Design, synthesis and screening of novel PCU-peptide/peptoid derived HIV protease inhibitors.

Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2011.The AIDS epidemic in Africa has reached dramatic proportions. Of the 42 million people infected with HIV worldwide, 30 million are in Africa. Current available therapies have begun to transform this fatal disease into a chronic condition but there are still major obstacles that have resulted in a great demand for new and better drugs. The aim of this study was to synthesize novel and effective HIV protease inhibitors. This work describes the first account of pentacycloundecane (PCU)-peptide and peptoid based protease inhibitors. These inhibitors are proposed to bind the wild type C-South African HIV protease (C-SA) catalytic site via the norstatine or dihydroxylethelene type functional group of the PCU. The desired compounds were synthesized by the coupling of the peptides and peptoids to the PCU cage which resulted in a series of promising and structurally diverse HIV-1 protease inhibitors. The inhibitors were characterized by Nuclear Magnetic Resonance (NMR) and evaluated against the wild type C-SA enzyme for its ability to inhibit 50 % of the enzyme’s activity (IC50). Two of the compounds reported herein, inhibited the enzyme activity at concentrations less than 80 nM. NMR investigations indicated that the activity was related to the chirality of the PCU moiety and its ability to induce conformations of the coupled peptide side chain. Employing the new Efficient Adiabatic Symmetrized Rotating Overhauser Effect Spectroscopy (EASY-ROESY) technique enabled us to obtain vital information about the 3D structure of these small linear peptides and peptoids in solution. This technique is the first example describing the successful through space correlations of such small peptides. Furthermore, docking and a combined quantum mechanics/molecular mechanics (QM/MM) molecular dynamics MD simulation at the AM1 semi empirical level mirrored the observed NMR results and the experimental IC50 activity profile of the considered inhibitors. The combination of these experimental and theoretical methods provided a powerful insight into the interaction mode of these cage peptide and peptoid inhibitors with the enzyme

Cytotoxic activity of crude extracts from Datura stramonium’s fungal endophytes against A549 lung carcinoma and UMG87 glioblastoma cell lines and LC-QTOF-MS/MS based metabolite profiling

Abstract : Background: Endophytic fungi are a proven source of bioactive secondary metabolites that may provide lead compounds for novel drug discovery. In this study, crude extracts from fungal endophytes isolated from Datura stramonium were evaluated for cytotoxic activity on two human cancer cell lines. Methods: Fungal endophytes were isolated from surface sterilized aerial parts of D. stramonium and identified using molecular, morphological and phylogenetic methods. Ethyl acetate crude extracts from these isolates were evaluated for cytotoxic activity on A549 lung carcinoma and UMG87 glioblastoma cell lines. Metabolite profiling was then performed by liquid chromatography coupled to quadrupole time-of-flight with tandem mass spectrometry (LC-QTOF-MS/MS) for the cytotoxic crude extract. Results: Eleven fungal endophytes were identified from D. stramonium. Significant cytotoxicity was only observed from the crude extract of Alternaria sp. KTDL7 on UMG87 glioblastoma cells (IC50 = 21.49 μg/ml). Metabolite profiling of this crude extract tentatively revealed the presence of the following secondary metabolites: 1,8-dihydroxynaphthalene (1), anserinone B (2), phelligridin B (3), metacytofilin (4), phomopsidin (5) and vermixocin A (6). Compounds 2 and 3 have been shown to be cytotoxic in literature. Conclusion: The findings in this study suggest that the crude extract of Alternaria sp. KTDL7 possesses compound(s) cytotoxic to glioblastoma multiforme cells. Future studies to isolate and characterize the cytotoxic compound(s) from this fungus could result in lead development of a fungal-based drug for glioblastoma multiforme treatment

Antibacterial and anticancer activity and untargeted secondary metabolite profiling of crude bacterial endophyte extracts from cinum macowanii baker leaves

Abstract: This study isolated and identified endophytic bacteria from the leaves of Crinum macowanii and investigated the potential of the bacterial endophyte extracts as antibacterial and anticancer agents and their subsequent secondary metabolites. Ethyl acetate extracts from the endophytes and the leaves (methanol: dichloromethane (1 : 1)) were used for antibacterial activity against selected pathogenic bacterial strains by using the broth microdilution method. The anticancer activity against the U87MG glioblastoma and A549 lung carcinoma cells was determined by the MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy-phenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay. Bacterial endophytes that were successfully isolated from C. macowanii leaves include Raoultella ornithinolytica, Acinetobacter guillouiae, Pseudomonas sp., Pseudomonas palleroniana, Pseudomonas putida, Bacillus safensis, Enterobacter asburiae, Pseudomonas cichorii, and Arthrobacter pascens. Pseudomonas cichorii exhibited broad antibacterial activity against both Gram-negative and Gram-positive pathogenic bacteria while Arthrobacter pascens displayed the least MIC of 0.0625 mg/mL. Bacillus safensis crude extracts were the only sample that showed notable cell reduction of 50% against A549 lung carcinoma cells at a concentration of 100 μg/mL. Metabolite profiling of Bacillus safensis, Pseudomonas cichorii, and Arthrobacter pascens crude extracts revealed the presence of known antibacterial and/or anticancer agents such as lycorine (1), angustine (2), crinamidine (3), vasicinol (4), and powelline. It can be concluded that the crude bacterial endophyte extracts obtained from C. macowanii leaves can biosynthesize bioactive compounds and can be bioprospected for medical application into antibacterial and anticancer agents

The LC-QTOF-MS/MS analysis data of detected metabolites from the crude extract of Datura stramonium leaves

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