Synergistic antimycobacterial activities of sesquiterpene lactones from Laurus spp

Deciphering the emerging role of phytocompounds: Implications in the management of drug-resistant tuberculosis and ATDs-induced hepatic damage

Tuberculosis is a disease of poverty, discrimination, and socioeconomic burden. Epidemiological studies suggest that the mortality and incidence of tuberculosis are unacceptably higher worldwide. Genomic mutations in embCAB, embR, katG, inhA, ahpC, rpoB, pncA, rrs, rpsL, gyrA, gyrB, and ethR contribute to drug resistance reducing the susceptibility of Mycobacterium tuberculosis to many antibiotics. Additionally, treating tuberculosis with antibiotics also poses a serious risk of hepatotoxicity in the patient's body. Emerging data on drug-induced liver injury showed that anti-tuberculosis drugs remarkably altered levels of hepatotoxicity biomarkers. The review is an attempt to explore the anti-mycobacterial potential of selected, commonly available, and well-known phytocompounds and extracts of medicinal plants against strains of Mycobacterium tuberculosis. Many studies have demonstrated that phytocompounds such as flavonoids, alkaloids, terpenoids, and phenolic compounds have antibacterial action against Mycobacterium species, inhibiting the bacteria's growth and replication, and sometimes, causing cell death. Phytocompounds act by disrupting bacterial cell walls and membranes, reducing enzyme activity, and interfering with essential metabolic processes. The combination of these processes reduces the overall survivability of the bacteria. Moreover, several phytochemicals have synergistic effects with antibiotics routinely used to treat TB, improving their efficacy and decreasing the risk of resistance development. Interestingly, phytocompounds have been presented to reduce isoniazid- and ethambutol-induced hepatotoxicity by reversing serum levels of AST, ALP, ALT, bilirubin, MDA, urea, creatinine, and albumin to their normal range, leading to attenuation of inflammation and hepatic necrosis. As a result, phytochemicals represent a promising field of research for the development of new TB medicines.

The chemistry of Vernonanthura nudiflora (Less.) H. Rob. flowers and its antimicrobial activities

Twenty-one known specialised metabolites were isolated from the flowers of Vernonanthura nudiflora (Less.) H. Rob., the structures of the compounds were established based on 1 D and 2 D NMR spectroscopic experiments. Others 28 compounds were putatively identified using the dereplication technique by UHPLC-HRMS/MS. Twenty-three of the compounds are being reported for the first time in this species. The mixture of sesquiterpene lactones piptocarphins A and B (17 + 18), and the flavone velutin (14) were tested against several microorganisms and showed promising activity against Mycobacterium tuberculosis with MIC of 15.6 μg/mL and 31.2 μg/mL, respectively. Furthermore, 17 + 18 showed greater cytotoxicity against VERO cells (IC₅₀ = 7.0 ± 1.73) compared to compound 14 (IC₅₀ 85.0 ± 10.6 µg/mL). These findings reveal the feasibility of using the UHPLC-ESI-HRMS/MS-based dereplication strategy in complex fractions to identify specialised metabolites, moreover to V. nudiflora flowers being a source of compounds with antimycobacterial potential.

Back to the Roots-An Overview of the Chemical Composition and Bioactivity of Selected Root-Essential Oils

Since ancient times, plant roots have been widely used in traditional medicine for treating various ailments and diseases due to their beneficial effects. A large number of studies have demonstrated that-besides their aromatic properties-their biological activity can often be attributed to volatile constituents. This review provides a comprehensive overview of investigations into the chemical composition of essential oils and volatile components obtained from selected aromatic roots, including Angelica archangelica, Armoracia rusticana, Carlina sp., Chrysopogon zizanioides, Coleus forskohlii, Inula helenium, Sassafras albidum, Saussurea costus, and Valeriana officinalis. Additionally, their most important associated biological impacts are reported, such as anticarcinogenic, antimicrobial, antioxidant, pesticidal, and other miscellaneous properties. Various literature and electronic databases-including PubMed, ScienceDirect, Springer, Scopus, Google Scholar, and Wiley-were screened and data was obtained accordingly. The results indicate the promising properties of root-essential oils and their potential as a source for natural biologically active products for flavor, pharmaceutical, agricultural, and fragrance industries. However, more research is required to further establish the mechanism of action mediating these bioactivities as well as essential oil standardization because the chemical composition often strongly varies depending on external factors.

Stevia Genus: Phytochemistry and Biological Activities Update

The Stevia genus (Asteraceae) comprises around 230 species, distributed from the southern United States to the South American Andean region. Stevia rebaudiana, a Paraguayan herb that produces an intensely sweet diterpene glycoside called stevioside, is the most relevant member of this genus. Apart from S. rebaudiana, many other species belonging to the Stevia genus are considered medicinal and have been popularly used to treat different ailments. The members from this genus produce sesquiterpene lactones, diterpenes, longipinanes, and flavonoids as the main types of phytochemicals. Many pharmacological activities have been described for Stevia extracts and isolated compounds, antioxidant, antiparasitic, antiviral, anti-inflammatory, and antiproliferative activities being the most frequently mentioned. This review aims to present an update of the Stevia genus covering ethnobotanical aspects and traditional uses, phytochemistry, and biological activities of the extracts and isolated compounds.

Antibacterial Activities of Echinops kebericho Mesfin Tuber Extracts and Isolation of the Most Active Compound, Dehydrocostus Lactone

Echinops kebericho Mesfin is traditionally used for the treatment of various infectious diseases. This study investigated antibacterial activity of the essential oil (EO) and the different fractions of ethanol extract. The most active component was isolated and identified. Isolation and purification was accomplished using chromatographic techniques while identification was done by spectroscopic method. Minimum inhibitory concentration (MIC) was determined using the broth micro-dilution method. In bioactive-guided isolation, percent inhibition was determined using optical density (OD) measurement. The MICs of the essential oil ranged from 78.125 μg/ml to 625 μg/ml, and its activity was observed against methicillin-resistant Staphylococcus aureus (MRSA, NCTC 12493). Ethyl acetate fraction showed high activity against MRSA (NCTC 12493), MIC = 39.075 μg/ml followed by Enterococcus faecalis (ATCC 49532), MIC = 78.125 μg/ml and was least active against Klebsiella pneumoniae (ATCC 700603), MIC = 1,250 μg/ml. MIC of hexane fraction ranged from 156.2 µg/ml to Escherichia coli (ATCC 49532) to 1,250 μg/ml to E. coli (NCTC 11954). The MICs of chloroform fraction ranged from 312.5 to 2500 μg/ml; while butanol fraction could be considered pharmacologically inactive as its MIC value was 2,500 μg/ml for all and no activity against E. coli (NCTC 11954). Dehydrocostus lactone was successfully isolated and identified whose MIC was 19.53 μg/ml against MRSA. Dehydrocostus lactone isolated from E. kebericho M. showed noteworthy antibacterial activity which lends support to ethnopharmacological use of the plant. Further optimization should be done to improve its antibacterial activities and pharmacokinetic profile.

Natural Sesquiterpene Lactones in the Prevention and Treatment of Inflammatory Disorders and cancer: A Systematic Study of this Emerging Therapeutic Approach based on Chemical and Pharmacological Aspect

Background and Introduction:

Sesquiterpene lactones are a class of secondary metabolite that contains sesquiterpenoids and lactone ring as pharmacophore moiety. A large group of bioactive secondary metabolites such as phytopharmaceuticals belong to this category. From the Asteraceae family-based medicinal plants, more than 5,000 sesquiterpene lactones have been reported so far. Sesquiterpene lactone-based pharmacophore moieties hold promise for broad-spectrum biological activities against cancer, inflammation, parasitic, bacterial, fungal, viral infection and other functional disorders. Moreover, these moiety based phytocompounds have been highlighted with a new dimension in the natural drug discovery program worldwide after the 2015 Medicine Nobel Prize achieved by the Artemisinin researchers.

Objective:

These bitter substances often contain an α, β-unsaturated-γ-lactone as a major structural backbone, which in recent studies has been explored to be associated with anti-tumor, cytotoxic, and anti-inflammatory action. Recently, the use of sesquiterpene lactones as phytomedicine has been increased. This study will review the prospect of sesquiterpene lactones against inflammation and cancer.

Methods:

Hence, we emphasized on the different features of this moiety by incorporating its structural diversity on biological activities to explore structure-activity relationships (SAR) against inflammation and cancer.

Results:

How the dual mode of action such as anti-inflammatory and anti-cancer has been exhibitedby these phytopharmaceuticals will be forecasted in this study. Furthermore, the correlation of anti-inflammatory and anti-cancer activity executed by the sesquiterpene lactones for fruitful phytotherapy will also be revealed in the present review in the milieu of pharmacophore activity relation and pharmacodynamics study as well.

Conclusion:

So, these metabolites are paramount in phytopharmacological aspects. The present discussion on the future prospect of this moiety based on the reported literature could be a guide for anti-inflammatory and anti-cancer drug discovery programs for the upcoming researchers.

Costunolide-A Bioactive Sesquiterpene Lactone with Diverse Therapeutic Potential

Sesquiterpene lactones constitute a major class of bioactive natural products. One of the naturally occurring sesquiterpene lactones is costunolide, which has been extensively investigated for a wide range of biological activities. Multiple lines of preclinical studies have reported that the compound possesses antioxidative, anti-inflammatory, antiallergic, bone remodeling, neuroprotective, hair growth promoting, anticancer, and antidiabetic properties. Many of these bioactivities are supported by mechanistic details, such as the modulation of various intracellular signaling pathways involved in precipitating tissue inflammation, tumor growth and progression, bone loss, and neurodegeneration. The key molecular targets of costunolide include, but are not limited to, intracellular kinases, such as mitogen-activated protein kinases, Akt kinase, telomerase, cyclins and cyclin-dependent kinases, and redox-regulated transcription factors, such as nuclear factor-kappaB, signal transducer and activator of transcription, activator protein-1. The compound also diminished the production and/expression of proinflammatory mediators, such as cyclooxygenase-2, inducible nitric oxide synthase, nitric oxide, prostaglandins, and cytokines. This review provides an overview of the therapeutic potential of costunolide in the management of various diseases and their underlying mechanisms.

New Isoflavonoids from the extract of Rhynchosia precatoria (Humb. & Bonpl. ex Willd.) DC. and their antimycobacterial activity

ETHNOPHARMACOLOGY RELEVANCE

The evaluation of the antimycobacterial activity of extracts of medicinal plants used by Mayos against tuberculosis and respiratory problems, allowed the identification of Rhynchosia precatoria (Humb. & Bonpl. ex Willd.) DC (Fabaceae) as the best candidate to find new antimycobacterial compounds.

AIM OF THE STUDY

To isolate and characterize the compounds of R. precatoria responsible for the inhibitory and bactericidal activity against Mycobacterium tuberculosis H37Rv and Mycobacterium smegmatis ATCC 700084. To determine antimycobacterial synergistic effect of pure compounds and their selectivity index towards Vero cells.

MATERIALS AND METHODS

A total of six flavonoids were purified by silica gel column chromatography. Structural elucidation of the isolated compounds was achieved by using 1D and 2D NMR spectroscopy techniques. The configuration at the C-3 chiral center was established by quantum mechanical calculation of the electronic circular dichroism (ECD) spectrum. In vitro inhibitory and bactericidal activity against M. tuberculosis and M. smegmatis were determined with the redox indicator Alamar Blue (resazurin). Synergy was determined by X/Y quotient. Cytotoxicity was measured by MTT assay.

RESULTS

The isolated compounds were identified as precatorin A (1), precatorin B (2), precatorin C (3), lupinifolin (4), cajanone (5) and lupinifolinol (6). Compounds 1-3 are new. Compounds 1 to 5 inhibited the growth of M. tuberculosis (MIC ≥31.25µg/mL); compounds 1, 2, 4 and 5 killed the bacteria (MBC ≥31.25µg/mL) and also inhibited M. smegmatis (MIC ≥125µg/mL), while 1 and 4 also resulted bactericidal (MBC ≥125µg/mL). Compounds 4 and 5 presented synergistic effect (X/Y quotient value <0.5) at a concentration of 1/2 MIC of each compound in the combination. Cytotoxicity in murine macrophages (RAW 264.7 cells) gave IC₅₀ values of 13.3-46.98µM, for compounds 1-5.

CONCLUSIONS

In this work we isolated two new isoflavanones (1 and 2), and one new isoflavone (3) with a weak antimycobacterial activity. The (3R) absolute configuration was assigned to 1 by computational analysis of its ECD spectrum and to 2 and 5 by similarity of their ECD spectra with that of 1. We are also reporting by first time, activity against virulent strain of M. tuberculosis for compounds 4 and 5 and their antimycobacterial synergistic effect.

Natural Compounds from Mexican Medicinal Plants as Potential Drug Leads for Anti-Tuberculosis Drugs

In Mexican Traditional Medicine 187 plant species are used in the treatment of respiratory conditions that may be associated with tuberculosis. In this contribution, we review the ethnobotany, chemistry and pharmacology of 63 species whose extracts have been assayed for antimycobacterial activity in vitro. Among these, the most potent is Aristolochia brevipes (MIC= 12.5 µg/mL), followed by Aristolochia taliscana, Citrus sinensis, Chrysactinia mexicana, Persea americana, and Olea europaea (MIC<64 µg/mL). Other potent extracts (inhibition > 95%, 50 µg/mL) include: Amphipterygium adstringens, Larrea divaricata, and Phoradendron robinsoni. Several active compounds have been identified, the most potent are: Licarin A (isolated from A. taliscana), and 9-amino-9-methoxy-3,4-dihydro-2H-benzo[h]-chromen-2-one (transformation product of 9-methoxytariacuripyrone isolated from Aristolochia brevipes), both with MIC= 3.125 µg/mL, that is 8-fold less potent than the reference drug Rifampicin (MIC= 0.5 µg/mL). Any of the compounds or extracts here reviewed has been studied in clinical trials or with animal models; however, these should be accomplished since several are active against strains resistant to common drugs.

Rapid and Efficient Extraction and HPLC Analysis of Sesquiterpene Lactones from Aucklandia lappa Root

The root of Aucklandia lappa Decne, family Asteraceae, is widely used in Asian traditional medicine due to its sesquiterpene lactones. The aim of this study was the development and optimization of the extraction and analysis of these sesquiterpene lactones. The current Chinese Pharmacopoeia reports a monograph for “Aucklandiae Radix”, but the extraction method is very long and tedious including maceration overnight and ultrasonication. Different extraction protocols were evaluated with the aim of optimizing the maceration period, solvent, and shaking and sonication times. The optimized method consists of only one hour of shaking plus 30 minutes of sonication using 100% MeOH as solvent. 1H NMR spectroscopy was used as a complementary analytical tool to monitor the residual presence of sesquitepene lactones in the herbal material. A suitable LC-DAD method was set up to quantify the sesquiterpene lactones. Recovery was ca. 97%, but a very high instability of constituents was found after powdering the herbal drug. A loss of about 20% of total sesquiterpenes was found after 15–20 days; as a consequence, it is strongly endorsed to use fresh powdered herbal material to avoid errors in the quantification.

Trilobolide-steroid hybrids: Synthesis, cytotoxic and antimycobacterial activity

Sesquiterpene lactone trilobolide is a sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) inhibitor, thus depleting the Ins(1,4,5)P3-sensitive intracellular calcium stores. Here, we describe a synthesis of a series of 6 trilobolide-steroids conjugates (estradiol, pregnene, dehydroepiandrosterone, and testosterone). We found that the newly synthesized Tb-based compounds possess different remarkable biological activities. Cancer cell cytotoxicity and preferential selectivity is represented in our study by a Tb-pregnene derivative. The most cytotoxic clickates of estradiol and pregnene were studied by FACS where impact on cell cycle and RNA synthesis was observed; live-cell microscopy revealed the impact on cell organelle morphology particularly endoplasmic reticulum, mitochondria and nucleus. Further, we have studied the estrogenic and androgenic properties of the clickate molecules using cell-based luciferase assays. Finally, antimycobacterial tests revealed that testosterone and estradiol derivatives potentiated the antimycobacterial activity up to IC50 of 10.6μM.

Antimycobacterial and HIV-1 Reverse Transcriptase Activity of Julianaceae and Clusiaceae Plant Species from Mexico

The extracts of 14 Julianaceae and 5 Clusiaceae species growing in Mexico were tested in vitro (50 µg/mL) against Mycobacterium tuberculosis H37Rv and HIV reverse transcriptase (HIV-RT). The Julianaceae bark and leaf extracts inhibited M. tuberculosis (>84.67%) and HIV-RT (<49.89%). The Clusiaceae leaves extracts also inhibited both targets (>58.3% and >67.6%), respectively. The IC50 values for six selected extracts and their cytotoxicity (50 µg/mL) to human macrophages were then determined. Amphipterygium glaucum, A. molle, and A. simplicifolium fairly inhibited M. tuberculosis with IC50 of 1.87-2.35 µg/mL; but their IC50 against HIV-RT was 59.25-97.83 µg/mL. Calophyllum brasiliense, Vismia baccifera, and Vismia mexicana effect on M. tuberculosis was noteworthy (IC50 3.02-3.64 µg/mL) and also inhibited RT-HIV (IC50 26.24-35.17 µg/mL). These 6 extracts (50 µg/mL) presented low toxicity to macrophages (<23.8%). The HPLC profiles of A. glaucum, A. molle, and A. simplicifolium indicated that their antimycobacterial activity cannot be related to masticadienonic, 3α, or 3β-hydromasticadienonic acids, suggesting that other compounds may be responsible for the observed activity or this might be a synergy result. The anti-HIV-RT and antimycobacterial activities induced by C. brasiliense can be attributed to the content of calanolides A, B, as well as soulatrolide.

Estimation of Costunolide and Dehydrocostus Lactone in Saussurea lappa and its Polyherbal Formulations followed by their Stability Studies Using HPLC-DAD

BACKGROUND

Saussurea lappa is one of the popular Ayurvedic herb; costunolide and dehydrocostus lactones are well-known sesquiterpene lactones contained in many plants used as popular herbs, such as S. lappa, and have been considered as potential candidates for the treatment of various types of tumor.

OBJECTIVE

The present study was used for the quantification of costunolide and dehydrocostus lactone in S. lappa and its polyherbal formulations, stability studies of markers and characterization of their degradants.

MATERIALS AND METHODS

HPLC analysis was performed on Waters NOVAPAK HR C18 column (300 mm × 3.9 mm i.d., 6 μm) using isocratic elution with acetonitrile and water (60:40% v/v).

RESULTS

The calibration curves of both analytes showed good linearity within the established range 5-100 μg/ml. The limits of detection (LOD) and quantification (LOQ) were 1.5 and 4.6 μg/ml for costunolide and 1.3 and 4.0 μg/ml for dehydrocostus lactone, respectively. Good results were achieved with respect to repeatability (%RSD < 2.0) and recovery (99.3-101.8%).

CONCLUSION

The method was found to be precise, accurate, specific, and was successfully used for analyzing costunolide and dehydrocostus lactone in S. lappa and its polyherbal formulations. The developed method was found to be suitable for stability studies of markers and characterization of their degradation products.

Study on the pharmacokinetics and metabolism of costunolide and dehydrocostus lactone in rats by HPLC-UV and UPLC-Q-TOF/MS

A method based on high-performance liquid chromatography coupled with ultraviolet detection was developed for studying the pharmacokinetics of costunolide (Cos) and dehydrocostus lactone (Dehy) in rats after intravenous (i.v.) administration. Following i.v. administration, the maximum plasma concentrations of Cos and Dehy were observed to be 12.29 ± 1.47 and 5.79 ± 0.13 µg/mL, respectively. The bioavailability of Cos was larger than that of Dehy; however, the clearance and the volume of distribution of Dehy were much larger than those of Cos. An ultraperformance liquid chromatography/quadrupole time-of-flight mass spectrometry system with automated MS(E) (E represents collision energy) data analysis software (MetaboLynx(TM)) was used to analyze and identify the metabolites of Cos and Dehy in vivo. Four metabolites of Cos and six metabolites of Dehy were discovered from the plasma, urine and feces of rats. The main metabolic pathway of Cos was phase II biotransformation, but the main metabolic pathways of Dehy was phase І biotransformation. Two sequential desaturations and N-acetylcysteine conjugation were the common metabolic pathways of Cos and Dehy in rats. This information may be useful for the further development of the two drug candidates.

In vitro anti-mycobacterial activity of nine medicinal plants used by ethnic groups in Sonora, Mexico

Background

Sonoran ethnic groups (Yaquis, Mayos, Seris, Guarijíos, Pimas, Kikapúes and Pápagos) use mainly herbal based preparations as their first line of medicinal treatment. Among the plants used are those with anti-tuberculosis properties; however, no formal research is available.

Methods

Organic extracts were obtained from nine medicinal plants traditionally used by Sonoran ethnic groups to treat different kinds of diseases; three of them are mainly used to treat tuberculosis. All of the extracts were tested against Mycobacterium tuberculosis H37Rv using the Alamar Blue redox bioassay.

Results

Methanolic extracts from Ambrosia confertiflora, Ambrosia ambrosioides and Guaiacum coulteri showed minimal inhibitory concentration (MIC) values of 200, 790 and 1000 μg/mL, respectively, whereas no effect was observed with the rest of the methanolic extracts at the concentrations tested. Chloroform, dichloromethane, and ethyl acetate extracts from Ambrosia confertiflora showed a MIC of 90, 120 and 160 μg/mL, respectively.

Conclusions

A. confertiflora and A. ambrosioides showed the best anti-mycobacterial activity in vitro. The activity of Guaiacum coulteri is consistent with the traditional use by Sonoran ethnic groups as anti-tuberculosis agent.

For these reasons, it is important to investigate a broader spectrum of medicinal plants in order to find compounds active against Mycobacterium tuberculosis.

Sesquiterpenoids in subtribe Centaureinae (Cass.) Dumort (tribe Cardueae, Asteraceae): distribution, (13)C NMR spectral data and biological properties

Asteraceae Bercht. & J. Presl is one of the biggest and most economically important plant families. The taxonomy and phylogeny of Asteraceae is rather complex and according to the latest and most reliable taxonomic classification of Panero & Funk, based on the analysis of nine chloroplast regions, the family is divided into 12 subfamilies and 35 tribes. One of the largest tribes of Asteraceae is Cardueae Cass. with four subtribes (Carlininae, Echinopinae, Carduinae and Centaureinae) and more than 2500 species. Susanna & Garcia-Jacas have organized the genera of Centaureinae (about 800 species) into seven informal groups, which recent molecular studies have confirmed: 1. Basal genera; 2. Volutaria group; 3. Rhaponticum group; 4. Serratula group; 5. Carthamus group; 6. Crocodylium group; 7. Centaurea group. This review summarizes reports on sesquiterpenoids from the Centaureinae subtribe of the Asteraceae family, as well as the (13)C NMR spectral data described in the literature. It further reviews studies concerning the biological activities of these metabolites. For this work, literature data on sesquiterpenes from the Centaureinae subtribe were retrieved with the help of the SciFinder database and other similar data banks. All entries from 1958 until the end of 2011 were considered. This review is addressed to scientists working in the metabolomics field such as chemists, botanists, etc., the spectroscopic data reported make this work a good tool for structural elucidation, the biological section gives useful information to those who wish to study the structure activity relationships.

Ursolic and oleanolic acids as antimicrobial and immunomodulatory compounds for tuberculosis treatment

BACKGROUND

New alternatives for the treatment of Tuberculosis (TB) are urgently needed and medicinal plants represent a potential option. Chamaedora tepejilote and Lantana hispida are medicinal plants from Mexico and their hexanic extracts have shown antimycobacterial activity. Bioguided investigation of these extracts showed that the active compounds were ursolic acid (UA) and oleanolic acid (OA).

METHODS

The activity of UA and OA against Mycobacterium tuberculosis H37Rv, four monoresistant strains, and two drug-resistant clinical isolates were determined by MABA test. The intracellular activity of UA and OA against M. tuberculosis H37Rv and a MDR clinical isolate were evaluated in a macrophage cell line. Finally, the antitubercular activity of UA and OA was tested in BALB/c mice infected with M. tuberculosis H37Rv or a MDR strain, by determining pulmonary bacilli loads, tissue damage by automated histomorphometry, and expression of IFN-γ, TNF-α, and iNOS by quantitative RT-PCR.

RESULTS

The in vitro assay showed that the UA/OA mixture has synergistic activity. The intracellular activity of these compounds against M. tuberculosis H37Rv and a MDR clinical isolate in a macrophage cell line showed that both compounds, alone and in combination, were active against intracellular mycobacteria even at low doses. Moreover, when both compounds were used to treat BALB/c mice with TB induced by H37Rv or MDR bacilli, a significant reduction of bacterial loads and pneumonia were observed compared to the control. Interestingly, animals treated with UA and OA showed a higher expression of IFN-γ and TNF-α in their lungs, than control animals.

CONCLUSION

UA and OA showed antimicrobial activity plus an immune-stimulatory effect that permitted the control of experimental pulmonary TB.

Anti-mycobacterial activity of plumericin and isoplumericin against MDR Mycobacterium tuberculosis

BACKGROUND AND OBJECTIVES

Because of the developing resistance of Mycobacterium species against currently available anti-mycobacterial drugs, there is an urgent need for new drug development. In this study, we have evaluated the in vitro anti-mycobacterial activity of Plumeria bicolor extract and its phytoconstituents - plumericin and isoplumericin against multi-drug resistance Mycobacterium tuberculosis.

METHODS

The in vitro anti-mycobacterial activity of chloroform extract of P. bicolor, plumericin and isoplumericin were tested against M. tuberculosis (H37Rv) and four multi-drug resistant (MDR) clinical isolates by measuring the minimum inhibitory concentration (MIC) using MTT (Tetrazolium bromide [3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide]) assay. The extract and both compounds were further evaluated by standard assay procedures to determine their minimum bactericidal concentration (MBC). Cytotoxicity of these compounds was performed against J774G8 murine macrophage cell lines. The activity was represented in the mean (±SD) of duplicate samples from three independent assays.

RESULTS

Plumericin showed better activity against pan sensitive as well as four MDR strains of M. tuberculosis with MIC values of 2.1 ± 0.12, 1.3 ± 0.15, 2.0 ± 0.07, 1.5 ± 0.13 & 2.0 ± 0.14 μg/mL and MBC values of 3.6 ± 0.22, 2.5 ± 0.18, 3.8 ± 0.27, 2.9 ± 0.20 & 3.7 ± 0.32 μg/mL than isoplumericin, respectively. Interestingly, both isolated active compounds showed an advantage over rifampicin (80 times) and isoniazid (8 times) by being highly active against the MDR strains. The extract and both compounds were found to be non-toxic against J774G8 macrophages up to the used concentrations.

CONCLUSION

Plumericin showed more potent activity than isoplumericin. The excellent activity of these compounds against MDR strains opens a possibility of obtaining new anti-mycobacterial drug candidate in near future.

In vitro and in vivo activities of ruthenium(II) phosphine/diimine/picolinate complexes (SCAR) against Mycobacterium tuberculosis

Rifampicin, discovered more than 50 years ago, represents the last novel class of antibiotics introduced for the first-line treatment of tuberculosis. Drugs in this class form part of a 6-month regimen that is ineffective against MDR and XDR TB, and incompatible with many antiretroviral drugs. Investments in R&D strategies have increased substantially in the last decades. However, the number of new drugs approved by drug regulatory agencies worldwide does not increase correspondingly. Ruthenium complexes (SCAR) have been tested in our laboratory and showed promising activity against Mycobacterium tuberculosis. These complexes showed up to 150 times higher activity against MTB than its organic molecule without the metal (free ligand), with low cytotoxicity and high selectivity. In this study, promising results inspired us to seek a better understanding of the biological activity of these complexes. The in vitro biological results obtained with the SCAR compounds were extremely promising, comparable to or better than those for first-line drugs and drugs in development. Moreover, SCAR 1 and 4, which presented low acute toxicity, were assessed by Ames test, and results demonstrated absence of mutagenicity.

Sesquiterpene lactones from the leaves of Hedyosmum brasiliense (Chloranthaceae)

Hedyosmum brasiliense Miq. is an endemic aromatic arborescent shrub that is the only representative of the Chloranthaceae in Brazil. There have been few studies seeking to determine its chemical constituents and/or pharmacological effects. This work describes the isolation and identification of sesquiterpene lactones from the leaves, including guaianolides, elemanolides and a lindenanolide. These were tested against Mycobacterium tuberculosis, together with podoandin, onoseriolide and some other common phenolics. The structures of the isolated compounds were determined based on extensive analysis of 1D and 2D NMR spectroscopic and MS data, as well as comparison with published data. The compounds found were the guaianolides, 1,2-epoxy-10α-hydroxy-podoandin and 1-hydroxy-10,15-methylenepodoandin, the elemenolide 15-acetoxy-isogermafurenolide and the lindenanolide 8α/β,9α-hydroxy-onoseriolide, along with the previously isolated guaianolide podoandin, the lindenanolide onoseriolide and the elemenolide 15-hydroxy-isogermafurenolide. The phenolic compounds isolated were scopoletin, vanillin, vanillic acid, protocatechuic aldehyde and ethyl caffeate. The isolated sesquiterpene lactones did not show anti-mycobacterial activity against isoniazid-sensitive M. tuberculosis cultures at concentrations of 1-30 μM.

Synergistic anticancer activities of the plant-derived sesquiterpene lactones salograviolide A and iso-seco-tanapartholide

We have previously shown that the two sesquiterpene lactones, salograviolide A (Sal A) and iso-seco-tanapartholide (TNP), isolated from the Middle Eastern indigenous plants Centaurea ainetensis and Achillea falcata, respectively, possess selective antitumor properties. Here, we aimed to assess the anticancer effects of the separate compounds and their combination, study their potential to generate reactive oxygen species (ROS), and investigate their underlying antitumor mechanisms in human colon cancer cell lines. Cells were treated with Sal A and TNP alone or in combination, and cell viability, cell cycle profile, apoptosis, ROS generation and changes in protein expression were monitored. Sal A and TNP in combination caused 80% decrease in HCT-116 and DLD-1 cell viability versus only 25% reduction when the drugs were used separately. The antitumor mechanism involved triggering ROS-dependent apoptosis as well as disruption of the mitochondrial membrane potential. Further studies showed that apoptosis by the Sal A and TNP combination was caspase-independent and that ERK, JNK and p38 of the serine/threonine MAPKs signaling pathway were involved in the cell death mechanism. Taken together, our data suggest that the combination of Sal A and TNP may be of therapeutic interest against colon cancer.

In vitro and in vivo assessment of the effect of Laurus novocanariensis oil and essential oil in human skin

Laurus novocanariensis is an endemic plant from the Madeira Island forest that derives a fatty oil, with a strong spicy odour, from its berries that has been used for centuries in traditional medicine to treat skin ailments. This work aimed to investigate the effect of the application of both the oil and its essential oil on normal skin, to assess their safety and potential benefits. Diffusion studies with Franz cells using human epidermal membranes were conducted. The steady-state fluxes of two model molecules through untreated skin were compared with those obtained after a 2-h pre-treatment with either the oil or the essential oil. Additionally, eleven volunteers participated in the in vivo study that was conducted on the forearm and involved daily application of the oil for 5 days. Measurements were performed every day in the treated site with bioengineering methods that measure erythema, irritation and loss of barrier function. Slightly higher steady-state fluxes were observed for both the lipophilic and the hydrophilic molecule when the epidermal membranes were pre-treated. Nevertheless, such differences had no statistical significance, which seems to confirm that neither the oil nor the essential oil impaired the epidermal barrier. Results collected with the Chromameter, the Laser Doppler Flowmeter and the visual scoring are in agreement with those established in the in vitro study. They indicate that the repeated application of the oil did not cause erythema, because the results observed in the first day of the study were maintained throughout the week. Application of the oil did not affect the skin barrier function, because the transepidermal water loss remained constant throughout the study. The stratum corneum hydration was slightly reduced on days 4 and 5. This work shows that both the oil and the essential oil were well tolerated by the skin and did not cause significant barrier impairment or irritation.

Enzymatic reduction of 9-methoxytariacuripyrone by Saccharomyces cerevisiae and its antimycobacterial activity

Biotransformation processes have been successfully utilized to obtain products of pharmaceutical, chemical, food, and agricultural interest, which are difficult to obtain by classic chemical methods. The compound with antituberculous activity, 9-methoxy-tariacuripyrone (1), isolated from Aristolochia brevipes, was submitted to biotransformation with the yeast Saccharomyces cerevisiae under culture, yielding 5-amino-9-methoxy-3,4-dihydro-2H-benzo[h]chromen-2-one (2). The structure of 2 was elucidated on the basis of spectroscopic analyses. The results mainly show the reduction of the double bond and the nitro group of compound 1. Metabolite 2 demonstrated an increase in anti-tuberculous activity (MIC = 3.12 µg/mL) against the drug-sensitive Mycobacterium tuberculosis (H37Rv) strain, with respect to that shown by 1.

Synthesis of potent inhibitors of β-ketoacyl-acyl carrier protein synthase III as potential antimicrobial agents

Mycobacterium tuberculosis FabH, an essential enzyme in the mycolic acid biosynthetic pathway, is an attractive target for novel anti-tubercolosis agents. Structure-based design and synthesis of 1-(4-carboxybutyl)-4-(4-(substituted benzyloxy)phenyl)-1H-pyrrole-2-carboxylic acid derivatives 7a–h, a subset of eight potential FabH inhibitors, is described in this paper. The Vilsmeier-Haack reaction was employed as a key step. The structures of all the newly synthesized compounds were identified by IR, ¹H-NMR, ¹³C-NMR, ESI-MS and HRMS. The alamarBlue™ microassay was employed to evaluate the compounds 7a–h against Mycobacterium tuberculosis H₃₇Rv. The results demonstrate that the compound 7d possesses good in vitro antimycobacterial activity against Mycobacterium tuberculosis H₃₇Rv (Minimum Inhibitory Concentration value [MIC], 12.5 µg/mL).These compounds may prove useful in the discovery and development of new anti-tuberculosis drugs.

Composition of Three Essential Oils, and their Mammalian Cell Toxicity and Antimycobacterial Activity against Drug Resistant-Tuberculosis and Nontuberculous Mycobacteria Strains

Tuberculosis (TB) is the most ancient epidemic disease in the world and a serious opportunistic disease in HIV/AIDS patients. The increase in multidrug resistant Mycobacterium tuberculosis (MDR-TB, XDR-TB) demands the search for novel antimycobacterial drugs. Essential oils (EOs) have been widely used in medicine and some EOs and their major components have been shown to be active against M. tuberculosis. The aim of this work was to evaluate the antimycobacterial and cell toxicity activities of three EOs derived from Salvia aratocensis, Turnera diffusa and Lippia americana, aromatics plants collected in Colombia. The EOs were isolated by hydrodistillation and analyzed by GC/MS techniques. The EOs were tested against 15 Mycobacterium spp using a colorimetric macrodilution method and against mammalian Vero and THP-1 cells by MTT. The activity was expressed as minimal concentration in μg/mL that inhibits growth, and the concentration that is cytotoxic for 50 or 90% of the cells (CC50 and CC90). The major components were epi-α-cadinol (20.1%) and 1,10-di- epi-cubenol (14.2%) for Salvia aratocensis; drima-7,9(11)-diene (22.9%) and viridiflorene (6.6%) for Turnera diffusa; and germacrene D (15.4%) and trans-β- caryophyllene (11.3%) for Lippia americana. The most active EO was obtained from S. aratocensis, with MIC values below 125 μg mL−1 for M. tuberculosis Beijing genotype strains, and 200 to 500 μg mL−1 for nontuberculous mycobacterial strains. The EOs were either partially or non toxic to Vero and THP-1 mammalian cells with CC50 values from 30 to >100 μg mL−1, and a CC90 >100 μg mL−1. The EOs obtained from the three aromatic Colombian plants are an important source of potential compounds against TB. Future studies using the major EO components are recommended.

Antibacterial activity of Aristolochia brevipes against multidrug-resistant Mycobacterium tuberculosis

The increased incidence of Multidrug-Resistant Mycobacterium tuberculosis (MDR-MT) requires the search for alternative antimycobacterial drugs. The main aim of this study was to evaluate the dichloromethane extract from Aristolochia brevipes (Rhizoma) and the compounds isolated from this extract against several mycobacterial strains, sensitive, resistant (monoresistant), and clinical isolates (multidrug-resistant), using the alamarBlue™ microassay. The extract was fractionated by column chromatography, yielding the following eight major compounds: (1) 6α-7-dehydro-N-formylnornantenine; (2) E/Z-N-formylnornantenine; (3) 7,9-dimethoxytariacuripyrone; (4) 9-methoxy-tariacuripyrone; (5) aristololactam I; (6) β-sitosterol; (7) stigmasterol; and (8) 3-hydroxy-α-terpineol. The structures of these compounds were elucidated by ¹H- and ¹³C- (1D and 2D) Nuclear Magnetic Resonance (NMR) spectroscopy. This study demonstrates that the dichloromethane extract (rhizome) of A. brevipes possesses strong in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv (Minimum Inhibitory Concentration value [MIC], 12.5 µg/mL). The most active compound against all mycobacterial strains tested was the compound aristolactam I (5), with MIC values ranging between 12.5 and 25 µg/mL. To our knowledge, this the first report of antimycobacterial activity in this plant.

Antitubercular potential of plants: a brief account of some important molecules

Mycobacterium tuberculosis is the most lethal pathogen causing tuberculosis in human. After the discovery of antitubercular drugs pyrazinamide, rifampicin, isoniazid, streptomycin, and ethambutol (PRISE), the disease was controlled for a limited period. However, over the course of their usage, the pathogen acquired resistance and evolved into multi-drug resistant, single-drug resistant, and extensive drug resistant forms. A good number of plant secondary metabolites are reported to have antitubercular activity comparable to the existing antitubercular drugs or sometimes even better in potency. A well-defined strategy is required to exploit these phytomolecules as antitubercular drugs. This review gives concise up-to-date information regarding the chemistry and pharmacology of plant-based leads and some insight into their structure-activity relationship.

Costunolide-induced apoptosis in human leukemia cells: involvement of c-jun N-terminal kinase activation

The authors previously reported that costunolide, an active compound isolated from the stem bark of Magnolia sieboldii, induced apoptosis via reactive oxygen species (ROS) and Bcl-2-dependent mitochondrial permeability transition in human leukemia cells. In the present study, the authors investigated whether mitogen-activated protein kinases (MAPKs) are involved in the costunolide-induced apoptosis in human promonocytic leukemia U937 cells. Treatment with costunolide resulted in the significant activation of c-Jun N-terminal kinase (JNK), but not of extracellular-signal-related kinase (ERK1/2) or p38. In vitro kinase assays showed that JNK activity was low in untreated cells but increased dramatically after 30 min of costunolide treatment. U937 cells co-treated with costunolide and sorbitol, a JNK activator, exhibited higher levels of cell death. In addition, inhibition of the JNK pathway using a dominant-negative mutation of c-jun and JNK inhibitor SP600125, significantly prevented costunolide-induced apoptosis. Furthermore, pretreatment with the antioxidant NAC (N-acetyl-L-cysteine) blocked the costunolide-stimulated activation of JNK while the overexpression of Bcl-2 failed to reverse JNK activation. Pretreatment with SP600125 recovered the costunolide-suppressed Bcl-2 expression. These results indicate that costunolide-induced JNK activation acts downstream of ROS but upstream of Bcl-2, and suggest that ROS-mediated JNK activation plays a key role in costunolide-induced apoptosis. Moreover, the administration of costunolide (intraperitoneally once a day for 7 d) significantly suppressed tumor growth and increased survival in 3LL Lewis lung carcinoma-bearing model.