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Genome mining using standard bioinformatics tools has allowed for the uncovering of hidden biosynthesis gene clusters for specialized metabolites in Streptomyces genomes. In this work, we have used an alternative approach consisting in seeking "Streptomyces Antibiotic Regulatory Proteins" (SARP) encoding genes and analyzing their surrounding DNA region to unearth cryptic gene clusters that cannot be identified using standard bioinformatics tools. This strategy has allowed the unveiling of the new ahb cluster in Streptomyces argillaceus, which had not been retrieved before using antiSMASH. The ahb cluster is highly preserved in other Streptomyces strains, which suggests a role for their encoding compounds in specific environmental conditions. By combining overexpression of three regulatory genes and generation of different mutants, we were able to activate the ahb cluster, and to identify and chemically characterize the encoded compounds that we have named ahbamycins (AHBs). These constitute a new family of metabolites derived from 3-amino-4-hydroxybenzoate (3,4-AHBA) known for having antibiotic and antitumor activity. Additionally, by overexpressing three genes of the cluster (ahbH, ahbI, and ahbL2) for the synthesis and activation of 3,4-AHBA, a new hybrid compound, AHB18, was identified which had been produced from a metabolic crosstalk between the AHB and the argimycin P pathways. The identification of this new BGC opens the possibility to generate new compounds by combinatorial biosynthesis. [ABSTRACT FROM AUTHOR]

Platensimycin (PTM) is an excellent natural product drug lead against various gram‐positive pathogens, including methicillin‐resistant Staphylococcus aureus and vancomycin‐resistant enterococci. In this study, twenty PTM derivatives with varying aminobenzoic acids were semisynthesized. In contrast to all the previous reported inactive aminobenzaote analogues, a few of them showed moderate antibacterial activities against S. aureus. Our study suggested that modification of the conserved aminobenzoic acid remains a viable approach to diversify the PTM scaffold. Platensimycin (PTM, 1) is a potent inhibitor of both bacterial and mammalian fatty acid synthases, and the previous structure‐activity relationship study suggested that its aminobenzoate moiety makes critical interactions with the enzyme active site. In this study, 20 platensimycin analogues with varying aminobenzoic acids were semisynthesized and a few of them showed moderate antibacterial activities against Staphylococcus aureus. These results suggested that modification of the aminobenzoate moiety remains a viable approach to diversify the PTM scaffold. [ABSTRACT FROM AUTHOR]

Highlights: [•] Pairs of isostructural Eu3+ and Tb3+ o-, m-, and p-aminobenzoates were examined. [•] The position of NH2 in the benzene ring defines an efficiency of Ln3+ excitation. [•] LMCT states in Eu3+ o- and p-aminobenzoates are luminescence quenchers. [•] Three outer-sphere H2O reduce distortions of Ln3+ luminescence center. [ABSTRACT FROM AUTHOR]

The aim of this work was to study the spectroscopic and magnetic properties of copper(II) o-, m-, p-aminobenzoates, o-, m-, p-methoxybenzoates and o-, m- and p-nitrobenzoates. The complexes were synthesized and their compositions were evaluated by elementary analysis. The infrared and Raman spectra for Cu(II) aminobenzoates, methoxybenzoates and nitrobenzoates were recorded and assigned. The obtained data were compared with those previously published for aminobenzoic, methoxybenzoic and nitrobenzoic acids and their sodium salts. The structures of Cu(II) o-, m-, p-aminobenzoates, o-, m-, p-methoxybenzoates and o-, m- and p-nitrobenzoates as well as the change in the electronic charges distribution caused by Cu(II) complex formation were discussed. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis and study of trimethyl-, tributyl- and triphenyltin esters of the 3- and 4-aminobenzoic acids are reported. The triorganotin derivatives are characterized by elemental analyses, FT-IR and solution 1H and 13C NMR spectra. The structure of the trimethyltin 4-aminobenzoate is solved by X-ray diffraction and proves to be polymeric in nature with bridging carboxylates and trigonal bipyramidal tin(IV) environment. However, all the compounds become monomeric in solution with a tetrahedral tin coordination environment in chloroform and trigonal bipyramidal in DMSO due to coordination of the solvent as the NMR spectra have revealed. The compounds exhibit variable cytotoxic activity when tested against Κ562 myelogenous leukaemia, HeLa cervical cancer and HepG2 hepatocellular carcinoma cell lines, with the butyl derivatives being the more effective and the methyl ones the less. Interestingly, their antibacterial action was significantly lower when tested against Escherichia coli, while not appreciable direct interaction with DNA has been observed. The above observations account for a mode of action that may be related to their potential interaction with cell membranes and the subsequent inhibition of various signaling processes. [Copyright &y& Elsevier]

Abstract: The possible stable conformers of free Ethyl 2- and 3-aminobenzoate molecules were searched via subsequent single point energy calculations carried out at semi-empirical PM3 theory level. The final equilibrium geometrical parameters for the obtained stable conformers were defined by performing geometry optimizations with B3LYP hybrid DFT method and basis sets of different size and type. The harmonic vibrational normal modes of the two molecules and their corresponding wavenumbers and IR intensities were calculated at the obtained equilibrium geometries using the same method and basis sets used in the geometry optimizations. In the light of these calculated spectral data, a successful assignment for the fundamental bands in the IR spectra of the two molecules was given. In order to fit the calculated harmonic wavenumbers to the experimentally observed ones, two different scaling procedures, called “scaling wavenumbers in Scaled Quantum Mechanics Force Field (SQM FF) methodology” and “scaling wavenumbers with dual empirical scale factors”, were proceeded independently. [Copyright &y& Elsevier]

X-ray structural analysis has been performed for two complex compounds: Cu(en)2( o-HB)2H2O (I) ( a = 16.873(4) Å, b = 8.713(2) Å, c = 14.803(3) Å, β = 91.15(2)°, V = 2175.8(8) Å3, C2/ c, Z = 4, R( F) = 0.0263, 1516 reflections with I > 3σ ( I)) and [Cu(en)2(OH2)2]2+( o-AB−)2 (II) ( a = 7.488(5) Å, b = 22.122(8) Å, c = 7.856(5) Å, β = 118.77(2)°, V = 1140.7(11) Å3, P21/ n, Z = 2, R( F) = 0.0432, 1684 reflections with I > 3σ( I)) synthesized under identical conditions (en is ethylenediamine, o-HB is o-hydroxybenzoate, and o-AB is o-aminobenzoate). Although the compounds were assumed to have similar structures and the Cu-Lig bond lengths and the cis and trans angles are acceptable for an octahedral structure, the geometric parameters of o-HB suggest that the copper atom has a plane square environment. [ABSTRACT FROM AUTHOR]

Following incubation of mesophilic methanogenic floccular sludge from a lab-scale upflow anaerobic sludge bed reactor used to treat cattle manure wastewater, a stable 5-aminosalicylate-degrading enrichment culture was obtained. Subsequently, a Citrobacter freundii strain, WA1, was isolated from the 5-aminosalicylate-degrading methanogenic consortium. The methanogenic enrichment culture degraded 5-aminosalicylate completely to CH4, CO2 and NH4+, while C. freundii strain WA1 reduced 5-aminosalicylate with simultaneous deamination to 2-hydroxybenzyl alcohol during anaerobic growth with electron donors such as pyruvate, glucose or serine. When grown on pyruvate, C. freundii WA1 converted 3-aminobenzoate to benzyl alcohol and also reduced benzaldehyde to benzyl alcohol. Pyruvate was fermented to acetate, CO2, H2 and small amounts of lactate, succinate and formate. Less lactate (30%) was produced from pyruvate when C. freundii WA1 grew with 5-aminosalicylate as co-substrate. [ABSTRACT FROM AUTHOR]

Natural amino donation: A PLP-dependent aminotransferase PctV, encoded in the pactamycin biosynthetic gene cluster, was found to catalyze the formation of 3-aminobenzoate from 3-dehydroshikimate with L-glutamate as the amino donor. The PctV reaction comprises a transamination and two dehydration reactions. This is the first report of a simple 3-ABA synthase in nature., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)