Terpenoids from Leaves of Guarea macrophylla Display In Vitro Cytotoxic Activity and Induce Apoptosis In Melanoma Cells

Guarea macrophylla is a Brazilian plant species that has been used in folk medicine to treat a range of diseases. Our ongoing work focuses on the discovery of new bioactive natural products derived from Brazilian flora. The current study describes the identification of cytotoxic compounds from the EtOH extract of leaves from G. macrophylla using bioactivity-guided fractionation. This approach resulted in the isolation and characterization of four compounds: cycloart-23E-ene-3β,25-diol (1), (23S*,24S*)-dihydroxycicloart-25-en-3-one (2), isopimara-7,15-diene-2α,3β-diol (3), and isopimara-7,15-dien-3β-ol (4), in which 2 and 3 are identified as new derivatives. In vitro assays were conducted to evaluate the cytotoxic activity of compounds 1-4 against a panel of cancer cell lines and to determine the possible mechanism(s) related to the activity of the compounds on B16F10Nex2 cells. The most active compound 1 induced cytotoxic effects on tumor cells, with IC₅₀ values of 18.3, 52.1, and 58.9 µM against HL-60, HeLa, and B16F10-Nex2 tumor cells, respectively. Furthermore, it was observed in melanoma cells that compound 1 induced several specific apoptotic hallmarks, such as morphological changes in the cell shape structure, nuclear DNA condensation, specific chromatin fragmentation, and disruption in the mitochondrial membrane potential, which are related to the intrinsic apoptotic pathway.

Antileishmanial Activity and Immunomodulatory Effects of Tricin Isolated from Leaves of Casearia arborea (Salicaceae)

Bioactivity-guided fractionation of antileishmanial active extract from leaves of Casearia arborea led to isolation of three metabolites: tricin (1), 1',6'-di-O-β-d-vanilloyl glucopyranoside (2) and vanillic acid (3). Compound 1 demonstrated the highest activity against the intracellular amastigotes of Leishmania infantum, with an IC₅₀ value of 56 μm. Tricin (1) demonstrated selectivity in mammalian cells (SI > 7) and elicited immunomodulatory effect on host cells. The present work suggests that tricin modulated the respiratory burst of macrophages to a leishmanicidal state, contributing to the parasite elimination. Therefore, the natural compound tricin could be further explored in drug design studies for leishmaniasis treatment.

Ergosterol isolated from the basidiomycete Pleurotus salmoneostramineus affects Trypanosoma cruzi plasma membrane and mitochondria

Background

Major drawbacks of the available treatment against Chagas disease (American trypanosomiasis) include its toxicity and therapeutic inefficiency in the chronic phase of the infection, which makes it a concern among neglected diseases. Therefore, the discovery of alternative drugs for treating chronic Chagas disease requires immediate action. In this work, we evaluated the mushroom Pleurotus salmoneostramineus in the search for potential antiparasitic compounds.

Methods

Fruit bodies of the basidiomycete Pleurotus salmoneostramineus were triturated and submitted to organic solvent extraction. After liquid-liquid partition of the crude extract, three fractions were obtained and the bioguided fractionation study was conducted to isolate the active metabolites. The elucidation of the chemical structure was performed using GC-MS and NMR techniques. The biological assays for antiparasitic activity were carried out using trypomastigotes of Trypanosoma cruzi and murine macrophages for mammalian cytotoxicity. The mechanism of action of the isolated compound used different fluorescent probes to evaluate the plasma membrane permeability, the potential of the mitochondrial membrane and the intracellular levels of reactive oxygen species (ROS).

Results

The most abundant fraction showing the antiparasitic activity was isolated and chemically elucidated, confirming the presence of ergosterol. It showed anti-Trypanosoma cruzi activity against trypomastigotes, with an IC₅₀ value of 51.3 μg/mL. The compound demonstrated no cytotoxicity against mammalian cells to the maximal tested concentration of 200 μg/mL. The mechanism of action of ergosterol in Trypanosoma cruzi trypomastigotes resulted in permeabilization of the plasma membrane, as well as depolarization of mitochondrial membrane potential, leading to parasite death. Nevertheless, no increase in ROS levels could be observed, suggesting damages to plasma membrane rather than an induction of oxidative stress in the parasite.

Conclusions

The selection of naturally antiparasitic secondary metabolites in basidiomycetes, such as ergosterol, may provide potential scaffolds for drug design studies against neglected diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s40409-017-0120-0) contains supplementary material, which is available to authorized users.

Chemical Composition and In Vitro Cytotoxic and Antimicrobial Activities of the Essential Oil from Leaves of Zanthoxylum monogynum St. Hill (Rutaceae)

Background: The Zanthoxylum monogynum species belongs to the family Rutaceae and is found in Southeast, Midwest, and Northeast Brazil. For this genus several biological activities have been described. Methods: The essential oil (EO) was obtained from the leaves of Zanthoxylum monogynum by hydro-distillation and was analyzed by gas chromatograph and gas chromatograph/mass spectrometry (GC and GC/MS). Also the EO of Z. monogynum was evaluated for in vitro cytotoxic activity against six tumor cell lines and for antimicrobial activity, performing disk diffusion and MIC assays with yeast and bacterial strains. Results: The chemical analysis afforded the identification of 18 components (99.0% of the EO). The major components were found to be citronellol (43.0%) and farnesol (32.0%). The in vitro cytotoxic activity against tumor cell lines, resulted in IC₅₀ values ranging from 11–65 µg/mL against all tested cell lines. Antimicrobial activity of the essential oil was also tested and oil was effective, especially against Cryptococcus sp. yeast. All the tested yeast strains showed at least 90% growth inhibition. Conclusions: the essential oil from leaves of Z. monogynum has a different qualitative and quantitative composition when compared to the composition previously described. Also this EO has significant cytotoxic activity and moderate activity against Cryptococcus sp. and Saccharomyces cereviseae yeasts.

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

BACKGROUND

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

PURPOSE

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

METHODS/STUDY DESIGN

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

RESULTS

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

CONCLUSION

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

Casearin D inhibits ERK phosphorylation and induces downregulation of cyclin D1 in HepG2 cells

Cancer is a public health problem which represents the second cause of death in the world. In this framework, it is necessary to identify novel compounds with antineoplastic potential. Plants are an important source for discovering novel compounds with pharmacological potential. In this study, we aimed to investigate the antiproliferative potential of isolated compounds from Casearia sylvestris on tumor cell lines. Crude extract effectively reduced cell viability of 4 tumor cell lines (HepG2, A549, U251-MG, and HT-144) after 48h treatment. HepG2 and HT-144 were the most responsive cells. Three fractions (aqueous ethanol, n-hexane and ethyl acetate) were tested against HepG2 and HT-144 cells and we observed that compounds with antiproliferative activity were concentrated in n-hexane and ethyl acetate fractions. The casearins A, G and J were isolated from n-hexane fraction, while casearin D was obtained from ethyl acetate fraction. We demonstrated that casearin D significantly inhibited the clonogenic capacity of HepG2 cells after 24h exposure indicating its antiproliferative activity. In addition, G1/S transition cell cycle arrest in HepG2 cells was also observed. These effects are related, at least in part, to ability of the casearin D in reducing ERK phosphorylation and cyclin D1 expression levels.

Cytotoxic and Antimicrobial Constituents from the Essential Oil of Lippia alba (Verbenaceae)

Backgroud:Lippia alba (Verbenaceae) is a plant widely used in folk medicine to treat various diseases. The present work deals with the chemical composition of the crude essential oil extracted from leaves of L. alba and evaluation of its antimicrobial and cytotoxic activities. Methods: Leaves of L. alba were extracted by hydrodistillation and analyzed by gas chromatography/mass spectrometry (GC/MS) as well as by nuclear magnetic resonance (NMR) spectroscopy. Cytotoxic and antimicrobial activities of crude essential oil were evaluated in vitro using MTT and broth microdilution assays, respectively. Results: Chemical analysis afforded the identification of 39 substances corresponding to 99.45% of the total oil composition. Concerning the main compounds, monoterpenes nerol/geraniol and citral correspond to approximately 50% of crude oil. The cytotoxic activity of obtained essential oil against several tumor cell lines showed IC₅₀ values ranging from 45 to 64 µg/mL for B16F10Nex2 (murine melanoma) and A549 (human lung adenocarcinoma). In the antimicrobial assay, was observed that all tested yeast strains, except C. albicans, were sensitive to crude essential oil. MIC values were two to four-folds lower than those determined to bacterial strains. Conclusion: Analysis of chemical composition of essential oils from leaves of L. alba suggested a new chemotype nerol/geraniol and citral. Based in biological evidences, a possible application for studied oil as an antifungal in medicine, as well as in agriculture, is described.

Assessing the Chemical Composition and Antimicrobial Activity of Essential Oils from Brazilian Plants-Eremanthus erythropappus (Asteraceae), Plectrantuns barbatus, and P. amboinicus (Lamiaceae)

The chemical composition and antimicrobial activity of essential oils obtained from three Brazilian plant species-leaves and branches of Eremanthus erythropappus (Asteraceae), leaves of Plectranthus barbatus, and leaves of P. amboinicus (Lamiaceae)-were determined. Analysis by GC/MS and determination of Kovats indexes both indicated δ-elemene (leaves-42.61% and branches-23.41%) as well as (-)-α-bisabolol (leaves-24.80% and stem bark-66.16%) as major constituents of E. erythropappus essential oils. The main components of leaves of P. barbatus were identified as (Z)-caryophyllene (17.98%), germacrene D (17.35%), and viridiflorol (14.13%); whereas those of leaves of P. amboinicus were characterized as p-cymene (12.01%), γ-terpinene (14.74%), carvacrol (37.70%), and (Z)-caryophyllene (14.07%). The antimicrobial activity against yeasts and bacteria was assessed in broth microdilution assays to determine the minimum inhibitory concentration (MIC) necessary to inhibit microbial growth. In addition, the crude oil of branches of E. erythropappus was subjected to chromatographic separation procedures to afford purified (-)-α-bisabolol. This compound displayed biological activity against pathogenic yeasts, thus suggesting that the antimicrobial effect observed with crude oils of E. erythropappus leaves and branches may be related to the occurrence of (-)-α-bisabolol as their main component. Our results showed that crude oils of Brazilian plants, specifically E. erythropappus, P. barbatus, and P. amboinicus and its components, could be used as a tool for the developing novel and more efficacious antimicrobial agents.

Chemical composition and in vitro cytotoxic and antileishmanial activities of extract and essential oil from leaves of Piper cernuum

Fractionation of the MeOH extract from leaves of Piper cernuum Vell. (Piperaceae) afforded six phenylpropanoid derivatives: 3',4'-dimethoxydihydrocinnamic acid (1), piplaroxide (2), methyl 4'-hydroxy-3',5'-dimethoxy cinnamate (3), 3',4',5'-trimethoxydihydrocinnamic acid (3), dihydropiplartine (5), and piplartine (6). The structures of isolated metabolites were characterized by NMR and MS spectral data analysis. The chemical composition of essential oil from the leaves was determined using GC/LREIMS followed by the determination of Kovats indexes. This procedure allowed the identification of nineteen terpenoids, with β-elemene (7), bicyclogermacrene (8), germacrene D (9), and (E)-caryophyllene (10) as the main compounds. Compounds 1 and 3-6 displayed no in vitro cytotoxicity against cancer cell lineages B16F10-Nex2, U87, HeLa, HL-60, HCT, and A2058 while 2 showed moderate activity against B16F10-Nex2 and HL-60 lines. Otherwise, compounds 7-10 displayed high cytotoxic activity. Evaluation against non-tumorigenic HFF cells indicated a reduced selectivity of compounds 7-10 to tumoral cells. No antileishmanial activity on macrophages infected with L. (L.) amnazonensis was found for the crude MeOH extract and compounds 1-6. The crude essential oil and compounds 7-10 reduced parasitism and eliminated the majority of infected and non-infected cells at 50 μg/mL.

Chemical Composition and in vitro Cytotoxic and Antileishmanial Activities of Extract and Essential Oil from Leaves of Piper cernuum

Fractionation of the MeOH extract from leaves of Piper cernuum Vell. (Piperaceae) afforded six phenylpropanoid derivatives: 3′,4′-dimethoxy-dihydrocinnamic acid (1), piplaroxide (2), methyl 4′-hydroxy-3′,5′-dimethoxy cinnamate (3), 3′,4′,5′-trimethoxydihydrocinnamic acid (3), dihydropiplartine (5), and piplartine (6). The structures of isolated metabolites were characterized by NMR and MS spectral data analysis. The chemical composition of essential oil from the leaves was determined using GC/LREIMS followed by the determination of Kovats indexes. This procedure allowed the identification of nineteen terpenoids, with β-elemene (7), bicyclogermacrene (8), germacrene D (9), and (E)-caryophyllene (10) as the main compounds. Compounds 1 and 3-6 displayed no in vitro cytotoxicity against cancer cell lineages B16F10-Nex2, U87, HeLa, HL-60, HCT, and A2058 while 2 showed moderate activity against B16F10-Nex2 and HL-60 lines. Otherwise, compounds 7-10 displayed high cytotoxic activity. Evaluation against non-tumorigenic HFF cells indicated a reduced selectivity of compounds 7-10 to tumoral cells. No antileishmanial activity on macrophages infected with L. (L.) amazonensis was found for the crude MeOH extract and compounds 1-6. The crude essential oil and compounds 7-10 reduced parasitism and eliminated the majority of infected and non-infected cells at 50μg/mL.

Chemical composition and in vitro cytotoxic effects of the essential oil from Nectandra leucantha leaves

CONTEXT

Nectandra (Lauraceae) species have been used in folk medicine as an antidiarrheal, analgesic, antifungal, etc., and have many pharmacological proprieties.

OBJECTIVE

Investigation of the chemical composition and cytotoxicity of essential oil from Nectandra leucantha Nees & Mart. leaves. This is the first study involving N. leucantha reported in the literature.

MATERIAL AND METHODS

The essential oil of N. leucantha leaves was obtained by hydrodistillation. Its chemical composition was determined using a combination of GC/FID, GC/MS, and determination of Kovats index (KI). In vitro cytotoxic activity was evaluated against six cancer cell lines - murine melanoma (B16F10-Nex2), human glioblastome (U-87), human cervical carcinoma (HeLa), human colon carcinoma (HCT), human breast adenocarcinoma (MCF7), and human cervical tumor (Siha) as well as against one non-tumorigenic cell line - human foreskin fibroblast (HFF).

RESULTS

Thirty-three compounds were identified primarily sesquiterpenes (81.41%), the main compounds being bicyclogermacrene (28.44%), germacrene A (7.34%), spathulenol (5.82%), and globulol (5.25%). Furthermore, monoterpenes were also found in the analyzed oil (12.84%), predominantly α- and β-pinenes (6.59 and 4.57%, respectively). The crude essential oil displayed significant cytotoxic activity against B16F10-Nex2 (IC50 33 ± 1 μg/mL) and U87 (IC50 75.95 ± 0.03 μg/mL) and HeLa (IC50 60 ± 12 μg/mL) cell lines. The main identified compound, bicyclogermacrene, displayed IC50 ranging from 3.1 ± 0.2 to 21 ± 6 μg/mL.

DISCUSSION AND CONCLUSION

The results indicate that the crude oils from leaves of N. leucantha displayed cytotoxic activity being bicyclogermacrene, the main compound identified in the crude oil responsible, at least in part, for this potential.

Structural crystalline characterization of sakuranetin--an antimicrobial flavanone from twigs of Baccharis retusa (Asteraceae)

Bioactivity-guided fractionation of an antimicrobial active extract from twigs of Baccharis retusa C. DC. (Asteraceae) yielded the flavanone 5,4'-dihydroxy-7-methoxy-flavanone (sakuranetin) as responsible for the detected activity. The structure of the bioactive compound was established on the basis of spectroscopic data analysis, including NMR and MS. Additionally, the structure of a new crystal form of sakuranetin was confirmed by X-ray diffratometry. The minimum inhibitory concentrations (MIC) of isolated compound were determined against pathogenic yeast belonging to the genus Candida (six species), Cryptococcus (two species/four serotypes) and S. cerevisiae BY 4742 (S288c background) and ranged from 0.32 to 0.63 μg/μL. Our results showed that sakuranetin, which structure was fully characterized, could be used as a tool for the design of novel and more efficacious antifungal agents.

Antileishmanial activity evaluation of adunchalcone, a new prenylated dihydrochalcone from Piper aduncum L

Bioactivity-guided fractionation of EtOH extract from the leaves of Piper aduncum L. (Piperaceae) afforded a new dihydrochalcone, named adunchalcone. Its structure was elucidated on the basis of their spectroscopic data, primarily NMR and MS. Adunchalcone was evaluated against promastigote forms of Leishmania (L.) amazonensis, L. (V.) braziliensis, L. (V.) shawi, and L. (L.) chagasi and displayed 50% effective concentrations (EC50) of 11.03, 26.70, and 11.26 μM, as well as selective indexes of 4.86, 2.01, 4.76 and 0.50, respectively. This compound was also tested against intracellular forms of L. (L.) amazonensis, displaying weak activity, in comparison to reference drug amphotericin B. However, despite reduced effect of adunchalcone against amastigotes of L. (L.) amazonensis, this work opens the perspective to use this particular molecule as a scaffold for the design of novel and selective drug candidates for neglected diseases, mainly leishmaniasis.

Antiparasitic activity and effect of casearins isolated from Casearia sylvestris on Leishmania and Trypanosoma cruzi plasma membrane

Leishmaniasis and Chagas disease are infectious diseases caused by parasite Leishmania sp. and Trypanosoma cruzi, respectively, and are included among the most neglected diseases in several underdeveloped and developing countries, with an urgent demand for new drugs. Considering the antiparasitic potential of MeOH extract from leaves of Casearia sylvestris Sw. (Salicaceae), a bioguided fractionation was conducted and afforded four active clerodane diterpenes (casearins A, B, G, and J). The obtained results indicated a superior efficacy of tested casearins against trypomastigotes of T. cruzi, with IC50 values ranging from 0.53 to 2.77 μg/ml. Leishmania infantum promastigotes were also susceptible to casearins, with IC50 values in a range between 4.45 and 9.48 μg/ml. These substances were also evaluated for mammalian cytotoxicity against NCTC cells resulting in 50% cytotoxic concentrations (CC50) ranging from 1.46 to 13.76 μg/ml. Additionally, the action of casearins on parasite membranes was investigated using the fluorescent probe SYTOX Green. The obtained results demonstrated a strong interaction of casearins A and B to the plasma membrane of T. cruzi parasites, corroborating their higher efficacy against these parasites. In contrast, the tested casearins induced no alteration in the permeability of plasma membrane of Leishmania parasites, suggesting that biochemical differences between Leishmania and T. cruzi plasma membrane might have contributed to the target effect of casearins on trypomastigotes. Thus, considering the importance of studying novel and selective drug candidates against protozoans, casearins A, B, G, and J could be used as tools to future drug design studies.