Antileishmanial Screening, Cytotoxicity, and Chemical Composition of Essential Oils: A Special Focus on Piper callosum Essential Oil.

Leishmania amazonensis is the etiological agent of tegumentary leishmaniasis, a disease characterized by the emergence of cutaneous and mucocutaneous ulcerated lesions that can evolve into severe destruction of skin tissue. Treatment of the disease is often accompanied by high toxicity and variable efficacy. Essential oils stand out for having diverse pharmacological properties. Here, we screened a panel of fourteen essential oils for their anti-L. amazonensis activity, cytotoxicity, and chemical profile. Lippia sidoides (LSEO) and Piper callosum (PCEO) oils displayed the best anti-promastigote and anti-amastigote activities with IC50 of 31 and 21 µg/ml, respectively. PCEO was the safest oil with a desirable selectivity index >10. In addition, PCEO showed no cytotoxicity against the VERO line and erythrocytes. PCEO-treated amastigotes displayed mitochondrial membrane depolarization and high levels of intracellular ROS. Safrole (54.72 %) was the main component of PCEO. The results described here highlight the use of essential oils to combat tegumentary leishmaniasis.

Appraisal of anti-protozoan activity of nitroaromatic benzenesulfonamides inhibiting carbonic anhydrases from Trypanosoma cruzi and Leishmania donovani.

Chagas disease and leishmaniasis are neglected tropical disorders caused by the protozoans Trypanosoma cruzi and Leishmania spp. Carbonic anhydrases (CAs, EC 4.2.1.1) from these protozoans (α-TcCA and ß-LdcCA) have been validated as promising targets for chemotherapic interventions. Many anti-protozoan agents, such as nitroimidazoles, nifurtimox, and benznidazole possess a nitro aromatic group in their structure which is crucial for their activity. As a continuation of our previous work on N-nitrosulfonamides as anti-protozoan agents, we investigated benzenesulfonamides bearing a nitro aromatic moiety against TcCA and LdcCA, observing selective inhibitions over human off-target CAs. Selected derivatives were assessed in vitro in different developmental stages of T. cruzi and Leishmania spp. A lack of significant growth inhibition has been found, which has been connected to the low permeability of this class of derivatives through cell membranes. Further strategies necessarily need to be designed for targeting Chagas disease and leishmaniasis with nitro-containing CA inhibitors.

Leishmania infantum arginase: biochemical characterization and inhibition by naturally occurring phenolic substances.

Inhibition of Leishmania arginase leads to a decrease in parasite growth and infectivity and thus represents an attractive therapeutic strategy. We evaluated the inhibitory potential of selected naturally occurring phenolic substances on Leishmania infantum arginase (ARGLi) and investigated their antileishmanial activity in vivo. ARGLi exhibited a Vmax of 0.28 ± 0.016 mM/min and a Km of 5.1 ± 1.1 mM for L-arginine. The phenylpropanoids rosmarinic acid and caffeic acid (100 µM) showed percentages of inhibition of 71.48 ± 0.85% and 56.98 ± 5.51%, respectively. Moreover, rosmarinic acid and caffeic acid displayed the greatest effects against L. infantum with IC50 values of 57.3 ± 2.65 and 60.8 ± 11 µM for promastigotes, and 7.9 ± 1.7 and 21.9 ± 5.0 µM for intracellular amastigotes, respectively. Only caffeic acid significantly increased nitric oxide production by infected macrophages. Altogether, our results broaden the current spectrum of known arginase inhibitors and revealed promising drug candidates for the therapy of visceral leishmaniasis.

Carbonic anhydrases from Trypanosoma and Leishmania as anti-protozoan drug targets.

Trypanosoma cruzi and Leishmania spp. are protozoa of the Trypanosomatidae family, being the etiological agents of two widespread parasitic diseases, Chagas disease and leishmaniasis, respectively. Both parasites are the focus of worldwide research with the aim to find effective and less toxic drugs than the few ones available so far, and for controlling the spread of the diseases. Carbonic anhydrases (CAs, EC 4.2.1.1) belonging to the α- and ß-class were recently identified in these protozoans and several studies suggested that they could be new targets for drug development. Sulfonamide, thiol and hydroxamate inhibitors effectively inhibited the α-CA from T. cruzi (TcCA) and the ß-CA from L. donovani chagasi (LdccCA) in vitro, and some of them also showed in vivo efficacy in inhibiting the growth of the parasites in animal models of Chagas disease and leishmaniasis. As few therapeutic options are presently available for these orphan diseases, protozoan CA inhibition may represent a novel strategy to address this stringent health problem.

Cytotoxicity and anti-Leishmania amazonensis activity of Citrus sinensis leaf extracts.

CONTEXT: Leishmania amazonensis is the main agent of diffuse cutaneous leishmaniasis, a disease characterized by lesional polymorphism and the commitment of skin surface. Previous reports demonstrated that the Citrus genus possess antimicrobial activity. OBJECTIVE: This study evaluated the anti-L. amazonensis activity of Citrus sinensis (L.) Osbeck (Rutaceae) extracts. MATERIALS AND METHODS: Citrus sinensis dried leaves were subjected to maceration with hexane (CH), ethyl acetate (CEA), dichloromethane/ethanol (CD/Et - 1:1) or ethanol/water (CEt/W - 7:3). Leishmania amazonensis promastigotes were treated with C. sinensis extracts (1-525 µg/mL) for 120 h at 27 °C. Ultrastructure alterations of treated parasites were evaluated by transmission electron microscopy. Cytotoxicity of the extracts was assessed on RAW 264.7 and J774.G8 macrophages after 48-h treatment at 37 °C using the tetrazolium assay. In addition, Leishmania-infected macrophages were treated with CH and CD/Et (10-80 µg/mL). RESULTS: CH, CD/Et and CEA displayed antileishmanial activity with 50% inhibitory activity (IC50) of 25.91 ± 4.87, 54.23 ± 3.78 and 62.74 ± 5.04 µg/mL, respectively. Parasites treated with CD/Et (131.2 µg/mL) presented severe alterations including mitochondrial swelling, lipid body formation and intense cytoplasmic vacuolization. CH and CD/Et demonstrated cytotoxic effects similar to that of amphotericin B in the anti-amastigote assays (SI of 2.16, 1.98 and 1.35, respectively). Triterpene amyrins were the main substances in CH and CD/Et extracts. In addition, 80 µg/mL of CD/Et reduced the number of intracellular amastigotes and the percentage of infected macrophages in 63% and 36%, respectively. CONCLUSION: The results presented here highlight C. sinensis as a promising source of antileishmanial agents.

Extracellular peptidases from Deinococcus radiodurans.

The extremophile Deinococcus radiodurans wild type R1 produces peptidases (metallo- and serine-) in TGY medium and in the media supplemented with human hair (HMY) and chicken feathers (FMY). Enzymatic screening on agar plates revealed peptidase activity. In TGY medium metallopeptidases were detected corresponding to a molecular mass range of 300-85 kDa (gelatinases); 280-130 (caseinases) and a 300 and a 170 kDa (keratinases); and a gelatinolytic serine peptidase (75 kDa). In HMY medium after 144 h, D. radiodurans produced keratinase (290 U/ml), gelatinase (619 U/ml) and sulfite (26 µg/ml). TGY medium produced higher proteolytic activity: 950 U/ml of gelatinolytic (24 h); 470 U/ml of keratinolytic (24 h) and 110 U/ml of caseinolytic (72 h). In the FMY medium, we found gelatinolytic (317 U/ml), keratinolytic (43 U/ml) and caseinolytic (85 U/ml) activities. The sulfite had a maximum release at 48 h (8.1 µg/ml). Enzymography analysis revealed that the keratinases degraded keratin after 24 h of reaction. The addition of sodium sulfite (1.0 %) improved the keratin degradation. Environmental Scanning Electron microscopy revealed alterations such as damage and holes in the hair fiber cuticle after D. radiodurans growth. This work presents for the first time D. radiodurans as a new keratinolytic microorganism.

Natural Products: Insights into Leishmaniasis Inflammatory Response.

Leishmaniasis is a vector-borne disease that affects several populations worldwide, against which there are no vaccines available and the chemotherapy is highly toxic. Depending on the species causing the infection, the disease is characterized by commitment of tissues, including the skin, mucous membranes, and internal organs. Despite the relevance of host inflammatory mediators on parasite burden control, Leishmania and host immune cells interaction may generate an exacerbated proinflammatory response that plays an important role in the development of leishmaniasis clinical manifestations. Plant-derived natural products have been recognized as bioactive agents with several properties, including anti-protozoal and anti-inflammatory activities. The present review focuses on the antileishmanial activity of plant-derived natural products that are able to modulate the inflammatory response in vitro and in vivo. The capability of crude extracts and some isolated substances in promoting an anti-inflammatory response during Leishmania infection may be used as part of an effective strategy to fight the disease.

In vitro cytocidal effects of the essential oil from Croton cajucara (red sacaca) and its major constituent 7- hydroxycalamenene against Leishmania chagasi.

BACKGROUND: Visceral leishmaniasis is the most serious form of leishmaniasis and can be lethal if left untreated. Currently available treatments for these parasitic diseases are frequently associated to severe side effects. The leaves of Croton cajucara are used as an infusion in popular medicine to combat several diseases. Previous studies have demonstrated that the linalool-rich essential oil from C. cajucara (white sacaca) is extremely efficient against the tegumentary specie Leishmania amazonensis. In this study, we investigated the effects of the 7-hydroxycalamenene-rich essential oil from the leaves of C. cajucara (red sacaca) against Leishmania chagasi, as well as on the interaction of these parasites with host cells. METHODS: Promastigotes were treated with different concentrations of the essential oil for determination of its minimum inhibitory concentration (MIC). In addition, the effects of the essential oil on parasite ultrastructure were analyzed by transmission electron microscopy. To evaluate its efficacy against infected cells, mouse peritoneal macrophages infected with L. chagasi promastigotes were treated with the inhibitory and sub-inhibitory concentrations of the essential oil. RESULTS: The minimum inhibitory concentrations of the essential oil and its purified component 7-hydroxycalamenene against L. chagasi were 250 and 15.6 µg/mL, respectively. Transmission electron microscopy analysis revealed important nuclear and kinetoplastic alterations in L. chagasi promastigotes. Pre-treatment of macrophages and parasites with the essential oil reduced parasite/macrophage interaction by 52.8%, while it increased the production of nitric oxide by L. chagasi-infected macrophages by 80%. CONCLUSION: These results indicate that the 7-hydroxycalamenene-rich essential oil from C. cajucara is a promising source of leishmanicidal compounds.

Anti-Leishmania amazonensis Activity, Cytotoxic Features, and Chemical Profile of Allium sativum (Garlic) Essential Oil.

Human tegumentary leishmaniasis (HTL) is a serious tropical disease caused by Leishmania amazonensis. Developing new leishmanicidal agents can help overcome current treatment challenges, such as drug resistance and toxicity. Essential oils are a source of lipophilic substances with diverse therapeutic properties. This study aimed to determine the anti-L. amazonensis activity, cytotoxicity, and chemical profile of Allium sativum essential oil (ASEO). The effect of ASEO on parasite and mammalian cells viability was evaluated using resazurin and MTT assays, respectively. The oil's effect against intracellular amastigotes was also determined. Transmission electron microscopy was used to assess the ultrastructural changes induced by ASEO. In addition, the chemical constituents of ASEO were identified by gas chromatography-mass spectrometry (GC-MS). The cytotoxic potential was evaluated in vitro and in silico. The oil displayed IC50 of 1.76, 3.46, and 3.77 µg/mL against promastigotes, axenic, and intracellular amastigotes, respectively. Photomicrographs of treated parasites showed plasma membrane disruption, increased lipid bodies, and autophagic-like structures. ASEO chemical profiling revealed 1,2,4,6-tetrathiepane (24.84%) and diallyl disulfide (16.75%) as major components. Computational pharmacokinetics and toxicological analysis of ASEO's major components demonstrated good oral bioavailability and better toxicological endpoints than the reference drugs. Altogether, the results suggest that ASEO could be an alternative drug candidate against HTL.

Electrospun Nanofibers Loaded with Plantago major L. Extract for Potential Use in Cutaneous Wound Healing.

Plantago major L. is a plant available worldwide that has been traditionally used for several medical applications due to its wound healing, anti-inflammatory, and antimicrobial properties. This work aimed to develop and evaluate a nanostructured PCL electrospun dressing with P. major extract encapsulated in nanofibers for applications in wound healing. The extract from leaves was obtained by extraction in a mixture of water:ethanol = 1:1. The freeze-dried extract presented a minimum inhibitory concentration (MIC) for Staphylococcus Aureus susceptible and resistant to methicillin of 5.3 mg/mL, a high antioxidant capacity, but a low content of total flavonoids. Electrospun mats without defects were successfully produced using two P. major extract concentrations based on the MIC value. The extract incorporation in PCL nanofibers was confirmed using FTIR and contact angle measurements. The PCL/P. major extract was evaluated using DSC and TGA demonstrating that the incorporation of the extract decreases the thermal stability of the mats as well as the degree of crystallinity of PCL-based fibers. The P. major extract incorporation on electrospun mats produced a significant swelling degree (more than 400%) and increased the capacity of adsorbing wound exudates and moisture, important characteristics for skin healing. The extract-controlled release evaluated using in vitro study in PBS (pH, 7.4) shows that the P. major extract delivery from the mats occurs in the first 24 h, demonstrating their potential capacity to be used in wound healing.

Enhanced keratinase production by Bacillus subtilis amr using experimental optimization tools to obtain feather protein lysate for industrial applications.

The poultry industry produces millions of tons of feathers waste that can be transformed into valuable products through bioprocess. The study describes the enhanced keratinase and feather hydrolysate production by Bacillus subtilis AMR. The metabolism of each microorganism is unique, so optimization tools are essential to determine the best fermentation parameters to obtain the best process performance. The evaluation of different propagation media indicated the constitutive production of two keratinases of approximately 80 kDa. The combination of Mn2+, Ca2+, and Mg2+ at 0.5 mM improved the keratinolytic activity and feather degradation 1.5-fold, while Cu2+ inhibited the enzymatic activity completely. Replace yeast extract for sucrose increased the feather hydrolysate production three times. The best feather concentration for hydrolysate production was 1.5% with an inoculum of 108 CFU/mL and incubation at 30 °C. None of the inorganic additional nitrogen sources tested increased hydrolysate production, although (NH4)2SO4 and KNO3 improved enzymatic activity. The optimization process improved keratinolytic activity from 205.4 to 418.7 U/mL, the protein concentration reached 10.1 mg/mL from an initial concentration of 3.9 mg/mL, and the feather degradation improved from 70 to 96%. This study characterized keratinase and feather hydrolysate production conditions offering valuable information for exploring and utilizing AMR keratinolytic strain for feather valorization. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-022-03153-y.

The Natural Alkaloid Tryptanthrin Induces Apoptosis-like Death in Leishmania spp.

Leishmaniasis is a vector-borne disease against which there are no approved vaccines, and the treatment is based on highly toxic drugs. The alkaloids consist of a chemical class of natural nitrogen-containing substances with a long history of antileishmanial activity. The present study aimed at determining the antileishmanial activity and in silico pharmacokinetic and toxicological potentials of tryptanthrin alkaloid. The anti-Leishmania amazonensis and anti-L. infantum assays were performed against both promastigotes and intracellular amastigotes. Cellular viability was determined by parasites' ability to grow (promastigotes) or differentiate (amastigotes) after incubation with tryptanthrin. The mechanisms of action were explored by mitochondrion dysfunction and apoptosis-like death evaluation. For the computational pharmacokinetics and toxicological analysis (ADMET), tryptanthrin was submitted to the PreADMET webserver. The alkaloid displayed anti-promastigote activity against L. amazonensis and L. infantum (IC50 = 11 and 8.0 µM, respectively). Tryptanthrin was active against intracellular amastigotes with IC50 values of 75 and 115 µM, respectively. Mitochondrial membrane depolarization was observed in tryptanthrin-treated promastigotes. In addition, parasites undergoing apoptosis-like death were detected after 18 h of exposure. In silico ADMET predictions revealed that tryptanthrin has pharmacokinetic and toxicological properties similar to miltefosine. The results presented herein demonstrate that tryptanthrin is an interesting drug candidate against leishmaniasis.

An innovative spectroscopic approach for qualitative and quantitative evaluation of Mb-CO from myoglobin carbonylation reaction through chemometrics methods.

In this work, an innovative approach using K-means and multivariate curve resolution-purity based algorithm (MCR-Purity) for the evaluation and quantification of carboxymyoglobin (Mb-CO) formation from Deoxy-Myoglobin (Deoxy-Mb) was presented. Through a multilevel multifactor experimental design, samples with different concentrations of Mb-CO were created. The UV-Vis spectra of these samples were submitted to K-means analysis, finding 3 clusters. The mean spectra of the clusters were extracted and it was possible to detect 2 totally differentiable groups through peaks 423 and 434 nm, which are wavelengths related to the Mb-CO and Deoxy-Mb components, respectively. The spectral data were subjected to MCR-Purity analysis. The MCR-Purity result successfully described the analyzed reaction, explaining more than 99.9% of the variance (R2) with a LOF of 1.43%. Then, a predictive model of MbCO was created through the linear relationship between MCR-Purity contributions and known concentrations of MbCO. The performance parameters of the created predictive model were R2CV = 0.98, RMSECV = 0.58 and RPDcv = 7.8 for the training set, and R2P = 0.98, RMSEP = 0.7 and RPDp = 6.8 for the test set. Thus, the predictive model presented an excellent performance considering that the Mb-CO variation is comprised between 0 and 21 µM. Therefore, these results demonstrate that the application of the proposed strategy to the analysis of spectral data presenting overlapping bands is feasible and robust.

Identification of Chalcone Derivatives as Inhibitors of Leishmania infantum Arginase and Promising Antileishmanial Agents.

Arginase catalyzes the hydrolysis of l-arginine into l-ornithine and urea, acting as a key enzyme in the biosynthesis of polyamines. Leishmania growth and survival is dependent on polyamine biosynthesis; therefore, inhibition of Leishmania arginase may be a promising therapeutic strategy. Here, we evaluated a series of thirty-six chalcone derivatives as potential inhibitors of Leishmania infantum arginase (LiARG). In addition, the activity of selected inhibitors against L. infantum parasites was assessed in vitro. Seven compounds exhibited LiARG inhibition above 50% at 100 µM. Among them, compounds LC41, LC39, and LC32 displayed the greatest inhibition values (72.3 ± 0.3%, 71.9 ± 11.6%, and 69.5 ± 7.9%, respectively). Molecular docking studies predicted hydrogen bonds and hydrophobic interactions between the most active chalcones (LC32, LC39, and LC41) and specific residues from LiARG's active site, such as His140, Asn153, His155, and Ala193. Compound LC32 showed the highest activity against L. infantum promastigotes (IC50 of 74.1 ± 10.0 µM), whereas compounds LC39 and LC41 displayed the best results against intracellular amastigotes (IC50 of 55.2 ± 3.8 and 70.4 ± 9.6 µM, respectively). Moreover, compound LC39 showed more selectivity against parasites than host cells (macrophages), with a selectivity index (SI) of 107.1, even greater than that of the reference drug Fungizone®. Computational pharmacokinetic and toxicological evaluations showed high oral bioavailability and low toxicity for the most active compounds. The results presented here support the use of substituted chalcone skeletons as promising LiARG inhibitors and antileishmanial drug candidates.

Bodo sp., a free-living flagellate, expresses divergent proteolytic activities from the closely related parasitic trypanosomatids.

We report the characterization of cell-associated and extracellular peptidases of Bodo sp., a free-living flagellate of the Bodonidae family, order Kinetoplastida, which is considered ancestral to the trypanosomatids. This bodonid isolate is phylogenetically related to Bodo caudatus and Bodo curvifilus. The proteolytic activity profiles of Bodo sp. were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis containing co-polymerized gelatin, casein, hemoglobin, or bovine serum albumin as substrates. The enzymatic complex degraded gelatin better in acidic pH, and under these conditions four proteolytic bands (120, 100, 90, and 75 kDa) were detected in the cellular or extracellular extracts. Two peptidases (250 and 200 kDa) were exclusively detected with the substrate casein. All these enzymes belong to the serine peptidase class, based on inhibition by aprotinin and phenylmethylsulfonyl fluoride. This is the first biochemical characterization of peptidases in a free-living Bodo sp., potentially providing insight into the physiology of these protozoa and the evolutionary importance of peptidases to the order Kinetoplastida as some of these enzymes are important virulence factors in pathogenic trypanosomatids.

Phytomonas serpens: immunological similarities with the human trypanosomatid pathogens.

The present review provides an overview of recent discoveries concerning the immunological similarities between Phytomonas serpens, a tomato parasite, and human trypanosomatid pathogens, with special emphasis on peptidases. Leishmania spp. and Trypanosoma cruzi express peptidases that are well-known virulence factors, named leishmanolysin and cruzipain. P. serpens synthesizes two distinct classes of proteolytic enzymes, metallo- and cysteine-type peptidases, that share common epitopes with leishmanolysin and cruzipain, respectively. The leishmanolysin-like and cruzipain-like molecules from P. serpens participate in several biological processes including cellular growth and adhesion to the salivary glands of Oncopeltus fasciatus, a phytophagous insect experimental model. Since previous reports demonstrated that immunization of mice with P. serpens induced a partial protective immune response against T. cruzi, this plant trypanosomatid may be a suitable candidate for vaccine studies. Moreover, comparative approaches in the Trypanosomatidae family may be useful to understand kinetoplastid biology, biochemistry and evolution.

Peptidases and gp63-like proteins in Herpetomonas megaseliae: possible involvement in the adhesion to the invertebrate host.

The cell-associated and extracellular peptidases of Herpetomonas megaseliae grown in brain-heart infusion and in modified Roitman's complex media were analyzed by measuring peptidase activity on gelatin, casein and hemoglobin in zymograms. Casein was the best proteinaceous substrate for the peptidase detection on both growth conditions. However, no proteolytic activity was detected when hemoglobin was used. Our results showed that cellular cysteine peptidase (115-100, 40 and 35 kDa) and metallopeptidase (70 and 60 kDa) activities were detected on both media in casein and gelatin zymograms. Additionally, the use of casein in the gel revealed a distinct acidic metallopeptidase of 50 kDa when the parasite was cultured in the modified Roitman's complex medium. Irrespective of the culture medium composition, H. megaseliae released metallopeptidases exclusively in the extracellular environment. The presence of gp63-like molecules on the H. megaseliae surface was shown by flow cytometry using anti-gp63 antibody raised against recombinant gp63 from Leishmania mexicana. The pre-treatment of parasites with phospholipase C reduced the number of gp63-positive cells, suggesting that these molecules were glycosylphosphatidylinositol-anchored to the surface. Additionally, the supernatant obtained from phospholipase C-treated cells and probed with anti-cross-reacting determinant confirmed that at least a 52 kDa gp63-like molecule is glycosylphosphatidylinositol-anchored. Furthermore, we assessed a possible function for the gp63-like molecules in H. megaseliae on the interaction with explanted guts of its original host, Megaselia scalaris, and with an experimental model employing Aedes aegypti. Parasites pre-treated with either anti-gp63 antibody or phospholipase C showed a significant reduction in the adhesion to M. scalaris and A. aegypti guts. Similarly, the pre-treatment of the explanted guts with purified gp63 diminished the interaction process. Collectively, these results corroborate the ubiquitous existence of gp63 homologues in insect trypanosomatids and the potential adhesion of these molecules to invertebrate host tissues.

Genome Sequence of KP-Rio/2015, a Novel Klebsiella pneumoniae (Podoviridae) Phage.

Klebsiella pneumoniae is a pathogen frequently associated with antibiotic-resistant nosocomial infections. Here, we describe the genome of KP-Rio/2015, a novel phage of K. pneumoniae belonging to the family Podoviridae.

Influence of the endosymbiont of Blastocrithidia culicis and Crithidia deanei on the glycoconjugate expression and on Aedes aegypti interaction.

Blastocrithidia culicis and Crithidia deanei are trypanosomatid protozoa of insects that normally contain intracellular symbiotic bacteria. The protozoa can be rid of their endosymbionts by antibiotics, producing a cured cell line. Here, we analyzed the glycoconjugate profiles of endosymbiont-harboring and cured strains of B. culicis and C. deanei by Western blotting and flow cytometry analyses using lectins that recognize specifically sialic acid and mannose-like residues. The absence of the endosymbiont increased the intensity of the lectins binding on both trypanosomatids. In addition, wild and cured strain-specific glycoconjugate bands were identified. The role of the surface saccharide residues on the interaction with explanted guts from Aedes aegypti gut was assessed. The aposymbiotic strains of B. culicis and C. deanei presented interaction rates 3.3- and 2.3-fold lower with the insect gut, respectively, when compared with the endosymbiont-bearing strains. The interaction rate of sialidase-treated cells of the wild and cured strains of B. culicis and C. deanei was reduced in at least 90% in relation to the control. The interaction of B. culicis (wild strain) with explanted guts was inhibited in the presence of mucin (56%), fetuin (62%), sialyllactose (64%) and alpha-methyl-D-mannoside (80%), while in C. deanei (wild strain) the inhibition was 53%, 56%, 79% and 34%, respectively. Collectively, our results suggest a possible involvement of sialomolecules and mannose-rich glycoconjugates in the interaction between insect trypanosomatids and the invertebrate host.

Arrabidaea chica hexanic extract induces mitochondrion damage and peptidase inhibition on Leishmania spp.

Currently available leishmaniasis treatments are limited due to severe side effects. Arrabidaea chica is a medicinal plant used in Brazil against several diseases. In this study, we investigated the effects of 5 fractions obtained from the crude hexanic extract of A. chica against Leishmania amazonensis and L. infantum, as well as on the interaction of these parasites with host cells. Promastigotes were treated with several concentrations of the fractions obtained from A. chica for determination of their minimum inhibitory concentration (MIC). In addition, the effect of the most active fraction (B2) on parasite's ultrastructure was analyzed by transmission electron microscopy. To evaluate the inhibitory activity of B2 fraction on Leishmania peptidases, parasites lysates were treated with the inhibitory and subinhibitory concentrations of the B2 fraction. The minimum inhibitory concentration of B2 fraction was 37.2 and 18.6 µg/mL for L. amazonensis and L. infantum, respectively. Important ultrastructural alterations as mitochondrial swelling with loss of matrix content and the presence of vesicles inside this organelle were observed in treated parasites. Moreover, B2 fraction was able to completely inhibit the peptidase activity of promastigotes at pH 5.5. The results presented here further support the use of A. chica as an interesting source of antileishmanial agents.