Correlation between secondary metabolites of Iris confusa Sealy and Iris pseudacorus L. and their newly explored antiprotozoal potentials

BACKGROUND

In the last few decades, the use of plant extracts and their phytochemicals as candidates for the management of parasitic diseases has increased tremendously. Irises are aromatic and medicinal plants that have long been employed in the treatment of different infectious diseases by traditional healers in many cultures. This study aims to explore the potential of three common Iris species (I. confusa Sealy, I. pseudacorus L. and I. germanica L.) against infectious diseases. Their in vitro antiprotozoal potency against Plasmodium falciparum, Trypanosoma brucei brucei, T. b. rhodesiense, T. cruzi and Leishmania infantum beside their cytotoxicity on MRC-5 fibroblasts and primary peritoneal murine macrophages were examined.

METHODS

The secondary metabolites of the tested extracts were characterized by UPLC-HRMS/MS and Pearsons correlation was used to correlate them with the antiprotozoal activity.

RESULTS

Overall, the non-polar fractions (NPF) showed a significant antiprotozoal activity (score: sc 2 to 5) in contrast to the polar fractions (PF). I. confusa NPF was the most active extract against P. falciparum [IC50 of 1.08 μg/mL, selectivity index (S.I. 26.11) and sc 5] and L. infantum (IC50 of 12.7 μg/mL, S.I. 2.22 and sc 2). I. pseudacorus NPF was the most potent fraction against T. b. rhodesiense (IC50 of 8.17 μg/mL, S.I. 3.67 and sc 3). Monogalactosyldiacylglycerol glycolipid (18:3/18:3), triaceylglycerol (18:2/18:2/18:3), oleic acid, and triterpenoid irridals (spirioiridoconfal C and iso-iridobelamal A) were the top positively correlated metabolites with antiplasmodium and antileishmanial activities of I. confusa NPF. Tumulosic acid, ceramide sphingolipids, corosolic, maslinic, moreollic acids, pheophytin a, triaceylglycerols, mono- and digalactosyldiacylglycerols, phosphatidylglycerol (22:6/18:3), phosphatidylcholines (18:1/18:2), and triterpenoid irridal iso-iridobelamal A, were highly correlated to I. pseudacorus NPF anti- T. b. rhodesiense activity. The ADME study revealed proper drug likeness properties for certain highly corelated secondary metabolites.

CONCLUSION

This study is the sole map correlating I. confusa and I. pseudacorus secondary metabolites to their newly explored antiprotozoal activity.

Influence of amino acid size at the P3 position of N-Cbz-tripeptide Michael acceptors targeting falcipain-2 and rhodesain for the treatment of malaria and human african trypanosomiasis

In recent decades, several structure-activity relationship (SAR) studies provided potent inhibitors of the cysteine proteases falcipain-2 (FP-2) and rhodesain (RD) from Plasmodium falciparum and Trypanosoma brucei rhodesiense, respectively. Whilst the roles of the warhead and residues targeting the P1 and P2 pockets of the proteases were extensively investigated, the roles of the amino acids occupying the S3 pocket were not widely assessed. Herein we report the synthesis and biological evaluation of a set of novel Michael acceptors bearing amino acids of increasing size at the P3 site (1a-g/2a-g, SPR20-SPR33) against FP-2, RD, P. falciparum, and T. brucei. Overall, the Michael acceptors bearing small amino acids at the P3 site exhibited the most potent inhibitory properties towards FP-2. In contrast, analogues with bulky residues at the P3 position were very potent rhodesain inhibitors. In cell based assays, single-digit micromolar EC₅₀ values against the two protozoa were observed. These findings can be a starting point for the development of peptide-based FP-2 and RD inhibitors.

Investigation of the effect of structure modification of furamidine on the DNA minor groove binding and antiprotozoal activity

New analogs of the antiprotozoal agent Furamidine were prepared utilizing Stille coupling reactions and amidation of the bisnitrile intermediate using lithium bis-trimethylsilylamide. Both the phenyl groups and the furan moiety of furamidine were replaced by heterocycles including thiophene, selenophene, indole or benzimidazole. Based upon the ΔTm and the CD results, the new compounds showed strong binding to the DNA minor groove. The new analogues are also more active both in vitro and in vivo than furamidine. Compounds 7a, 7b, and 7f showed the highest activity in vivo by curing 75% of animals, and this merits further evaluation.

Quinolone: a versatile therapeutic compound class

The discovery of nalidixic acid is one pinnacle in medicinal chemistry, which opened a new area of research that has led to the discovery of several life-saving antimicrobial agents (generally referred to as fluoroquinolones) for over decades. Although fluoroquinolones are frequently encountered in the literature, the utility of quinolone compounds extends far beyond the applications of fluoroquinolones. Quinolone-based compounds have been reported for activity against malaria, tuberculosis, fungal and helminth infections, etc. Hence, the quinolone scaffold is of great interest to several researchers in diverse disciplines. This article highlights the versatility of the quinolone pharmacophore as a therapeutic agent beyond the fluoroquinolone profile.

Synthesis and evaluation of tetrahydroisoquinoline derivatives against Trypanosoma brucei rhodesiense

Human African Trypanosomiasis (HAT) is a neglected tropical disease caused by the parasitic protozoan Trypanosoma brucei (T. b.), and affects communities in sub-Saharan Africa. Previously, analogues of a tetrahydroisoquinoline scaffold were reported as having in vitro activity (IC₅₀ = 0.25-70.5 μM) against T. b. rhodesiense. In this study the synthesis and antitrypanosomal activity of 80 compounds based around a core tetrahydroisoquinoline scaffold are reported. A detailed structure activity relationship was revealed, and five derivatives (two of which have been previously reported) with inhibition of T. b. rhodesiense growth in the sub-micromolar range were identified. Four of these (3c, 12b, 17b and 26a) were also found to have good selectivity over mammalian cells (SI > 50). Calculated logD values and preliminary ADME studies predict that these compounds are likely to have good absorption and metabolic stability, with the ability to passively permeate the blood brain barrier. This makes them excellent leads for a blood-brain barrier permeable antitrypanosomal scaffold.

New antiparasitic flexible triaryl diamidines, their prodrugs and aza analogues: Synthesis, in vitro and in vivo biological evaluation, and molecular modelling studies

Dicationic diamidines have been well established as potent antiparasitic agents with proven activity against tropical diseases like trypanosomiasis and malaria. This work presents the synthesis of new mono and diflexible triaryl amidines (6a-c, 13a,b and 17), their aza analogues (23 and 27) and respective methoxyamidine prodrugs (5, 7, 12a,b, 22 and 26). All diamidines were assessed in vitro against Trypanosoma brucei rhodesiense (T. b. r.) and Plasmodium falciparum (P. f.) where they displayed potent to moderate activities at the nanomolar level with IC₅₀s = 11-378 nM for T. b. r. and 4-323 nM against P. f.. In vivo efficacy testing against T. b. r. STIB900 has shown the monoflexible diamidine 6c as the most potent derivative in this study eliciting 4/4 cures of infected mice for a treatment period of >60 days upon a 4 × 5 mg/kg dose i. p. treatment. Moreover, thermal melting analysis measurement ΔT_m for this series of diamidines/poly (dA-dT) complexes fell between 0.5 and 19 °C with 6c showing the highest binding to the DNA minor groove. Finally, a 50 ns molecular dynamics study of an AT-rich DNA dodecamer with compound 6c revealed a strong binding complex supported by vdW and electrostatic interactions.

Preparation of new 1,3-dibenzyl tetrahydropyridinylidene ammonium salts and their antimicrobial and anticellular activities

New 1,3 dibenzyl -tetrahydropyridinylidene ammonium salts have been prepared from unsubstituted or N-benzylated tetrahydropyridinylidene ammonium salts. The antiplasmodial and antitrypanosomal activities as well as their cytotoxic effects were determined using microplate assays. In addition, their activities against two gram positive and two gram negative bacteria strains and a yeast strain were examined. Furthermore, anticancer effects against two cell lines were investigated. Physicochemical parameters were calculated and structure-activity-relationships discussed. One compound showed antiplasmodial activity against a multiresistant strain of Plasmodium falciparum in subnanomolar concentration. Antitrypanosomal activities were detected in low nanomolar concentrations. A single compound was active against grampositive and gramnegative bacteria, as well as yeast. One compound inhibited the growth of a HCT cell line in low concentration.

The discovery of novel antitrypanosomal 4-phenyl-6-(pyridin-3-yl)pyrimidines

Human African trypanosomiasis, or sleeping sickness, is a neglected tropical disease caused by Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense which seriously affects human health in Africa. Current therapies present limitations in their application, parasite resistance, or require further clinical investigation for wider use. Our work herein describes the design and syntheses of novel antitrypanosomal 4-phenyl-6-(pyridin-3-yl)pyrimidines, with compound 13, the 4-(2-methoxyphenyl)-6-(pyridine-3-yl)pyrimidin-2-amine demonstrating an IC₅₀ value of 0.38 μM and a promising off-target ADME-Tox profile in vitro. In silico molecular target investigations showed rhodesain to be a putative candidate, supported by STD and WaterLOGSY NMR experiments, however, in vitro evaluation of compound 13 against rhodesain exhibited low experimental inhibition. Therefore, our reported library of drug-like pyrimidines present promising scaffolds for further antikinetoplastid drug development for both phenotypic and target-based drug discovery.

Compound isolation and biological activities of Piptadeniastrum africanum (hook.f.) Brennan roots

ETHNOPHARMACOLOGICAL RELEVANCE

The dicotyledonous plant Piptadeniastrum africanum (hook.f.) Brennan (Fabaceae) is used in traditional medicine to treat various human complaints including bronchitis, coughing, urino-genital ailments, meningitis, abdominal pain, treatment of wounds, malaria and gastrointestinal ailments, and is used as a purgative and worm expeller.

AIM OF THE STUDY

The present study describes the phytochemical investigation and the determination of the antimicrobial, antiplasmodial and antitrypanosomal activities of crude extract, fractions and compounds extracted from Piptadeniastrum africanum roots.

MATERIALS AND METHODS

Isolated compounds were obtained using several chromatographic techniques. The structures of all compounds were determined by comprehensive spectroscopic analyses (1D and 2D NMR) and by comparing their NMR data with those found in literature. In vitro antimicrobial activity of samples was evaluated using the microdilution method on bacterial (Escherichia coli, Proteus mirabilis, Staphylococcus aureus) and fungal (Candida krusei) strains, while in vitro cell-growth inhibition activities were assessed against two parasites (Trypanosoma brucei brucei and Plasmodium falciparum strain 3D7). The cytotoxicity properties of samples were assayed against HeLa human cervical carcinoma.

RESULTS

Five compounds were isolated and identified as: tricosanol 1, 5α-stigmasta-7,22-dien-3-β-ol 2, betulinic acid 3, oleanolic acid 4 and piptadenamide 5. This is the first report of the isolation of these five compounds from the roots of P. africanum. The (Hex:EtOAc 50:50) fraction exhibited moderate antibacterial activity against P. mirabilis (MIC 250 μg/mL), while the other fractions and isolated compounds had weak antimicrobial activities. Only the EtOAc fraction presented a moderate antimalarial activity with an IC₅₀ of 16.5 μg/mL. The MeOH crude extract and three fractions (Hexane, Hexane-EtOAc 25% and EtOAc-MeOH 25%) exhibited significant trypanocidal activity with IC₅₀ values of 3.0, 37.5, 3.8 and 9.5 μg/mL, respectively.

CONCLUSION

These results demonstrated a scientific rational of the traditional uses of P. africanum and indicate that this plant should be further investigated to identify some of the chemical components that exhibited the activities reported in this study and therefore may constitute new lead candidates in parasiticidal drug discovery.

Design, synthesis and antitrypanosomal activity of heteroaryl-based 1,2,4-triazole and 1,3,4-oxadiazole derivatives

Two series of novel 1,2,4-triazol-3-yl-thioacetamide 3a-b and 4a-b and 5-pyrazin-2-yl-3H-[1,3,4]oxadiazole-2-thiones 9a-h were designed and synthesized. The compounds prepared have been identified using ¹H NMR, ¹³C NMR and elemental analyses. The synthesized compounds 3a, 3b, 4a, 4b, 9a, 9b, 9d-e and 9f have been evaluated with α-difluoromethylornithine (DFMO) as a control drug for their in vitro antitrypanosomal activity against Trypanosoma brucei. Results showed that 3b was the most active compound in general and also more potent than control DFMO. 3b was 8 folds more potent than the reference with IC₅₀ of 0.79 μM and IC₉₀ of 1.35 μM, respectively compared to DFMO (IC₅₀ = 6.10 μM and IC₉₀ of 8.66 μM). The tested compounds showed moderate cytotoxicity with selectivity indices ranging from 12 (9d) to 102 (3b) against L6 cells. Docking study was performed into ten of T. brucei enzymes which have been identified as potential/valid targets for most of the antitrypanosomal agents. The results of the docking study revealed high binding scores toward many of the selected enzymes. A good correlation was observed only between log (IC₅₀) of antitrypanosomal activity of the new compounds and their calculated Ki values against TryR enzyme (R² = 0.726). Compound 3b, the most active as antitrypanosomal agents exhibited similar binding orientation and interaction to those of WP6 against TryR enzyme. However, in a next round of work, a complementary studies will be carried out to clarify the mechanism of action of these compounds.

Synthesis, Antitrypanosomal and Antimycobacterial Activities of Coumarin N-acylhydrazonic Derivatives

BACKGROUND

Near to 5-7 million people are infected with T. cruzi in the world, and about 10,000 people per year die of problems associated with this disease.

METHODS

Herein, the synthesis, antitrypanosomal and antimycobacterial activities of seventeen coumarinic N-acylhydrazonic derivatives have been reported.

RESULTS

These compounds were synthesized using methodology with reactions global yields ranging from 46%-70%. T. cruzi in vitro effects were evaluated against trypomastigote and amastigote, forming M. tuberculosis activity towards H37Rv sensitive strain and resistant strains.

DISCUSSION

Against T. cruzi, the more active compounds revealed only moderate activity IC₅₀/96h~20 μM for both trypomastigotes and amastigotes intracellular forms. (E)-2-oxo-N'- (3,4,5-trimethoxybenzylidene)-2H-chromene-3-carbohydrazide showed meaningful activity in INH resistant/RIP resistant strain.

CONCLUSION

These compound acting as multitarget could be good leads for the development of new trypanocidal and bactericidal agents.

Dibenzylbutane neolignans from Saururus cernuus L. (Saururaceae) displayed anti-Trypanosoma cruzi activity via alterations in the mitochondrial membrane potential

The MeOH extract from leaves of Saururus cernuus L. (Saururaceae) displayed in vitro activity against trypomastigote forms of T. cruzi (100% of parasite death at 200 μg/mL), suggesting the presence of bioactive compounds. Thus, the bioactivity-guided fractionation was carried out, leading to the isolation of three related neolignan derivatives, identified as threo-austrobailignan-5 (1), threo-austrobailignan-6 (2), and threo-dihydroguaiaretic acid (3). Anti-T. cruzi activity of compounds 1-3 was performed against cell-derived trypomastigotes and intracellular amastigotes. Additionally, the mammalian cytotoxicity was investigated using NCTC cells. Compound 2 was the most effective against extracellular trypomastigotes with IC₅₀ of 3.7 μM, while compound 3 showed activity in both clinically relevant forms of the parasite, trypomastigotes and amastigotes, with IC₅₀ values of 7.0 and 16.2 μM, respectively. However, the structurally related compound 1 was inactive. Based on these results, compounds 2 and 3 were selected to evaluate the mechanism of cellular death. Compound 2 induced alteration in the plasma membrane permeability and consequently in the ROS levels after 120 min of incubation. By using flow cytometry and fluorescence microscopy, compound 3 showed alterations in the mitochondrial membrane potential (ΔΨ_m) of trypomastigotes. Considering the promising chemical and biological properties of neolignans 2 and 3, these compounds could be used as starting points to develop new lead compounds for Chagas disease.

New bioactive metabolites from the elicited marine sponge-derived bacterium Actinokineospora spheciospongiae sp. nov

Several approaches have been dedicated to activate the cryptic gene clusters in the genomes of actinomycetes for the targeted discovery of new fascinating biomedical lead structures. In the current study, N-acetylglucosamine was used to maximize the chemical diversity of sponge-derived actinomycete Actinokineospora spheciospongiae sp. nov. HR-ESI-MS was employed for dereplication study and orthogonal partial least square-discriminant analysis was applied to evaluate the HR-ESI-MS data of the different fractions. As a result, two new fridamycins H (1) and I (2), along with three known compounds actinosporin C (3), D (4), and G (5) were isolated from the solid culture of sponge-associated actinomycete Actinokineospora spheciospongiae sp. nov., elicited with N-acetylglucosamine. Characterization of the isolated compounds was pursued using mass spectrometry and NMR spectral data. Fridamycin H (1) exhibited significant growth inhibitory activity towards Trypanosoma brucei strain TC221. These results highlight the potential of elicitation in sponge-associated actinomycetes as an effective strategy for the discovery of new anti-infective natural products.

Biological evaluation and structure-activity relationships of imidazole-based compounds as antiprotozoal agents

We discovered a series of azole antifungal compounds as effective antiprotozoal agents. They displayed promising inhibitory activities within the micromolar-submicromolar range against P. falciparum, L. donovani, and T. b. rhodesiense. Moreover, most of such compounds showed excellent nanomolar IC₅₀ against T. cruzi, showing also very low cytotoxicity. Discussion of structure-activity relationships and biological data for these compounds are provided against the different parasites. To assess the mechanism of action against T. cruzi we proved that the most potent compounds (3b, 3j-l) inhibited the T. cruzi CYP51. Moreover, the most active derivative 3j dramatically reduced parasitemia in T. cruzi mouse model without acute toxicity.

Synthesis and evaluation of analogs of 5'-(((Z)-4-amino-2-butenyl)methylamino)-5'-deoxyadenosine (MDL 73811, or AbeAdo) - An inhibitor of S-adenosylmethionine decarboxylase with antitrypanosomal activity

We describe our efforts to improve the pharmacokinetic properties of a mechanism-based suicide inhibitor of the polyamine biosynthetic enzyme S-adenosylmethionine decarboxylase (AdoMetDC), essential for the survival of the eukaryotic parasite Trypanosoma brucei responsible for Human African Trypanosomiasis (HAT). The lead compound, 5'-(((Z)-4-amino-2-butenyl)methylamino)-5'-deoxyadenosine (1, also known as MDL 73811, or AbeAdo), has curative efficacy at a low dosage in a hemolymphatic model of HAT but displayed no demonstrable effect in a mouse model of the CNS stage of HAT due to poor blood-brain barrier permeation. Therefore, we prepared and evaluated an extensive set of analogs with modifications in the aminobutenyl side chain, the 5'-amine, the ribose, and the purine fragments. Although we gained valuable structure-activity insights from this comprehensive dataset, we did not gain traction on improving the prospects for CNS penetration while retaining the potent antiparasitic activity and metabolic stability of the lead compound 1.

Biological activities of plant extracts from Ficus elastica and Selaginella vogelli: An antimalarial, antitrypanosomal and cytotoxity evaluation

The cytotoxic, antiplasmodial, and antitrypanosomal activities of two medicinal plants traditionally used in Cameroon were evaluated. Wood of Ficus elastica Roxb. ex Hornem. aerial roots (Moraceae) and Selaginella vogelii Spring (Selaginellaceae) leaves were collected from two different sites in Cameroon. In vitro cell-growth inhibition activities were assessed on methanol extract of plant materials against Plasmodium falciparum strain 3D7 and Trypanosoma brucei brucei, as well as against HeLa human cervical carcinoma cells. Criteria for activity were an IC₅₀ value < 10 μg/mL. The extract of S. vogelii did not significantly reduce the viability of P. falciparum at a concentration of 25 μg/mL but dramatically affected the trypanosome growth with an IC₅₀ of 2.4 μg/mL. In contrast, at the same concentration, the extract of F. elastica exhibited plasmodiacidal activity (IC₅₀ value of 9.5 μg/mL) and trypanocidal (IC₅₀ value of 0.9 μg/mL) activity. Both extracts presented low cytotoxic effects on HeLa cancer cell line. These results indicate that the selected medicinal plants could be further investigated for identifying compounds that may be responsible for the observed activities and that may represent new leads in parasitical drug discovery.

Pollen extracts and constituent sugars increase growth of a trypanosomatid parasite of bumble bees

Phytochemicals produced by plants, including at flowers, function in protection against plant diseases, and have a long history of use against trypanosomatid infection. Floral nectar and pollen, the sole food sources for many species of insect pollinators, contain phytochemicals that have been shown to reduce trypanosomatid infection in bumble and honey bees when fed as isolated compounds. Nectar and pollen, however, consist of phytochemical mixtures, which can have greater antimicrobial activity than do single compounds. This study tested the hypothesis that pollen extracts would inhibit parasite growth. Extracts of six different pollens were tested for direct inhibitory activity against cell cultures of the bumble bee trypanosomatid gut parasite Crithidia bombi. Surprisingly, pollen extracts increased parasite growth rather than inhibiting it. Pollen extracts contained high concentrations of sugars, mainly the monosaccharides glucose and fructose. Experimental manipulations of growth media showed that supplemental monosaccharides (glucose and fructose) increased maximum cell density, while a common floral phytochemical (caffeic acid) with inhibitory activity against other trypanosomatids had only weak inhibitory effects on Crithidia bombi. These results indicate that, although pollen is essential for bees and other pollinators, pollen may promote growth of intestinal parasites that are uninhibited by pollen phytochemicals and, as a result, can benefit from the nutrients that pollen provides.

Antitrypanosomal activity and evaluation of the mechanism of action of dehydrodieugenol isolated from Nectandra leucantha (Lauraceae) and its methylated derivative against Trypanosoma cruzi

BACKGROUND

From a previous screening of Brazilian biodiversity for antiprotozoal activity, the hexane extract from leaves of Nectandra leucantha (Nees & Mart.) (Lauraceae) demonstrated activity against Trypanosoma cruzi. Chromatographic separation of this extract afforded bioactive dehydrodieugenol (1). Furthermore, methylated derivative 2 (dehydrodieugenol dimethyl ether) was prepared and also tested against T. cruzi.

PURPOSE

To examine the therapeutical potential of compounds 1 and 2 against T. cruzi as well as to elucidate the mechanism of action of bioactive compound 1 against T. cruzi.

METHODS/STUDY DESIGN

Crude hexane extract from leaves was subjected to chromatographic steps to afford bioactive compound 1. In order to analyze the effect of additional methyl group in the antiparasitic activity of 1, derivative 2 was prepared (both are no pan-assay interference compounds - PAINS). These compounds were evaluated in vitro against T. cruzi (trypomastigote and amastigote forms) and analyzed for the potential effect in host cells through the production of nitric oxide and reactive oxygen species. Finally, the plasma membrane effect of the most potent compound 1 was investigated in T. cruzi trypomastigotes.

RESULTS

Compounds 1 and 2 displayed activity against amastigotes of T. cruzi. Although both compounds promoted activity against intracellular amastigotes, the production of nitric oxide and reactive oxygen species of host cells were unaltered, suggesting an antiparasitic activity other than host cell activation. Considering 1 the most effective compound against T. cruzi, the interference in the plasma membrane of the trypomastigotes was investigated using the fluorescent probe SYTOX^® Green. After a short-term incubation, the fluidity and integrity of the plasma membrane was completely altered, suggesting it as a primary target for compound 1 in T. cruzi.

CONCLUSION

Compounds 1 and 2 selectively eliminated the intracellular parasites without host cell activation and could be important scaffolds for the search of new hit compounds.

In vivo ameliorative effects of methanol leaf extract of Lawsonia inermis Linn on experimental Trypanosoma congolense infection in Wistar rats

The aim of this study was to investigate the ameliorative effect of Lawsonia inermis Linn used traditionally against trypanosomosis. Twenty-five adult Wistar rats of both sex were individually infected intraperitoneally (IP) with 10⁶Trypanosoma congolense per ml of blood. Following establishment of infection, the rats were randomly divided into five groups of 5 rats each. Rats in groups I, II, and III were treated with 125, 250 and 500 mg/kg of the extract, respectively, while rats in groups IV and V were treated with 3.5 mg/kg and 2 ml/kg of diminazene aceturate (DM) once and physiological buffered saline, respectively. All treatments except DM were given orally for 7 days IP. The antitrypanosomal effect of the plant was assessed by observing the level of parasitaemia daily, packed cell volume (PCV) weekly, erythrocyte osmotic fragility (EOF) and malondialdehyde (MDA) concentration on day 21. Phytochemical screening of the extract revealed the presence of alkaloids, carbohydrates, triterpenes, steroids, cardiac glycosides, saponins, tannins and flavonoids. The extract significantly (P < 0.05) reduced levels of parasitaemia at 250 mg/kg. PCV was higher (P > 0.05) in extract treated groups but significantly higher (P < 0.05) in group II at week 2 when compared to group V. Rats in group II had significantly lower values of EOF and MDA when compared with groups IV and V. Thus, the leaf of L. inermis has in addition to an antitrypanosomal effect against T. congolense in rats, an attenuating effect on the trypanosomosis pathology probably mediated via protection of the erythrocyte membrane against trypanosome-induced oxidative damage to the erythrocytes.

Synthesis of novel amide and urea derivatives of thiazol-2-ethylamines and their activity against Trypanosoma brucei rhodesiense

2-(2-Benzamido)ethyl-4-phenylthiazole (1) was one of 1035 molecules (grouped into 115 distinct scaffolds) found to be inhibitory to Trypanosoma brucei, the pathogen causing human African trypanosomiasis, at concentrations below 3.6μM and non-toxic to mammalian (Huh7) cells in a phenotypic high-throughput screen of a 700,000 compound library performed by the Genomics Institute of the Novartis Research Foundation (GNF). Compound 1 and 72 analogues were synthesized in this lab by one of two general pathways. These plus 10 commercially available analogues were tested against T. brucei rhodesiense STIB900 and L6 rat myoblast cells (for cytotoxicity) in vitro. Forty-four derivatives were more potent than 1, including eight with IC50 values below 100nM. The most potent and most selective for the parasite was the urea analogue 2-(2-piperidin-1-ylamido)ethyl-4-(3-fluorophenyl)thiazole (70, IC50=9nM, SI>18,000). None of 33 compounds tested were able to cure mice infected with the parasite; however, seven compounds caused temporary reductions of parasitemia (⩾97%) but with subsequent relapses. The lack of in vivo efficacy was at least partially due to their poor metabolic stability, as demonstrated by the short half-lives of 15 analogues against mouse and human liver microsomes.

New cycloartane saponin and monoterpenoid glucoindole alkaloids from Mussaenda luteola

A new cycloartane-type saponin with unusual hydroxylation at C-17 and a unique side chain, 9 (R), 19, 22 (S), 24 (R) bicyclolanost-3β, 12α, 16β, 17α tetrol-25-one 3-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside (1) and two new monoterpenoid glucoindole alkaloids, 10-methoxy pumiloside (2) and the previously chemically synthesized, 10-methoxy strictosidine (3) along with other five known compounds, 7α-morroniside (4), 7-epi-loganin (5), (7β)-7-O-methylmorroniside (6), 5(S)-5-carboxystrictisidine (7) and apigenin-7-O-neohesperidoside (8) were isolated from the aerial parts of Mussaenda luteola (Rubiaceae). The structural elucidation of the isolates was accomplished by extensive (1D and 2D NMR) spectroscopic data analysis and HR-ESI-MS. Compounds 4-8 were reported for the first time from the genus Mussaenda. Interestingly, this is the first report for the occurrence of the monoterpenoid glucoindole-type alkaloids in the genus which might be useful for the chemotaxonomic evaluation of the genus Mussaenda. All isolates were evaluated for their antiprotozoal activities. Compound 7 showed good antitrypanosomal activity with IC50 and IC90 values of 13.7 and 16.6 μM compared to IC50 and IC90 values of 13.06 and 28.99 μM for the positive control DFMO, difluoromethylornithine.

Potent antitrypanosomal triterpenoid saponins from Mussaenda luteola

Five new triterpenoid saponins, heinsiagenin A 3-O-[α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosyl-(1→2)]-β-d-glucopyranoside (1), heinsiagenin A 3-O-[α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosyl-(1→2)]-[β-d-glucopyranosyl-(1→4)]-β-d-glucopyranoside (2), 2α-hydroxyheinsiagenin A 3-O-[α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosyl-(1→2)]-β-d-glucopyranoside (3), 2α-hydroxyheinsiagenin A 3-O-[β-d-glucopyranosyl-(1→2)]-[β-d-glucopyranosyl-(1→4)]-β-d-glucopyranoside (4) and N-(2S, 3R, 4R-3-methyl-4-pentanolid-2-yl)-18-hydroxylanosta-8 (9), 22E, 24E-trien-27-amide-3-O-[α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosyl-(1→2)]-[β-d-glucopyranosyl-(1→4)]-β-d-glucopyranoside (5) were isolated from the aerial parts of Mussaenda luteola Delile (Rubiaceae). Structural elucidation was based on the analysis of spectroscopic data (1D and 2D NMR) and HR-ESI-MS. Compound 1 showed potent antitrypanosomal activity with an IC50 value of 8.80μM. Compounds 2-4 showed highly potent antitrypanosomal activity with IC50 values ranging between (2.57-2.84μM) and IC90 values ranging between (3.36-4.35μM), which are 5 fold greater than the positive control DFMO (IC50 and IC90 values of 13.06 and 28.99μM, respectively). Compounds 1 and 2 showed moderate affinity to μ-opioid receptors with Ki values of 9.936μM and 0.872μM, respectively compared to a Ki value of 1.958nM for the positive control, naloxone HCl.

Synthesis, antileishmanial and antitrypanosomal activities of N-substituted tetrahydro-β-carbolines

A series of N-substituted tetrahydro-β-carbolines were synthesized and screened for antileishmanial activity through an in vitro assay that involves promastigotes and axenic amastigotes of Leishmania donovani, the causative agent for visceral leishmaniasis. The thiophen-2-yl analogs 9b and 11f and naphthyl analog 11h were found to show significant activity against promastigotes with IC50 values of 12.7, 9.1 and 22.1 μM, respectively. Analogs 9b and 11h were also effective against axenic amastigotes with IC50 values of 62.8 and 87.6 μM, respectively. The antileishmanial activity of analogs was then tested in human macrophage cell line infected with L. donovani amastigotes and 2-naphthyl linked analog 11h was found to be effective with IC50 value of 28.3 μM. Several analogs also displayed antitrypanosomal activity against Trypanosoma brucei, the causative agent for human African trypanosomiasis. Compounds 11e, 11f and 11h were more effective than others with IC50 values of 1.0, 8.9 and 10.2 μM, respectively. All synthesized analogs were not cytotoxic towards mammalian cell lines including Vero (monkey kidney fibroblasts), HEPG2 (human hepatoma cells), LLC-PK1 (pig kidney epithelial cells) and THP-1 (human macrophages).

Antiprotozoal activity of dicationic 3,5-diphenylisoxazoles, their prodrugs and aza-analogues

Fifty novel prodrugs and aza-analogues of 3,5-bis(4-amidinophenyl)isoxazole and its derivatives were prepared. Eighteen of the 24 aza-analogues exhibited IC₅₀ values below 25 nM against Trypanosoma brucei rhodesiense or Plasmodium falciparum. Six compounds had antitrypanosomal IC₅₀ values below 10 nM. Twelve analogues showed similar antiplasmodial activities, including three with sub-nanomolar potencies. Forty-four diamidines (including 16 aza-analogues) and the 26 prodrugs were evaluated for efficacy in mice infected with T. b. rhodesiense STIB900. Six diamidines cured 4/4 mice at daily 5 mg/kg intraperitoneal doses for 4 days, giving results far superior to pentamidine and furamidine. One prodrug attained 3/4 cures at daily 25 mg/kg oral doses for 4 days.