Search results for "Enone"

Intramolecular Interactions in the Triplet Excited States of Benzophenone–Thymine Dyads

2005

Time-resolved and product studies on the synthesized dyads 1 and 2 have provided evidence that the benzophenone-to-thymine orientation strongly influences intramolecular photophysical and photochemical processes. The prevailing reaction mechanism has been established as a Paterno-Büchi cycloaddition to give oxetanes 3-6; however, the ability of benzophenone to achieve a formal hydrogen abstraction from the methyl group of thymidine has also been evidenced by the formation of photoproducts 7 and 8. These processes have been observed only in the case of the cisoid dyad 1. Adiabatic photochemical cycloreversion of the oxetane ring is achieved upon direct photolysis to give the starting dyad 1 …

Resolving the Benzophenone DNA-Photosensitization Mechanism at QM/MM Level

2015

International audience; Benzophenone, the parent of the diarylketone family, is a versatile compound commonly used as a UV blocker. It may also trigger triplet-based DNA photosensitization. Therefore, benzophenone is involved in DNA photodamage induction. In the absence of experimentally resolved structure, the mechanism of DNA damage production remains elusive. Employing a hybrid quantum mechanics/molecular mechanics approach, here we address the spin transfer mechanism between this drug and proximal thymine, that is, the DNA nucleobase most prone to suffer triplet damages.

Protective effect of apocynin in a mouse model of chemically-induced colitis.

2013

Apocynin, a constituent of Picrorhiza kurroa, successfully inhibits NADPH oxidase and shows promise as an anti-inflammatory drug. Now, we report anti-inflammatory effects of apocynin in an experimental colitis model induced by dextran sulfate sodium as well as the effects on the mediators involved in this process. Apocynin reduced the colitis induced in mice by administration of 5 % dextran sulfate sodium during 7 days. Mice were fed a control diet or a diet supplemented with 2 % of apocynin or 2 % of rutin. Sulfasalazine (50 mg/kg, p. o.) was used as a positive control. Treatment with apocynin and rutin ameliorated the course of colonic inflammation with results similar to those of the ref…

Study of quantitative and qualitative variations in essential oils of Sicilian Rosmarinus officials L.

2015

In this study the chemical characterizations of 10 sicilian biotypes of Rosmarinus officinalis L. essential oils are reported. The main goal was to analyze the relationship between the essential oils yield and the geographical distribution of the species plants. The essential oils were analyzed by GC-FID and GC-MS. The statistical methods Hierarchical Cluster Analysis and Principal Component Analysis were used to cluster biotypes according to the chemical composition of the essential oils. The essential oil yield ranged from 0.8 - 2.3 (v/w). 82 compounds have been identified, these represent 96.7-99.9% of the essential oil. The compounds mostly represented in the essential oils were: 1.8- C…

Chemical Composition of the Essential Oil of Mentha pulegium Growing Wild in Sicily and its Activity on Microorganisms Affecting Historical Art Crafts

2017

The chemical composition of the essential oil from aerial parts of Mentha pulegium L. (Linné) collected in Sicily was evaluated by GC and GC-MS. The main components were pulegone (50.6%), piperitenone (27.8%) and menthone (6.9%). Comparison of this oil with other studied oils of different populations is discussed. The oil showed good antibacterial and antifungal activities against some microorganisms that infest historical art works.

Generation of 6,7-Dihydro-5H-1,3,4-thiadiazolo[3,2-a]pyridines — Unexpected Products in the Reaction of 5-Ethylthio-1,3,4-thiadiazole-2-amine and 3-(…

1998

ChemInform Abstract: Auxiliary-Controlled Stereoselective Enolate Protonation: Enantioselective Synthesis of cis and trans Annulated Decahydroquinoli…

2010

Abstract The diastereoselective synthesis of the octahydroquinoline enone precursor of pumiliotoxin C is achieved via tandem Mannich-Michael reaction on N-galactosyl imines. Conjugate cuprate addition to the bicyclic enone stereoselectively forms the trans annulated 4a- epi -pumiliotoxin C skeleton in the presence of the carbohydrate auxiliary, and the cis annulated pumiliotoxin C skeleton in its absence.

Synthesis of 6,12-Disubstituted Methanodibenzo[

2019

The preparation of unprecedented 6,12-disubstituted methanodibenzo[b,f][1,5]dioxocins from pyrrolidine catalyzed self-condensation of 2′-hydroxyacetophenones is herein described. This method provides easy access to this highly bridged complex core, resulting in construction of two C–O and two C–C bonds, a methylene bridge and two quaternary centers in a single step. The intricate methanodibenzo[b,f][1,5]dioxocin compounds were obtained in up to moderate yields after optimization of the reaction conditions concerning solvent, reaction times and the use of additives. Several halide substituted methanodibenzo[b,f][1,5]dioxocins could be prepared from correspondent 2′-hydroxyacetophenones.

Size Reduction of CdSe/ZnS Core−Shell Quantum Dots Photosensitized by Benzophenone: Where Does the Cd(0) Go?

2011

The size of core-shell CdSe/ZnS quantum dots can be decreased by using the combined action of an n,π* aromatic ketone and UVA light. Energy-dispersive X-ray spectroscopy as well as X-ray photoelectron spectroscopy techniques gave information on the photosensitization mechanism and the eventual destiny of Cd(2+) and Se(2-) core ions. Our data support the electron transfer from the BP ketyl radical to Cd(2+), leading to Cd(0) and H(+), as well as to the recovery of benzophenone. Elemental Cd remains on the core and, eventually, can be oxidized to CdO. In addition, Se(2-) counterions disperse inside the solution mainly attached to protonated amine ligands. The Se(2-) combines with H(+), leadin…

Efficient flow injection and sequential injection methods for spectrophotometric determination of oxybenzone in sunscreens based on reaction with Ni(…

2001

Spectrophotometric determination of a widely used UV-filter, such as oxybenzone, is proposed. The method is based on the complexation reaction between oxybenzone and Ni(II) in ammoniacal medium. The stoichiometry of the reaction, established by the Job method, was 1:1. Reaction conditions were studied and the experimental parameters were optimized, for both flow injection (FI) and sequential injection (SI) determinations, with comparative purposes. Sunscreen formulations containing oxybenzone were analyzed by the proposed methods and results compared with those obtained by HPLC. Data show that both FI and SI procedures provide accurate and precise results. The ruggedness, sensitivity and LO…