Prenylated xanthone derivatives with antiplasmodial activity from Allanblackia monticola STANER L.C

Further study of the methanol extract of the stem bark of Allanblackia monticola STANER L.C. resulted in the isolation of a new prenylated xanthenedione, designated allanxanthone C, together with the five known xanthones, garciniafuran, tovophyllin A, rubraxanthone, norcowanin and mangostin and one saponin, stigmasterol-3-O-beta-D-glucopyranoside. The structure of the new compound was established by detailed spectroscopic analysis to be 1,2-dihydro-3,6,8-trihydroxy-1,1,7-tri(3-methylbut-2-enyl)xanthen-2,9-dione (3-hydroxyapetalinone C). The methanol extract and pure compounds were tested on two strains of Plasmodium falciparum, F32 (chloroquine sensitive) and FcM29 (chloroquine resistant). The IC50 values obtained ranged from 0.6 to 8.9 microg/ml. Their cytotoxicity was estimated on human melanoma cells (A375) and the cytotoxicity/antiplasmodial ratio was found to be between 15.45 and 30.46. The antimicrobial activities against a range of microorganisms of the crude extract and some of these compounds are also reported.     

Towards the Application of Structure–Property Relationship Modeling in Materials Science: Predicting the Seebeck Coefficient for Ionic Liquid/Redox Couple Systems

This work focuses on determining the influence of both ionic‐liquid (IL) type and redox couple concentration on Seebeck coefficient values of such a system. The quantitative structure–property relationship (QSPR) and read‐across techniques are proposed as methods to identify structural features of ILs (mixed with LiI/I₂ redox couple), which have the most influence on the Seebeck coefficient (S_e) values of the system. ILs consisting of small, symmetric cations and anions with high values of vertical electron binding energy are recognized as those with the highest values of S_e. In addition, the QSPR model enables the values of S_e to be predicted for each IL that belongs to the applicability domain of the model. The influence of the redox‐couple concentration on values of S_e is also quantitatively described. Thus, it is possible to calculate how the value of S_e will change with changing redox‐couple concentration. The presence of the LiI/I₂ redox couple in lower concentrations increases the values of S_e, as expected.     

Tailoring the properties of boron-dipyrromethene dyes with acetylenic functions at the 2,6,8 and 4-B substitution positions

Substitution of F-Bodipy with alkynylaryl residues at boron, at the pyrrolic core or at the meso position, provides unique tri-, tetra-, and pentasubstituted dyes. Substitution at the (pyrrolic) 2,6-positions provides substantial red shifts with quantum yields in the 40-90% range and excited-state lifetimes of 3-7 ns. ON/OFF fluorescence switching can be produced by protonation of dibutylamino subunits.     

Microdeformation in Heterogeneous Polymers,Revealed by Electron Microscopy

Recent investigations of the tensile fracture behaviour of representative glassy and semicrystalline impact-resistant polymers are reviewed, with emphasis on the microdeformation behaviour as revealed by electron microscopy of sections from bulk specimens, where the crack-tip damage zone has been embedded and/or stained under load, and on thin films deformed in situ. The insight that such techniques have provided into the toughening mechanisms is discussed.