Synthesis and antimycobacterial evaluation of various 6-substituted pyrazolo[3,4-d]pyrimidine derivatives

Various pyrazolo[3,4-d]pyrimidines carrying a variety of substituents in the 6-position have been synthesised and their ability to inhibit growth of Mycobacterium tuberculosis in vitro has been determined. Compounds 5a, 5b, 6c, 7a, 7b, 8d, 8e and 8f demonstrated a minimum inhibitory concentration (MIC) of <6.25?μg/mL and were found to be active against Mycobacterium tuberculosis strain H(37)RV. Compound 8d was found to be the most active compound in vitro with a MIC of <6.25?μg/mL and inhibitory concentration IC(90) of 1.53?μg/mL.     

Inhibition of eukaryotic translation elongation by the antitumor natural product Mycalamide B

Mycalamide B (MycB) is a marine sponge-derived natural product with potent antitumor activity. Although it has been shown to inhibit protein synthesis, the molecular mechanism of action by MycB remains incompletely understood. We verified the inhibition of translation elongation by in vitro HCV IRES dual luciferase assays, ribosome assembly, and in vivo [(35)S]methinione labeling experiments. Similar to cycloheximide (CHX), MycB inhibits translation elongation through blockade of eEF2-mediated translocation without affecting the eEF1A-mediated loading of tRNA onto the ribosome, AUG recognition, or dipeptide synthesis. Using chemical footprinting, we identified the MycB binding site proximal to the C3993 28S rRNA residue on the large ribosomal subunit. However, there are also subtle, but significant differences in the detailed mechanisms of action of MycB and CHX. First, MycB arrests the ribosome on the mRNA one codon ahead of CHX. Second, MycB specifically blocked tRNA binding to the E-site of the large ribosomal subunit. Moreover, they display different polysome profiles in vivo. Together, these observations shed new light on the mechanism of inhibition of translation elongation by MycB.     

Wine biotechnology in South Africa: towards a systems approach to wine science

The wine industry in South Africa is over three centuries old and over the last decade has reemerged as a significant competitor in world wine markets. The Institute for Wine Biotechnology (IWBT) was established in partnership with the Department of Viticulture and Oenology at Stellenbosch University to foster basic fundamental research in the wine sciences leading to applications in the broader wine and grapevine industries. This review focuses on the different research programmes of the Institute (grapevine, yeast and bacteria biotechnology programmes, and chemical-analytical research), commercialisation activities (SunBio) and new initiatives to integrate the various research disciplines. An important focus of future research is the Wine Science Research Niche Area programme, which connects the different research thrusts of the IWBT and of several research partners in viticulture, oenology, food science and chemistry. This 'Functional Wine-omics' programme uses a systems biology approach to wine-related organisms. The data generated within the programme will be integrated with other data sets from viticulture, oenology, analytical chemistry and the sensory sciences through chemometrics and other statistical tools. The aim of the programme is to model aspects of the wine making process, from the vineyard to the finished product.     

Anti-tubercular activity and molecular docking studies of indolizine derivatives targeting mycobacterial InhA enzyme

A series of 1,2,3-trisubstituted indolizines (2a–2f, 3a–3d, and 4a–4c) were screened for in vitro whole-cell anti-tubercular activity against the susceptible H37Rv and multidrug-resistant (MDR) Mycobacterium tuberculosis (MTB) strains. Compounds 2b–2d, 3a–3d, and 4a–4c were active against the H37Rv-MTB strain with minimum inhibitory concentration (MIC) ranging from 4 to 32 µg/mL, whereas the indolizines 4a–4c, with ethyl ester group at the 4-position of the benzoyl ring also exhibited anti-MDR-MTB activity (MIC = 16–64 µg/mL). In silico docking study revealed the enoyl-acyl carrier protein reductase (InhA) and anthranilate phosphoribosyltransferase as potential molecular targets for the indolizines. The X-ray diffraction analysis of the compound 4b was also carried out. Further, a safety study (in silico and in vitro) demonstrated no toxicity for these compounds. Thus, the indolizines warrant further development and may represent a novel promising class of InhA inhibitors and multi-targeting agents to combat drug-sensitive and drug-resistant MTB strains.     

CD45 signals outside of lipid rafts to promote ERK activation, synaptic raft clustering, and IL-2 production

CD45 is dynamically repositioned within lipid rafts and the immune synapse during T cell activation, although the molecular consequences of CD45 repositioning remain unclear. In this study we examine the role of CD45 membrane compartmentalization in regulating murine T cell activation. We find that raft-localized CD45 antagonizes IL-2 production by opposing processive TCR signals, whereas raft-excluded CD45 promotes ERK-dependent polarized synaptic lipid raft clustering and IL-2 production. We propose that these dual CD45 activities ensure that only robust TCR signals proceed, whereas signals meeting threshold requirements are potentiated. Our findings highlight membrane compartmentalization as a key regulator of CD45 function and elucidate a novel signal transduction pathway by which raft-excluded CD45 positively regulates T cell activation.     

Novel dihydropyrimidines as a potential new class of antitubercular agents

A small library of 30 dihydropyrimidines was synthesized and evaluated for their in vitro antitubercular activity against Mycobacterium tuberculosis H₃₇Rv. Two compounds, ethyl 4-[3-(4-fluorophenyl)-1-phenyl-1H-pyrazol-4-yl]-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5 carboxylate 4a and ethyl 4-[3-(4-nitrophenyl)-1-phenyl-1H-pyrazol-4-yl]-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate 4d were found to be the most active compounds in vitro with MIC of 0.02 μg/mL against MTB and were more potent than isoniazid.     

Structural determinants of blockade of eosinophil activation, adhesion and secretion by synthetic analogs of phomactin

We examined the structural determinants of phomactin analogs to assess their efficacy as antagonist of PAF. Six analogs of phomactin were synthesized to determine their inhibitory effects on adhesion, superoxide release, leukotriene C4 (LTC4) synthesis and [3H]PAF binding in human eosinophils. Phomactin analogs inhibited both PAF- and IL-5-induced eosinophil adhesion. Analog A, which bears an alkene moiety between C-1 and C-14, a ketone at the C-2 position, and an alkyne moiety between C-3 and C-4, had the greatest anti-adhesive effect. Change of the alkene between C-1 and C-14 to an alkane (analog I) decreased the anti-adhesive effect by 2.5-4 fold, while substitution of ketone by hydroxyl (analog G) at the C-2 position caused an 11-fold decrease in the anti-adhesive effect. Substitution of the alkyne moiety between C-3 and C-4 by an alkene (B and E) or alkane (D) blocked completely the anti-adhesive effect. Analogs A and I completely blocked superoxide release from eosinophils caused by phorbol-12-myristate-13-acetate or PAF and LTC4-release caused by fMLP plus cytochalasin B. Change of the alkyne moiety between C-3 and C-4 to an alkene (B and E) or alkane (D) blocked completely these inhibitory effects of phomactin. Analog A decreased the maximal binding of [3H]PAF binding to eosinophils without change of the apparent dissociation constant. We conclude that phomactin analogs are specific non-competitive PAF antagonists and have exceptional efficacy in inhibiting adhesion, metabolic activity and leukotriene secretion in human eosinophils. We further define the structural alterations in the phomactin molecule that regulate its inhibitory functions.     

Synthesis and biological evaluation of some novel N-aryl-1,4-dihydropyridines as potential antitubercular agents

1,4-Dihydropyridines are the emerging class of antitubercular agent. Recently, studies have revealed that 1,4-dihydropyridine-3,5-dicarbamoyl derivatives with lipophilic groups have demonstrated excellent antitubercular activity. We have synthesized new N-aryl-1,4-dihydropyridines bearing carbethoxy and acetyl group at C-3 and C-5 of the DHP ring. In addition, 1H-pyrazole ring is substituted at C-4 position. The lowest minimum inhibitory concentration value, 0.02 μg/mL, was found for diethyl 1-(2-chlorophenyl)-1,4-dihydro-2,6-dimethyl-4-(1,3-diphenyl-1H-pyrazol-4-yl)pyridine-3,5-dicarboxylate 4e making it more potent than first line antitubercular drug isoniazid. In addition, this compound exhibited relatively low cytotoxicity.