Aaron Monte

Abyssomicins from the South China Sea deep-sea sediment Verrucosispora sp.: natural thioether michael addition adducts as antitubercular prodrugs

Tuberculosis (TB) is a leading cause of death in the world today, and is exacerbated by the prevalence of multi- (MDR-TB), extensively (XDR-TB), and totally (TDR-TB) drug resistant strains. Despite the threat to human health, existing frontline TB therapeutics remain constrained to a handful of vintage antibiotics prescribed in a combinatorial format to achieve efficacy. The current shortfall in antitubercular drugs demands urgent attention, to develop new antibiotics effective against all strains of tuberculosis.

Stereo- and Regiospecific Cu-Catalyzed Cross-Coupling Reaction of Vinyl Iodides and Thiols: A Very Mild and General Route for the Synthesis of Vinyl Sulfides

A mild and efficient method for the copper-catalyzed formation of vinylic carbon-sulfur bonds has been developed. The desired vinyl sulfides are obtained in good to excellent yields, with full retention of stereochemistry. This method is particularly noteworthy given its mild reaction conditions, simplicity, and generality, as well as low cost of the catalyst system.

Antibacterial Compounds from Mushrooms II: Lanostane Triterpenoids and an Ergostane Steroid with Activity Against Bacillus cereus Isolated from Fomitopsis pinicola

Anti- Bacillus cereus bioassay-guided fractionation of a crude extract of the American mushroom, Fomitopsis pinicola, was performed using thin-layer chromatography, Sephadex LH-20 column chromatography, and preparative-scale HPLC. Five lanostane triterpenoids (1-5) and one ergostane steroid (6) were isolated and identified. Compound 1 is a new lanostane triterpenoid, and its structure was determined using 1D and 2D NMR experiments, HR-MS, and physical data. Each of the purified compounds (1-6) was tested for antibacterial activity against B. cereus using standard MIC assays. Compounds 1-6 had MIC values of 32, 16, 32, 32, 128, and 64 microg/mL, respectively.

New classes of Gram-positive selective antibacterials: inhibitors of MRSA and surrogates of the causative agents of anthrax and tuberculosis.

Abstract An antimicrobial phenolic stilbene, (E)-3-hydroxy-5-methoxystilbene, 1 was recently isolated from the leaves of Comptonia peregrina (L.) Coulter and shown to possess inhibitory activity against several Gram-positive bacteria, including isolates of methicillin-resistant Staphylococcus aureus (MRSA), Mycobacterium bovis BCG, and avirulent Bacillus anthracis (Sterne strain), among others. These results prompted the design and synthesis of two new classes of compounds, phenoxystyrenes and phenothiostyrenes, as analogs of the natural antimicrobial stilbene. These and additional stilbenoid analogs were synthesized using new, efficient, copper-mediated coupling strategies. Minimum inhibitory concentration (MIC) antimicrobial assays were performed on all compounds prepared. These preliminary structure–activity relationship studies indicated that both new classes of synthetic analogs, as well as the stilbenes, show promising activity against Gram-positive bacteria when at least one phenolic moiety is present, but not when absent. The potencies of the phenolic phenoxystyrenes and phenothiostyrenes were found to be comparable to those of the phenolic stilbenes tested.

Antibacterial Compounds from Mushrooms I: A Lanostane-Type Triterpene and Prenylphenol Derivatives from Jahnoporus hirtus and Albatrellus flettii and Their Activities Against Bacillus cereus and Enterococcus faecalis

Antibacterial bioassay-guided fractionation of two American mushroom species, Jahnoporus hirtus and Albatrellus flettii, led to the isolation and identification of their major antibacterial constituents: 3,11-dioxolanosta-8,24( Z)-diene-26-oic acid (1) from J. hirtus and confluentin (2), grifolin (3), and neogrifolin (4) from A. flettii. Compound 1 is a new lanostane-type triterpene. All purified compounds were evaluated for their ability to inhibit the growth of Bacillus cereus and Enterococcus faecalis using standard MIC assays. Compounds 1- 4 demonstrated MIC values of 40, 20, 10, and 20 microg/mL, respectively, against B. cereus and MIC values of 32, 1.0, 0.5, and 0.5 microg/mL, respectively, against E. faecalis. Thus, one novel compound and three others were shown to possess antimicrobial activities against these gram-positive bacteria employed as surrogates for more virulent and dangerous pathogens.

Zebrafish Heart Failure Models for the Evaluation of Chemical Probes and Drugs

Heart failure is a complex disease that involves genetic, environmental, and physiological factors. As a result, current medication and treatment for heart failure produces limited efficacy, and better medication is in demand. Although mammalian models exist, simple and low-cost models will be more beneficial for drug discovery and mechanistic studies of heart failure. We previously reported that aristolochic acid (AA) caused cardiac defects in zebrafish embryos that resemble heart failure. Here, we showed that cardiac troponin T and atrial natriuretic peptide were expressed at significantly higher levels in AA-treated embryos, presumably due to cardiac hypertrophy. In addition, several human heart failure drugs could moderately attenuate the AA-induced heart failure by 10%-40%, further verifying the model for drug discovery. We then developed a drug screening assay using the AA-treated zebrafish embryos and identified three compounds. Mitogen-activated protein kinase kinase inhibitor (MEK-I), an inhibitor for the MEK-1/2 known to be involved in cardiac hypertrophy and heart failure, showed nearly 60% heart failure attenuation. C25, a chalcone derivative, and A11, a phenolic compound, showed around 80% and 90% attenuation, respectively. Time course experiments revealed that, to obtain 50% efficacy, these compounds were required within different hours of AA treatment. Furthermore, quantitative polymerase chain reaction showed that C25, not MEK-I or A11, strongly suppressed inflammation. Finally, C25 and MEK-I, but not A11, could also rescue the doxorubicin-induced heart failure in zebrafish embryos. In summary, we have established two tractable heart failure models for drug discovery and three potential drugs have been identified that seem to attenuate heart failure by different mechanisms.

A new class of potential anti-tuberculosis agents: Synthesis and preliminary evaluation of novel acrylic acid ethyl ester derivatives

Novel acrylic acid ethyl ester derivatives were synthesized and evaluated as potential agents against Mycobacterium species. A versatile and efficient copper-catalyzed coupling process was developed and used to prepare a library of substituted acrylic acid ethyl ester analogs. Minimum inhibitory concentration assays indicated that two of these compounds 3 and 4 have greater in vitro activity against Mycobacterium smegmatis than rifampin, one of the current, first-line anti-mycobacterial chemotherapeutic agents. Moreover, members of this new class of compounds appear to exhibit a specific anti-mycobacterial effect and do not inhibit the growth of the other Gram-positive or Gram-negative species tested.

One-pot Claisen rearrangement/O-methylation/alkene isomerization in the synthesis of ortho-methoxylated phenylisopropylamines

Abstract An improved synthesis of a potent serotonin agonist 1a and its novel derivative 1b is described, making use of a Claisen rearrangement whose unstable phenolic product is methylated and isomerized in situ . This method may be of general use in the synthesis of o -methoxylated phenethylamine derivatives. The synthesis also includes an unusual, one pot demethylation/primary alcohol bromination with boron tribromide.

Screening a mushroom extract library for activity against Acinetobacter baumannii and Burkholderia cepacia and the identification of a compound with anti-Burkholderia activity

BackgroundAcinetobacter baumannii and species within the Burkholderia cepacia complex (BCC) are significant opportunistic bacterial pathogens of humans. These species exhibit a high degree of antibiotic resistance, and some clinical isolates are resistant to all currently available antimicrobial drugs used for treatment. Thus, new drugs are needed to treat infections by these species. Mushrooms could be a potential source for new drugs to treat A. baumannii and BCC infections.MethodsThe aim of this study was to screen a library of crude extracts from 330 wild mushrooms by disk diffusion assays for antibacterial activity against A. baumannii and Burkholderia cepacia in the hope of identifying a novel natural drug that could be used to treat infections caused by these species. Once positive hits were identified, the extracts were subjected to bioassay-guided separations to isolate and identify the active drug molecules. MICs were performed to gauge the in vitro activity of the purified compounds.ResultsOnly three crude extracts (0.9%) had activity against A. baumannii and B. cepacia. Compounds from two of these extracts had MICs greater than 128 μg/ml, and further analyses were not performed. From the third extract, prepared from Leucopaxillus albissimus, 2-aminoquinoline (2-AQ) was isolated. This compound exhibited a modest MIC in vitro against strains from nine different BCC species, including multi-drug resistant clinical isolates (MIC = 8-64 μg/ml), and a weak MIC (128 μg/ml) against A baumannii. The IC50 against a murine monocyte line was 1.5 mg/ml.ConclusionThe small number of positive hits in this study suggests that finding a new drug from mushrooms to treat Gram-negative bacterial infections may be difficult. Although 2-AQ was identified in one mushroom, and it was shown to inhibit the growth of multi-drug resistant BCC isolates, the relatively high MICs (8-128 μg/ml) for both A. baumannii and BCC strains suggests that 2-AQ is not suitable for further drug development in its current form.

Substituted hexahydrobenzodipyrans as 5-HT2A/2C receptor probes.

A pair of substituted hexahydrobenzodipyrans was designed as molecular probes for determining the steric restrictions of the agonist binding site of serotonin 5-HT2A and 5-HT2C receptors. The rationale for the design of these receptor ligands, their chemical synthesis, rat behavioral pharmacology in the two-lever drug discrimination assay using LSD-trained rats, affinity for cloned rat 5-HT2A and 5-HT2C receptors and agonist functional activities are reported.