Formation of apocarotenals and epoxycarotenoids from β-carotene by chemical reactions and by autoxidation in model systems and processed foods

By modifying a physical property of a solution like its density or viscosity, chemical reactions can modify and even trigger convective flows. These flows in turn affect the spatiotemporal distribution of the chemical species. A nontrivial coupling between reactions and flows then occurs. We present simple model systems of this chemo-hydrodynamic coupling. In particular, we illustrate the possibility of chemical reactions controlling or triggering viscous fingering, Rayleigh–Taylor, double-diffusive, and convective dissolution instabilities. We discuss laboratory experiments performed to study these phenomena and compare the experimental results to theoretical predictions. In each case we contrast the chemo-hydrodynamic patterns and instabilities with those that develop in nonreactive systems and unify the different dynamics in terms of the common features of the related spatial mobility profiles.

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X-ray photoelectron spectroscopy study of the metal/polymer contacts involving aluminum and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) derivatives

Journal of Materials Research ◽

10.1557/jmr.2003.0167 ◽

2003 ◽

Vol 18 (5) ◽

pp. 1219-1226 ◽

Cited By ~ 21

Author(s):

S. K. M. Jönsson ◽

W. R. Salaneck ◽

M. Fahlman

Keyword(s):

Chemical Reactions ◽

Photoelectron Spectroscopy ◽

Interfacial Layer ◽

Model Systems ◽

Reaction Site ◽

Benzenesulfonic Acid ◽

Spectroscopy Study ◽

X Ray ◽

Thin Region ◽

Metal Polymer

The contact formed between aluminum and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT-PSS) derivatives was studied using x-ray photoelectron spectroscopy. The aluminum/PEDOT-PSS contact contains an interfacial layer formed by chemical reactions between aluminum and mainly poly(styrenesulfonic acid) (PSSH). These chemical interactions were studied with the help of model systems (PSSH, benzenesulfonic acid, and sodium benzenesulfonate). The preferred reaction site of aluminum is the SO3− and SO3−H+ groups of the PSS chains, giving rise to C-S-Al(-O) and C-O-Al species. The resulting contact formed consists of an insulating aluminum/PSS layer and a thin region of partially dedoped PEDOT-PSS. There is significant aluminum diffusion into films of the highly conducting form of PEDOT-PSS that have substantially less PSS at the surface. Hence, no (thick) aluminum/PSS layer is formed in this case, though the PEDOT chains close to the aluminum contact will still be partially dedoped as for the aluminum/PEDOT-PSS case.

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Influence of microwave assisted extraction on antioxidant and antiplasmodial activities of Trichilia roka extracts

The Journal of Phytopharmacology ◽

10.31254/phyto.2015.4502 ◽

2015 ◽

Vol 4 (5) ◽

pp. 248-252

Author(s):

Olga Nana ◽

◽

Jean Momeni ◽

Fabrice Fekam Boyom ◽

Martin Benoît Ngassoum ◽

...

Keyword(s):

Antioxidant Activity ◽

Antioxidant Properties ◽

Model Systems ◽

Antiplasmodial Activity ◽

Root Bark ◽

Microwave Assisted Extraction ◽

Mechanical Agitation ◽

Microwave Assisted ◽

Assisted Extraction ◽

Β Carotene

Antiplasmodial and antioxidant activities of extracts derived from Trichilia roka (Chiov) (Meliaceae) root bark were determined respectively in vitro and using two methods as well as 1,1-diphenyl-2-picrylhydrazyl radicalscavenging and β-carotene-linoleate model systems. The microwave assisted extraction extract was more effective concern antioxydant activity than the antiplasmodial activity compare to conventional mechanical agitation extraction method. Extracts obtained by microwave assisted extraction showed a high total polyphenol content of 126766 μg Equivalent of Gallic acid /g Dry Mater and a total flavonoid content of 789.22 μg Equivalent of Quercetin/g dry mater but a low antiplasmodial activity with and inhibition concentration of 48.386 μg /mL and 23.983 μg/mL for mechanical agitation extract. The evaluation of the antioxidant properties of the two extracts showed that those obtained by microwave assisted extraction shown in the 1,1-diphenyl-2-picrylhydrazyl assay and in the β-carotene bleaching test, the highest antioxidant activity respectively, with an antioxidant activity of 82.12% and with a radical-scavenging activity with inhibition percentage of 88.78%..

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