Antibacterial Activity of Pharmaceutical-Grade Rose Bengal: An Application of a Synthetic Dye in Antibacterial Therapies.

Rose bengal has been used in the diagnosis of ophthalmic disorders and liver function, and has been studied for the treatment of solid tumor cancers. To date, the antibacterial activity of rose bengal has been sporadically reported; however, these data have been generated with a commercial grade of rose bengal, which contains major uncontrolled impurities generated by the manufacturing process (80-95% dye content). A high-purity form of rose bengal formulation (HP-RBf, >99.5% dye content) kills a battery of Gram-positive bacteria, including drug-resistant strains at low concentrations (0.01-3.13 µg/mL) under fluorescent, LED, and natural light in a few minutes. Significantly, HP-RBf effectively eradicates Gram-positive bacterial biofilms. The frequency that Gram-positive bacteria spontaneously developed resistance to HP-RB is extremely low (less than 1 × 10-13). Toxicity data obtained through our research programs indicate that HP-RB is feasible as an anti-infective drug for the treatment of skin and soft tissue infections (SSTIs) involving multidrug-resistant (MDR) microbial invasion of the skin, and for eradicating biofilms. This article summarizes the antibacterial activity of pharmaceutical-grade rose bengal, HP-RB, against Gram-positive bacteria, its cytotoxicity against skin cells under illumination conditions, and mechanistic insights into rose bengal's bactericidal activity under dark conditions.

Phytochemical analysis and evaluation of antioxidant and antimycobacterial activity of Colletia paradoxa from Brazil.

Colletia paradoxa (Spreng.) Esc. (Rhamnaceae, Colletieae) is a medicinal plant, threatened with extinction in Brazil, presenting great morphological variability. Our objective is to investigate the phytochemical components, antioxidant capacity and antimycobacterial activity of different morphotypes of C. paradoxa in different environments. For this, the crude extract of the leaves and branches of the individuals sampled was used. The elimination capacity of the free radicals was determined by the DPPH method, the antimycobacterial activity by the broth microdilution method and the phenolic content by the spectrophotometric method using the Folin-Ciocalteu reagent and by HPLC. The extracts of C. paradoxa and its morphotypes showed significant amounts of phenolic compounds, including quercetin, quercitrin and rutin, besides considerable antioxidant and antimycobacterial activity No connection was detected between the phytochemical composition and different morphotypes of C. paradoxa.

Structure-activity relationship analyses of fusidic acid derivatives highlight crucial role of the C-21 carboxylic acid moiety to its anti-mycobacterial activity.

Fusidic acid (FA) is a potent congener of the fusidane triterpenoid class of antibiotics. Structure-activity relationship (SAR) studies suggest the chemical structure of FA is optimal for its antibacterial activity. SAR studies from our group within the context of a drug repositioning approach in tuberculosis (TB) suggest that, as with its antibacterial activity, the C-21 carboxylic acid group is indispensable for its anti-mycobacterial activity. Further studies have led to the identification of 16-deacetoxy-16ß-ethoxyfusidic acid (58), an analog which exhibited comparable activity to FA with an in vitro MIC99 value of 0.8 µM. Preliminary SAR studies around the FA scaffold suggested that the hydrophobic side chain at C-20, like the C-11 OH group, was required for activity. The C-3 OH group, however, can be functionalized to obtain more potent compounds.

The Chemical Composition and Anti-mycobacterial Activities of Trachyspermum copticum and Pelargonium graveolens Essential Oils.

BACKGROUND: Microbial resistance to antibiotics and their adverse effects related to these antibiotics are a matter of global public health in the 21th century. The emergence of drug-resistant strains, has gained the interest of the scientists to discover new antimicrobial agents from the essential oil of medicinal plants. METHODS: Anti-mycobacterial effects of Trachyspermum copticum and Pelargonium graveolens essential oils were determined against multi-drug resistant clinical strains of Mycobacterium tuberculosis, Mycobacterium kansasii, Mycobacterium fortuitum and standard strain of Mycobacterium tuberculosis H37Rv by a Broth micro-dilution method. Pelargonium graveolens plant named Narmada was discovered by Kulkarni R.N et al. (Patent ID, USPP12425P2) and a formulation comprising thymol obtained from Trachyspermum is useful in the treatment of drug-resistant bacterial infections (Patent ID, US6824795B2). The chemical composition of hydro-distilled essential oils was determined by GC and GC-MS. RESULTS: Minimum Inhibitory Concentration (MIC) values for T. copticum essential oil against tested isolates were ranged from 19.5 µg/mL to 78 µg/mL. The least minimum inhibitory concentration of P. graveolens extract against M. Kansasii and MDR-TB was 78 µg/ml. CONCLUSION: The results of the present research introduced T. copticum and P. graveolens essential oils as a remarkable natural anti-mycobacterial agent, but more pharmacological studies are required to evaluate their efficacy in animal models.

Ginger essential oil and fractions against Mycobacterium spp.

ETHNOPHARMACOLOGICAL RELEVANCE: Zingiber officinale (ginger) is a perennial herbaceous plant native in tropical Asia and generally cultivated in most American tropical countries with widespread use in popular medicine. Ginger essential oil (GEO) has been reported to exhibit several biological activities, such as antimicrobial. AIMS OF THE STUDY: The aim of this study was to determine the composition and the property of GEO and related fractions against Mtb and NTM, as well as their cytotoxicity. METHODS AND MATERIALS: GEO was obtained by hydrodistillation and fractionation was performed. Chemical characterization of GEO and fractions were carried out by gas chromatography/mass spectrometry. The antimycobacterial activity was evaluated by resazurin microtiter assay plate and broth microdilution method for Mtb and NTM, respectively. The cytotoxicity in Vero cells was assessed by MTT colorimetric assay. RESULTS: The analyses showed 63 compounds in the GEO sample, characterized by a high number of monoterpenes and sesquiterpenes. GEO fractionation rendered 11 fractions (FR1 to FR11). GEO and fractions minimum inhibitory concentration ranged from 31.25 to >250 µg/mL against Mtb and from 15.6 to >250 µg/mL against NTM. GEO showed better activity against NTM, M. chelonae, and M. abscessus sub. massiliense, than the semi-pure fractions. One fraction (FR5), containing γ-eudesmol as the main compound, was the most active against Mtb and NTM. The GEO and semi-pure fractions cytotoxicity assay showed CC50 63.3 µg/mL, and 36.3-312.5 µg/mL, respectively. CONCLUSIONS: In general, GEO showed a mix of monoterpenes and sesquiterpenes and a better antimycobacterial activity than the semi-pure fractions. Cytotoxic effects of GEO and its fractions should be better investigated.

Biophysical characterization of mycobacterial model membranes and their interaction with rifabutin: Towards lipid-guided drug screening in tuberculosis.

Lipid structure critically dictates the molecular interactions of drugs with membranes influencing passive diffusion, drug partitioning and accumulation, thereby underpinning a lipid-composition specific interplay. Spurring selective passive drug diffusion and uptake through membranes is an obvious solution to combat growing antibiotic resistance with minimized toxicities. However, the spectrum of complex mycobacterial lipids and lack thereof of suitable membrane platforms limits the understanding of mechanisms underlying drug-membrane interactions in tuberculosis. Herein, we developed membrane scaffolds specific to mycobacterial outer membrane and demonstrate them as improvised research platforms for investigating anti-tubercular drug interactions. Combined spectroscopy and microscopy results reveal an enhanced partitioning of model drug Rifabutin in trehalose dimycolate-containing mycobacterial membrane systems. These effects are apportioned to specific changes in membrane structure, order and fluidity leading to enhanced drug interaction. These findings on the membrane biophysical consequences of drug interactions will offer valuable insights for guiding the design of more effective antibiotic drugs coupled with tuned toxicity profiles.

In-vitro evaluation of the antibacterial activity of the essential oils of Micromeria barbata, Eucalyptus globulus and Juniperus excelsa against strains of Mycobacterium tuberculosis (including MDR), Mycobacterium kansasii and Mycobacterium gordonae.

BACKGROUND: Mycobacterium spp. are responsible for several diseases, particularly in immunocompromised populations. The spreading of the resistance to antimycobacterial drugs is a significant problem to the public health and requires to find out a new and innovative alternative for the treatment of drug resistant mycobacterial strains. In this study, the antimycobacterial activity of Micromeria barbata, Eucalyptus globulus and Juniperus excelsa essential oils extracted from Lebanese plants was investigated against selected Mycobacterium spp. strains. METHODS: Several dilutions of the three aforementioned essential oils were studied for antimycobacterial activity against four Mycobacterium spp. strains: Mycobacterium tuberculosis subsp. tuberculosis (ATCC® 27294™), multidrug-resistant M. tuberculosis (CMUL 157), Mycobacterium kansasii Hauduroy (ATCC® 12478™) and Mycobacterium gordonae Bojalil et al. (ATCC® 14470™). RESULTS: Even with high dilutions, all tested essential oils showed a high antimycobacterial activity against targeted strains. Our data showed that M. barbata, E. globulus and J. excelsa essential oils totally inhibit the mycobacterial growth whatever the tested strains for the dilution 1/250, 1/100 and 1/250, respectively. CONCLUSION: To our knowledge, this is the first study regarding the antimycobacterial activity of essential oils in Lebanon. Our data show promising results, and encourage to investigate more on these medicinal plants, especially M. barbata.

Photochemical "In-Air" Combinatorial Discovery of Antimicrobial Co-polymers.

There is an urgent need to identify new, non-traditional antimicrobials. The discovery of new polymeric antimicrobials is limited by current low-throughput synthetic tools, which means that limited chemical space has been explored. Herein, we employ photochemical "in-air" reversible addition-fragmentation chain-transfer (RAFT) polymerization with microwell plates, using liquid-handling robots to assemble large libraries of cationic polymers, without the need for degassing or purification steps, facilitating transfer to screening. Several lead polymers were identified including a co-polymer with propylene glycol side chains with significantly enhanced antimicrobial activity and increased therapeutic window. Mechanistic studies showed that this polymer was bacteriostatic, and surprisingly did not lyse the cell membranes, implying an alternative mode of action. This versatile method using simple robotics will help to develop new biomaterials with emergent properties.

Scientific rationale for traditional use of plants to treat tuberculosis in the eastern region of the OR Tambo district, South Africa.

ETHNOPHARMACOLOGICAL RELEVANCE: Tuberculosis (TB) remains a major health problem for humans worldwide, and was responsible for 1.4 million human deaths in 2015 alone. Although there is treatment for TB, emerging multi-drug, extensively drug and totally drug resistant forms of this disease, as well as co-infection with human immunodefiency virus (HIV) continue to worsen the situation. South Africa is among countries with reported traditional use and published documentation of such knowledge concerning the use of plants against TB. Based on a previous study where plants used traditionally for treating TB in the eastern region of OR Tambo district, South Africa, were documented, the present study aimed to determine the antimycobacterial effect, cytotoxicity and genotoxicity of plants selected from that list. MATERIAL AND METHODS: Acetone, 70% ethanol, cold and hot water extracts were tested for antimycobacterial activity against saprophytic Mycobacterium species including M. aurum, M. bovis BCG, M. gordonae, M. fortuitum, and M. smegmatis using a microdilution method. Extracts with MIC values less than 1 mg/ml against at least three Mycobacterium strains were evaluated for antimycobacterial activity against pathogenic Mycobacterium strains including M. tuberculosis H37RV, M. tuberculosis and M. bovis, cytotoxicity (against Vero monkey kidney and bovine dermis cells), and genotoxicity (against Salmonella typhimurium TA98 and TA100). RESULTS: The MIC values of the extracts ranged from 0.02 to 2.50 mg/ml, LC50 values of twenty-nine extracts ranged from 0.001 to > 1 mg/ml and the highest selectivity index was 79.50, an extremely promising value. Phymaspermum acerosum roots and leaves (ethanol and water) extracts had the best MIC value (0.02 mg/ml) against at least one Mycobacterium strain. It was interesting to note the lack of cytotoxicity of these extracts with the highest selectivity index value of 39.75. Pterocelastrus echinatus bark acetone and Protorhus longifolia leaf hot water extracts were the most cytotoxic with LC50 = 0.001 and 0.008 mg/ml, respectively, whereas Pittosporum viridiflorum bark water extract was genotoxic. Among non-pathogenic strains, M. gordonae, M. aurum, M. smegmatis showed good correlation of activity with pathogenic M. tuberculosis H37Rv, M. tuberculosis and M. bovis, however, M. aurum was the best predictor with Mycobacterium tuberculosis H37Rv (correlation coefficient value = 0.73). CONCLUSION: The results indicate that Heteromorpha trifoliata and Phymaspermum acerosum should be investigated further for antimycobacterial efficacy against drug resistant strains of Mycobacterium.

Antimycobacterial potential of the juniper berry essential oil in tap water.

Mycobacterium avium complex-related diseases are often associated with poorly maintained hot water systems. This calls for the development of new control strategies. The aim of this study was to investigate the activity of essential oils (EOs) from the Mediterranean plants, common juniper, immortelle, sage, lavandin, laurel, and white cedar against Mycobacterium avium ssp. avium, Mycobacterium intracellulare, and Mycobacterium gordonae in culturing broth and freshwater as their most common habitat. To do that, we developed a new method of water microdilution to determine their minimal effective concentrations (MEC). The most active EO was the one from the common juniper with the MEC of 1.6 mg mL-1. Gas chromatography / mass spectrometry the juniper EO identified monoterpenes (70.54 %) and sesquiterpenes (25.9 %) as dominant component groups. The main monoterpene hydrocarbons were α-pinene, sabinene, and ß-pinene. The juniper EO significantly reduced the cell viability of M. intracellulare and M. gordonae at MEC, and of M. avium at 2xMEC. Microscopic analysis confirmed its inhibitory effect by revealing significant morphological changes in the cell membrane and cytoplasm of all three bacteria. The mode of action of the juniper EO on the cell membrane was confirmed by a marked leakage of intracellular material. Juniper EO has a great practical potential as a complementary or alternative water disinfectant in hot water systems such as baths, swimming pools, spa pools, hot tubs, or even foot baths/whirlpools.

Bioprospecting of Diaporthe terebinthifolii LGMF907 for antimicrobial compounds.

Antibiotic-resistant bacteria have been observed with increasing frequency over the past decades, driving the search for new drugs and stimulating the interest in natural products sources. Endophytic fungi from medicinal plants represent a great source of novel bioactive compounds useful to pharmaceutical and agronomical purposes. Diaporthe terebinthifolii is an endophytic species isolated from Schinus terebinthifolius, a plant used in popular medicine for several health problems. The strain D. terebinthifolii LGMF907 was previously reported by our group to produce secondary metabolites with biological activity against phytopathogens. Based on these data, strain LGMF907 was chosen for bioprospecting against microorganisms of clinical importance and for characterization of major secondary metabolites. In this study, different culture conditions were evaluated and the biological activity of this strain was expanded. The crude extracts demonstrated high antibacterial activity against Escherichia coli, Micrococcus luteus, Saccharomyces cerevisiae, methicillin-sensitive Staphylococcus aureus, and methicillin-resistant S. aureus. The compounds diaporthin and orthosporin were characterized and also showed activity against the clinical microorganisms evaluated. This study discloses the first isolation of diaporthin and orthosporin from D. terebinthifolii, and revealed the potential of this endophytic fungus to produce secondary metabolites with antimicrobial activity.

Quercetin 3-O-glucoside recovered from the wild Egyptian Sahara plant, Euphorbia paralias L., inhibits glutamine synthetase and has antimycobacterial activity.

Tuberculosis remains a major health problem accentuated by the rise of resistance to all available drugs. Therefore, this study was launched to discover a novel antituberculosis agent from wild Egyptian Sahara plants. Twelve such plants were screened, in vitro, for their activity against various Mycobacterium species. The most active plant, Euphorbia paralias, was further fractionated with different organic solvents, and the activity of the obtained fractions was determined by the agar diffusion and broth microdilution methods. The methanol fraction was the most active against Mycobacterium spp., and was non-toxic in doses up to 10 g/kg of animal weight. Its main component was separated by column chromatography, and then identified by ultraviolet spectroscopy and nuclear magnetic resonance analysis as quercetin-3-O-ß-D-glucoside. Docking analysis suggested that quercetin-3-O-ß-D-glucoside inhibits the glutamine synthetase enzyme, a promising target for the development of antituberculosis drugs. This prediction was confirmed by an in vitro glutamine synthetase biosynthetic assay. To the best of our knowledge, and based on bioinformatics mining of the BioPhytMol database, this is the first report on the antimycobacterial activity of Euphorbia paralias plant. It is also the first report on the inhibition of mycobacterial glutamine synthetase by the flavonoid quercetin.

Lipase-catalyzed kinetic resolution of novel antitubercular benzoxazole derivatives.

Novel benzoxazole derivatives were synthesized, and their antitubercular activity against sensitive and drug-resistant Mycobacterium tuberculosis strains (M. tuberculosis H37 Rv, M. tuberculosis sp. 210, M. tuberculosis sp. 192, Mycobacterium scrofulaceum, Mycobacterium intracellulare, Mycobacterium fortuitum, Mycobacterium avium, and Mycobacterium kansasii) was evaluated. The chemical step included preparation of ketones, alcohols, and esters bearing benzoxazole moiety. All racemic mixtures of alcohols and esters were separated in Novozyme SP 435-catalyzed transesterification and hydrolysis, respectively. The transesterification reactions were carried out in various organic solvents (tert-butyl methyl ether, toluene, diethyl ether, and diisopropyl ether), and depending on the solvent, the enantioselectivity of the reactions ranged from 4 to >100. The enzymatic hydrolysis of esters was performed in 2 phase tert-butyl methyl ether/phosphate buffer (pH = 7.2) system and provided also enantiomerically enriched products (ee 88-99%). The antitubercular activity assay has shown that synthesized compounds exhibit an interesting antitubercular activity. Racemic mixtures of alcohols, (±)-4-(1,3-benzoxazol-2-ylsulfanyl)butan-2-ol ((±)-3a), (±)-4-[(5-bromo-1,3-benzoxazol-2-yl)sulfanyl]butan-2-ol ((±)-3b), and (±)-4-[(5,7-dibromo-1,3-benzoxazol-2-yl)sulfanyl]butan-2-ol ((±)-3c), displayed as high activity against M. scrofulaceum, M. intracellulare, M. fortuitum, and M. kansasii as commercially available antituberculosis drug-Isoniazid. Moreover, these compounds exhibited twice higher activity toward M. avium (MIC 12.5) compared with Isoniazid (MIC 50).

Targeting Mycolic Acid Transport by Indole-2-carboxamides for the Treatment of Mycobacterium abscessus Infections.

Mycobacterium abscessus is a fast-growing, multidrug-resistant organism that has emerged as a clinically significant pathogen in cystic fibrosis (CF) patients. The intrinsic resistance of M. abscessus to most commonly available antibiotics seriously restricts chemotherapeutic options. Herein, we report the potent activity of a series of indolecarboxamides against M. abscessus. The lead compounds, 6 and 12, exhibited strong activity in vitro against a wide panel of M. abscessus isolates and in infected macrophages. High resistance levels to the indolecarboxamides appear to be associated with an A309P mutation in the mycolic acid transporter MmpL3. Biochemical analyses demonstrated that while de novo mycolic acid synthesis remained unaffected, the indolecarboxamides strongly inhibited the transport of trehalose monomycolate, resulting in the loss of trehalose dimycolate production and abrogating mycolylation of arabinogalactan. Our data introduce a hereto unexploited chemical structure class active against M. abscessus infections with promising translational development possibilities for the treatment of CF patients.

Acetone leaf extracts of some South African trees with high activity against Escherichia coli also have good antimycobacterial activity and selectivity index.

BACKGROUND: Tuberculosis is a world-wide problem affecting humans and animals. There is increasing development of resistance of the pathogens to current antimycobacterial agents. Many authors have investigated activities of extracts and isolated compounds from plants. The traditional uses of plants have frequently been the criterion to select plants investigated. In this contribution, we investigate whether plant extracts with very good activity against Escherichia coli may also be active against mycobacteria. METHODS: The antimycobacterial activity of eight South African tree leaf extracts with high activity against Escherichia coli were determined in vitro against Mycobacterium smegmatis, M. fortuitum and M. aurum, using a serial microdilution method. The cellular cytotoxicity was also determined by the MTT assay using Vero monkey kidney cells. The selectivity index was determined by dividing the cytotoxicity of extracts by MIC. RESULTS: The antimycobacterial activity of the extracts ranged from 0.02 to 2.5 mg/ml. Mycobacterium smegmatis was more sensitive to the extracts (Average MIC = 0.96 mg/ml) and Mycobacterium aurum was comparatively resistant (Average MIC = 2.04 mg/ml). The extracts of Cremaspora triflora had strong antimycobacterial activity with a MIC of 0.05 mg/ml that compared reasonably well with that of streptomycin (0.01 mg/ml) and rifampicin (0.03 mg/ml), p > 0.05. Cremaspora triflora had the best selectivity index of 2.87 against Mycobacterium fortuitum. CONCLUSION: The high activity of C. triflora extracts against the fast-growing mycobacteria and good cellular safety is promising. It may be interesting to investigate extracts against pathogenic M. tuberculosis, M. bovis and M. avium cultures and to isolate active antimycobacterial compounds.

Antimycobacterial, docking and molecular dynamic studies of pentacyclic triterpenes from Buddleja saligna leaves.

Buddleja saligna (family Buddlejaceae) is a medicinal plant endemic to South Africa. Two isomeric pentacyclic triterpenes, oleanolic acid and ursolic acid, were isolated from the leaves of B. saligna using silica gel column chromatography. Compounds oleanolic acid and ursolic acid were subjected to derivatization with acetic anhydride in the presence of pyridine to obtain oleanolic acid-3-acetate and ursolic acid-3-acetate, respectively. The structures of these compounds were fully characterized by detailed nuclear magnetic resonance (NMR) investigations, which included 1H and 13C NMR. Molecular docking studies predicted the free binding energy of the four triterpenes inside the steroid binding pocket of Mycobacterium tuberculosis fadA5 thiolase compared to a reported inhibitor. Thus, their ability to inhibit the growth of M. tuberculosis was predicted and was confirmed to possess significant antimycobacterial activity when tested against Mycobacterium smegmatis, M. tuberculosis H37Rv (ATCC 25177), clinical isolates of multi-drug-resistant M. tuberculosis (MDR-TB) and extensively drug-resistant M. tuberculosis (XDR-TB) using the Micro Alamar Blue Assay. Ursolic acid was isolated from this plant for the first time.

Improvement of AD Biosynthesis Response to Enhanced Oxygen Transfer by Oxygen Vectors in Mycobacterium neoaurum TCCC 11979.

In steroid biotransformation, soybean oil can improve the productivity of steroids by increasing substrate solubility and strengthen the cell membrane permeability. However, little is known of its role as oxygen carrier and its mechanism of promoting the steroid biotransformation. In this work, soybean oil used as oxygen vector for the enhancement of androst-4-ene-3,17-dione (AD) production by Mycobacterium neoaurum TCCC 11979 (MNR) was investigated. Upon the addition of 16% (v/v) soybean oil, the volumetric oxygen transfer coefficient (K L a) value increased by 44%, and the peak molar yield of AD (55.76%) was achieved. Analysis of intracellular cofactor levels showed high NAD+, ATP level, and a low NADH/NAD+ ratio. Meanwhile, the two key enzymes of the tricarboxylic acid (TCA) cycle, namely, isocitrate dehydrogenase and α-ketoglutarate dehydrogenase, were upregulated after incubation with soybean oil. These enhancements induced by the increasing of oxygen supply showed positive effects on phytosterol (PS) bioconversion. Results could contribute to the understanding of effects of soybean oil as oxygen vector on steroid biotransformation and provided a convenient method for enhancing the efficiency of aerobic steroid biocatalysis.

Functional characterization of the cutI gene for the transcription of carbon monoxide dehydrogenase genes in Mycobacterium sp. strain JC1 DSM 3803.

Carbon monoxide dehydrogenase (CO-DH) in Mycobacterium sp. strain JC1 is a key enzyme for the carboxydotrophic growth, when carbon monoxide (CO) is supplied as a sole source of carbon and energy. This enzyme is also known to act as nitric oxide dehydrogenase (NO-DH) for the detoxification of NO. Several accessory genes such as cutD, cutE, cutF, cutG, cutH, and cutI, are clustered together with two copies of the CO-DH structural genes (cutB1C1A1 and cutB2C2A2) in Mycobacterium sp. strain JC1 and are well conserved in carboxydotrophic mycobacteria. Transcription of the CO-DH structural and accessory genes was demonstrated to be increased significantly by acidified sodium nitrate as a source of NO. A cutI deletion (ΔcutI) mutant of Mycobacterium sp. strain JC1 was generated to identity the function of CutI. Lithoautotrophic growth of the ΔcutI mutant was severely affected in mineral medium supplemented with CO, while the mutant grew normally with glucose. Western blotting, CO-DH activity staining, and CO-DH-specific enzyme assay revealed a significant decrease in the cellular level of CO-DH in the ΔcutI mutant. Northern blot analysis and promoter assay showed that expression of the cutB1 and cutB2 genes was significantly reduced at the transcriptional level in the ΔcutI mutant, compared to that of the wildtype strain. The ΔcutI mutant was much more susceptible to NO than was the wild type.

Anti-dormant Mycobacterial Activity of Viomellein and Xanthomegnin, Naphthoquinone Dimers Produced by Marine- derived Aspergillus sp.

In the course of a search for anti-dormant mycobacterial substances from marine-derived microorganisms, viomellein (1) and xanthomegnin (2) were re- discovered from the active fraction of the culture of a marine-derived Aspergillus sp. together with rubrosulphin (3) and asteltoxin (4) on the guidance of bioassay-guided separation. In particular, compound 1 showed higher activity against the dormant than against actively growing Mycobacterium bovis BCG and weak activity against M smegmatis. Furthermore, evidence that compound 1 did not directly bind to plasmid DNA suggests its anti-mycobacterial activity differs from its direct chelating effect on the mycobacterial genome.

Extracts of six Rubiaceae species combined with rifampicin have good in vitro synergistic antimycobacterial activity and good anti-inflammatory and antioxidant activities.

BACKGROUND: The Rubiaceae family has played a significant role in drug discovery by providing molecules with potential use as templates for the development of therapeutic drugs. This study was designed to study the in vitro synergistic effect of six Rubiaceae species in combination with a known anti-TB drug. The antioxidant and anti-inflammatory activity of these species were also evaluated to investigate additional benefits in antimycobacterial treatment. METHODS: The checkerboard method was used to determine the antimycobacterial synergistic activity of plant extracts combined with rifampicin. The antioxidant activity of extracts was determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. Anti-inflammatory activity via inhibition of nitric oxide (NO) production was performed in LPS-activated RAW 264.7 macrophages using the Griess assay. RESULTS: Combination of rifampicin with the crude extracts resulted in a 4 to 256-fold increase of activity of extracts. The crude extract of Cremaspora triflora produced the best synergistic effect with rifampicin, with a fractional inhibitory concentration (FIC) index of 0.08 against Mycobacterium aurum. Extracts of Psychotria zombamontana had the best antioxidant activity with an IC50 value of 1.77 µg/mL, lower than the IC50 of trolox and ascorbic acid (5.67 µg/mL and 4.66 µg/mL respectively). All the extracts tested inhibited nitric oxide (NO) production in a concentration dependent manner with the percentage of inhibition varying from 6.73 to 86.27 %. CONCLUSION: Some of the Rubiaceae species investigated have substantial in vitro synergistic effects with rifampicin and also good free radical scavenging ability and anti-inflammatory activity. These preliminary results warrant further study on these plants to determine if compounds isolated from these species could lead to the development of bioactive compounds that can potentiate the activity of rifampicin even against resistant mycobacteria.