,8-trihydroxy-4,5-dimethoxyxanthen-9-one; Mol. Wt.: 304.25; CLogP: 3.07) and lead B (5,7-dihydroxy-2-propylchromone; Mol. Wt.: 220.22; CLogP: 3.02), the aglycones of Agri 1 and Agri 2, respectively, were carried out with the target AsnRS. The in silico investigations of the aglycones suggest that the lead B could be a suitable fragment-like lead molecule for anti-filarial drug discovery.

Antifilarial activity of ethyl acetate extract of Vitex negundo leaves in vitro.

OBJECTIVE: To evaluate the possible antifilarial effect of ethyl acetate extract of Vitex negundo (Verbenaceae) leaves against Setaria cervi filarial parasite in vitro. METHODS: In vitro screening was done by the method of motility inhibition and MTT reduction assay with concentrations of 0.03 to 1.00 mg/mL for 2 to 24 h incubation periods respectively, for possible antifilarial effect by comparing with control. RESULTS: In motility assay, complete inhibition of motility was observed and in MTT reduction assay which gave >50% reduction for concentrations 0.20, 0.50 and 1.00 mg/mL at 10, 6 and 2 h incubation periods respectively in a dose dependent manner (P<0.05). An antifilarial effect imparted by plant extract was found to be a function of their relative concentrations. Inhibitory concentration (IC50) for the plant extract was found to be 0.16 mg/mL. CONCLUSIONS: The present study recorded significant antifilarial effect of Vitex negundo plant extract and contributed toward the development of database for novel drug candidates for lymphatic filariasis.

Glycyrrhetinic acid and its analogs: a new class of antifilarial agents.

Although a number of chemicals have been isolated from Glycyrrhiza glabra, only a few have been evaluated for their biological significance. As part of our drug discovery program for antifilarial agents from Indian medicinal plants, the roots of G. glabra were chemically investigated, which resulted in the isolation and characterization of an antifilarial agent, glycyrrhetinic acid (GA, 1a) effective against microfilariae (mf) in vitro (LC100: 12.5 µM; IC50: 1.20 µM), but was inactive against adult worms. Further, GA (1a) was converted into six analogs (2a-7a) and their antifilarial potential was evaluated by studying in vitro motility and MTT reduction assays employing mf and adult worms of Brugia malayi. The results showed that out of six GA analogs, the benzyl amide analog (6a) killed adults and mf at 25 and 50 µM concentration, respectively, and inhibited 49% MTT reduction potential of the adult parasites. The IC50 values were found to be 8.8 and 2.2 µM for adults and mf, respectively. The SI of the compound was >60. On the other hand the octylamide analog (7a) required much higher concentration to adversely affect the parasites. Finally, both active amide analogs (6a and 7a) were in vivo evaluated using B. malayi-jird model, which showed that analog 6a possesses promising macrofilaricidal activity at 100mg/kg, s.c. ×5 days and around 40% of the treated animals showed calcified masses of worm fragments in peritoneal cavity of the animals. To the best of our knowledge this is the first ever report on the antifilarial potential of GA analogs. Further work on optimization of the antifilarial lead is under progress.

Antifilarial diarylheptanoids from Alnus nepalensis leaves growing in high altitude areas of Uttarakhand, India.

Lymphatic filariasis continues to be a major health problem in tropical and subtropical countries. A macrofilaricidal agent capable of eliminating adult filarial parasites is urgently needed. Platyphyllenone (A), alusenone (B), hirustenone (C) and hirsutanonol (D) are important biologically active diarylheptanoids present in Alnus nepalensis. In the present study, we report the antifilarial activity in diarylheptanoids isolated from the leaves of A. nepalensis. Out of four compounds (A-D) tested in vitro one has shown promising anti-filarial activity both in vitro and in vivo studies. This is the first ever report on antifilarial efficacy of a compound of the plant and warrants further studies around this scaffold. In addition, a sensitive, selective and robust densitometric high-performance thin-layer chromatographic method was developed and validated for the above four biomarker compounds. The separation was performed on silica gel 60F(254) high-performance thin layer chromatography plates using chloroform:methanol (9:1, v/v) as mobile phase. The quantitation of marker compounds was carried out using densitometric reflection/absorption mode at 600 nm after post-chromatographic derivatization using vanillin-sulfuric acid reagent. The method was validated for peak purity, precision, robustness, limit of detection (LOD) and quantitation (LOQ) etc., as per the International Conference on Harmonization (ICH) guidelines.

Synthesis and screening of 1-methyl-4-substituted benzoyl piperazides against adult Setaria digitata for antifilarial activity.

There is no safe and effective drug for killing the adult worms for the elimination/control of lymphatic filariasis and research is very much warranted towards the development of a macrofilaricidal drug. Therefore, the synthesis and evaluation of 1-N-methyl-substituted benzoyl/phenyl acetyl piperazides for macrofilaricidal activity were carried out. The title compounds, 1-N-methyl-substituted benzoyl/phenyl acetyl piperazides were synthesized and purified by slightly modifying the reported procedure and characterized by FT-IR, NMR and mass spectral data. The compounds were screened for macrofilaricidal activity against adult Setaria digitata, the bovine filarial worm for motility and MTT reduction assays using the reported procedures. All the compounds synthesized were characterized by spectral data. Out of 26 compounds synthesized and screened for macrofilaricidal activity, six compounds exhibited moderate antifilarial activity. The structure-activity relationships are discussed. In the case of benzoyl piperazides chloro-substitution in the para position enhanced the activity compared to its substitution in meta and ortho positions. In the case of phenyl acetyl piperazides when methyl group was in the meta position it was more active than when it was in para position. In dimethyl substituted compounds, substitutions at 3, 5-positions were more effective than 2, 3 and 3, 4 substitutions.

Chemical constituents and antifilarial activity of Lantana camara against human lymphatic filariid Brugia malayi and rodent filariid Acanthocheilonema viteae maintained in rodent hosts.

Lymphatic filariasis continues to be a major health problem in tropical and subtropical countries. A macrofilaricidal agent capable of eliminating adult filarial parasites is urgently needed. In the present study, we report the antifilarial activity in the extract of stem portion of the plant Lantana camara. The crude extract at 1 g/kg for 5 days by oral route killed 43.05% of the adult Brugia malayi parasites and sterilized 76% of surviving female worms in the rodent model Mastomys coucha. A 34.5% adulticidal activity along with sterilization of 66% of female worms could be demonstrated in the chloroform fraction. Remarkable antifilarial activity was observed in the adult B. malayi transplanted gerbil model where up to 80% of the adult worms could be killed at the same dose and all the surviving female parasites were found sterilized. The extract was also found effective against a subcutaneous rodent filariid Acanthocheilonema viteae maintained in Mastomys coucha, where it exerted strong microfilaricidal (95.04%) and sterilization (60.66%) efficacy with mild macrofilaricidal action. Two compounds, oleanonic acid and oleanolic acid, isolated from hexane and chloroform fractions showed LC100 at 31.25 and 62.5 mug/ml, respectively, on B. malayi in vitro. This is the first ever report on the antifilarial efficacy of Lantana camara.

Syntheses and antifilarial profile of 7-chloro-4-(substituted amino) quinolines: a new class of antifilarial agents.

The syntheses of 7-chloro-4-(substituted amino) quinolines (2-22) and their antifilarial activities are delineated. Some of the screened compounds have shown promising filarial response and sterilization effect on female Acanthocheilonema viteae in rodents.

Exploration of antifilarial potential and possible mechanism of action of the root extracts of Saxifraga stracheyion on cattle filarial parasite Setaria cervi.

The effect of aqueous and alcohol extracts of the roots of Saxifraga stracheyi Engl. On the spontaneous movements of both the whole worm and the nerve muscle preparation of Setaria cervi and on the survival of microfilariae in vitro was studied. Both extracts caused the inhibition of spontaneous movements of the whole worm and the nerve-muscle preparation of S. cervi, characterized by an increase in the amplitude and a decrease in the rate of contractions, while the tone of the contractions remained visibly unaffected. The concentration required to inhibit the movements of the whole worm preparation was 140 microg/ml for the aqueous and 250 microg/ml for the alcohol extract. The concentration of S. stracheyi extracts required to produce an equivalent effect on the nerve-muscle preparation was 30 microg/ml for aqueous, and 20 microg/ml for the alcohol extract, suggesting a cuticular permeability barrier.

Trehalose-6-phosphate-potent anti-onchocerciatic agent.

Onchocerciasis is a disease that engages the attention of most researchers. Presently, there is not an ideal onchocerciatic agent, hence the search must continues. Consequently alpha, alpha-trehalose-6-phosphate was synthesised and assessed for onchocerciatic activity against O. volvulus; using diethylcarbamizine citrate as the control drug. Results from this study showed that alpha, alpha-trehalose-6-phosphate is a glucose analogue with effective micro and macro-filaricidal agent, better than that of the control drug. The inhibitory action of this compound on enzyme trehalase is a postulate for the mechanism of action of trehalose-6-phosphate. The structure-activity relationship of this new compound is fully discussed. This study postulates that this compound could be used to eradicate onchocerciasis both in man and animals.

Evaluation of vanillic acid analogues as a new class of antifilarial agents.

A number of vanillic acid analogues (1-14) have been synthesised and evaluated against experimental filarial infections using cotton rats (Sigmodon hispidus) infected with Litomosoides carinii, a primary screening model, at a dose of 30 mg/kg, ip for 5 days. Of the 8 compounds tested, 4 (5,7, 11 and 12) exhibited high micro- and macro-filaricidal activity with sterilization of surviving female worms. Compounds 5, 7, 12 showed remarkable adulticidal action (> 80%). Sterilization of the female worms by compounds 11 and 12 was highly significant (80-100%).