Trypanosoma cruzi: Activity of essential oils from Achillea millefolium L., Syzygium aromaticum L. and Ocimum basilicum L. on epimastigotes and trypomastigotes

In Situ Preparation of Dehydrodieugenol-Loaded Silver Nanoparticles and their Antischistosomal Activity

Schistosomiasis is a major neglected disease that imposes a substantial worldwide health burden, affecting approximately 250 million people globally. As praziquantel is the only available drug to treat schistosomiasis, there is a critical need to identify new anthelmintic compounds, particularly from natural sources. To enhance the activity of different natural products, one potential avenue involves its combination with silver nanoparticles (AgNP). Based on this approach, a one-step green method for the in situ preparation of dehydrodieugenol (DHDG) by oxidation coupling reaction using silver and natural eugenol is presented. AgNP formation was confirmed by UV-Vis spectroscopy due to the appearance of the surface plasmon resonance (SPR) band at 430 nm which is characteristic of silver nanoparticles. The nanoparticles were spherical with sizes in the range of 40 to 50 nm. Bioassays demonstrated that the silver nanoparticles loaded with DHDG exhibited significant anthelmintic activity against Schistosoma mansoni adult worms without toxicity to mammalian cells and an in vivo animal model (Caenorhabditis elegans), contributing to the development of new prototypes based on natural products for the treatment of schistosomiasis.

Lupeol Acetate and α-Amyrin Terpenes Activity against Trypanosoma cruzi: Insights into Toxicity and Potential Mechanisms of Action

BACKGROUND

Chagas disease is a potentially fatal disease caused by the parasite Trypanosoma cruzi. There is growing scientific interest in finding new and better therapeutic alternatives for this disease's treatment.

METHODS

A total of 81 terpene compounds with potential trypanocidal activity were screened and found to have potential T. cruzi cysteine synthase (TcCS) inhibition using molecular docking, molecular dynamics, ADME and PAIN property analyses and in vitro susceptibility assays.

RESULTS

Molecular docking analyses revealed energy ranges from -10.5 to -4.9 kcal/mol in the 81 tested compounds, where pentacyclic triterpenes were the best. Six compounds were selected to assess the stability of the TcCS-ligand complexes, of which lupeol acetate (ACLUPE) and α-amyrin (AMIR) exhibited the highest stability during 200 ns of molecular dynamics analysis. Such stability was primarily due to their hydrophobic interactions with the amino acids located in the enzyme's active site. In addition, ACLUPE and AMIR exhibited lipophilic characteristics, low intestinal absorption and no structural interferences or toxicity. Finally, selective index for ACLUPE was >5.94, with moderate potency in the trypomastigote stage (EC₅₀ = 15.82 ± 3.7 μg/mL). AMIR's selective index was >9.36 and it was moderately potent in the amastigote stage (IC₅₀ = 9.08 ± 23.85 μg/mL).

CONCLUSIONS

The present study proposes a rational approach for exploring lupeol acetate and α-amyrin terpene compounds to design new drugs candidates for Chagas disease.

Eugenol Essential Oil and Nanoemulsion as Antihydatic Agents with Antifibrotic and Immunomodulatory Effects in Cystic Echinococcosis

Conventional scolicidal agents are still unsatisfactory in combating hydatid disease due to their low efficacy and increased drug side effects. Therefore, novel scolicides are required. This study aimed to evaluate the antihydatic and immunomodulatory effects of eugenol essential oil (Eug) and its nanoemulsion (Eug-NE) in cystic echinococcosis (CE). Eug and Eug-NE were administered orally to CE-infected rats and compared to albendazole (ABZ). Hydatid cyst development was assessed based on organ weight and hypertrophy indicators of the infected organs, along with a histopathological and histochemical evaluation of collagen content. The immunomodulatory effects of treatment on CE were evaluated by serum cytokine levels measurement of interferon-γ (IFN-γ) and interleukin (IL)-4 and immunohistochemical (IHC) analysis of signal transducer and activator of transcription 4 (STAT4) and GATA-binding protein 3 (GATA3) markers. Eug-NE was the most effective in reducing the cyst weights, organ weights, and hypertrophy indicators and improving histopathological lesions with reduced collagen content. Eug and Eug-NE significantly increased the IFN-γ levels and decreased the IL-4 levels, while IHC analysis demonstrated a significant reduction in STAT4 and GATA3 expression in all treated groups. Eug and Eug-NE demonstrated antihydatic and preventative effects, with a substantial decrease in liver fibrosis compared to that of ABZ. Besides their promising immunomodulatory effects, their good treatment response suggests their use as alternatives or complementary scolicidal agents in hydatid cyst treatment.

Anti-Candida, docking studies, and in vitro metabolism-mediated cytotoxicity evaluation of Eugenol derivatives

The high morbidity and mortality rates of Candida infections, especially among immunocompromised patients, are related to the increased resistance rate of these species and the limited therapeutic arsenal. In this context, we evaluated the anti-Candida potential and the cytotoxic profile of eugenol derivatives. Anti-Candida activity was evaluated on C. albicans and C. parapsilosis strains by minimum inhibitory concentration (MIC), scanning electron microscopy (SEM), and molecular docking calculations at the site of the enzyme lanosterol-14-α-demethylase active site, responsible for ergosterol formation. The cytotoxic profile was evaluated in HepG2 cells, in the presence and absence of the metabolizing system (S9 system). The results indicated compounds 1b and 1d as the most active ones. The compounds have anti-Candida activity against both strains with MIC ranging from 50 to 100 μg ml^-1 . SEM analyses of 1b and 1d indicated changes in the envelope architecture of both C. albicans and C. parapsilosis like the ones of eugenol and fluconazole, respectively. Docking results of the evaluated compounds indicated a similar binding pattern of fluconazole and posaconazole at the lanosterol-14-α-demethylase binding site. In the presence of the S9 system, compound 1b showed the same cytotoxicity profile as fluconazole (1.08 times) and compound 1d had 1.23 times increase in cytotoxicity. Eugenol and other evaluated compounds showed a significant increase in cytotoxicity. Our results suggest compound 1b as a promising starting point candidate to be used in the design of new anti-Candida agent prototypes.

In Vitro Evaluation of Antiprotozoal Properties, Cytotoxicity Effect and Anticancer Activity of New Essential-Oil Based Phytoncide Mixtures

Protozoa, in both humans and animals, are one of the leading causes of disease. International programmes introduced in many countries have helped reduce the incidence of disease. However, it has recently become increasingly difficult to achieve the goals set for the coming years. One of the main reasons for this, as with other pathogenic organisms, such as bacteria and fungi, is the increasing resistance to current methods of treating and preventing infection. Therefore, new therapies with high efficacy are needed. In the present study, the novel mixtures of essential oils (EOs), clove, garlic, Ceylon cinnamon, and rosemary with organic acids (acetic, propionic, lactic) and metal ions (Cu, Mn, Zn) were tested against five selected model protozoa (Euglena gracilis, Gregarina blattarum, Amoeba proteus, Paramecium caudatum, Pentatrichomonas hominis). The cytotoxicity and potential anticancer activity of the obtained combinations were tested on the human fibroblasts (NHDF) and human cancer cell lines (A549, MCF7, LoVo, HT29). All of the mixtures showed very good antiprotozoal properties. The most efficient were the combination of clove and rosemary essential oils, mixtures of acids, and Mn ions. The LD₅₀ values were in the range of 0.001-0.006% and the LD₁₀₀ values were 0.002-0.008%. All of the tested mixtures did not show cytotoxicity against normal cells, but did show growth inhibition against cancer cell lines. The most cytotoxic against cancer cells were combinations with cinnamon essential oil. Nevertheless, the proposed combinations containing essential oils, organic acids, and metal ions have high antiprotozoal activity, with low toxicity to healthy human cells.

Clove (Syzygium aromaticum) and its Derivatives in Poultry Feed

Production of safe and healthy poultry diets of high profitability is the central aim of poultry men. This safety is achieved by using natural products as growth stimulants. Natural feed additives such as medicinal products derived from herbs and spices are mainly used in the poultry feed industry as appetite and enzyme secretion stimulants. The use of clove (Syzygium aromaticum) and its derivatives has lately received much greater attention as an alternative to traditional antibiotics. The clove exhibited strong antibacterial, antioxidant, anti-septic and anti-inflammatory properties and appetite and digestion stimulants. The clove and its derivatives contain bioactive components, including eugenol, eugenyl acetate, ᵦ-caryophyllene, salicylic acid, ferulic acid, caffeic acid, ellagic acid, kaempferol, methyl amyl ketone, humulene, gallotannic acid, and crategolic acid that have beneficial effects. Eugenol is the main bioactive component present in the clove. The potential advantages of utilizing clove extracts in poultry diets include improved growth performance, egg production and feed conversion ratio, enhanced digestion, and down-regulated disease incidence. From the available literature, clove and its essential oil is one of the beneficial plant extracts to increase growth performance in poultry by improving the intestinal microbiota population. Clove extract contains various molecules (principally eugenol) that have self-biological activities in poultry physiology and metabolism. This chapter includes information on clove and its derivatives in poultry nutrition.

Antiparasitic effects of three floral volatiles on trypanosomatid infection in honey bees

Trypanosomatid gut parasites are common in pollinators and costly for social bees. The recently described honey bee trypanosomatid Lotmaria passim is widespread, abundant, and correlated with colony losses in some studies. The potential for amelioration of infection by antimicrobial plant compounds has been thoroughly studied for closely related trypanosomatids of humans and is an area of active research in bumble bees, but remains relatively unexplored in honey bees. We recently identified several floral volatiles that inhibited growth of L. passim in vitro. Here, we tested the dose-dependent effects of four such compounds on infection, mortality, and food consumption in parasite-inoculated honey bees. We found that diets containing the monoterpenoid carvacrol and the phenylpropanoids cinnamaldehyde and eugenol at >10-fold the inhibitory concentrations for cell cultures reduced infection, with parasite numbers decreased by >90% for carvacrol and cinnamaldehyde and >99% for eugenol; effects of the carvacrol isomer thymol were non-significant. However, both carvacrol and eugenol also reduced bee survival, whereas parasite inoculation did not, indicating costs of phytochemical exposure that could exceed those of infection itself. To our knowledge, this is the first controlled screening of phytochemicals for effects on honey bee trypanosomatid infection, identifying potential treatments for managed bees afflicted with a newly characterized, cosmopolitan intestinal parasite.

In vitro and in silico evaluation of the schistosomicidal activity of eugenol derivatives using biochemical, molecular, and morphological tools

Background

Eugenol shows both antibacterial and antiparasitic activities, suggesting that it might be evaluated as an option for the treatment of praziquantel-resistant schistosome.

Methods

The in vitro activities of three eugenol derivatives (FB1, FB4 and FB9) on adult worms from Schistosoma mansoni were examined by fluorescence and scanning electron microscopy to analyze effects on the excretory system and integument damage, respectively. Biochemical tests with verapamil (a calcium channel antagonist) and ouabain (a Na⁺/K⁺-ATPase pump inhibitor) were used to characterize eugenol derivative interactions with calcium channels and the Na⁺/K⁺-ATPase, while in silico analysis identified potential Na⁺/K⁺-ATPase binding sites.

Results

The compounds showed effective doses (ED₅₀) of 0.324 mM (FB1), 0.167 mM (FB4), and 0.340 mM (FB9). In addition, FB4 (0.322 mM), which showed the lowest ED_50, ED₉₀ and ED₁₀₀ (p < 0.05), caused the most damage to the excretory system and integument, according to both fluorescence and scanning electron microscopy analysis. The death of adult worms was delayed by ouabain treatment plus FB1 (192 versus 72 hours) and FB9 (192 versus 168 hours), but the response to FB4 was the same in the presence or absence of ouabain. Besides, no changes were noted when all of the eugenol derivatives were combined with verapamil. Moreover, FB1 and FB9 inhibited Na⁺/K⁺-ATPase activity according to in silico analysis but FB4 did not show a time-dependent relationship and may act on targets other than the parasite Na+/K+-ATPase.

Conclusion

Eugenol derivatives, mainly FB4 when compared to FB1 and FB9, seem to act more effectively on the integument of adult S. mansoni worms.

Novel Formula of Antiprotozoal Mixtures

Antimicrobial resistance (AMR) is becoming more common in both bacteria and pathogenic protozoa. Therefore, new solutions are being sought as alternatives to currently used agents. There are many new ideas and solutions, especially compounds of natural origin, including essential oils. In the present study, the antiprotozoal activity of a mixture of essential oils (eucalyptus, lavender, cedar and tea tree), organic acids (acetic acid, propionic acid and lactic acid) and metal ions (Cu, Zn, Mn) were tested. As a model, protozoans were selected: Euglena gracilis, Gregarina blattarum, Amoeba proteus, Paramecium caudatum, Pentatrichomonas hominis. The tested concentrations of mixtures were in the range of 0.001–1.5%. The analyses show unexpected, very strong protozoicidal activity of combinations, presenting the synergy of compounds via determination of LD50 and LD100 values. Obtained mixtures showed significantly higher activity against protozoans, compared to chloramphenicol and metronidazole. Most of the analyzed samples show high antiprotozoal activity at very low concentration, in the range of 0.001–0.009%. The most effective combinations for all analyzed protozoans were the cedar essential oil and tea tree essential oil with a mixture of acids and manganese or zinc ions. Innovative combinations of essential oils, organic acids and metal ions are characterized by very high antiprotozoal activity at low doses, which, after further investigation, can be applicable for control of protozoan pathogens.

Natural Products from Annonaceae as Potential Antichagasic Agents

Chagas disease, a neglected tropical disease, is endemic in 21 Latin American countries and particularly prevalent in Brazil. Chagas disease has drawn more attention in recent years due to its expansion into non-endemic areas. The aim of this work was to computationally identify and experimentally validate the natural products from an Annonaceae family as antichagasic agents. Through the ligand-based virtual screening, we identified 57 molecules with potential activity against the epimastigote form of T. cruzi. Then, 16 molecules were analyzed in the in vitro study, of which, six molecules displayed previously unknown antiepimastigote activity. We also evaluated these six molecules for trypanocidal activity. We observed that all six molecules have potential activity against the amastigote form, but no molecules were active against the trypomastigote form. 13-Epicupressic acid seems to be the most promising, as it was predicted as an active compound in the in silico study against the amastigote form of T. cruzi, in addition to having in vitro activity against the epimastigote form.

A terpenoid-rich extract from Clethra fimbriata exhibits anti-Trypanosoma cru zi activity and induces T cell cytokine production

Chagas disease, a worldwide public health concern, is a chronic infection caused by Trypanosoma cruzi. Considering T. cruzi chronic persistence correlates with CD4⁺ and CD8⁺ T cell dysfunction and the safety and efficacy profiles of Benznidazol and Nifurtimox, the two drugs currently used for its etiological treatment, are far from ideal, the search of new trypanocidal treatment options is a highly relevant issue. Therefore, the objective of this work was to evaluate the trypanocidal effect and cytokine production induction of three extracts (hexane, dichloromethane and hydroalcoholic) obtained from Clethra fimbriata, a plant traditionally used as a febrifuge in Colombia. Additionally, the extracts’ major components with the highest trypanocidal activity were determined. It was evidenced C. fimbriata hexane extract exhibited the highest activity capable of inhibiting the three parasite developmental stages with an IC₅₀/EC₅₀ of 153.9 ± 29.5 (epimastigotes), 39.3 ± 7.2 (trypomastigotes), and 45.6 ± 10.5 (amastigotes) μg/mL, presenting a low cytotoxicity in VERO cells with a selectivity index ranging from 6.49 to 25.4. Moreover, this extract induced trypomastigote apoptotic death and inhibited parasite cell infection. The extract also induced IFN-γ and TNF production in CD4⁺ and CD8⁺ T cells, as well as de novo production of the cytotoxic molecules granzyme B and perforin in CD8⁺ T cells from healthy donors. Fatty acids and terpenes represented C. fimbriata key compounds. Thus, the trypanocidal activity and cytokine production induction of the hexane extract may be associated with terpene presence, particularly, triterpenes.

Eugenol carbonate activity against Plasmodium falciparum, Leishmania braziliensis, and Trypanosoma cruzi

Neglected tropical diseases are a major health problem throughout the world, and there are few effective and safe drugs. In this study, we report the design and synthesis of a novel series of carbonates of eugenol using different aliphatic alcohols and N,N-carbonyldiimidazole. Spectroscopic techniques, including ¹ H nuclear magnetic resonance (NMR), ¹³ C NMR, Fourier transform infrared, and high-resolution mass spectrometry, were used to confirm the structures of the synthesized compounds. In vitro and in silico studies of prodrugs of eugenol were performed to determine their antiplasmodial, trypanocidal, and leishmanicidal activities, and also their cytotoxicity. Compounds were highly active against Leishmania braziliensis and Plasmodium falciparum, whereas the activity shown for Trypanosoma cruzi was moderate. Molecular docking was used to determine a possible mode of action of eugenol against the dihydroorotate dehydrogenase of the three parasites (TcDHODH, LbDHODH, and PfDHODH). Notably, the docking results showed that eugenol not only has binding energy similar to that of the natural substrate (-7.2 and -7.1, respectively) but also has interactions with relevant biological residues of PfDHODH. This result indicates that eugenol could act as a substrate for PfDHODH in the pyrimidine biosynthesis pathway of P. falciparum. In conclusion, the combination of certain aliphatic alcohols and eugenol through a carbonate bond could significantly increase the antiparasitic activity of this class of compounds, which merits further studies.

Evaluation of the scolicidal activities of eugenol essential oil and its nanoemulsion against protoscoleces of hydatid cysts

BACKGROUND

Cystic echinococcosis caused by the cestode Echinococcus granulosus remains a serious helminthic zoonosis affecting humans and animals in many endemic developing countries. Surgical intervention is the best management choice, although it is associated with high recurrence rates and serious complications. Also, the commonly used chemotherapeutics exhibited serious side effects. This study aimed to evaluate the protoscolicidal effects of eugenol (Eug) essential oil and its nanoemulsion (Eug-NE) against protoscoleces (PCs) of hydatid cysts in vitro.

METHODS

Eug-NE was prepared and characterized. Their cytotoxicity on macrophages was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. E. granulosus PCs were treated with various concentrations of Eug and Eug-NE at different exposure times. The viability of protoscoleces was evaluated by the eosin exclusion test, and the changes in the morphology of protoscoleces were assessed. Albendazole (ABZ) was used as a positive control.

RESULTS

The cellular cytotoxicity of Eug and Eug-NE on macrophage cells, in minimum and maximum concentrations (0.2 and 1 μl/mL), were nearly negligible ranging from 4.7% to 8.3% and 3.7% to 7.2%, respectively. The results showed highly significant activity of Eug-NE and Eug against hydatid PCs compared to ABZ (P < 0.05). Eug and Eug-NE have similar protoscolicidal effects at all used concentrations. Their highest scolicidal activity (100% mortality rate) was recorded at 1 μl/ml after 30 min incubation (LC50 = 0.298-LC90 = 0.521 and LC50 = 0.309-LC90 = 0.646, respectively). Both formulations showed time- and dose-dependent effects.

CONCLUSIONS

This study suggested the potent scolicidal activities of Eug and Eug-NE as promising alternative scolicidal agents. Future studies are recommended to explore the mechanism of action and treatment response in vivo and clinical settings.

Trypanocidal Activity of Dysphania ambrosioides, Lippia alba, and Tetradenia riparia Essential Oils against Trypanosoma cruzi

Despite the current treatments against Chagas Disease (CD), this vector-borne parasitic disease remains a serious public health concern. In this study, we have explored the in vitro and/or in vivo trypanocidal and cytotoxic activities of the essential oils (EOs) obtained from Dysphania ambrosioides (L.) Mosyakin & Clemants (Amaranthaceae) (DA-EO), Lippia alba (Mill.) N.E. Brown (Verbenaceae) (LA-EO), and Tetradenia riparia (Hochst.) Codd (Lamiaceae) (TR-EO) grown in Brazil Southeast. DA-EO was the most active against the trypomastigote and amastigote forms in vitro; the IC₅₀ values were 8.7 and 12.2 μg mL^-1 , respectively. The EOs displayed moderate toxicity against LLCMK2 cells, but the DA-EO showed high selectivity index (SI) for trypomastigote (SI=33.2) and amastigote (SI=11.7) forms. Treatment with 20 mg/kg DA-EO, LA-EO, or TR-EO for 20 days by intraperitoneal administration reduced parasitemia by 6.36 %, 4.74 %, and 32.68 % on day 7 and by 12.04 %, 27.96 %, and 65.5 % on day 9. These results indicated that DA-EO, LA-EO, and TR-EO have promising trypanocidal potential in vitro, whereas TR-EO has also potential trypanocidal effects in vivo.

Plinia cauliflora (Mart.) Kausel (Jaboticaba) leaf extract: In vitro anti-Trypanosoma cruzi activity, toxicity assessment and phenolic-targeted UPLC-MSE metabolomic analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Plinia cauliflora (Mart.) Kausel, known as Brazilian grape or jaboticaba, is widely used in Brazilian traditional medicine to treat infectious and inflammatory disorders. However, several aspects of its biological potential remain unclear, such as toxicity and effects on pathogenic protozoa.

AIM OF THE STUDY

Investigate the phenolic composition, the in vitro and in silico toxicity profile, and the anti-Trypanosoma cruzi activity of the phenolics-enriched hydromethanolic extract of P. cauliflora leaf.

MATERIAL AND METHODS

Phytochemical analysis was performed ultra-performance liquid chromatography-mass spectrometry (UPLC-MS^E). Mutagenicity, genotoxicity and eukaryotic cytotoxicity was evaluated by Ames test, cytokinesis-block micronucleus and colorimetric assays, respectively, alongside with a computational prediction of the major compound's pharmacokinetics and toxicity. Anti-T. cruzi activity was investigated on T. cruzi bloodstream trypomastigotes.

RESULTS

A total of 14 phenolic compounds were identified, including 11 flavonoids and 2 phenolic acids. No positive response regarding mutagenic potential was detected in Salmonella strains TA97, TA98, TA100, TA102, TA104, both in absence or presence of metabolic activation. The extract induced significant dose-response reduction on nuclear division indexes of HepG2 cells, suggesting cytostatic effects, with no micronuclei induction on cytokinesis-block micronucleus assay. Likewise, it also presented cytotoxic effects, inducing HepG2 and F C3H dose and time dependently cell death through cell membrane damage and more evidently by mitochondrial dysfunction. A dose-response curve of in vitro trypanocidal activity was observed against T. cruzi bloodstream trypomastigotes after 2 and 24 h of exposure. In silico predictions of most abundant compounds' structural alerts, pharmacokinetics and toxicity profile indicates a moderately feasible druglikeness profile and low toxicity for them, which is compatible with in vitro results.

CONCLUSIONS

The present study demonstrated that P. cauliflora leaf extract is a potential source of antiparasitic bioactive compounds, however it presents cytotoxic effects in liver cell lines.

Essential oils from Ocimum basilicum cultivars: analysis of their composition and determination of the effect of the major compounds on Haemonchus contortus eggs

The continuous use of synthetic anthelmintics against gastrointestinal nematodes (GINs) has resulted in the increased resistance, which is why alternative methods are being sought, such as the use of natural products. Plant essential oils (EOs) have been considered as potential products for the control of GINs. However, the chemical composition and, consequently, the biological activity of EOs vary in different plant cultivars. The aim of this study was to evaluate the anthelmintic activity of EOs from cultivars of Ocimum basilicum L. and that of their major constituents against Haemonchus contortus. The EOs from 16 cultivars as well the pure compound linalool, methyl chavicol, citral and eugenol were used in the assessment of the inhibition of H. contortus egg hatch. In addition, the composition of three cultivars was simulated using a combination of the two major compounds from each. The EOs from different cultivars showed mean Inhibition Concentration (IC50) varying from 0.56 to 2.22 mg/mL. The cultivar with the highest egg-hatch inhibition, Napoletano, is constituted mainly of linalool and methyl chavicol. Among the individual compounds tested, citral was the most effective (IC50 0.30 mg/mL). The best combination of compounds was obtained with 11% eugenol plus 64% linalool (IC50 0.44 mg/mL), simulating the Italian Large Leaf (Richters) cultivar. We conclude that different cultivars of O. basilicum show different anthelmintic potential, with cultivars containing linalool and methyl chavicol being the most promising; and that citral or methyl chavicol isolated should also be considered for the development of new anthelmintic formulations.

Essential oils from Syzygium aromaticum and Zingiber officinale, administered alone or in combination with benznidazole, reduce the parasite load in mice orally inoculated with Trypanosoma cruzi II

BACKGROUND

Trypanosoma cruzi is the etiological agent of Chagas disease (CD) or American trypanosomiasis, an important public health problem in Latin America. Benznidazole (BZ), a drug available for its treatment, has limited efficacy and significant side effects. Essential oils (EOs) have demonstrated trypanocidal activity and may constitute a therapeutic alternative. Our aim was to evaluate the efficacy of the EOs of clove (CEO - Syzygium aromaticum) and ginger (GEO - Zingiber officinale), administered alone and in combination with BZ, in Swiss mice infected with T. cruzi.

METHODS

The animals were inoculated with 10,000 blood trypomastigotes of the Y strain of T. cruzi II by gavage and divided into four groups (n = 12 to 15): 1) untreated control (NT); 2) treated with BZ; 3) treated with CEO or GEO; and 4) treated with BZ + CEO or GEO. The treatments consisted of oral administration of 100 mg/kg/day, from the 5th day after parasite inoculation, for 20 consecutive days. All groups were submitted to fresh blood examination (FBE), blood culture (BC), conventional PCR (cPCR) and real-time PCR (qPCR), before and after immunosuppression with cyclophosphamide.

RESULTS

Clove and ginger EOs, administered alone and in combination with BZ, promoted suppression of parasitemia (p < 0.0001), except for the animals treated with CEO alone, which presented a parasitemia curve similar to NT animals. However, there was a decrease in the BC positivity rate (p < 0.05) and parasite load (< 0.0001) in this group. Treatment with GEO alone, on the other hand, besides promoting a decrease in the BC positivity rate (p < 0.05) and parasite load (p < 0.01), this EO also resulted in a decrease in mortality rate (p < 0.05) of treated mice.

CONCLUSIONS

Decreased parasite load, as detected by qPCR, was observed in all treatment groups (BZ, CEO, GEO and BZ + EOs), demonstrating benefits even in the absence of parasitological cure, thus opening perspectives for further studies.

GC-MS Characterization of Antibacterial, Antioxidant, and Antitrypanosomal Activity of Syzygium aromaticum Essential Oil and Eugenol

Syzygium aromaticum has a diversity of biological activities due to the chemical compounds found in its plant products such as total phenolic compounds and flavonoids. The present work describes the chemical analysis and antimicrobial, antioxidant, and antitrypanosomal activity of the essential oil of S. aromaticum. Eugenol (53.23%) as the major compound was verified by gas chromatography-mass spectrometry. S. aromaticum essential oil was more effective against S. aureus (MIC 50 μg/mL) than eugenol (MIC 250 μg/mL). Eugenol presented higher antioxidant activity than S. aromaticum essential oil, with an EC₅₀ of 12.66 and 78.98 µg/mL, respectively. S. aromaticum essential oil and eugenol exhibited Trypanosoma cruzi inhibitory activity, with IC₅₀ of 28.68 ± 1.073 and 31.97 ± 1.061 μg/mL against epimastigotes and IC₅₀ of 64.51 ± 1.658 and 45.73 ± 1.252 μg/mL against intracellular amastigotes, respectively. Both compounds presented low cytotoxicity, with S. aromaticum essential oil displaying 15.5-fold greater selectivity for the parasite than the cells. Nitrite levels in T. cruzi-stimulated cells were reduced by essential oil (47.01%; p = 0.002) and eugenol (48.05%; p = 0.003) treatment. The trypanocidal activity of S. aromaticum essential oil showed that it is reasonable to use it in future research in the search for new therapeutic alternatives for trypanosomiasis.

Preliminary chemical characterization of ethanolic extracts from Colombian plants with promising anti - Trypanosoma cruzi activity

Chagas disease is caused by Trypanosoma cruzi, and it is an important cause of morbidity and mortality in Latin America. There are no vaccines, and the chemotherapy available to treat this infection has serious side effects. In a search for alternative treatments, we determined the in vitro susceptibility of epimastigote and trypomastigote forms of T. cruzi and the cytotoxic effects on peripheral blood mononuclear cells (PBMCs) of ethanolic extracts obtained from six different plant species. The ethanolic extracts of Ageratina vacciniaefolia, Clethra fimbriata and Siparuna sessiliflora showed antiprotozoal activity against epimastigotes and low cytotoxicity in mammalian cells. However, only the ethanolic extract of C. fimbriata showed activity against T. cruzi trypomastigotes, and it had low cytotoxicity in PBMCs. An analysis on the phytochemical composition of C. fimbriata extract showed that its metabolites were primarily represented by two families of compounds: flavonoids and terpenoids. Lastly, we analyzed whether the A. vacciniaefolia, C. fimbriata, or S. sessiliflora ethanolic extracts induced IFN-γ or TNF-α production. Significantly, ethanolic extracts of C. fimbriata induced TNF-α production and S. sessiliflora induced both cytokines. In addition, C. fimbriata and S. sessiliflora induced the simultaneous secretion of IFN-γ and TNF-α in CD8⁺ T cells. The antiprotozoal and immunomodulatory activity of C. fimbriata may be related to the presence of flavonoid and triterpene compounds in the extract. Thus, these findings suggest that C. fimbriata may represent a valuable source of new bioactive compounds for the therapeutic treatment of Chagas disease that combines trypanocidal activity with the capacity to boost the immune response.

Aniba rosaeodora (Var. amazonica Ducke) Essential Oil: Chemical Composition, Antibacterial, Antioxidant and Antitrypanosomal Activity

Aniba rosaeodora is one of the most widely used plants in the perfumery industry, being used as medicinal plant in the Brazilian Amazon. This work aimed to evaluate the chemical composition of A. rosaeodora essential oil and its biological activities. A. rosaeodora essential oil presented linalool (93.60%) as its major compound. The A. rosaeodora essential oil and linalool showed activity against all the bacteria strains tested, standard strains and marine environment bacteria, with the lower minimum inhibitory concentration being observed for S. aureus. An efficient antioxidant activity of A. rosaeodora essential oil and linalool (EC₅₀: 15.46 and 6.78 µg/mL, respectively) was evidenced by the inhibition of the 2,2-azinobis- (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical. The antitrypanosomal activity of A. rosaeodora essential oil and linalool was observed at high concentrations against epimatigote forms (inhibitory concentration for 50% of parasites (IC₅₀): 150.5 ± 1.08 and 198.6 ± 1.12 µg/mL, respectively), and even higher against intracellular amastigotes of T. cruzi (IC₅₀: 911.6 ± 1.15 and 249.6 ± 1.18 µg/mL, respectively). Both A. rosaeodora essential oil and linalool did not exhibit a cytotoxic effect in BALB/c peritoneal macrophages, and both reduced nitrite levels in unstimulated cells revealing a potential effect in NO production. These data revealed the pharmacological potential of A. rosaeodora essential oil and linalool, encouraging further studies.

Trypanocidal Essential Oils: A Review

Trypanosomiases are diseases caused by parasitic protozoan trypanosomes of the genus Trypanosoma. In humans, this includes Chagas disease and African trypanosomiasis. There are few therapeutic options, and there is low efficacy to clinical treatment. Therefore, the search for new drugs for the trypanosomiasis is urgent. This review describes studies of the trypanocidal properties of essential oils, an important group of natural products widely found in several tropical countries. Seventy-seven plants were selected from literature for the trypanocidal activity of their essential oils. The main chemical constituents and mechanisms of action are also discussed. In vitro and in vivo experimental data show the therapeutic potential of these natural products for the treatment of infections caused by species of Trypanosoma.

Syzygium aromaticum L. (Myrtaceae): Traditional Uses, Bioactive Chemical Constituents, Pharmacological and Toxicological Activities

Herbal medicinal products have been documented as a significant source for discovering new pharmaceutical molecules that have been used to treat serious diseases. Many plant species have been reported to have pharmacological activities attributable to their phytoconstituents such are glycosides, saponins, flavonoids, steroids, tannins, alkaloids, terpenes, etc. Syzygium aromaticum (clove) is a traditional spice that has been used for food preservation and possesses various pharmacological activities. S. aromaticum is rich in many phytochemicals as follows: sesquiterpenes, monoterpenes, hydrocarbon, and phenolic compounds. Eugenyl acetate, eugenol, and β-caryophyllene are the most significant phytochemicals in clove oil. Pharmacologically, S. aromaticum has been examined toward various pathogenic parasites and microorganisms, including pathogenic bacteria, Plasmodium, Babesia, Theileria parasites, Herpes simplex, and hepatitis C viruses. Several reports documented the analgesic, antioxidant, anticancer, antiseptic, anti-depressant, antispasmodic, anti-inflammatory, antiviral, antifungal, and antibacterial activity of eugenol against several pathogenic bacteria including methicillin-resistant Staphylococcus epidermidis and S. aureus. Moreover, eugenol was found to protect against CCl_4-induced hepatotoxicity and showed a potential lethal efficacy against the multiplication of various parasites including Giardia lamblia, Fasciola gigantica, Haemonchus contortus, and Schistosoma mansoni. This review examines the phytochemical composition and biological activities of clove extracts along with clove essential oil and the main active compound, eugenol, and implicates new findings from gas chromatography-mass spectroscopy (GC-MS) analysis.

Teleost antimicrobial peptide hepcidin contributes to host defense of goldfish (Carassius auratus L.) against Trypanosoma carassii

Hepcidin is an antimicrobial peptide and an iron regulatory protein that prevents the release of excess iron in the blood. There is evidence suggesting that teleost hepcidin is a major player in antimicrobial defense against various bacteria species, but little is known regarding the effects of teleost hepcidin in protozoan parasitic infections. We examined the role of hepcidin during the course of infection of goldfish with Trypanosoma carassii. Quantitative real-time PCR was used to determine the expression of hepcidin in goldfish immune organs during the course of T. carassii infection. During the acute phase of the T. carassii infection, the mRNA levels of hepcidin were up-regulated in liver and kidney. In contrast, an up-regulation of hepcidin mRNA expression in spleen was observed during the chronic phase of the infection. Furthermore, a synthetic goldfish hepcidin peptide induced trypanosome lysis in vitro, and parasite surface disruption was confirmed by scanning electron microscopy (SEM) analysis. These results suggest that, in addition to well-characterized direct antibacterial activities, teleost hepcidin also exhibits trypanocidal activity.

Inhibitory effects of Syzygium aromaticum and Camellia sinensis methanolic extracts on the growth of Babesia and Theileria parasites

Currently, chemotherapeutics against piroplasmosis are also associated with toxicity and the emergence of drug-resistant parasites. Therefore, the discovery of new drug compounds is necessary for the effective control of bovine and equine piroplasms. Syzygium aromaticum (clove) and Camellia sinensis (green tea) have several documented medicinal properties. In the present study, the growth-inhibiting effects of S. aromaticum and C. sinensis methanolic extracts were evaluated in vitro and in vivo. The half-maximal inhibitory concentration (IC₅₀) values for methanolic S. aromaticum against Babesia bovis, B. bigemina, B. divergens, B. caballi, and Theileria equi were 109.8 ± 3.8, 8.7 ± 0.09, 76.4 ± 4.5, 19.6 ± 2.2, and 60 ± 7.3 μg/ml, respectively. Methanolic C. sinensis exhibited IC₅₀ values of 114 ± 6.1, 71.3 ± 3.7, 35.9 ± 6.8, 32.7 ± 20.3, and 60.8 ± 7.9 μg/ml against B. bovis, B. bigemina, B. divergens, B. caballi, and T. equi, respectively. The toxicity assay on Madin-Darby bovine kidney (MDBK), mouse embryonic fibroblast (NIH/3T3), and human foreskin fibroblast (HFF) cell lines showed that methanolic S. aromaticum and methanolic C. sinensis affected only the viability of the MDBK cell line with half-maximal effective concentrations (EC₅₀) of 894.7 ± 4.9 and 473.7 ± 7.4 μg/ml, respectively, while the viability of NIH/3T3 and HFF cell lines was not affected even at 1000 μg/ml. In the in vivo experiment, methanolic S. aromaticum and methanolic C. sinensis oral treatments at 150 mg/kg inhibited the growth of Babesia microti in mice by 69.2% and 42.4%, respectively. These findings suggest that methanolic S. aromaticum and methanolic C. sinensis extracts have the potential as alternative remedies for treating piroplasmosis.

Untargeted LC-MS metabolomic studies of Asteraceae species to discover inhibitors of Leishmania major dihydroorotate dehydrogenase

INTRODUCTION

Interesting data about the family Asteraceae as a new source of Leishmania major dihydroorotate dehydrogenase (LmDHODH) inhibitors are presented. This key macromolecular target for parasites causing neglected diseases catalyzes the fourth reaction of the de novo pyrimidine biosynthetic pathway, which takes part in major cell functions, including DNA and RNA biosynthesis.

OBJECTIVES

We aimed to (1) determine LmDHODH inhibitor candidates, revealing the type of chemistry underlying such bioactivity, and (2) predict the inhibitory potential of extracts from new untested plant species, classifying them as active or inactive based on their LC-MS based metabolic fingerprints.

METHODS

Extracts from 150 species were screened for the inhibition of LmDHODH, and untargeted UHPLC-(ESI)-HRMS metabolomic studies were carried out in combination with in silico approaches.

RESULTS

The IC₅₀ values determined for a subset of 59 species ranged from 148 µg mL^-1 to 9.4 mg mL^-1. Dereplication of the metabolic fingerprints allowed the identification of 48 metabolites. A reliable OPLS-DA model (R² > 0.9, Q² > 0.7, RMSE_CV < 0.3) indicated the inhibitor candidates; nine of these metabolites were identified using data from isolated chemical standards, one of which-4,5-di-O-E-caffeoylquinic acid (IC₅₀ 73 µM)-was capable of inhibiting LmDHODH. The predictive OPLS model was also effective, with 60% correct predictions for the test set.

CONCLUSION

Our approach was validated for (1) the discovery of LmDHODH inhibitors or interesting starting points for the optimization of new leishmanicides from Asteraceae species and (2) the prediction of extracts from untested species, classifying them as active or inactive.

Eugenol, a potential schistosomicidal agent with anti-inflammatory and antifibrotic effects against Schistosoma mansoni, induced liver pathology

Introduction

Schistosomiasis is one of the most prevalent parasitic infections in developing countries. Although chemotherapy is one of the main strategies in controlling the disease, it is less effective in reversal of schistosome-induced pathology especially in the chronic and advanced stages of schistosomiasis. New strategies and prospective therapeutic agents with antifibrotic effects are needed. Eugenol has a wide anti-inflammatory effect. In the present study, we investigated the possible antischistosomal effect of eugenol on Schistosoma mansoni.

Materials and methods

The murine model of S. mansoni was established in three groups of adult male Balb-c mice; group I (infected non-treated group) and groups II and III (infected groups) treated orally with eugenol and praziquantel (PZQ), respectively. The expression of the sensitive immunohistochemical marker α-smooth muscle actin (α-SMA) in schistosome-infected tissues was determined. In addition, parasitological, biochemical, and histological parameters that reflect disease severity and morbidity were examined.

Results

Eugenol treatment showed significant reduction in total worm burden by 19.2%; however, the oogram pattern showed no marked difference compared to that of the PZQ group. Yet, eugenol significantly reduced the serum levels of hepatic enzymes: aspartate aminotransferase and alanine aminotransferase. Histopathological examination revealed a significant reduction in both numbers and diameters of hepatic granulomata, which was consistent with reduction in collagen fiber deposition. Additionally, the antifibrotic effect of eugenol was validated by its considerable reduction in the expression of the sensitive marker α-SMA in both eugenol- and PZQ-treated groups.

Conclusion

Although eugenol could not totally eradicate adults of S. mansoni, the significant amelioration of liver enzymes and hepatic fibrosis potentiate eugenol’s role as a promising antifibrotic and a complementary antischistosomal agent.

Active Essential Oils and Their Components in Use against Neglected Diseases and Arboviruses

The term neglected diseases refers to a group of infections caused by various classes of pathogens, including protozoa, viruses, bacteria, and helminths, most often affecting impoverished populations without adequate sanitation living in close contact with infectious vectors and domestic animals. The fact that these diseases were historically not considered priorities for pharmaceutical companies made the available treatments options obsolete, precarious, outdated, and in some cases nonexistent. The use of plants for medicinal, religious, and cosmetic purposes has a history dating back to the emergence of humanity. One of the principal fractions of chemical substances found in plants are essential oils (EOs). EOs consist of a mixture of volatile and hydrophobic secondary metabolites with marked odors, composed primarily of terpenes and phenylpropanoids. They have great commercial value and were widely used in traditional medicine, by phytotherapy practitioners, and in public health services for the treatment of several conditions, including neglected diseases. In addition to the recognized cytoprotective and antioxidative activities of many of these compounds, larvicidal, insecticidal, and antiparasitic activities have been associated with the induction of oxidative stress in parasites, increasing levels of nitric oxide in the infected host, reducing parasite resistance to reactive oxygen species, and increasing lipid peroxidation, ultimately leading to serious damage to cell membranes. The hydrophobicity of these compounds also allows them to cross the membranes of parasites as well as the blood-brain barrier, collaborating in combat at the second stage of several of these infections. Based on these considerations, the aim of this review was to present an update of the potential of EOs, their fractions, and their chemical constituents, against some neglected diseases, including American and African trypanosomiasis, leishmaniasis, and arboviruses, specially dengue.

The Phytochemistry of Cherokee Aromatic Medicinal Plants

Background: Native Americans have had a rich ethnobotanical heritage for treating diseases, ailments, and injuries. Cherokee traditional medicine has provided numerous aromatic and medicinal plants that not only were used by the Cherokee people, but were also adopted for use by European settlers in North America. Methods: The aim of this review was to examine the Cherokee ethnobotanical literature and the published phytochemical investigations on Cherokee medicinal plants and to correlate phytochemical constituents with traditional uses and biological activities. Results: Several Cherokee medicinal plants are still in use today as herbal medicines, including, for example, yarrow (Achillea millefolium), black cohosh (Cimicifuga racemosa), American ginseng (Panax quinquefolius), and blue skullcap (Scutellaria lateriflora). This review presents a summary of the traditional uses, phytochemical constituents, and biological activities of Cherokee aromatic and medicinal plants. Conclusions: The list is not complete, however, as there is still much work needed in phytochemical investigation and pharmacological evaluation of many traditional herbal medicines.

Antioxidant, Antifungal, Antibiofilm, and Cytotoxic Activities of Mentha spp. Essential Oils

Since ancient times, plants have been used to preserve food, or for their health properties. Essential oils are complex mixtures of volatile compounds that are obtained from botanical material, specifically from aromatic plants. Lamiaceae is one of the most important families in the production of essential oils, as it has both antioxidant and antimicrobial properties. The essential oils of Mentha (the Lamiaceae family) have been extensively studied for their biological actions. In this review, we report the antioxidant, antifungal, antibiofilm, and cytotoxic properties of Mentha spp. essential oils. The first objective is to provide comprehensive information about the use of essential oils in the treatment of fungal infections, or as antioxidants and integrative anticancer therapy. The second is to explore the evidence supporting its effectiveness in treating diseases without causing any serious adverse reactions.

In vitro susceptibility of Trypanosoma brucei brucei to selected essential oils and their major components

Aiming for discovering effective and harmless antitrypanosomal agents, 17 essential oils and nine major components were screened for their effects on T. b. brucei. The essential oils were obtained by hydrodistillation from fresh plant material and analyzed by GC and GC-MS. The trypanocidal activity was assessed using blood stream trypomastigotes cultures of T. b. brucei and the colorimetric resazurin method. The MTT test was used to assess the cytotoxicity of essential oils on macrophage cells and Selectivity Indexes were calculated. Of the 17 essential oils screened three showed high trypanocidal activity (IC₅₀ < 10 μg/mL): Juniperus oxycedrus (IC₅₀ of 0.9 μg/mL), Cymbopogon citratus (IC₅₀ of 3.2 μg/mL) and Lavandula luisieri (IC₅₀ of 5.7 μg/mL). These oils had no cytotoxic effects on macrophage cells showing the highest values of Selectivity Index (63.4, 9.0 and 11.8, respectively). The oils of Distichoselinum tenuifolium, Lavandula viridis, Origanum virens, Seseli tortuosom, Syzygium aromaticum, and Thymbra capitata also exhibited activity (IC₅₀ of 10-25 μg/mL) but showed cytotoxicity on macrophages. Of the nine compounds tested, α-pinene (IC₅₀ of 2.9 μg/mL) and citral (IC₅₀ of 18.9 μg/mL) exhibited the highest anti-trypanosomal activities. Citral is likely the active component of C. citratus and α-pinene is responsible for the antitrypanosomal effects of J. oxycedrus. The present work leads us to propose the J. oxycedrus, C. citratus and L. luisieri oils as valuable sources of new molecules for African Sleeping Sickness treatment.

Cymbopogon citratus and Cymbopogon giganteus essential oils have cytotoxic effects on tumor cell cultures. Identification of citral as a new putative anti-proliferative molecule

Cymbopogon species are used as traditional remedies in Burkina Faso for treating several diseases. We aimed to study the effects of their essential oils on cancer cell lines. For that purpose, Cymbopogon citratus (DC.) Stapf. and Cymbopogon giganteus Chiov. were studied for their essential oils after various chemical extractions. Antioxidant, potential anti-inflammatory action (inhibition of lipoxygenase) and cytotoxic activities were also tested on various prostate cancer and glioblastoma cell lines. Thirty-three compounds were identified in the essential oil of C. giganteus: Limonene (19.33%), Mentha-1(7),8-dien-2-ol cis (17.34%), Mentha-1(7),8-dien-2-ol trans (13.95%), trans-Mentha-2,8-diene-para-ol 1 (13.91%) and Mentha-2,8-diene-1-ol, cis-para (8.10%) were the most abundant. C. citratus essential oil contained 15 compounds and the major ones were geranial/citral A (48.18%) and neral/citral B (34.37%). Essential oil of C. citratus showed the highest ability to scavenge DPPH⁺ radicals (approximately 68% at 8 mg/mL) while C. giganteus exhibited the highest capability to reduce ABTS⁺ (0.59μmolET/g). The essential oil of C. citratus was the most effective on prostate cell lines LNCaP (IC₅₀ = 6.36 μg/ml) and PC-3 (IC₅₀ = 32.1 μg/ml), and on glioblastoma cell lines (SF-767 (IC₅₀ = 45.13 μg/ml) and SF-763 (IC₅₀ = 172.05 μg/ml). Interestingly, the activity of essential oil of C. citratus was statistically equal to that of its major component, citral. Combination of both oils showed antagonist, additive, indifferent and synergistic effects on LNCaP, PC-3, SF-767 and SF-763 cell lines, respectively. In conclusion, plants from the traditional medicine in Burkina Faso could be of interest for identifying new compounds, such as citral, for the treatment of prostate cancer and glioblastoma.

Effects of the floral phytochemical eugenol on parasite evolution and bumble bee infection and preference

Ecological and evolutionary pressures on hosts and parasites jointly determine infection success. In pollinators, parasite exposure to floral phytochemicals may influence between-host transmission and within-host replication. In the bumble bee parasite Crithidia bombi, strains vary in phytochemical resistance, and resistance increases under in vitro selection, implying that resistance/infectivity trade-offs could maintain intraspecific variation in resistance. We assessed costs and benefits of in vitro selection for resistance to the floral phytochemical eugenol on C. bombi infection in Bombus impatiens fed eugenol-rich and eugenol-free diets. We also assessed infection-induced changes in host preferences for eugenol. In vitro, eugenol-exposed cells initially increased in size, but normalized during adaptation. Selection for eugenol resistance resulted in considerable (55%) but non-significant reductions in infection intensity; bee colony and body size were the strongest predictors of infection. Dietary eugenol did not alter infection, and infected bees preferred eugenol-free over eugenol-containing solutions. Although direct effects of eugenol exposure could influence between-host transmission at flowers, dietary eugenol did not ameliorate infection in bees. Limited within-host benefits of resistance, and possible trade-offs between resistance and infectivity, may relax selection for eugenol resistance and promote inter-strain variation in resistance. However, infection-induced dietary shifts could influence pollinator-mediated selection on floral traits.

Efficacy of essential oil of Syzygium aromaticum alone and in combination with benznidazole on murine oral infection with Trypanosoma cruzi IV

Chagas disease (CD), caused by Trypanosoma cruzi, remains a serious public health problem. One of the causes of the high morbidity and mortality in patients is the lack of an effective drug therapy. Thus, the aim of this study was to evaluate the efficacy of the essential oil of Syzygium aromaticum alone and in combination with benznidazole (BZ) in mice orally inoculated with strain of T. cruzi IV obtained from oral CD outbreak occurred in Western Brazilian Amazonia. All the animals inoculated with metacyclic trypomastigote forms (AM14 strain, BZ resistant), derived from the insect Rhodnius robustus, became infected and there was no difference in the mortality rate between the experimental groups. When compared with untreated control animals (UTC), the treatment with essential oil of S. aromaticum (EOSA) alone promoted reduction in 1/5 parameters derived from the parasitemia curve, whereas the treatments with BZ alone or in combination (BZ + EOSA) promoted reduction in 4/5 of those parameters, presenting similar profiles of parasitemia curve. The animals treated with BZ and with the combination BZ + EOSA presented lower patency periods in comparison with the animals in EOSA group, and lower positivity of blood cultures when compared with the UTC group. The results of molecular analysis by qPCR in both blood and cardiac tissue did not show differences between the groups. The cure rates obtained with the different treatments presented the following ascending order: EOSA = 12.5% (1/8), BZ = 25.0% (2/8) and BZ + EOSA = 37.5% (3/8). Although there are no significant differences between them, these results claims that the use of this essential oil could be of interest for treatment of Chagas disease.

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.

Synergistic effects of floral phytochemicals against a bumble bee parasite

Floral landscapes comprise diverse phytochemical combinations. Individual phytochemicals in floral nectar and pollen can reduce infection in bees and directly inhibit trypanosome parasites. However, gut parasites of generalist pollinators, which consume nectar and pollen from many plant species, are exposed to phytochemical combinations. Interactions between phytochemicals could augment or decrease effects of single compounds on parasites. Using a matrix of 36 phytochemical treatment combinations, we assessed the combined effects of two floral phytochemicals, eugenol and thymol, against four strains of the bumblebee gut trypanosome Crithidia bombi. Eugenol and thymol had synergistic effects against C. bombi growth across seven independent experiments, showing that the phytochemical combination can disproportionately inhibit parasites. The strength of synergistic effects varied across strains and experiments. Thus, the antiparasitic effects of individual compounds will depend on both the presence of other phytochemicals and parasite strain identity. The presence of synergistic phytochemical combinations could augment the antiparasitic activity of individual compounds for pollinators in diverse floral landscapes.

Linalool, a Piper aduncum essential oil component, has selective activity against Trypanosoma cruzi trypomastigote forms at 4°C

BACKGROUND

Recent studies showed that essential oils from different pepper species (Piper spp.) have promising leishmanicidal and trypanocidal activities.

OBJECTIVES

In search for natural compounds against Trypanosoma cruzi, different forms of the parasite were incubated for 24 h at 28ºC or 4ºC with Piper aduncum essential oil (PaEO) or its main constituents linalool and nerolidol.

METHODS

PaEO chemical composition was obtained by GC-MS. Drug activity assays were based on cell counting, MTT data or infection index values. The effect of PaEO on the T. cruzi cell cycle and mitochondrial membrane potential was evaluated by flow cytometry.

FINDINGS

PaEO was effective against cell-derived (IC50/24 h: 2.8 μg/mL) and metacyclic (IC50/24 h: 12.1 μg/mL) trypomastigotes, as well as intracellular amastigotes (IC50/24 h: 9 μg/mL). At 4ºC - the temperature of red blood cells (RBCs) storage in blood banks - cell-derived trypomastigotes were more sensitive to PaEO (IC50/24 h = 3.8 μg/mL) than to gentian violet (IC50/24 h = 24.7 mg/mL). Cytotoxicity assays using Vero cells (37ºC) and RBCs (4ºC) showed that PaEO has increased selectivity for cell-derived trypomastigotes. Flow cytometry analysis showed that PaEO does not affect the cell cycle of T. cruzi epimastigotes, but decreases their mitochondrial membrane potential. GC-MS data identified nerolidol and linalool as major components of PaEO, and linalool had trypanocidal effect (IC50/24 h: 306 ng/mL) at 4ºC.

MAIN CONCLUSION

The trypanocidal effect of PaEO is likely due to the presence of linalool, which may represent an interesting candidate for use in the treatment of potentially contaminated RBCs bags at low temperature.

Evolution of resistance to single and combined floral phytochemicals by a bumble bee parasite

Repeated exposure to inhibitory compounds can drive the evolution of resistance, which weakens chemical defence against antagonists. Floral phytochemicals in nectar and pollen have antimicrobial properties that can ameliorate infection in pollinators, but evolved resistance among parasites could diminish the medicinal efficacy of phytochemicals. However, multicompound blends, which occur in nectar and pollen, present simultaneous chemical challenges that may slow resistance evolution. We assessed evolution of resistance by the common bumble bee gut parasite Crithidia bombi to two floral phytochemicals, singly and combined, over 6 weeks (~100 generations) of chronic exposure. Resistance of C. bombi increased under single and combined phytochemical exposure, without any associated costs of reduced growth under phytochemical-free conditions. After 6 weeks' exposure, phytochemical concentrations that initially inhibited growth by > 50%, and exceeded concentrations in floral nectar, had minimal effects on evolved parasite lines. Unexpectedly, the phytochemical combination did not impede resistance evolution compared to single compounds. These results demonstrate that repeated phytochemical exposure, which could occur in homogeneous floral landscapes or with therapeutic phytochemical treatment of managed hives, can cause rapid evolution of resistance in pollinator parasites. We discuss possible explanations for submaximal phytochemical resistance in natural populations. Evolved resistance could diminish the antiparasitic value of phytochemical ingestion, weakening an important natural defence against infection.

Effects of linalool and eugenol on the survival of Leishmania (L.) infantum chagasi within macrophages

The most commonly used drugs against visceral leishmaniasis are based on pentavalent antimonial compounds, which have played a fundamental role in therapy for over 70 years. However, the treatment is painful and has severe toxic side effects that can be fatal. Antimonial resistance is spreading and reaching alarming proportions. Linalool and eugenol have been shown to kill Leishmania (L.) amazonensis and Trypanosoma cruzi at low doses. In the present study, we demonstrate the effects of linalool and eugenol, components of essential oils, on Leishmania (L.) infantum chagasi, one of the causative agents of visceral leishmaniasis. We compared the effects of those compounds to the effects of glucantime, a positive control. In L. infantum chagasi killing assays, the LD₅₀ for eugenol was 220μg/ml, and that for linalool was 550μg/ml. L. infantum chagasi was added to cultures of peritoneal mouse macrophages for four hours prior to drug treatment. Eugenol and linalool significantly decreased the number of parasites within the macrophages. Eugenol and linalool enhanced the activities of the L. infantum chagasi protein kinases PKA and PKC. Linalool also decreased L. infantum chagasi oxygen consumption. In conclusion, both linalool and eugenol promoted a decrease in the proliferation and viability of L. infantum chagasi. These effects were more pronounced during the interaction between the parasites and peritoneal mouse macrophages.

Bumble bee parasite strains vary in resistance to phytochemicals

Nectar and pollen contain diverse phytochemicals that can reduce disease in pollinators. However, prior studies showed variable effects of nectar chemicals on infection, which could reflect variable phytochemical resistance among parasite strains. Inter-strain variation in resistance could influence evolutionary interactions between plants, pollinators, and pollinator disease, but testing direct effects of phytochemicals on parasites requires elimination of variation between bees. Using cell cultures of the bumble bee parasite Crithidia bombi, we determined (1) growth-inhibiting effects of nine floral phytochemicals and (2) variation in phytochemical resistance among four parasite strains. C. bombi growth was unaffected by naturally occurring concentrations of the known antitrypanosomal phenolics gallic acid, caffeic acid, and chlorogenic acid. However, C. bombi growth was inhibited by anabasine, eugenol, and thymol. Strains varied >3-fold in phytochemical resistance, suggesting that selection for phytochemical resistance could drive parasite evolution. Inhibitory concentrations of thymol (4.53–22.2 ppm) were similar to concentrations in Thymus vulgaris nectar (mean 5.2 ppm). Exposure of C. bombi to naturally occurring levels of phytochemicals—either within bees or during parasite transmission via flowers—could influence infection in nature. Flowers that produce antiparasitic phytochemicals, including thymol, could potentially reduce infection in Bombus populations, thereby counteracting a possible contributor to pollinator decline.

Immunotherapeutic Potential of Eugenol Emulsion in Experimental Visceral Leishmaniasis

BACKGROUND

The therapy of visceral leishmaniasis (VL) is limited by resistance, toxicity and decreased bioavailability of the existing drugs coupled with dramatic increase in HIV-co-infection, non-availability of vaccines and down regulation of cell-mediated immunity (CMI). Thus, we envisaged combating the problem with plant-derived antileishmanial drug that could concomitantly mitigate the immune suppression of the infected hosts. Several plant-derived compounds have been found to exert leishmanicidal activity via immunomodulation. In this direction, we investigated the antileishmanial activity of eugenol emulsion (EE), complemented with its immunomodulatory and therapeutic efficacy in murine model of VL.

METHODOLOGY/PRINCIPAL FINDINGS

Oil-in-water emulsion of eugenol (EE) was prepared and size measured by dynamic light scattering (DLS). EE exhibited significant leishmanicidal activity with 50% inhibitory concentration of 8.43±0.96 μg ml-1 and 5.05±1.72 μg ml─1, respectively against the promastigotes and intracellular amastigotes of Leishmania donovani. For in vivo effectiveness, EE was administered intraperitoneally (25, 50 and 75 mg/kg b.w./day for 10 days) to 8 week-infected BALB/c mice. The cytotoxicity of EE was assessed in RAW 264.7 macrophages as well as in naive mice. EE induced a significant drop in hepatic and splenic parasite burdens as well as diminution in spleen and liver weights 10 days post-treatment, with augmentation of 24h-delayed type hypersensitivity (DTH) response and high IgG2a:IgG1, mirroring induction of CMI. Enhanced IFN-γ and IL-2 levels, with fall in disease-associated Th2 cytokines (IL-4 and IL-10) detected by flow cytometric bead-based array, substantiated the Th1 immune signature. Lymphoproliferation and nitric oxide release were significantly elevated upon antigen revoke in vitro. The immune-stimulatory activity of EE was further corroborated by expansion of IFN-γ producing CD4+ and CD8+ splenic T lymphocytes and up-regulation of CD80 and CD86 on peritoneal macrophages. EE treated groups exhibited induction of CD8+ central memory T cells as evidenced from CD62L and CD44 expression. No biochemical alterations in hepatic and renal enzymes were observed.

CONCLUSIONS

Our results demonstrate antileishmanial activity of EE, potentiated by Th1 immunostimulation without adverse side effects. The Th1 immune polarizing effect may help to alleviate the depressed CMI and hence complement the leishmanicidal activity.

Essential Oils' Chemical Characterization and Investigation of Some Biological Activities: A Critical Review

This review covers literature data summarizing, on one hand, the chemistry of essential oils and, on the other hand, their most important activities. Essential oils, which are complex mixtures of volatile compounds particularly abundant in aromatic plants, are mainly composed of terpenes biogenerated by the mevalonate pathway. These volatile molecules include monoterpenes (hydrocarbon and oxygenated monoterpens), and also sesquiterpenes (hydrocarbon and oxygenated sesquiterpens). Furthermore, they contain phenolic compounds, which are derived via the shikimate pathway. Thanks to their chemical composition, essential oils possess numerous biological activities (antioxidant, anti-inflammatory, antimicrobial, etc…) of great interest in food and cosmetic industries, as well as in the human health field.

Antibacterial activity of Syzygium aromaticum seed: Studies on oxidative stress biomarkers and membrane permeability

Oxidative stress and membrane permeability as mode of antibacterial activity of aqueous extract of Syzygium aromaticum seeds against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus was investigated. The concentration of phytochemical constituents of Syzygium aromaticum was determined using gas chromatography. Syzygium aromaticum seeds contain eugenol acetate > β-carophyllene > eugenin > eugenol > methyl salicylate > β-humulene > rhamnatin > fernesol > α-copeane > β-ylangene > kaempferol > cinnamic acid > oleanolic acid > benzaldehyde > α-humulene > vanillin > α-cubebene > carvicol > benzoic acid. Syzygium aromaticum showed antimicrobial activity with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values as 0.06 and 0.10 mg/mL respectively. Time kill susceptibility by Syzygium aromaticum at MBC values showed significant decrease in the optical density and colony-forming unit (CFU) of Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. Superoxide anion radical content of the bacterial cells increased significantly following exposure to the extract. In a similar vein, superoxide dismutase and catalase activities increased significantly, while the level of reduced glutathione reduced, malondialdehyde increased significantly in bacterial cells exposed to the extract. The extract at MBC also enhanced the leakage of 260 nm absorbing materials and outer membrane permeability. It is evident from the data generated from this study that aqueous extract of Syzygium aromaticum seeds enhanced membrane permeability and oxidative stress in Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus.

Repellent Effect and Metabolite Volatile Profile of the Essential Oil of Achillea millefolium Against Aegorhinus nodipennis (Hope) (Coleoptera: Curculionidae)

Aegorhinus nodipennis (Hope) (Coleoptera: Curculionidae) is an important native pest in fruit crops that is mainly found in European hazelnut fields in the south of Chile. We investigated the behavioral response of A. nodipennis to volatile compounds released from the essential oil of Achillea millefolium and its main constituent using olfactometric bioassays. Gas chromatographic and mass spectral analysis of the A. millefolium essential oil revealed the presence of 11 compounds. Monoterpene β-thujone (96.2%) was the main component of the oil. Other compounds identified were α-thujone, 1,8-cineole, p-cymene, and 4-terpineol, all with percentages below 1%. Both A. millefolium essential oil and thujone exhibited a repellent activity against this insect at the higher doses tested (285.7 ng/cm(2)), demonstrating their potential as repellents for this species.

Leishmanicidal activities of Artemisia annua leaf essential oil against Visceral Leishmaniasis

Visceral leishmaniasis (VL), the second-most dreaded parasitic disease after malaria, is currently endemic in 88 countries. Dramatic increases in the rates of infection, drug resistance, and non-availability of safe vaccines have highlighted the need for identification of novel and inexpensive anti-leishmanial agents from natural sources. In this study, we showed the leishmanicidal effect of essential oil from Artemisia annua leaves (AALEO) against Leishmania donovani in vitro and in vivo. AALEO was extracted by hydrodistillation and characterized by GC-MS, the most abundant compounds were found to be camphor (52.06 %) followed by β-caryophyllene (10.95 %). AALEO exhibited significant leishmanicidal activity against L. donovani, with 50 % inhibitory concentration of 14.63 ± 1.49 μg ml(-1) and 7.3 ± 1.85 μg ml(-1), respectively, against the promastigotes and intracellular amastigotes. The effect was mediated through programmed cell death as confirmed by externalization of phosphatidylserine, DNA nicking by TdT-mediated dUTP nick-end labeling assay, dyskinetoplastidy, cell cycle arrest at sub-G0-G1 phase, loss of mitochondrial membrane potential and reactive oxygen species generation in promastigotes and nitric oxide generation in ex vivo model. AALEO presented no cytotoxic effects against mammalian macrophages even at 200 μg ml(-1). Intra-peritoneal administration of AALEO (200 mg/ kg.b.w.) to infected BALB/c mice reduced the parasite burden by almost 90% in the liver and spleen with significant reduction in weight. There was no hepato- or nephro-toxicity as demonstrated by normal levels of serum enzymes. The promising antileishmanial activity shown by camphor-rich AALEO may provide a new lead in the treatment of VL.

Thymol and eugenol derivatives as potential antileishmanial agents

In Northeastern Brazil visceral leishmaniasis is endemic with lethal cases among humans and dogs. Treatment is toxic and 5-10% of humans die despite treatment. The aim of this work was to survey natural active compounds to find new molecules with high activity and low toxicity against Leishmania infantum chagasi. The compounds thymol and eugenol were chosen to be starting compounds to synthesize acetyl and benzoyl derivatives and to test their antileishmanial activity in vitro and in vivo against L. i. chagasi. A screening assay using luciferase-expressing promastigotes was used to measure the growth inhibition of promastigotes, and an ELISA in situ was performed to evaluate the growth inhibition of amastigote. For the in vivo assay, thymol and eugenol derivatives were given IP to BALB/c mice at 100mg/kg/day for 30 days. The thymol derivatives demonstrated the greater activity than the eugenol derivatives, and benzoyl-thymol was the best inhibitor (8.67 ± 0.28 μg/mL). All compounds demonstrated similar activity against amastigotes, and acetyl-thymol was more active than thymol and the positive control drug amphotericin B. Immunohistochemistry demonstrated the presence of Leishmania amastigote only in the spleen but not the liver of mice treated with acetyl-thymol. Thus, these synthesized derivatives demonstrated anti-leishmanial activity both in vitro and in vivo. These may constitute useful compounds to generate new agents for treatment of leishmaniasis.