Identification of Selected Kinetoplastids 18S rRNA Residues required for Efficient Recruitment of Initiator tRNA Met and AUG Selection in silico

High Resolution 18S rRNA structures of kinetoplastids ribosomes from theoretical methods have provided atomic level details about the process of translation. This process entails detailed information on the mRNA and tRNA binding and decoding centers within the 18S rRNA that was previously not very well understood. We identified residues in selected kinetoplastids 18S rRNA critical in recruiting the first methionyl tRNA to the small ribosome subunit during initiation and comparing them to see the differences. The Kozak sequence presence on eukaryotic mRNAs tethers it to the AUG start codon. Kinetoplastids are a closely related group, and the three chosen exhibited differences in the A-site in terms of position and nucleotides found there. Interactions are found at the A-site (543-UUU-546 for T. cruzi, 560-CCUA-563 for T. brucei, and 540-UUUG-543 for Leishmania major), where the different mRNA get complementary sequences at the 16th helix. The current findings show that each messenger RNA has a sequence that is complementary to the appropriate 18S rRNA sequence, tethering the mRNA to the small ribosomal subunit, which then recruits the bigger subunit. When compared to the Kozak region that flanks the AUG start codon, this method effectively promotes start codon placement

The synthesis and reactivity of 1,5-dioxaspiro[3.2]hexanes

A general synthesis of 1,5-dioxaspiro[3.2]hexanes is described. This was accomplished via epoxidation of 2-methyleneoxetanes with dry dimethyldioxirane. A study on the chemoselectivity of the epoxidation of the double bond of 2-methyleneoxetanes against that of an isolated alkene was undertaken and resulted in the exclusive epoxidation of the enol ether double bond. ^ The efficient access to 1,5-dioxaspiro[3.2]hexanes afforded us the opportunity of exploring the reactivity of these systems. Studies on their ring opening reactions with nucleophiles revealed an interesting dichotomy in reactivity. Most of the nucleophiles employed provided α-substituted, β ′-hydroxyketones in good yields. However, those nucleophiles that incorporated a Lewis acid produced 2,2-disubstituted oxetanes. ^ We were intrigued by the potential application of sequences derived from the mode of ring opening leading to α-substituted, β′ -hydroxyketones. The ease of manipulation of products of this reaction pathway into multifunctionalized compounds was fairly obvious. One class of natural products targeted was the glycosphingolipids, ubiquitous components of cell membranes, involved in virtually all aspects of cellular interactions. Herein, we demonstrate the utility of 3-amino-1,5-dioxaspiro[3.2]hexane in the formal synthesis of an analog of KRN7000, an α-galactosylceramide currently in clinical trials as a chemotherapeutic agent for the treatment of liver tumors.

Evaluation of β-Sitosterol Loaded PLGA and PEG-PLA Nanoparticles for Effective Treatment of Breast Cancer: Preparation, Physicochemical Characterization, and Antitumor Activity

β-Sitosterol (β-Sit) is a dietary phytosterol with demonstrated anticancer activity against a panel of cancers, but its poor solubility in water limits its bioavailability and therapeutic efficacy. In this study, poly(lactide-co-glycolic acid) (PLGA) and block copolymers of poly(ethylene glycol)-block-poly(lactic acid) (PEG-PLA) were used to encapsulate β-Sit into nanoparticles with the aim of enhancing its in vitro anticancer activity. β-Sitosterol-loaded PLGA and PEG-PLA nanoparticles (β-Sit-PLGA and β-Sit-PEG-PLA) were prepared by using a simple emulsion-solvent evaporation technique. The nanoparticles were characterized for size, particle size distribution, surface charge, and encapsulation efficiency. Their cellular uptake and antiproliferative activity was evaluated against MCF-7 and MDA-MB-231 human breast cancer cells using flow cytometry and MTT assays, respectively. β-Sit-PLGA and β-Sit-PEG-PLA nanoparticles were spherical in shape with average particle sizes of 215.0 ± 29.7 and 240.6 ± 23.3 nm, a zeta potential of −13.8 ± 1.61 and −23.5 ± 0.27 mV, respectively, and with narrow size distribution. The encapsulation efficiency of β-Sit was 62.89 ± 4.66 and 51.83 ± 19.72 % in PLGA and PEG-PLA nanoparticles, respectively. In vitro release in phosphate-buffered saline (PBS) and PBS/with 0.2% Tween 20 showed an initial burst release, followed by a sustained release for 408 h. β-Sit-PLGA nanoparticles were generally stable in a protein-rich medium, whereas β-Sit-PEG-PLA nanoparticles showed a tendency to aggregate. Flow cytometry analysis (FACS) indicated that β-Sit-PLGA nanoparticles were efficiently taken up by the cells in contrast to β-Sit-PEG-PLA nanoparticles. β-Sit-PLGA nanoparticles were therefore selected to evaluate antiproliferative activity. Cell viability was inhibited by up to 80% in a concentration range of 6.64⁻53.08 μg/mL compared to the untreated cells. Taken together, encapsulation of β-Sitosterol in PLGA nanoparticles is a promising strategy to enhance its anticancer activity against breast cancer cells

A new β-hydroxydihydrochalcone from Tephrosia uniflora, and the revision of three β-hydroxydihydrochalcones to flavanones

The CH2Cl2/MeOH (1:1) extract of the stems of Tephrosia uniflora yielded the new β-hydroxydihydrochalcone (S)-elatadihydrochalcone-2'-methyl ether (1) along with the three known compounds elongatin (2), (S)-elatadihydrochalcone (3), and tephrosin (4). The structures were elucidated by NMR spectroscopic and mass spectrometric data analyses. Elongatin (2) showed moderate antibacterial activity (EC50 of 25.3 μM and EC90 of 32.8 μM) against the Gram-positive bacterium Bacilus subtilis, and comparable toxicity against the MCF-7 human breast cancer cell line (EC50 of 41.3 μM). Based on the comparison of literature and predicted NMR data with that obtained experimentally, we propose the revision of the structures of three β-hydroxydihydrochalcones to flavanones

Anthraquinones of the Roots of Pentas micrantha

molecule

Benzo[b]naphtho[2,1-d]furans and 2-Phenylnaphthalenes from Streblus usambarensis

Three new benzo[b]naphtho[2,1-d]furans, usambarins A–C (1–3), five new 2-phenylnaphthalenes, usambarins D–H (4–8), a new flavan (9), and a new phenyl-1-benzoxepin (10) as well as two known compounds (11 and 12) were isolated from the extract of the stem and roots of Streblus usambarensis (Moraceae). The structures were deduced using NMR spectroscopic and mass spectrometric analyses, and those of compounds 1 and 4 were confirmed by X-ray crystallography. Usambarin D (4) demonstrated moderate antibacterial activity (MIC 9.0 μM) against Bacillus subtilis, while none of the tested compounds were effective against Escherichia coli

A xanthone and a phenylanthraquinone from the roots of Bulbine frutescens, and the revision of six seco-anthraquinones into xanthones

Abdissa N, Heydenreich M, Midiwo JO, et al. A xanthone and a phenylanthraquinone from the roots of Bulbine frutescens, and the revision of six seco-anthraquinones into xanthones. Phytochemistry Letters. 2014;9:67-73.Phytochemical investigation of the dichloromethane/methanol (1:1) extract of the roots of Bulbine frutescens led to the isolation of a new xanthone, 8-hydroxy-6-methylxanthone-1-carboxylic acid (1) and a new phenylanthraquinone, 6',8-O-dimethylknipholone (2) along with six known compounds. The structures were elucidated on the basis of NMR and MS spectral data analyses. The structure of compound 1 was confirmed through X-ray crystallography which was then used as a reference to propose the revision of the structures of six seco-anthraquinones into xanthones. The isolated compounds were evaluated for cytotoxicity against human cervix carcinoma KB-3-1 cells with the phenylanthraquinone knipholone being the most active (IC50 = 0.43 mu M). Two semi-synthetic knipholone derivatives, knipholone Mannich base and knipholone-1,3-oxazine, were prepared and tested for cytotoxic activity; both showed moderate activities (IC50 value of 1.89 and 2.50 mu M, respectively). (C) 2014 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved

Four Prenylflavone Derivatives with Antiplasmodial Activities from the Stem of Tephrosia purpurea subsp. leptostachya

Four new flavones with modified prenyl groups, namely (E)-5-hydroxytephrostachin (1), purleptone (2), (E)-5-hydroxyanhydrotephrostachin (3), and terpurlepflavone (4), along with seven known compounds (5–11), were isolated from the CH2Cl2/MeOH (1:1) extract of the stem of Tephrosia purpurea subsp. leptostachya, a widely used medicinal plant. Their structures were elucidated on the basis of NMR spectroscopic and mass spectrometric evidence. Some of the isolated compounds showed antiplasmodial activity against the chloroquine-sensitive D6 strains of Plasmodium falciparum, with (E)-5-hydroxytephrostachin (1) being the most active, IC50 1.7 ± 0.1 μM, with relatively low cytotoxicity, IC50 > 21 μM, against four cell-lines

Cytotoxicity of isoflavones from <i>Millettia dura</i>

The first phytochemical investigation of the flowers of Millettia dura resulted in the isolation of seven isoflavones, a flavonol and a chalcone. Eleven isoflavones and a flavonol isolated from various plant parts from this plant were tested for cytotoxicity against a panel of cell lines, and six of these showed good activity with IC50 values of 6-14 μM. Durmillone was the most active with IC50 values of 6.6 μM against A549 adenocarcinomic human alveolar basal epithelial cancer cell line with low cytotoxicity against the non-cancerous cell lines BEAS-2B (IC50 = 58.4 μM), LO2 hepatocytes (IC50 78.7 μM) and CCD19Lu fibroblasts (IC50 >100 μM). </p