Selective enhancement of (6-4) photoproduct formation in dithymine dinucleotides driven by specific sugar puckering.

Four dinucleotide analogs of thymidylyl(3'-5')thymidine (TpT) have been designed and synthesized with a view to increase the selectivity, with respect to CPD, of efficient UV-induced (6-4) photoproduct formation. The deoxyribose residues of these analogs have been modified to increase north and south conformer populations at 5'- and 3'-ends, respectively. Dinucleotides whose 5'-end north population exceeds ca. 60% and whose 3'-end population is almost completely south display a three-fold selective enhancement in (6-4) adduct production when exposed to UV radiation, compared to TpT. These experimental results undoubtedly provide robust foundations for studying the singular ground-state proreactive species involved in the (6-4) photoproduct formation mechanism.

Preparation of New Glycerol-Based Dendrimers and Studies on Their Behavior toward Essential Oil Encapsulation.

Two new families of glycerol-based dendrimers (glyceroladendrimers (GADs) and glyceroclickdendrimers (GCDs)) have been synthesized. Three generations have been isolated for each family with good yields and were fully analyzed. The encapsulation of essential oils (citronella and cinnamon) in GADs, GCDs, and also in previously described glycerodendrimers GD-PAMAMs and GD-PPIs has been studied by dynamic-headspace gas chromatography coupled to mass spectrometry. The retention rates obtained were from -35.8 to 26.65% for citronella essential oil and from 2.14 to 38.84% for the cinnamon essential oil. In addition, the best results were obtained with GD-PAMAMs and GD-PPIs of higher generation. The interaction study between essential oils or more precisely their major components have been performed through NMR spectroscopy (1H NMR and DOSY NMR). No direct interactions between dendrimers and essential oils have been observed, but a surprising behavior of compression of the dendrimer in stable emulsions was observed. Indeed, the hydrodynamic radius of GD-PPI-3 has been reduced in the presence of cinnamon essential oil.

Triterpene saponins from the roots of Parkia bicolor A. Chev.

Five undescribed triterpene-type saponins, parkibicolorosides A-E, a cassane-type diterpene, and a known trimethoxy benzene glucoside were isolated from the roots of Parkia bicolor A. Chev. Their structures were elucidated by different spectroscopic methods including 1D- and 2D-NMR experiments as well as HR-ESI-MS analysis. Their cytotoxic activity against the chronic myeloid leukemia (K562) cell line was evaluated. The monosaccharides saponins exhibited a moderate antiproliferative activity with IC50 ranging from 48.49 ±â€¯0.16 to 81.66 ±â€¯0.17 µM.