A potential CARB-pharmacophore for antineoplastic activity: Part 1

New N-Adducts of Thiadiazole and Thiazoline with Levoglucosenone and Evaluation of Their Significant Cytotoxic (Anti-Cancer) Activity

The conjugate N-adducts of thio-1,3,4-diazole and 2-thiazoline with levoglucosenone were synthesized via a stereoselective, base-catalyzed conjugate N-Michael addition to levoglucosenone at C-4. Structural assignments were established using 1H and 13C NMR analysis, and X-ray single-crystal analysis for one of the compounds. The biological properties of the novel compounds were tested on a cell model. Cytotoxicity was analyzed via colorimetric assay. Two distinct types of cell death, apoptosis and necrosis, were analyzed by determining the phosphatidylserine levels from the outer leaflet of the plasma membrane, caspase activation, and lactate dehydrogenase release. We also evaluated DNA damage using an alkaline comet assay. The level of oxidative stress was measured with a modified comet assay and an H2DCFDA probe. The thio-1,3,4-diazole adduct (FCP23) and the 2-thiazoline adduct (FCP26) exhibit similar cytotoxicity values for cancer cells (ovarian (A2780), breast (MCF-7), cervix (HeLa), colon (LoVo), and brain (MO59J and MO59K)), but their mechanism of action is drastically different. While FCP23 induces oxidative stress, DNA damage, and necrosis, FCP26 induces apoptosis through caspase activation.

Biological properties of (1-4)-thio disaccharides

Thio sugars are carbohydrate derivatives in which one or more oxygen atoms have been replaced with sulfur. Thio sugars are effective inhibitors of glycosylases, have considerable therapeutic potential, and are used as drugs in the treatment of diabetes and infectious diseases. The development of this branch of carbohydrate chemistry would not be possible without the development of novel methods for its synthesis and the analysis of their biochemical properties. In this Review Article, we summarize our findings on the biological properties of a collection of thio sugars and their derivatives synthesized by the Witczak and Bielski team using their original methods based on the Michael addition of sugar thiols to levoglucosenone.

(1-4)-Thiodisaccharides as anticancer agents. Part 5. Evaluation of anticancer activity and investigation of mechanism of action

(1-4)-Thiodisaccharides, thiosugars with the 1-4-thio bridge, were recently shown to induce oxidative stress, as well as, apoptosis in cancer cells in the low micromolar range; however, the detailed mechanism of their anticancer action still remains unknown. In order to clarify the mechanism of (1-4)- thiodisaccharides action, we performed a series of tests including cytotoxic, clonogenic and apoptosis assays using an in vitro glioma cancer model with one ATCC cell line U87 and two novel glioma cell lines derived from cancer patients - H6PX and H7PX. We also evaluated the ability of (1-4)-thiodisaccharides to interfere with protein folding and synthesis processes, as well as, the thioredoxin system. (1-4)-thiodisaccharides induced glioma cell death, which were found to be accompanied with endoplasmic reticulum stress, inhibition of global protein synthesis, reduced overall cellular thiol level and thioredoxin reductase activity. We also performed a RT-PCR and Elisa analysis of (1-4)-thiodisaccharides-treated glioma cells to identify any changes within the pathway affected by (1-4)-thiodisaccharides. We observed a significant increase of expression in key markers of endoplasmic reticulum stress and pro-apoptotic protein, FASLG. We proposed that (1-4)-thiodisaccharides react with cellular thiols and disturb any cellular thiol-depended processes like thioredoxin system or protein folding.

Synthesis and Evaluation of Oligomeric Thioether-Linked Carbacyclic β-(1→3)-Glucan Mimetics

Extrapolating from lessons learnt with previous low-molecular-weight β-(1→3)-glucan mimetics, we designed a series of minimal 2,4-dideoxy-thioether-linked carbacyclic β-(1→3)-glucan mimetics and synthesized di-, tri-, and tetramers in an enantiomerically pure form by an iterative sequence based on a simple building block readily available from commercial ( S)-(-)-3-cyclohexenecarboxylic acid. These substances were screened for their ability to inhibit anti-CR3-fluorescein isothiocyanate (FITC) staining of human neutrophils and anti-Dectin-1-FITC staining of mouse macrophages as well as for their ability to stimulate phagocytosis and pinocytosis. In each assay, the synthetic compounds displayed comparable activity to the corresponding native β-(1→3)-glucans, laminaritriose, and tetraose, suggesting that the exploitation of hydrophobic patches in the lectin-binding domains of CR3 and Dectin-1 is a promising strategy for the development of small-molecule analogues of β-(1→3)-glucans.

Synthesis and Evaluation of 1,5-Dithia-d-laminaribiose, Triose, and Tetraose as Truncated β-(1→3)-Glucan Mimetics

The preparation and characterization of a series of di-, tri-, and tetrasaccharide analogues of β-(1→3)-glucans is described in which each pyranoside ring is replaced by a 5-thiopyranosyl ring and each glycosidic oxygen by a thioether. These oligomeric 1,5-dithio-d-glucopyranose derivatives were shown to inhibit the staining of human neutrophils and of mouse macrophages by fluorescent anti-CR3 and anti-Dectin-1 antibodies, respectively. The compounds were also demonstrated to stimulate phagocytosis and pinocytosis indicative of binding to the carbohydrate binding domains of complement receptor 3 (CR3) and Dectin-1. Activity in all three assays was optimum at the level of the trisaccharide mimic, suggesting that, while the replacement of ethereal oxygens by thioethers results in a greater affinity for the aromatic lined hydrophobic binding pockets, the presence of multiple longer C-S bonds eventually results in a mismatch and a loss of affinity.

Evaluation of the Mycobactericidal Effect of Thio-functionalized Carbohydrate Derivatives

Sugars with heteroatoms other than oxygen have attained considerable importance in glycobiology and in drug design since they are often more stable in blood plasma due to their resistance to enzymes, such as glycosidases, phosphorylases and glycosyltransferases. The replacement of oxygen atoms in sugars with sulfur forms thio-sugars, which are potentially useful for the treatment of diabetes and some bacterial and viral infections. Here, we evaluated the antibacterial activity of thio-functionalized carbohydrate derivatives. A set of 21 compounds was screened against acid-fast Mycobacterium tuberculosis (Mtb), gram-negative Escherichia coli and gram-positive Staphylococcus aureus. The tested carbohydrate derivatives were most effective against tubercle bacilli, with as many as five compounds (thioglycoside 6, thiosemicarbazone 16A, thiosemicarbazone 20, aminothiadiazole 23, and thiazoline 26) inhibiting its growth with MIC₅₀ ≤ 50 µM/CFU. Only two compounds (aminothiadiazole 23 and thiazoline 26) were able to inhibit the growth of E. coli at concentrations below 1 mM, and one of them, aminothiadiazole 23, inhibited the growth of S. aureus at a concentration ≤1 mM. The five compounds affecting the growth of mycobacteria were either thiodisaccharides (6, 16A, and 20) or thioglycosides (23 and 26). All of these compounds (6, 16A, 20, 23, and 26) were able to inhibit the growth of Mtb deposited within human macrophages. However, three of the five selected compounds (6, 23, and 26) exhibited relatively high cytotoxicity in mouse fibroblasts at micromolar concentrations. The selected thio-sugars are very promising compounds, thus making them candidates for further modifications that would decrease their cytotoxicity against eukaryotic cells without affecting their antimycobacterial potential.

Designing sugar mimetics: non-natural pyranosides as innovative chemical tools

The importance of oligosaccharides in myriad biological processes is becoming increasingly clear. However, these carbohydrate-mediated processes are often challenging to dissect due to the often poor affinity, stability and selectivity of the oligosaccharides involved. To circumvent these issues, non-natural carbohydrates-carbohydrate mimics-are being designed as innovative tools to modify biomolecules of interest or to understand biological pathways using fluorescence microscopy, X-ray or nuclear magnetic resonance spectroscopy (NMR). This review focuses on key examples of recently developed non-natural sugars to answer specific biological needs.

Effect of a novel compound as dietary supplement on growth of decapod crustaceans

The concern over water quality, environmental hazard, human health and food safety has led us to develop a novel alternative growth enhancer, CGE-1 which significantly improve the growth of decapod crustaceans without any harmful effects.