Antimonial Drugs Research Articles

Patent characteristics for leishmaniasis treatment as a basis for freedom-to-operate analysis

Among the main zoonoses with the highest morbidity burden is leishmaniasis. The parasite of the genus Leishmania is its etiological agent. There are three forms of the disease: cutaneous, mucocutaneous and visceral. Pentavalent antimonial drugs are used for leishmaniasis treatment, however toxic side effects and parasite resistance have been detected. Intellectual Property Rights (IPRs) protect inventions that promote benefits to society, and patents are particularly notable for preserving advancements in biotechnology. To introduce innovative technologies, it is necessary to analyze the elements and processes involved in the development of products that may be protected by IPRs. This process consists of product deconstruction into its elements for an intellectual property analysis to contemplate commercial viability, and to determine strategies to avoid infringing third party rights (Freedom-to-Operate approach). In this project, a sample of patents protecting treatments directed against leishmaniasis were evaluated in order to know their characteristics, and to establish useful elements for Freedom-to-operate strategies. Open access patent databases were used (The Lens, Google patents, Patentscope, among others), and relevant characteristics such as claims, owners, technology protection region, or year of application for protection were determined. The sample obtained includes patents from 1967 to 2023. The majority of patents were found to be located in countries such as Brazil or the United States, and described developments focused on compounds derived from chemical synthesis, polypeptides, extracts, antigens, or structural components of the parasite. There are several patents that have already expired and whose information can be freely used. The Bolar exemption would allow the use of information from these patents for regulatory compliance purposes. This study provides an overview of what has been patented for leishmaniasis treatment, and information on Freedom-to-operate focus.

Susceptibility of Leishmania to novel pentavalent organometallics: Investigating impact on DNA and membrane integrity in antimony(III)-sensitive and -resistant strains.

The aim the present study was to investigate the impact of novel pentavalent organobismuth and organoantimony complexes on membrane integrity and their interaction with DNA, activity against Sb(III)-sensitive and -resistant Leishmania strains and toxicity in mammalian peritoneal macrophages. Ph3M(L)2 type complexes were synthesized, where M = Sb(V) or Bi(V) and L = deprotonated 3-(dimethylamino)benzoic acid or 2-acetylbenzoic acid. Both organobismuth(V) and organoantimony(V) complexes exhibited efficacy at micromolar concentrations against Leishmania amazonensis and L. infantum but only the later ones demonstrated biocompatibility. Ph3Sb(L1)2 and Ph3Bi(L1)2 demonstrated distinct susceptibility profiles compared to inorganic Sb(III)-resistant strains of MRPA-overexpressing L. amazonensis and AQP1-mutated L. guyanensis. These complexes were able to permeate the cell membrane and interact with the Leishmania DNA, suggesting that this effect may contribute to the parasite growth inhibition via apoptosis. Taken altogether, our data substantiate the notion of a distinct mechanism of uptake pathway and action in Leishmania for these organometallic complexes, distinguishing them from the conventional inorganic antimonial drugs.

Chemical Structure Elucidation in the Development of Inorganic Drugs: Evidence from Ru‐, Au‐, As‐, and Sb‐based Medicines

AbstractStructure elucidation plays a critical role across the landscape of medicinal chemistry, including medicinal inorganic chemistry. Herein, we discuss the importance of structure elucidation in drug development and then provide three vignettes that capture key instances of its relevance in the development of biologically active inorganic compounds. In the first, we describe the exploration of the biological activity of the trinuclear Ru compound called ruthenium red and the realization that this activity derived from a dinuclear impurity. We next explore the development of Au‐based antitubercular and antiarthritic drugs, which features a key step whereby ligands were discovered to bind to Au through S atoms. The third exposition traces the development of As‐based antiparasitic drugs, a key step of which was the realization that the reaction of arsenic acid and aniline does not produce an anilide of arsenic acid, as originally thought, but rather an amino arsonic acid. These case studies provide the motivation for an outlook in which the development of Sb‐based antiparasitic drugs is described. Although antileishmanial pentavalent antimonial drugs remain in widespread use to this day, their chemical structures remain unknown.

Supramolecular assemblies from antimony(V) complexes for the treatment of leishmaniasis.

The pentavalent meglumine antimoniate (MA) is still a first-line drug in the treatment of leishmaniasis in several countries. As an attempt to elucidate its mechanism of action and develop new antimonial drugs with improved therapeutic profile, Sb(V) complexes with different ligands, including β-cyclodextrin (β-CD), nucleosides and non-ionic surfactants, have been studied. Interestingly, Sb(V) oxide, MA, its complex with β-CD, Sb(V)-guanosine complex and amphiphilic Sb(V) complexes with N-alkyl-N-methylglucamide, have shown marked tendency to self-assemble in aqueous solutions, forming nanoaggregates, hydrogel or micelle-like nanoparticles. Surprisingly, the resulting assemblies presented in most cases slow dissociation kinetics upon dilution and a strong influence of pH, which impacted on their pharmacokinetic and therapeutic properties against leishmaniasis. To explain this unique property, we raised the hypothesis that multiple pnictogen bonds could contribute to the formation of these assemblies and their kinetic of dissociation. The present article reviews our current knowledge on the structural organization and physicochemical characteristics of Sb-based supramolecular assemblies, as well as their pharmacological properties and potential for treatment of leishmaniasis. This review supports the feasibility of the rational design of new Sb(V) complexes with supramolecular assemblies for the safe and effective treatment of leishmaniasis.

Intralesional Antimonial Drug Treatment for Leishmania braziliensis Cutaneous Leishmaniasis: The Knowns and the Unknowns.

Intralesional Antimonial Drug Treatment for Leishmania braziliensis Cutaneous Leishmaniasis: The Knowns and the Unknowns.

Cutaneous leishmaniasis: Review Article

Leishmaniasis is a protozoal infection caused by a number of different species in the Leishmania genus. Sandflies are the vectors for the transmission of these protozoa to humans. When macrophages are triggered into a leishmanicidal state, a clinical recovery occurs. In particular, the T-helper cell type 1 (Th1) response is responsible for this, and it is also responsible for preventing the recurrence of latent chronic infection. Regardless of the disease's clinical manifestation, antimonial drugs are the treatment of choice. Amphotericin B is the second-best treatment option. This study focuses on the pathology and treatment of cutaneous leishmaniasis.

Cutaneous leishmaniasis in an albino child: a peculiar presentation

Cutaneous leishmaniasis (CL) is the most common form of leishmaniasis. It is characterized by nodulo-ulcerative skin lesions and occasionally nodular, papular/plaque, and/or impetiginous lesions on exposed parts of the body. However, other atypical lesions of CL have been reported worldwide such as lupoid, eczematous, erysipeloid, verrucous, dry, zosteriform, paronychial, sporotrichoid, chancriform, annular and erythematous volcanic ulcers. These non-specific lesions often make the diagnosis challenging due to the large number of differential diagnoses and may lead to a delay in the implementation of CL therapy and therefore a higher risk of lifelong scars and major quality of life issues and stigma. We report a case of an 11-year-old immunocompetent albino child boy that presented with 3 years’ history of persistent multiple asymptomatic, small ulcers and cribriform scars of the forehead. Diagnosis of CL was confirmed by detecting Leishmania parasites in tissue specimens, and treatment by antimony drugs resulted in healing of lesion within one month. This is a novel case of a rare, atypical form of CL, which resulted in delayed diagnosis and management. Clinicians, especially those practicing in CL endemic areas like the Americas and the Mediterranean basin, should consider systematically the diagnosis of CL in front of long-lasting and/or non-specific lesions.

Quantum Dynamics and Bi Metal Force Field Parameterization Yielding Significant Antileishmanial Targets.

Amid emerging drug resistance to metal inhibitors, high toxicity, and onerous drug delivery procedures, the computational design of alternate formulations encompassing functional metal-containing compounds greatly relies on large-scale atomistic simulations. Simulations particularly with Au(I), Ag, Bi(V), and Sb(V) pose a major challenge to elucidate their molecular mechanism due to the absence of force field parameters. This study thus quantum mechanically derives force field parameters of Bi(V) as an extension of the previous experimental study conducted on heteroleptic triorganobismuth(V) biscarboxylates of type [BiR3(O2CR')2]. We have modeled two organo-bismuth(V) carboxylates, which are optimized and parameterized along with the famous pentavalent antimonial drug: meglumine antimoniate using quantum mechanics original Seminarian methods with the SBKJC effective core potential (ECP) basis set. Furthermore, molecular dynamics (MD) simulations of bismuth- and antimony-containing compounds in complex with two enzymes, trypanothione synthetase-amidase (TSA) and trypanothione reductase, are performed to target the (T(SH)2) pathway at multiple points. MD simulations provide novel insights into the binding mechanism of TSA and highlight the role of a single residue Arg569 in modulating the ligand dynamics. Moreover, the presence of an ortho group in a ligand is emphasized to facilitate interactions between Arg569 and the active site residue Arg313 for higher inhibitory activity of TSA. This preliminary generation of parameters specific to bismuth validated by simulations in replica will become a preamble of future computational and experimental research work to open avenues for newer and suitable drug targets.

Models of the putative antimony(V)-diolate motifs in antileishmanial pentavalent antimonial drugs.

The structures of the pentavalent antimonials, small-molecule Sb-containing drugs used to treat the neglected tropical disease leishmaniasis, remain unknown despite their widespread use for over half a century. These drugs are prepared by combination of an Sb(V) precursor and a sugar derivative and proposed structures frequently invoke a cyclic stiborane motif in which a vicinal diolate ligand chelates an Sb(V) center. As a step towards better understanding the structures of the pentavalent antimonial drugs, a series of cyclic organostiboranes spanning the stereochemical space afforded by a vicinal diolate motif has been synthesized and characterized. X-ray crystallography and NMR spectroscopy provide unambiguous characterization of the structures of these model compounds and of the interaction of the diolate with the Sb(V) center. Particularly notable are the systematic trends observed in the NMR spectroscopic signals as a function of the stereochemistry of the diolate. The spectroscopic signatures identified with these model compounds will provide a framework for elucidating the structures of the pentavalent antimonial drugs.

HAS 1: A natural product from soil-isolated Streptomyces species with potent activity against cutaneous leishmaniasis caused by Leishmania tropica.

Cutaneous Leishmaniasis (CL) is a neglected tropical disease, classified by the World Health Organization (WHO) as one of the most unrestrained diseases. The Syrian war and the significant displacement of refugees aggravated the spread of this ailment into several neighboring countries in the Eastern Mediterranean Region (EMR). In Syria, Leishmania tropica is identified as one of the most aggressive and endemic identified species, causing localized or generalized lesions, often chronic or relapsing. Pentavalent antimonial drugs are currently used as first line treatment against CL. Nonetheless, these drugs exhibit several limitations, including the repetitive painful injections, high cost, poor availability, and mainly systemic toxicity. Besides, the emergence of acquired parasitic resistance hinders their potency, stressing the need for new therapies to combat CL. Natural products (NPs) epitomize a valuable source in drug discovery. NPs are secondary metabolites (SMs) produced by plants, sponges, or a wide variety of organisms, including environmental microorganisms. The EMR is characterized by its immense biodiversity, yet it remains a relatively untapped area in drug discovery. NPs of the region were explored over the last 2 decades, but their discoveries lack biogeographical diversity and are limited to the Red Sea. Here, we isolated previously uncultured environmental soil-dwelling Streptomyces sp. HAS1, from Hasbaya region in southeast Lebanon. When fermented in one of our production media named INA, HAS1 produced a crude extract with significant potency against a clinical Leishmania tropica isolate. Using bio-guided fractionation, the bioactive compound was purified and the structure was elucidated by NMR and LC-HRMS. Our findings establish NPs as strong candidates for treating Leishmania tropica and further dwells on the importance of these natural sources to combat microbial infections.

Therapeutic effects of Lucilia sericata larval excretion/secretion products on Leishmania major under in vitro and in vivo conditions

BackgroundLeishmaniasis is a neglected infectious disease caused by protozoa of the genus Leishmania. The disease generally manifests as characteristic skin lesions which require lengthy treatment with antimonial drugs that are often associated with adverse side effects. Therefore, a number of studies have focused on natural compounds as promising drugs for its treatment. This study aimed to evaluate the effects of larval excretion/secretion products (ES) of Lucilia sericata in crude and fractionated forms on Leishmania major, by using in vitro and in vivo models.MethodsThe in vitro experiments involved evaluation of ES on both promastigotes and macrophage-engulfed amastigotes, whereas the in vivo experiments included comparative treatments of skin lesions in L. major-infected mice with Eucerin-formulated ES and Glucantime.ResultsThe half maximal inhibitory concentrations of the crude ES, > 10-kDa ES fraction, < 10-kDa ES fraction, and Glucantime were 38.7 μg/ml, 47.6 μg/ml, 63.3 μg/ml, and 29.1 μg/ml, respectively. Significant differences were observed between percentage viabilities of promastigotes treated with the crude ES and its fractions compared with the negative control (P < 0.0001). The crude ES was more effective on amastigotes than the two ES fractions at 300 μg/ml. The macroscopic measurements revealed that the reduction of lesion size in mice treated with the crude ES followed quicker cascades of healing than that of mice treated with Glucantime and the ES fractions.ConclusionsThe present study showed that the larval ES of L. sericata in both crude and fractionated forms are effective for both intracellular and extracellular forms of L. major. Also, the ES exert both topical and systemic effects on mice experimentally infected with L. major.Graphical abstract

Availability, Toxicology and Medical Significance of Antimony

Antimony has been known and used since ancient times, but its applications have increased significantly during the last two centuries. Aside from its few medical applications, it also has industrial applications, acting as a flame retardant and a catalyst. Geologically, native antimony is rare, and it is mostly found in sulfide ores. The main ore minerals of antimony are antimonite and jamesonite. The extensive mining and use of antimony have led to its introduction into the biosphere, where it can be hazardous, depending on its bioavailability and absorption. Detailed studies exist both from active and abandoned mining sites, and from urban settings, which document the environmental impact of antimony pollution and its impact on human physiology. Despite its evident and pronounced toxicity, it has also been used in some drugs, initially tartar emetics and subsequently antimonials. The latter are used to treat tropical diseases and their therapeutic potential for leishmaniasis means that they will not be soon phased out, despite the fact the antimonial resistance is beginning to be documented. The mechanisms by which antimony is introduced into human cells and subsequently excreted are still the subject of research; their elucidation will enable us to better understand antimony toxicity and, hopefully, to improve the nature and delivery method of antimonial drugs.

Early reduction in PD-L1 expression predicts faster treatment response in human cutaneous leishmaniasis.

Cutaneous leishmaniasis (CL) is caused by Leishmania donovani in Sri Lanka. Pentavalent antimonials (e.g., sodium stibogluconate [SSG]) remain first-line drugs for CL with no new effective treatments emerging. We studied whole blood and lesion transcriptomes from Sri Lankan patients with CL at presentation and during SSG treatment. From lesions but not whole blood, we identified differential expression of immune-related genes, including immune checkpoint molecules, after onset of treatment. Using spatial profiling and RNA-FISH, we confirmed reduced expression of programmed death-ligand 1 (PD-L1) and indoleamine 2,3-dioxygenase 1 (IDO1) proteins on treatment in lesions of a second validation cohort and further demonstrated significantly higher expression of these checkpoint molecules on parasite-infected compared with noninfected lesional CD68+ monocytes and macrophages. Crucially, early reduction in PD-L1 but not IDO1 expression was predictive of rate of clinical cure (HR = 4.88) and occurred in parallel with reduction in parasite load. Our data support a model whereby the initial anti–leishmanial activity of antimonial drugs alleviates checkpoint inhibition on T cells, facilitating immune-drug synergism and clinical cure. Our findings demonstrate that PD-L1 expression can be used as a predictor of rapidity of clinical response to SSG treatment in Sri Lanka and support further evaluation of PD-L1 as a host-directed therapeutic in leishmaniasis.

Potency and Preclinical Evidence of Synergy of Oral Azole Drugs and Miltefosine in an Ex Vivo Model of Leishmania (Viannia) panamensis Infection.

Failure of treatment of cutaneous leishmaniasis with antimonial drugs and miltefosine is frequent. Use of oral combination therapy represents an attractive strategy to increase efficacy of treatment and reduce the risk of drug resistance. We evaluated the potency of posaconazole, itraconazole, voriconazole, and fluconazole and the potential synergy of those demonstrating the highest potency, in combination with miltefosine (HePC), against infection with Leishmania (Viannia) panamensis. Synergistic activity was determined by isobolograms and calculation of the fractional inhibitory concentration index (FICI), based on parasite quantification using an ex vivo model of human peripheral blood mononuclear cells (PBMCs) infected with a luciferase-transfected, antimony and miltefosine sensitive line of L. panamensis. The drug combination and concentrations that displayed synergy were then evaluated for antileishmanial effect in 10 clinical strains of L. panamensis by reverse transcription-quantitative (qRT-PCR) of Leishmania 7SLRNA. High potency was substantiated for posaconazole and itraconazole against sensitive as well as HePC- and antimony-resistant lines of L. panamensis, whereas fluconazole and voriconazole displayed low potency. HePC combined with posaconazole (Poz) demonstrated evidence of synergy at free drug concentrations achieved in plasma during treatment (2 μM HePC plus 4 μM Poz). FICI, based on 70% and 90% reduction of infection, was 0.5 for the sensitive line. The combination of 2 μM HePC plus 4 μM Poz effected a significantly greater reduction of infection by clinical strains of L. panamensis than individual drugs. Orally administrable miltefosine/posaconazole combinations demonstrated synergistic antileishmanial capacity ex vivo against L. panamensis, supporting their potential as a novel therapeutic strategy to improve efficacy and effectiveness of treatment.

Neutrophil Activation: Influence of Antimony Tolerant and Susceptible Clinical Strains of L. (V.) panamensis and Meglumine Antimoniate.

Emerging evidence indicates that innate host response contributes to the therapeutic effect of antimicrobial medications. Recent studies have shown that Leishmania parasites derived by in vitro selection for resistance to pentavalent antimony (SbV) as meglumine antimoniate (MA) modulate the activation of neutrophils. However, whether modulation of neutrophil activation extends to natural resistance to this antileishmanial drug has not been established. We have evaluated the influence of clinical strains of L. (V.) panamensis having intrinsic tolerance/resistance to SbV, on the inflammatory response of neutrophils during ex vivo exposure to MA. Accordingly, neutrophils obtained from healthy donors were infected with clinical strains that are sensitive (n = 10) or intrinsically tolerant/resistant to SbV (n = 10) and exposed to a concentration approximating the maximal plasma concentration (Cmax) of SbV (32 µg/ml). The activation profile of neutrophils was evaluated as the expression of the surface membrane markers CD66b, CD18, and CD62L by flow cytometry, measurement of reactive oxygen species (ROS) by luminometry, and NET formation using Picogreen to measure dsDNA release and quantification of NETs by confocal microscopy. These parameters of activation were analyzed in relation with parasite susceptibility to SbV and exposure to MA. Here, we show that clinical strains presenting intrinsic tolerance/resistance to SbV induced significantly lower ROS production compared to drug-sensitive clinical strains, both in the presence and in the absence of MA. Likewise, analyses of surface membrane activation markers revealed significantly higher expression of CD62L on cells infected with intrinsically SbV tolerant/resistant L. (V.) panamensis than cells infected with drug-sensitive strains. Expression of other activation markers (CD18 and CD66b) and NET formation were similar for neutrophils infected with SbV sensitive and tolerant clinical strains under the conditions evaluated. Exposure to MA broadly impacted the activation of neutrophils, diminishing NET formation and the expression of CD62L, while augmenting ROS production and CD66b expression, independently of the parasite susceptibility phenotype. These results demonstrated that activation of human neutrophils ex vivo is differentially modulated by infection with clinical strains of L. (V.) panamensis having intrinsic tolerance/resistance to SbV compared to sensitive strains, and by exposure to antimonial drug.

Amino-Substituted 3-Aryl- and 3-Heteroarylquinolines as Potential Antileishmanial Agents.

Leishmaniasis, a disease caused by protozoa of the Leishmania species, afflicts roughly 12 million individuals worldwide. Most existing drugs for leishmaniasis are toxic, expensive, difficult to administer, and subject to drug resistance. We report a new class of antileishmanial leads, the 3-arylquinolines, that potently block proliferation of the intramacrophage amastigote form of Leishmania parasites with good selectivity relative to the host macrophages. Early lead 34 was rapidly acting and possessed good potency against L. mexicana (EC50 = 120 nM), 30-fold selectivity for the parasite relative to the macrophage (EC50 = 3.7 μM), and also blocked proliferation of Leishmania donovani parasites resistant to antimonial drugs. Finally, another early lead, 27, which exhibited reasonable in vivo tolerability, impaired disease progression during the dosing period in a murine model of cutaneous leishmaniasis. These results suggest that the arylquinolines provide a fruitful departure point for the development of new antileishmanial drugs.

Metabolite Biomarkers of Leishmania Antimony Resistance.

Leishmania parasites cause leishmaniasis, one of the most epidemiologically important neglected tropical diseases. Leishmania exhibits a high ability of developing drug resistance, and drug resistance is one of the main threats to public health, as it is associated with increased incidence, mortality, and healthcare costs. The antimonial drug is the main historically implemented drug for leishmaniasis. Nevertheless, even though antimony resistance has been widely documented, the mechanisms involved are not completely understood. In this study, we aimed to identify potential metabolite biomarkers of antimony resistance that could improve leishmaniasis treatment. Here, using L. tropica promastigotes as the biological model, we showed that the level of response to antimony can be potentially predicted using 1H-NMR-based metabolomic profiling. Antimony-resistant parasites exhibited differences in metabolite composition at the intracellular and extracellular levels, suggesting that a metabolic remodeling is required to combat the drug. Simple and time-saving exometabolomic analysis can be efficiently used for the differentiation of sensitive and resistant parasites. Our findings suggest that changes in metabolite composition are associated with an optimized response to the osmotic/oxidative stress and a rearrangement of carbon-energy metabolism. The activation of energy metabolism can be linked to the high energy requirement during the antioxidant stress response. We also found that metabolites such as proline and lactate change linearly with the level of resistance to antimony, showing a close relationship with the parasite’s efficiency of drug resistance. A list of potential metabolite biomarkers is described and discussed.

A Molecular Modeling Approach to Identify Potential Antileishmanial Compounds Against the Cell Division Cycle (cdc)-2-Related Kinase 12 (CRK12) Receptor of Leishmania donovani.

The huge burden of leishmaniasis caused by the trypanosomatid protozoan parasite Leishmania is well known. This illness was included in the list of neglected tropical diseases targeted for elimination by the World Health Organization. However, the increasing evidence of resistance to existing antimonial drugs has made the eradication of the disease difficult to achieve, thus warranting the search for new drug targets. We report here studies that used computational methods to identify inhibitors of receptors from natural products. The cell division cycle-2-related kinase 12 (CRK12) receptor is a plausible drug target against Leishmania donovani. This study modelled the 3D molecular structure of the L. donovani CRK12 (LdCRK12) and screened for small molecules with potential inhibitory activity from African flora. An integrated library of 7722 African natural product-derived compounds and known inhibitors were screened against the LdCRK12 using AutoDock Vina after performing energy minimization with GROMACS 2018. Four natural products, namely sesamin (NANPDB1649), methyl ellagic acid (NANPDB1406), stylopine (NANPDB2581), and sennecicannabine (NANPDB6446) were found to be potential LdCRK12 inhibitory molecules. The molecular docking studies revealed two compounds NANPDB1406 and NANPDB2581 with binding affinities of −9.5 and −9.2 kcal/mol, respectively, against LdCRK12 which were higher than those of the known inhibitors and drugs, including GSK3186899, amphotericin B, miltefosine, and paromomycin. All the four compounds were predicted to have inhibitory constant (Ki) values ranging from 0.108 to 0.587 μM. NANPDB2581, NANPDB1649 and NANPDB1406 were also predicted as antileishmanial with Pa and Pi values of 0.415 and 0.043, 0.391 and 0.052, and 0.351 and 0.071, respectively. Molecular dynamics simulations coupled with molecular mechanics Poisson–Boltzmann surface area (MM/PBSA) computations reinforced their good binding mechanisms. Most compounds were observed to bind in the ATP binding pocket of the kinase domain. Lys488 was predicted as a key residue critical for ligand binding in the ATP binding pocket of the LdCRK12. The molecules were pharmacologically profiled as druglike with inconsequential toxicity. The identified molecules have scaffolds that could form the backbone for fragment-based drug design of novel leishmanicides but warrant further studies to evaluate their therapeutic potential.

Multivariate Optimization Applied to the Synthesis of Meglumine Antimoniate with Low Levels of Trivalent Antimony

Meglumine antimoniate (MA) is a pentavalent antimony (SbV) drug recommended for the treatment of leishmaniasis. It is known that the trivalent antimony (SbIII) present as a residue in MA contributes to the drug side effects. In this article, multivariate optimization was used in the synthesis of MA in order to obtain a drug with low levels of SbIII. Four variables (source of antimony, temperature, water volume and pH) were preliminarily evaluated by 24-1 fractional factorial design. Central composite design (CCD) was used to determine the optimal synthesis conditions, using two different sources of SbV and the significant variables selected in a fractional factorial design. Response surface methodology obtained by CCD provided a model with non-significant regression (p = 0.05) for the synthetic route via KSb(OH)6. On the other hand, synthetic route via SbCl5 reached minimum value of SbIII content of 0.172% and significant regression, and it was selected for further evaluations. The analysis of MA formulations synthesized with SbCl5 under optimized conditions revealed the efficiency of multivariate optimization to reduce SbIII content. In addition, the monitoring of some physicochemical parameters of these formulations maintained at 40 ºC for 90 days, showed that stability was not altered at 95% confidence level.

In Vitro Antileishmanial Activities of Olea europaea, Kigelia africana, Terminalia mollis, Croton Macrostachyus and Bridella micrantha, Kenyan Medicinal Plants

Leishmaniasis is a major public health problem globally. Visceral leishmaniasis is known to be fatal if left untreated, while cutaneous leishmaniasis is the most neglected. The first-line treatment of leishmaniasis is based on pentavalent antimonial drugs which are expensive, requiring inpatient treatment and toxic. The Plants containing active compounds against other protozoan diseases may offer alternatives against leishmania parasites. This study determined the in vitro antileishmanial activity of Olea europaea, Kigelia africana, Terminalia mollis, Croton macrostachyus and Bridella micrantha extracts. The plant samples were dried, pulverized into fine powders and extracted using ethanol at the Center for Traditional Medicine and Drugs Research, KEMRI. The in vitro assays were carried out at the Leishmania laboratory, Centre for Biotechnology Research and Development, KEMRI. In in- vitro assays the inhibitory concentrations (IC50) and Minimum Inhibition Concentration (MIC) on L. major promastigotes, percentage rates of macrophages infected by amastigotes and cytotoxicity on Vero cells were determined. For each parameter analyzed, differences among treatment groups exposed to different drugs were tested by logistic regression. Results showed that promastogote and amastigote growth inhibition was significantly affected by the crude extracts from the plants (P &lt; 0.05) after 24 hours of exposure where the most effective drug was the standard drug (Amphotericin B) while among the crude extracts of the herbal drugs, T. mollis was the most effective against amastigote followed by C. macrostachyus while O. europaea was the least effective. Mammalian cell viability was significantly affected by the various test compounds (P &lt; 0.05) after 24 hours exposure where % cell viability of herbal drugs, B. microstachyus, O. africana resulted to the most toxic effects by reducing the % cell viability to less than 50%. The study recommends the use of T. mollis in management of leishmaniasis in areas they occur. Further analysis of the active compounds that that affect efficacy of the plant extracts is advised.