Anti-Mycobacterium tuberculosis activity and cytotoxicity of Calophyllum brasiliense Cambess (Clusiaceae)

Synthesis of 1,3,4-oxadiazoles with 4-methoxynaphthalene ring: discovering new compounds with antimicrobial activity

Background: Paracoccidioidomycosis (PCM) is a systemic infection caused by Paracoccidioides spp. (Pb). PCM can be associated or clinically confused with tuberculosis (TB), another pulmonary infection, caused by Mycobacterium tuberculosis (Mtb). Futhermore, the long treatment time of TB and PCM and the cases of TB drug resistance impose difficulties for the cure of these diseases. Results: New 1,3,4-oxadiazoles containing the 4-methoxynaphthalene ring were synthesized and their antimicrobial activity was evaluated against Pb and Mtb. The derivative 6n (with 2-hydroxy-5-nitrophenyl subunit) is the most promising of the series. Conclusion: The 1,3,4-oxadiazole 6n can be used as a prototype drug candidate, with anti-Pb and anti-MTb activities, showing a broad-spectrum profile for the treatment of both pulmonary infections.

3,5-dinitrobenzoylhydrazone derivatives as a scaffold for antituberculosis drug development

Background: The development of drugs is essential to eradicate tuberculosis. Materials & methods: Sixteen 3,5-dinitrobenzoylhydrazone (2-17) derivatives and their synthetic precursors 3,5-dinitrobenzoylhydrazide (1) and methyl ester (18) were screened for their anti-Mycobacterium tuberculosis (Mtb) potential. Results: Twelve compounds had minimum inhibitory concentration (MIC) ranging from 0.24 to 7.8 μg/ml against the Mtb strain. The activity was maintained in multidrug-resistant Mtb clinical isolates. Only compound (17) showed activity against nontuberculous mycobacteria. The compounds exhibited a limited spectrum of activity, with an MIC >500 μg/ml against Gram-positive and -negative bacteria. Compounds (2), (5) and (11) showed a synergistic effect with rifampicin. An excellent selectivity index value was found, with values reaching 583.33. Conclusion: 3,5-dinitrobenzoylhydrazone derivatives could be considered as a scaffold for the development of antituberculosis drugs.

New Investigations with Lupane Type A-Ring Azepane Triterpenoids for Antimycobacterial Drug Candidate Design

Twenty lupane type A-ring azepano-triterpenoids were synthesized from betulin and its related derivatives and their antitubercular activity against Mycobacterium tuberculosis, mono-resistant MTB strains, and nontuberculous strains Mycobacterium abscessus and Mycobacterium avium were investigated in the framework of AToMIc (Anti-mycobacterial Target or Mechanism Identification Contract) realized by the Division of Microbiology and Infectious Diseases, NIAID, National Institute of Health. Of all the tested triterpenoids, 17 compounds showed antitubercular activity and 6 compounds were highly active on the H37Rv wild strain (with MIC 0.5 µM for compound 7), out of which 4 derivatives also emerged as highly active compounds on the three mono-resistant MTB strains. Molecular docking corroborated with a machine learning drug-drug similarity algorithm revealed that azepano-triterpenoids have a rifampicin-like antitubercular activity, with compound 7 scoring the highest as a potential M. tuberculosis RNAP potential inhibitor. FIC testing demonstrated an additive effect of compound 7 when combined with rifampin, isoniazid and ethambutol. Most compounds were highly active against M. avium with compound 14 recording the same MIC value as the control rifampicin (0.0625 µM). The antitubercular ex vivo effectiveness of the tested compounds on THP-1 infected macrophages is correlated with their increased cell permeability. The tested triterpenoids also exhibit low cytotoxicity and do not induce antibacterial resistance in MTB strains.

Antituberculosis Activities of Lapachol and β-Lapachone in Combination with Other Drugs in Acidic pH

Background: The treatment of multidrug-resistant tuberculosis (MDR-TB) is a challenge to be overcome. The increase of resistant isolates associated with serious side effects during therapy leads to the search for substances that have anti-TB activity, which make treatment less toxic, and also act in the macrophage acidic environment promoted by the infection. Objective: The aim of this study was to investigate lapachol and β-lapachone activities in combination with other drugs against Mycobacterium tuberculosis at neutral and acidic pH and its cytotoxicity. Design: Inhibitory and bactericidal activities against M. tuberculosis and clinical isolates were determined. Drug combination and cytotoxicity assay were carried out using standard TB drugs and/or N-acetylcysteine (NAC). Results: Both naphthoquinones presented activity against MDR clinical isolates. The combinations with the first-line TB drugs demonstrated an additive effect and β-lapachone+NAC were synergic against H₃₇Rv. Lapachol activity at acidic pH and its association with NAC improved the selectivity index. Lapachol and β-lapachone produced cell morphological changes in bacilli at pH 6.0 and 6.8, respectively. Conclusion: Lapachol revealed promising anti-TB activity, especially associated with NAC.

Structure-activity relationship of natural and synthetic coumarin derivatives against Mycobacterium tuberculosis

Aim: Eight coumarin derivatives (1a-h) obtained from natural (-)-mammea A/BB (1) and 13 synthetic coumarins (2-14) had their cytotoxicity and biological activity evaluated against Mycobacterium tuberculosis H₃₇Rv reference strain and multidrug-resistant clinical isolates. Materials & methods: Anti-M. tuberculosis activity was evaluated by resazurin microtiter assay plate, and the cytotoxicity of natural and synthetic products using J774A.1 macrophages by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. Results: Compounds 1g, 5, 6, 12 and 14 were more active against M. tuberculosis H₃₇Rv and multidrug-resistant clinical isolates with MIC values ranging from 15.6 to 62.5 μg/ml. Conclusion: These results demonstrate that the coumarin derivatives were active against multidrug-resistant clinical isolates, becoming potential candidates to be used in the treatment of resistant tuberculosis.

Synthesis and biological evaluation of 12 novel (-)-camphene-based 1,3,4-thiadiazoles against Mycobacterium tuberculosis

Aim: To evaluate the activity, cytotoxicity and efflux pumps inhibition of a series of 12 novels (-)-camphene-based 1,3,4-thiadiazoles (TDZs) against Mycobacterium tuberculosis ( Mtb). Materials & methods: The minimum inhibitory concentration (MIC), cytotoxicity for three cell lines, ethidium bromide accumulation and checkerboard methods were carried out. Results: Compounds (6a, 6b, 6c, 6g, 6h and 6j) showed significant anti- Mtb activity (MIC 3.9–7.8 μg/ml) and no antagonism with anti-TB drugs already used in the TB treatment. Selectivity index (SI) was also determined, with values reaching 42.9 for H37Rv strain and 97.1 for clinical isolate. Five compounds also showed bacterial efflux pumps inhibition and one showed modulator effect with three drugs. Conclusion: These six TDZs should be considered as new scaffolds to develop anti-TB drugs.

The Genus Calophyllum: Review of Ethnomedicinal Uses, Phytochemistry and Pharmacology

The species of genus Calophyllum have been reported for several ethnomedicinal uses in the traditional systems of medicine. The scientific study of the genus Calophyllum revealed that it is a rich source of bioactive secondary metabolites. These phytochemicals have shown a wide range of biological activities. Some of these have reached to the clinical developmental stage. The Calophyllum inophyllum seed oil has been proved to be an acceptable sustainable source of biodiesel. Few species of the genus are endangered and have been included in the red list of threatened species by the IUCN Red List. Owing to the importance of the genus a review of its ethnomedicinal uses, phytochemistry, and pharmacology has been carried out. It will further help to explore the molecular mechanism of phytochemicals for health benefits.

Hydrazone, benzohydrazones and isoniazid-acylhydrazones as potential antituberculosis agents

Aim: To evaluate the potential of three benzohydrazones (1–3), four acylhydrazones derived from isoniazid (INH-acylhydrazones) (4–7) and one hydrazone (8) as antituberculosis agents. Materials & methods: Inhibitory and bactericidal activities were determined for the reference Mycobacterium tuberculosis ( Mtb) strain and clinical isolates. Cytotoxicity, drug combinations and ethidium bromide accumulation assays were also performed. Results: The tested compounds (1–8) presented excellent antituberculosis activity with surprisingly inhibitory (0.12–250 μg/ml) and bactericidal values, even against multidrug-resistant Mtb clinical isolates. Compounds showed high selectivity index, with values reaching 1833.33, and a limited spectrum of activity. Some of the compounds (2 & 8) are also great inhibitors of bacillus efflux pumps. Conclusion: Benzohydrazones and INH-acylhydrazones may be considered scaffolds for the development of new anti- Mtb drugs.

New insights on Ethambutol Targets in Mycobacterium tuberculosis

BACKGROUND

In recent years, very few effective drugs against Mycobacterium tuberculosis have emerged, which motivates the research with drugs already used in the treatment of tuberculosis. Ethambutol is a bacteriostatic drug that affects cell wall integrity, but the effects of this drug on bacilli are not fully exploited.

OBJECTIVE

Based on the need to better investigate the complex mechanism of action of ethambutol, our study presented the proteome profile of M. tuberculosis after different times of ethambutol exposure, aiming to comprehend the dynamics of bacilli response to its effects. M. tuberculosis was exposed to ½ MIC of ethambutol at 24 and 48 hours. The proteins were identified by MALDI-TOF/TOF.

RESULTS

The main protein changes occurred in metabolic proteins as dihydrolipoyl dehydrogenase (Rv0462), glutamine synthetase1 (Rv2220), electron transfer flavoprotein subunit beta (Rv3029c) and adenosylhomocysteinase (Rv3248c).

CONCLUSION

Considering the functions of these proteins, our results support that the intermediary metabolism and respiration were affected by ethambutol and this disturbance provided proteins that could be explored as additional targets for this drug.

Calophyllum brasiliense Modulates the Immune Response and Promotes Leishmania amazonensis Intracellular Death

Calophyllum brasiliense is a plant from the Brazilian rain forests and has been used in folk medicine for the treatment of various diseases, including leishmaniasis. This infectious disease depends on the Leishmania sp. and the host immune response. C. brasiliense antileishmanial activity is well known, but the effects on immune response remain to be investigated. This study showed the leishmanicidal and immunomodulatory effects of a 30 μg/mL of hydroalcoholic extract of C. brasiliense in murine macrophages before and after Leishmania (Leishmania) amazonensis infection. The semiquantitative cytokine RNA expression was determined by RT-PCR and the anti-Leishmania activity was measured by infection index (IF). Hydroalcoholic extract of C. brasiliense reduced more than 95% of IF when used before and after Leishmania infection, with 3 and 24 h of treatment (p < 0.05). C. brasiliense inhibited or reduced significantly (p < 0.05) the TNF-α, IL-1β, IL-18, and IL-10 mRNA expression. The antileishmanial and anti-inflammatory effects showed the potential of C. brasiliense as an alternative therapy for leishmaniasis and it must be investigated.

Screening of antitubercular compound library identifies novel ATP synthase inhibitors of Mycobacterium tuberculosis

A limited number of anti-tuberculosis drug candidates with novel mode of action have entered clinical trials in recent years. ATP synthase is one such validated drug target which has yielded a drug recently. The aim of this study was to identify the novel chemical scaffolds targeting the Mycobacterium tuberculosis (M. tuberculosis) ATP synthase. In this study, inverted membrane vesicles of Mycobacterium smegmatis were prepared to establish luciferin based ATP estimation assay. This assay was used to screen 700 compounds which were earlier found to be active on the whole cell of M. tuberculosis. Antibacterial activity of hits against various susceptible and drug-resistant strains of M. tuberculosis was evaluated using the microplate alamar blue assay and their cytotoxicity was also determined to select the safe compounds for further study. Screening of 700 compounds resulted in the identification of two compounds (5228485 and 5220632) exhibiting an IC₅₀ of 0.32 and 4.0 μg/ml respectively. Both compounds showed excellent anti-TB activity (MIC of 0.5-2.0 μg/ml against Mtb H₃₇Rv) and low cytotoxicity in human cell line and sub-mitochondrial particles. The three-dimensional structure of M. tuberculosis ATPase was predicted using in-silico approach and docking studies were performed with the active compounds. The interaction between compounds and bacterial ATP synthase was confirmed by molecular docking analysis. In conclusion screening of compound library has resulted in the identification of two novel chemical scaffolds targeting mycobacterial ATP synthase.

Antibacterial activities of medicinal plants used in Mexican traditional medicine

ETHNOPHARMACOLOGICAL RELEVANCE

We provide an extensive summary of the in vitro antibacterial properties of medicinal plants popularly used in Mexico to treat infections, and we discuss the ethnomedical information that has been published for these species.

MATERIALS AND METHODS

We carried out a bibliographic investigation by analyzing local and international peer-reviewed papers selected by consulting internationally accepted scientific databases from 1995 to 2014. We provide specific information about the evaluated plant parts, the type of extracts, the tested bacterial strains, and the inhibitory concentrations for each one of the species. We recorded the ethnomedical information for the active species, as well as their popular names and local distribution. Information about the plant compounds that has been identified is included in the manuscript. This review also incorporates an extensive summary of the available toxicological reports on the recorded species, as well as the worldwide registries of plant patents used for treating bacterial infections. In addition, we provide a list with the top plant species with antibacterial activities in this review RESULTS: We documented the in vitro antibacterial activities of 343 plant species pertaining to 92 botanical families against 72 bacterial species, focusing particularly on Staphylococcus aureus, Mycobacterium tuberculosis, Escherichia coli and Pseudomonas aeruginosa. The plant families Asteraceae, Fabaceae, Lamiaceae and Euphorbiaceae included the largest number of active species. Information related to popular uses reveals that the majority of the plants, in addition to treating infections, are used to treat other conditions. The distribution of Mexican plants extended from those that were reported to grow in just one state to those that grow in all 32 Mexican states. From 75 plant species, 225 compounds were identified. Out of the total plant species, only 140 (40.57%) had at least one report about their toxic effects. From 1994 to July 2014 a total of 11,836 worldwide antibacterial patents prepared from different sources were recorded; only 36 antibacterial patents from plants were registered over the same time period. We offered some insights on the most important findings regarding the antibacterial effects, current state of the art, and research perspectives of top plant species with antibacterial activities in vitro.

CONCLUSIONS

Studies of the antibacterial in vitro activity of medicinal plants popularly used in Mexico to treat infections indicate that both the selection of plant material and the investigation methodologies vary. Standardized experimental procedures as well as in vivo pharmacokinetic studies to document the effectiveness of plant extracts and compounds are necessary. This review presents extensive information about the medicinal plants possessing antibacterial activity that has been scientifically studied and are popularly used in Mexico. We anticipate that this review will be of use for future studies because it constitutes a valuable information tool for selecting the most significant plants and their potential antibacterial properties.

Proteomic profile of Mycobacterium tuberculosis after eupomatenoid-5 induction reveals potential drug targets

Aim: We investigated a proteome profile, protein–protein interaction and morphological changes of Mycobacterium tuberculosis after different times of eupomatenoid-5 (EUP-5) induction to evaluate the cellular response to the drug-induced damages. Methods: The bacillus was induced to sub-minimal inhibitory concentration of EUP-5 at 12 h, 24 h and 48 h. The proteins were separated by 2D gel electrophoresis, identified by LC/MS-MS. Scanning electron microscopy and Search Tool for the Retrieval of Interacting Genes/Proteins analyses were performed. Results: EUP-5 impacts mainly in M. tuberculosis proteins of intermediary metabolism and interactome suggests a multisite disturbance that contributes to bacilli death. Scanning electron microscopy revealed the loss of bacillary form. Conclusion: Some of the differentially expressed proteins have the potential to be drug targets such as citrate synthase (Rv0896), phosphoglycerate kinase (Rv1437), ketol-acid reductoisomerase (Rv3001c) and ATP synthase alpha chain (Rv1308).

Bioactive Coumarins and Xanthones From Calophyllum Genus and Analysis of Their Druglikeness and Toxicological Properties

Calophyllum spp. (Calophyllaceae) is a genus of tropical trees valued in the chemopharmacological industry as an important source of biogenetically related coumarins and xanthones, which can lead to the development of new drugs due to their relevant pharmacological activities and diversity of molecular structural. These compounds have relevant pharmacological activities, such as: cytotoxicity against human tumor cell lines (especially leukemia), parasites (Plasmodium, Leshmania, and Trypanosoma), retroviruses (e.g., HIV), and Mycobacterium tuberculosis. Chemoinformatic and toxicoinformatic tools were used here to perform a computational analysis of 70 coumarins and 70 xanthones isolated from this genus in order to explore their potential as new drugs. Most coumarins from this genus possess similar patterns of druglikeness with differences in its physicochemical properties. Xanthones, on the other hand, show quite similar physicochemical properties and druglikeness. It is interesting to note that the vast majority of these compounds (57 coumarins and 59 xanthones) are in compliance with Lipinski´s Rule of Five. Remarkably, two xanthones (2-hydroxyxanthone and caledonixanthone-B) have leadlikeness potential that accordingly with chemoinformatic analysis may target MAO A and B, respectively, and therefore may exhibit antidepressant potential. These compounds also target tyrosine-phosphorilation-regulated kinase 1A (DYRK1A) which is over-expressed in a variety of hematological and brain cancers, therefore they could act as anticancer compounds. Several toxicological predictions were also depicted. Coumarins could be an irritant and may affect the reproductive system, while xanthones may have mutagenic results. To our knowledge, this is the first chemoinformatic report on the main active compounds of this genus and its potential for drug development.

Risk assessment of Soulatrolide and Mammea (A/BA+A/BB) coumarins from Calophyllum brasiliense by a toxicogenomic and toxicological approach

Calophyllum brasiliense (Calophyllaceae) is a tropical rain forest tree distributed in Central and South America. It is an important source of tetracyclic dipyrano coumarins (Soulatrolide) and Mammea type coumarins. Soulatrolide is a potent inhibitor of HIV-1 reverse transcriptase and displays activity against Mycobacterium tuberculosis. Meanwhile, Mammea A/BA and A/BB, pure or as a mixture, are highly active against several human leukemia cell lines, Trypanosoma cruzi and Leishmania amazonensis. Nevertheless, there are few studies evaluating their safety profile. In the present work we performed toxicogenomic and toxicological analysis for both type of compounds. Soulatrolide, and the Mammea A/BA + A/BB mixture (2.1) were slightly toxic accordingly to Lorke assay classification (DL50 > 3000 mg/kg). After a short-term administration (100 mg/kg/daily, orally, 1 week) liver toxicogenomic analysis revealed 46 up and 72 downregulated genes for Mammea coumarins, and 665 up and 1077 downregulated genes for Soulatrolide. Gene enrichment analysis identified transcripts involved in drug metabolism for both compounds. In addition, network analysis through protein-protein interactions, tissue evaluation by TUNEL assay, and histological examination revealed no tissue damage on liver, kidney and spleen after treatments. Our results indicate that both type of coumarins displayed a safety profile, supporting their use in further preclinical studies to determine its therapeutic potential.

Trends in the chemical and pharmacological research on the tropical trees Calophyllum brasiliense and Calophyllum inophyllum, a global context

Tropical trees of Calophyllum genus (Calophyllaceae) have chemical and biological importance as potential source of secondary active metabolites which can lead to the development of new drugs. Research on this species has been rising since 1992 due to the discovering of anti-HIV properties of Calanolide A found in Calophyllum inophyllum leaves. This compound is the most important natural product for potential development of new anti-HIV drugs and phytomedicines. The scientometric analysis (1953–2014) here performed revealed that the most studied species of Calophyllum genus are: C. inophyllum and C. brasiliense, distributed in the Asian, and American continents, respectively. Current research on these species is carried out mainly in India and Brazil, respectively, where these species grow. Research on C. brasiliense is focused mainly on ecological, antiparasitic, cytotoxic properties, and isolation of new compounds. Chemical studies and biodiesel development are the main topics in the case of C. inophyllum. Text mining analysis revealed that coumarins, and xanthones are the main secondary active metabolites responsible for most of the reported pharmacological properties, and are potential compounds for the treatment of leukemia and against intracellular parasites causing American Trypanosomiasis and Leshmaniasis. On the other hand, C. inophyllum represents an important source for the development of 2nd generation biodiesel. Medicinal and industrial applications of these species may impulse sustainable forest plantations. To our knowledge this is the first scientometric and text mining analysis of chemical and biomedical research on Calophyllum genus, C. brasiliense and C. inophyllum.