Anthelmintic activity of aminoalcohol and diamine derivatives against the gastrointestinal nematode Teladorsagia circumcincta.

Gastrointestinal nematodes (GIN) infections are a serious problem in livestock production due to the great economic losses they cause. Their control is increasingly difficult because of the rapid development of drug resistance and the limited number of available drugs. Therefore, this study evaluated 18 aminoalcohol and 16 diamine derivatives against eggs, first and third stage larvae from a susceptible and a resistant isolate of Teladorsagia circumcincta collected from sheep. The effectiveness of the in vitro anthelmintic activity of the compounds was evaluated using three different procedures: Egg Hatch Test (EHT), Larval Mortality Test (LMT) and Larval Migration Inhibition Test (LMIT). Those compounds with activities higher than 90 % in the initial screening at 50 µM were selected to determine their half maximal effective concentration (EC50). In parallel, cytotoxicity assays were conducted on Caco2 and HepG2 cell lines to calculate Selectivity Indexes (SI) for each compound. The diamine 30 presented the best results in preventing egg hatching, displaying the lowest EC50 value (1.01 ±â€¯0.04 µM) of all compounds tested and the highest SI (21.21 vs. Caco-2 cells). For the LMIT, the diamine 34 showed the highest efficacy, with EC50 values of 2.67 ±â€¯0.08 and 3.02 ±â€¯0.09 µM on the susceptible and resistant isolate of the parasite, respectively.

Synthesis, bioevaluation and docking studies of some 2-phenyl-1H-benzimidazole derivatives as anthelminthic agents against the nematode Teladorsagia circumcincta.

Gastrointestinal nematode infections are the main diseases in herds of small ruminants. Resistance to the main established drugs has become a worldwide problem. The purpose of this study is to obtain and evaluate the in vitro ovicidal and larvicidal activity of some 2-phenylbenzimidazole derivatives on susceptible and resistant strains of Teladorsagia circumcincta. Compounds were prepared by known procedures from substituted o-phenylenediamines and arylaldehydes or intermediate sodium 1-hydroxyphenylmethanesulfonate derivatives. Egg Hatch Test (EHT), Larval Mortality Test (LMT) and Larval Migration Inhibition Test (LMIT) were used in the initial screening of compounds at 50 µM concentration, and EC50 values were determined for the most potent compounds. Cytotoxicity evaluation of compounds was conducted on human Caco-2 and HepG2 cell lines to calculate their Selectivity Indexes (SI). At 50 µM concentration, nine out of twenty-four compounds displayed more than 98% ovicidal activity on a susceptible strain, and four of them showed more than 86% on one resistant strain. The most potent ovicidal benzimidazole (BZ) 3 showed EC50 = 6.30 µM, for the susceptible strain, while BZ 2 showed the lowest EC50 value of 14.5 µM for the resistant strain. Docking studies of most potent compounds in a modelled Teladorsagia tubulin indicated an inverted orientation for BZ 1 in the colchicine binding site, probably due to its fair interaction with glutamic acid at codon 198, which could justify its inactivity against the resistant strain of T. circumcincta.

Imidazo[2,1-a]isoindole scaffold as an uncharted structure active on Leishmania donovani.

The human protozoan parasites Leishmania donovani and L. infantum are the causative agents of visceral leishmaniasis, as such, responsible for approximately 30,000 deaths annually. The available chemotherapeutic treatments are reduced to a few drugs whose effectiveness is limited by rising drug resistance/therapeutic failure, and noxious side-effects. Therefore, new therapeutic hits are needed. Compounds displaying the imidazo[2,1-a]isoindole skeleton have shown antichagasic, anti-HIV, antimalarial and anorectic activities. Here, we report the leishmanicidal activity of thirty one imidazo[2,1-a]isoindol-5-ol derivatives on promastigotes and intracellular amastigotes of L. donovani. Eight out of thirty one assayed compounds showed EC50 values ranging between 1 and 2 µM with selectivity indexes from 29 to 69 on infected THP-1 cells. Six compounds were selected for further elucidation of their leishmanicidal mechanism. In this regard, compound 29, the imidazoisoindolol with the highest activity on intracellular amastigotes, induced an early decrease of intracellular ATP levels, as well as mitochondrial depolarization, together with a partial plasma membrane destructuration, as assessed by transmission electron microscopy. Consequently, the inhibition of the energy metabolism of Leishmania plays an important role in the leishmanicidal mechanism of this compound, even when other additional targets cannot be ruled out. In all, the results supported the inclusion of the imidazoisoindole scaffold for the development of new leishmanicidal drugs.

Anti-hyperalgesic effects of two sphingosine derivatives in different acute and chronic models of hyperalgesia in mice.

BACKGROUND: The study evaluated the effects of two sphingosine derivatives N-(2-tert-butoxycarbamylhexadecyl)glutaramide (AA) and N-(1-benzyloxyhexadec-2-yl)glutaramide (OA) in different models of hypersensitivity in mice. METHODS: Male Swiss mice were orally pre-treated with AA or OA (0.3-3mg/kg). After 1h, they received λ-carrageenan (300µg/paw), lipopolysaccharide (LPS; 100ng/paw), bradykinin (BK; 500ng/paw) or prostaglandin E2 (PGE2; 0.1nmol/paw) or epinephrine (100ng/paw), and the mechanical withdrawal thresholds were evaluated using von Frey filament (0.6g) at different time points. The effect of the compounds against inflammatory and neuropathic pain was also evaluated using complete Freund's adjuvant (CFA), or by performing partial sciatic nerve ligation (PSNL). RESULTS: Animals pre-treated with AA and OA reduced hypersensitivity induced by carrageenan, LPS and BK, and modest inhibition of PGE2-induced hypersensitivity and carrageenan-induced paw oedema were observed in mice treated with OA. Though the partial effect presented by AA and OA, when dosed once a day, both compounds were able to significantly reduce the persistent inflammatory and neuropathic pain induced by CFA and PSNL, respectively. CONCLUSION: These results demonstrate that the sphingosine derivatives AA and OA present important anti-hypersensitive effects, suggesting a possible interaction with the kinin signalling pathway. This may represent an interesting tool for the management of acute and chronic pain, with good bioavailability and safety.

Efficacious In Vitro and In Vivo Effects of Dihydrosphingosine-Ethambutol Analogues Against Susceptible and Multi-drug-resistant Mycobacterium tuberculosis.

BACKGROUND AND AIMS: Tuberculosis (TB) is a major worldwide health problem in part due to the lack of new drugs and the emergence of multidrug-resistant strains (MDR). The aim of this study was to select anti-tuberculosis drug candidates from a collection of 69 synthetic sphingosine-ethambutol analogues through in vitro and in vivo evaluations. METHODS: The 69 compounds were evaluated in vitro against two Mycobacterium tuberculosis strains, a drug susceptible (H37Rv) and a MDR clinical isolate (CIBIN-99). Four selected compounds, those that exhibited the highest potency in vitro, were tested in vivo using a model of progressive TB in BALB/c mice infected with the drug susceptible strain, either alone or combined with conventional chemotherapy, as well as in mice infected with the MDR strain. The acute toxicity was evaluated on male and female adult BALB/c mice. RESULTS: Ten of the evaluated compounds resulted more potent in vitro than ethambutol. The experimental compound 2b (2-aminopalmitol benzyl ether) was the most efficacious and also showed additive effects in combination with conventional chemotherapy. It did not exhibit toxicity (LD50 >2000 mg/kg). CONCLUSIONS: Compound 2b can be considered as a new drug candidate to continue its development against M. tuberculosis MDR strains.

In vitro and in vivo evaluation of 2-aminoalkanol and 1,2-alkanediamine derivatives against Strongyloides venezuelensis.

BACKGROUND: Strongyloidiasis is a parasitic disease widely present in tropical and subtropical areas. Strongyloides stercoralis represents the main species that infects human beings. Ivermectin is the current drug of choice; however, issues related with treatment failure in patients with diabetes or infected with T-lymphotropic virus-1 make the identification of new molecules for alternative treatment a priority. In the present study, the activity of sphingosine-related aminoalcohol and diamine were evaluated against Strongyloides venezuelensis third-stage larva (L3) cultures and experimental infections in mice. METHODS: The efficacy of each compound against L3 was assessed using both XTT (2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide) assay and microscopic observation with concentrations ranging from 1 to 350 µM. Cytotoxicity was evaluated using J774.2 macrophage cell line and XTT assay. Lethal concentration 50 (LC50), selectivity index (SI) and structure-activity relationships were established. The activity compounds 4 (2-(ethylamino) hexadecan-1-ol), 6 (2-(butylamino) hexadecan-1-ol), 17 (tert-butyl N-(1-aminododecan-2-yl) carbamate) and 18 (tert-butyl N-(1-aminohexadecan-2-yl) carbamate) were further assessed against experimental S. venezuelensis infections in CD1 mice measuring reductions in the numbers of parthenogenetic females and egg passed in faeces. Mice were infected with 3,000 L3 and treated with 20 mg/kg/day for five days. RESULTS: In the screening study of 15 aminoalcohols [lauryl (n = 9); palmityl (n = 13); stearyl (n = 15) and alcohol derivatives], the presence of a palmitol chain was associated with the highest efficacy against L3 (LC50 31.9-39.1 µM). Alkylation of the 2-amino group with medium size fragments as ethyl or n-butyl showed the best larvicidal activity. The dialkylation did not improve efficacy. Aminoalcohols 4 and 6 showed the highest SI (1.5 and 1.6, respectively). With respect to diamine derivative compounds, a chain size of sixteen carbon atoms (palmitoyl chain, n = 13), and the alkylation of the 2-amino group with medium-sized fragments, were associated with the highest lethal activities. The presence of carbamoyl group in diamines 17 and 18 yielded high SI (1.7 and 1.4, respectively). Infected mice treated with aminoalcohol 6 showed reduction in parthenogenetic females (59 %) and eggs in faeces (51 %). CONCLUSIONS: These results support the potentiality of aminoalcohol and diamine sphingosine-related compounds as suitable prototypes for developing new promising drugs against strongyloidiasis.

Trypanocidal Activity of Long Chain Diamines and Aminoalcohols.

Thirteen aminoalcohols and eight diamines were obtained and tested against Trypanosoma cruzi epimastigotes strains MG, JEM and CL-B5 clone. Some of them were equal or more potent (1.0-6.6 times) than the reference compound nifurtimox. From them, three aminoalcohols and two diamines were selected for amastigotes assays. Compound 5 was as potent as the reference drug nifurtimox against amastigotes of the CL-B5 strain (IC50 = 0.6 µM), with a selectivity index of 54.

Diterpenes Synthesized from the Natural Serrulatane Leubethanol and Their in Vitro Activities against Mycobacterium tuberculosis.

Seventeen new derivatives of the natural diterpene leubethanol, including some potential pro-drugs, with changes in the functionality of the aliphatic chain or modifications of aromatic ring and the phenolic group, were synthesized and tested in vitro by the MABA technique for their activity against the H37Rv strain of Mycobacterium tuberculosis. Some compounds showed antimycobacterial selectivity indices higher than leubethanol.

Mechanisms of action of substituted ß-amino alkanols on Leishmania donovani.

Leishmaniasis is the protozoan disease second in importance for human health, superseded only by malaria; however, the options for chemotherapeutic treatment are increasingly limited due to drug resistance and toxicity. Under this perspective, a quest for new chemical compounds is urgently needed. An N-substituted 2-aminoalkan-1-ol scaffold has been shown to be a versatile scaffold for antiparasitic activity. Knowledge about its mechanism of action is still rather limited. In this work, we endeavored to define the leishmanicidal profile of such ß-amino alkanol derivatives using a set of 15 N-mono- and disubstituted surrogates, tested on Leishmania donovani promastigotes and intracellular amastigotes. The best compound (compound 5), 2-ethylaminododecan-1-ol, had a 50% effective concentration (EC50) of 0.3 µM and a selectivity index of 72 for infected THP-1 cells and was selected for further elucidation of its leishmanicidal mechanism. It induced fast depletion of intracellular ATP content in promastigotes in the absence of vital dye intracellular entry, ruling out plasma membrane permeabilization as its origin. Confocal and transmission electron microscopy analyses showed that compound 5 induced severe mitochondrial swelling and vesiculation. Polarographic analysis using an oxygen electrode demonstrated that complex II of the respiratory chain (succinate reductase) was strongly inhibited by compound 5, identifying this complex as one of the primary targets. Furthermore, for other ß-amino alkanols whose structures differed subtly from that of compound 5, plasma membrane permeabilization or interference with membrane traffic was also observed. In all, N-substituted ß-amino alkanols were shown as appealing leishmanicidal candidates deserving further exploration.

Synthesis of Leubethanol derivatives and evaluation against Mycobacterium tuberculosis.

Twenty-five derivatives of the natural diterpene leubethanol, including several potential pro-drugs, with changes in the functionality of the aliphatic chain or modifications of the phenolic group, were synthesized and tested in vitro by the MABA technique for their activity against the H37Rv strain of Mycobacterium tuberculosis. Several compounds showed antimycobacterial potencies similar to that of the lead compound and two of them displayed higher selectivity indexes.

Diamine and aminoalcohol derivatives active against Trypanosoma brucei.

Twenty compounds selected as representative members of three series of long-chain 1,2-diamines, 2-amino-1-alkanols and 1-amino-2-alkanols structurally related to dihydrosphingosin, were synthesized and tested in vitro for their ability to inhibit the sleeping sickness parasites Trypanosoma bruceirhodesiense and Trypanosoma brucei gambiense. Eight compounds showed EC(50) values in the submicromolar range, with selectivity indexes up to 39 related to the respective cytotoxicity values for Vero cells. The parasite phenotype detected after treatment with the most potent compounds showed irreversible cell morphology alterations of the flagellar pocket that lead to inhibition of cell growth and parasite death.

New antinociceptive agents related to dihydrosphingosine.

The main objective of this study was to evaluate the antinociceptive activity of three ethylenediamine derivatives and three ß-aminoethanol lipidic derivatives structurally related to dihydrosphingosine. These derivatives were selected on the basis of previous results from in vitro and in vivo anti-inflammatory studies. For all of the assayed compounds, an intraperitoneal dose of 3 mg/kg caused pronounced pain inhibition as measured by the acetic acid-induced writhing model in mice. Compounds 3 and 6 demonstrated strong antinociceptive activity at doses as low as 1 mg/kg and proved to be considerably more potent than the common nonsteroidal anti-inflammatory drugs (NSAIDs), acetylsalicylic acid (ASA) and acetaminophen (ACE). We further analyzed these compounds using the capsaicin- and glutamate-induced pain tests. Compounds 3 and 6 also exhibited considerable antinociceptive effects under these conditions, but their inhibitory effects in the formalin test were less pronounced. The exact mechanism of action for these compounds has yet to be established. However, based the results from a hot-plate test, it can be stated that these new drugs do not interact with the opioid system.

Simple dihydrosphyngosine analogues with potent activity against MDR-Mycobacterium tuberculosis.

Fifteen dihydrosphingosine analogues have been synthesized and tested in vitro against Mycobacterium tuberculosis (MTB). Two ether (3 and 4b) and one diamine (8b) derivatives have displayed high mycobactericidal potency, with similar MIC values of 1.25 microg/mL, against the virulent strain H37Rv, as well as against a clinical isolate resistant to the five first-line anti-TB drugs. The three compounds, tested on other eleven cultured MTB strains with different multi-drug-resistance (MDR) patterns, retained their MIC values for most strains, or even lowered it, as in the case of compound 4b, which, assayed on strain No. 332, also resistant to all first-line anti-TB drugs, attained the MIC value of 0.78 microg/mL.

Guatemalan plants extracts as virucides against HIV-1 infection.

Prevention methods to avoid transmission of pathogens, including HIV, are crucial in the control of infectious diseases, not only to block epidemic spread but to avoid long-term treatments leading to emergence of resistances and drug associated side effects. Together with vaccine development, the discovery of new virucidal agents represents a research priority in this setting. In the screening of new compounds with antiviral activity, three Guatemalan plant extracts from Justicia reptans, Neurolaena lobata and Pouteria viridis were evaluated with a classic antiviral assay and were found to inhibit HIV replication. This activity was corroborated by an original recombinant virus assay, leading us to perform a deeper study of the virucidal activity. Active fractions were non-toxic in vitro and also inhibited other enveloped viruses. Moreover, these fractions were able to inhibit the transfer of HIV from dendritic cells (DCs) to lymphocytes, that represents the main way of HIV spread in vivo.