α-Alkylidene δ-lactones inhibit quorum sensing phenotypes in Chromobacterium strain CV026 showing interaction with the CviR receptor.

Disruption of bacterial quorum sensing (QS) is presented as a promising strategy to overcome clinically relevant and phytopathogenic bacteria. This work presents α-alkylidene δ-lactones as new chemical scaffolds that inhibit the biosynthesis of violacein in the biosensor strain Chromobacterium CV026. Three molecules displayed higher than 50% violacein reduction when tested at concentrations lower than 625 µM. The most active α-alkylidene δ-lactone inhibited the hydrolysis of chitin concomitantly with the inhibition of violacein production in CV026, suggesting the disruption of its QS machinery. Further, RT-qPCR and competition experiments showed this molecule to be a transcriptional inhibitor of the QS-regulated operon vioABCDE. Docking calculations suggested a good correlation between binding affinity energies and inhibition effects, with all molecules positioned within the CviR autoinducer-binding domain (AIBD). The most active lactone yielded the best binding affinity energy, most probably due to its unprecedented binding with the AIBD. Our results show α-alkylidene δ-lactones as promising chemical scaffolds for the development of new QS inhibitors affecting LuxR/LuxI-systems.

Unprecedented E-stereoselectivity on the sigmatropic Hurd-Claisen rearrangement of Morita-Baylis-Hillman adducts: a joint experimental-theoretical study.

Herein we report the first systematic investigation of the tandem mercury(ii) catalysed transvinylation/Hurd-Claisen rearrangement of MBH adducts derived from alkyl acrylates. This is the first report of E-selectivity for MBH adducts with alkyl side chains and is complementary to the previously reported Johnson-Claisen and Eschenmoser-Claisen rearrangements. The rearrangement products were obtained in good yields and could be readily converted to 2-alkenyl δ-valerolactones. Combined DFT and F-SAPT studies demonstrate that reaction rates are primarily governed by non-covalent interactions dictating the relative stability of the transition states. Our F-SAPT calculations revealed that the hyperconjugative effects are not so significant, but that electrostatic interactions, instead, are the driving forces for the relative E : Z stereoselectivity.

Applications in environmental bioinorganic: Nutritional and ultrastructural evaluation and calculus of thermodynamic and structural properties of metal-oxalate complexes.

Lead (Pb) is known by its toxicity both for animals and plants. In order to evaluate its toxicity, plants of Brachiaria brizantha were cultivated on nutritive solution of Hoagland during 90 days and submitted to different concentrations of Pb. The content of macro and micronutrients was evaluated and there was a reduction on root content of Ca, besides the lowest dosages of Pb had induced an increase of N, S, Mn, Cu, Zn and Fe. The cell ultrastructure of leaves and roots were analyzed by transmission electronic microscopy (TEM). Among the main alterations occurred there were invaginations on cell walls, the presence of crystals on the root cells, accumulation of material on the interior of cells and vacuolar compartmentalization. On the leaves the degradation of chloroplasts was observed, as well as the increase of vacuoles. Structures for the formation of oxalate crystals were proposed through molecular modeling and thermodynamic stability. Calculi suggest the formation of highly stable metal-oxalate complexes.