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The biosynthetic pathway for the branched-chain amino acids is present in plants, fungi and bacteria, but not in animals, making it an attractive target for herbicidal and antimicrobial drug discovery. Ketol-acid reductoisomerase (KARI; EC 1.1.1.86) is the second enzyme in this pathway, converting in a Mg2+- and NADPH-dependent reaction either 2-acetolactate or 2-aceto-2-hydroxybutyrate to their corresponding 2,3-dihydroxy-3- alkylbutyrate products. Here, we have determined the crystal structure of Mycobacterium tuberculosis (Mt) KARI, a class I KARI, with two magnesium ions bound in the active site. X-ray data were obtained to 1.0 Å resolution and the final model has an Rfree of 0.163. The structure shows that the active site is solvent-accessible with the two metal ions separated by 4.7 Å. A comparison of this structure with that of Mg2+-free Pseudomonas aeruginosa KARI suggests that upon magnesium binding no movement of the N domain relative to the C domain occurs. However, upon formation of the Michaelis complex, as illustrated in the structure of Slackia exigua KARI in complex with NADH.Mg2+. N-hydroxy-N-isopropyloxamate (IpOHA, a transition state analog), domain movements and reduction of the metal-metal distance to 3.5 Å are observed. This inherent flexibility therefore appears to be critical for initiation of the KARIcatalyzed reaction. This study provides new insights into the complex structural rearrangements required for activity of KARIs, particularly those belonging to class I, and provides the framework for the rational design of Mt KARI inhibitors that can be tested as novel antituberculosis agents. [ABSTRACT FROM AUTHOR]

Novel ester derivatives of 2, 10-dichloro-12 H-dibenzo [d,g] 1,3 dioxocin-6-carboxylic acid were synthesized and evaluated for their in vitro human cholesteryl ester transfer protein (CETP) inhibition. Three out of twelve synthesized compounds showed good inhibition of CETP (more than 50 %). Compound 10 showed 81.32 % inhibition of CETP at the dose of 0.5 nM whereas compound 11 showed 75.78 % inhibition when tested at the same concentration. Compound 8 and 13 also showed modest activity with 57.44 and 38.02 % inhibition. All other synthesized compounds were devoid of significant inhibitory activity against CETP. We also performed molecular docking to predict the mode of binding of all compounds at the active site of CETP. Compound 10 showed the dock score of −9.16 whereas the dock score of compound 11 was found to be −9.09. [ABSTRACT FROM AUTHOR]

Desmodium gangeticum is a traditional Ayurvedic plant used for centuries as an anthelminthic, anti-catarrahal, diuretic, expectorant, astringent, febrifuge, nervine tonic, anti diarrheal, bronchiodilator, vasopressor, analgesic, antipyretic, cardio tonic, stimulant, antioxidant and antiinflammatory agent. The whole plant, its extract and isolates have been extensively investigated in several laboratories for their different biological activities. In addition researchers have evaluated the anti-inflammatory, antioxidant, immunomodulatory and other pharmacological effects of Desmodium gangeticum preparations/extracts. [ABSTRACT FROM AUTHOR]

Abstract: AgNO3 facilitated the intramolecular ring closure of o-(1-alkynyl)benzenesulfonamides via a regioselective C–N bond forming reaction leading to the formation of 3-substituted benzothiazine derivatives. A number of compounds were prepared in good yields by using this inexpensive and safe methodology. All the compounds synthesized were evaluated for their cyclooxygenase (COX) inhibiting properties in vitro. A number of compounds that do not contain an enolic hydroxyl group showed selectivities toward COX-2 over COX-1 inhibition. This was further supported by the predictive binding mode of two compounds with COX-1 and -2 proteins through molecular docking studies. [Copyright &y& Elsevier]

Abstract: AlCl3 facilitated C–N bond forming reaction between 2,3-dichloroquinoxaline and anilines affording a convenient method for the preparation of N-aryl substituted 3-chloroquinoxalin-2-amines. A related N-benzyl derivative, however, was prepared via a conventional method. These N-alkyl/aryl substituted 3-chloroquinoxalin-2-amines on coupling with terminal alkynes in toluene under Pd/C–Cu catalysis afforded a range of 1,2-disubstituted pyrrolo[2,3-b]quinoxalines within 3–5h in good to excellent yields. Some of the compounds synthesized showed promising anti-proliferative properties when tested in vitro against two cancer cell lines. Docking studies indicated that these molecules interact well with human Akt in silico. [Copyright &y& Elsevier]

Ketol-acid reductoisomerase (KARI) is an NAD(P)H and Mg 2+ -dependent enzyme of the branched-chain amino acid (BCAA) biosynthesis pathway. Here, the first crystal structures of Staphylococcus aureus (Sa) KARI in complex with two transition state analogues, cyclopropane-1,1-dicarboxylate (CPD) and N-isopropyloxalyl hydroxamate (IpOHA) are reported. These compounds bind competitively and in multi-dentate manner to KARI with K i values of 2.73 μm and 7.9 nm, respectively; however, IpOHA binds slowly to the enzyme. Interestingly, intact IpOHA is present in only ≈25 % of binding sites, whereas its deoxygenated form is present in the remaining sites. This deoxy form of IpOHA binds rapidly to Sa KARI, but with much weaker affinity (K i =21 μm). Thus, our data pinpoint the origin of the slow binding mechanism of IpOHA. Furthermore, we propose that CPD mimics the early stage of the catalytic reaction (preceding the reduction step), whereas IpOHA mimics the late stage (after the reduction took place). These structural insights will guide strategies to design potent and rapidly binding derivatives of these compounds for the development of novel biocides., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A number of novel 1,8-disubstituted 5,5-dimethyl-4,5-dihydro-1H-benzo[g]indazoles based on a conformationally restricted pyrazole framework have been designed as potential inhibitors of PDE4. All these compounds were readily prepared by using simple chemistry strategy. The in vitro PDE4B inhibitory properties and molecular modeling studies of some of the compounds synthesized along with the X-ray single crystal data of a representative compound is presented., (Copyright © 2012 Elsevier Ltd. All rights reserved.)