Synthesis,characterization, thermal properties and biological activity of diazine-ring containing hydrazones and their metal complexes

Journal of Thermal Analysis and Calorimetry - New coordination compounds have been synthesized by reacting Zn(II) and Co(II) nitrate or acetate in the presence of triethylamine with Schiff-base...     

Antiproliferative Phenanthrenes from Juncus tenuis: Isolation and Diversity-Oriented Semisynthetic Modification

The occurrence of phenanthrenes is limited in nature, with such compounds identified only in some plant families. Phenanthrenes were described to have a wide range of pharmacological activities, and numerous research programs have targeted semisynthetic derivatives of the phenanthrene skeleton. The aims of this study were the phytochemical investigation of Juncus tenuis, focusing on the isolation of phenanthrenes, and the preparation of semisynthetic derivatives of the isolated compounds. From the methanolic extract of J. tenuis, three phenanthrenes (juncusol, effusol, and 2,7-dihydroxy-1,8-dimethyl-5-vinyl-9,10-dihydrophenanthrene) were isolated. Juncusol and effusol were transformed by hypervalent iodine(III) reagent, using a diversity-oriented approach. Four racemic semisynthetic compounds possessing an alkyl-substituted p-quinol ring (1–4) were produced. Isolation and purification of the compounds were carried out by different chromatographic techniques, and their structures were elucidated by means of 1D and 2D NMR, and HRMS spectroscopic methods. The isolated secondary metabolites and their semisynthetic analogues were tested on seven human tumor cell lines (A2780, A2780cis, KCR, MCF-7, HeLa, HTB-26, and T47D) and on one normal cell line (MRC-5), using the MTT assay. The effusol derivative 3, substituted with two methoxy groups, showed promising antiproliferative activity on MCF-7, T47D, and A2780 cell lines with IC₅₀ values of 5.8, 7.0, and 8.6 µM, respectively.     

A special case of the Stahl conjecture

Let _Gn,k$G_{n,k}$ denote the Kneser graph whose vertices are the n$n$-element subsets of a (2n+k)$(2n+k)$-element set and whose edges are the disjoint pairs. In this paper we prove that for any non-negative integer s$s$ there is no graph homomorphism from _G4,2$G_{4,2}$ to _G4s+1,2s+1$G_{4s+1,2s+1}$. This confirms a conjecture of Stahl in a special case.     

Determination of complex type free,non-conjugated oligosaccharide glucose unit values in tomato xylem sap for early detection of nutrient deficiency

Although knowledge on glycan biosynthesis and processing is continuously maturing, there are still a limited number of studies that examine biological functions of N-glycan structures in plants, which remain virtually unknown. Here, the statistical correlation between nutrient (nitrogen) deficiency symptoms of crops and changes in 8-aminopyrene-1,3,6-trisulfonic acid (APTS)-labeled complex type free oligosaccharides is reported. While deficiency symptoms are predicted by multispectral images and Kjeldahl digestion, APTS-labeled complex type free oligosaccharides are identified by their glucose unit (GU) values in tomato xylem sap, using capillary electrophoresis with laser induced fluorescence detection (CE-LIF). Given the limited number of structures obtained from plants, archived in the literature, in the future, it is intended to create an open access database of promising indicators, namely, glycan structures that are presumably responsible for the nutrient deficiency caused stress in plants ( http://glycoplants.org ).     

Triterpenes and Phenolic Compounds from the Fungus Fuscoporia torulosa: Isolation,Structure Determination and Biological Activity

Investigation of the methanol extract of the poroid fungus Fuscoporia torulosa resulted in the isolation of a novel triterpene, fuscoporic acid (1), together with inoscavin A and its previously undescribed Z isomer (2 and 3), 3,4-dihydroxy-benzaldehide (4), osmundacetone (5), senexdiolic acid (6), natalic acid (7), and ergosta-7,22-diene-3-one (8). The structures of fungal compounds were determined on the basis of NMR and MS spectroscopic analyses, as well as molecular modeling studies. Compounds 1, 6–8 were examined for their antibacterial properties on resistant clinical isolates, and cytotoxic activity on human colon adenocarcinoma cell lines. Compound 8 was effective against Colo 205 (IC₅₀ 11.65 ± 1.67 µM), Colo 320 (IC₅₀ 8.43 ± 1.1 µM) and MRC-5 (IC₅₀ 7.92 ± 1.42 µM) cell lines. Potentially synergistic relationship was investigated between 8 and doxorubicin, which revealed a synergism between the examined compounds with a combination index (CI) at the 50% growth inhibition dose (ED₅₀) of 0.521 ± 0.15. Several compounds (1 and 6–8) were tested for P-glycoprotein modulatory effect in Colo 320 resistant cancer cells, but none of the compounds proved to be effective in this assay. Fungal metabolites 2–5 were evaluated for their antioxidant activity using the oxygen radical absorbance capacity (ORAC) and DPPH assays. Compounds 4 and 5 were found to have a considerable antioxidant effect with EC₅₀ 0.25 ± 0.01 (DPPH) and 12.20 ± 0.92 mmol TE/g (ORAC). The current article provides valuable information on both the chemical and pharmacological profiles of Fuscoporia torulosa, paving the way for future studies with this species.     

The topological type of the α-sections of convex sets

An α=(α₁,…,αk)(0?αi?1) section of a family {K₁,…,Kk} of convex bodies in Rd is a transversal halfspace H⁺ for which Vold(Ki∩H⁺)=αi⋅Vold(Ki) for every 1?i?k. Our main result is that for any well-separated family of strictly convex sets, the space of α-sections is diffeomorphic to Sd−k.     

How big can the circuits of a bridge of a maximal circuit be?

IfCE(G) is a maximum cardinality cocircuit of a 2-connected graphG, then no other maximum cocircuit is contained in one and the same block ofG-C. The analogous conjecture for real representable matroids would have important applications to classifying convex bodies with a certain Helly type property.     

On polytopes cut by flats

We prove that if we cut ad-polytope by ak-flat, then the complex of the uncut faces has the same simple-homotopy type as the boundary complex of a (d−k)-polytope. We also investigate the combinatorial properties of the complex of the uncut faces and, as a corollary, we answer negatively a question of Goodman and Pach.