Hydrogen abstraction from neurotransmitters by active oxygen species facilitated by intramolecular hydrogen bonding in the radical intermediates

2006 ◽  
Vol 4 (6) ◽  
pp. 999 ◽  
Author(s):  
Kei Ohkubo ◽  
Yoshihiko Moro-oka ◽  
Shunichi Fukuzumi
Keyword(s):  
Hydrogen Bonding ◽  
Active Oxygen Species ◽  
Hydrogen Abstraction ◽  
Intramolecular Hydrogen Bonding ◽  
Active Oxygen ◽  
Oxygen Species ◽  
Radical Intermediates ◽  
Intramolecular Hydrogen

Investigation of hydrogen abstraction from methyl glucoside by active oxygen species under oxygen delignification conditions. Part 1: Study on the anomeric position

Holzforschung ◽  
2009 ◽  
Vol 63 (1) ◽  
Author(s):  
Fumiko Konishi ◽  
Tomoya Yokoyama ◽  
Yuji Matsumoto
Keyword(s):  
Active Oxygen Species ◽  
Hydrogen Abstraction ◽  
Active Oxygen ◽  
Anomeric Effect ◽  
Oxygen Species ◽  
Oxygen Delignification ◽  
Paper Mills ◽  
Kinetic Isotope ◽  
Hydrogen Peroxide Treatment

Abstract We investigated whether active oxygen species (AOS) abstract the anomeric hydrogen from a carbohydrate model compound, methyl β-d-glucopyranoside (MGPβ) under conditions simulating oxygen delignification in pulp and paper mills (0.5 mol l-1 NaOH, 0.36 mmol l-1 Fe3+, 1.1 MPa O2, 95°C). The simulation involved in situ AOS generation by reaction of 2,4,6-trimethylphenol with O2, so that various types of AOS were operative in the system. MGPβ was degraded slightly more than methyl α-d-glucopyranoside (MGPα) when they were jointly reacted with AOS. Thus, we suggest that the configurational difference in their anomeric positions has some effects on their reactions with AOS. When MGPβ and methyl β-d-(1-2 H)glucopyranoside (MGPβ-1D) were jointly reacted with AOS, MGPβ was degraded slightly more than MGPβ-1D. This difference results from the kinetic isotope effect, indicating that the anomeric hydrogen of MGPβ is undoubtedly abstracted by AOS, although the contribution of this abstraction to the overall degradation of MGPβ has not been clarified yet. MGPβ and MGPβ-1D were also jointly subjected to alkaline hydrogen peroxide treatment (0.5 mol l-1 NaOH, 0.36 mmol l-1 Fe3+, 95°C) in which the oxyl anion radical (O-·), the conjugate base of hydroxyl radical (HO·), is likely only one of the AOS to degrade these compounds. Since no difference in degradation was observed, some AOS other than O-· must participate in anomeric hydrogen abstraction from MGPβ in these oxygen-alkali treatments. When MGPα and methyl α-d-(1-2 H)glucopyranoside were jointly reacted with AOS, almost no difference in degradation was observed. This result suggests that abstraction of the anomeric hydrogen from MGPα by AOS is no more than a very minor reaction. It was confirmed that the anomeric hydrogen of MGPβ is activated towards AOS reaction owing to the anomeric effect, which is in fact a stereoelectronic effect.

Theoretical study of intramolecular hydrogen bonding and molecular geometry of 2-trifluoromethylphenol

10.1002/jcc.2 ◽  
1996 ◽  
Vol 17 (16) ◽  
pp. 1804-1819 ◽  
Author(s):  
Attila Kov�cs ◽  
Istv�n Kolossv�ry ◽  
G�bor I. Csonka ◽  
Istv�n Hargittai
Keyword(s):  
Hydrogen Bonding ◽  
Theoretical Study ◽  
Molecular Geometry ◽  
Intramolecular Hydrogen Bonding ◽  
Intramolecular Hydrogen

Characterization and functional properties of new everbearing strawberry (Fragaria x ananasa Duch.) cultivar, ‘Summertiara’ berries

2014 ◽  
Vol 4 (1) ◽  
pp. 1 ◽  
Author(s):  
Takeshi Nagai ◽  
Misuzu Tamai ◽  
Masato Sato ◽  
Yasuhiro Tanoue ◽  
Norihisa Kai ◽  
...  
Keyword(s):  
Vitamin C ◽  
Sensory Evaluation ◽  
Functional Properties ◽  
Active Oxygen Species ◽  
Active Oxygen ◽  
Antihypertensive Activity ◽  
Oxygen Species ◽  
Total Anthocyanins ◽  
Strawberry Cultivar ◽  
The Stability

Background: In recent years, a new everbearing strawberry cultivar, ‘Summertiara’ was cultivated to supply the strawberries in pre-harvest season from July to October in Japan. For highly research and development of processing of this cultivar, ‘Summertiara’ berries, the objective of this study was to characterize these berries, with relation to chemical parameters, total phenols, total flavonoids, total vitamin C, and total anthocyanins, and was to investigate the solubility and the stability of anthocyanins from the berries. Moreover, the functional properties such as antioxidative activity, active oxygen species scavenging activity, and antihypertensive activity were also evaluated.Methods: Chemical analysis, colour measurement, and sensory evaluation of new everbearing strawberry cultivar, ‘Summertiara’ berries were performed. Next, the solubility of anthocyanins from the berries and stability of these against pH, temperature, and an incandescent lighting were investigated. Moreover, functional properties of the extracts prepared from berries were elucidated using 5 different methods.Results: The contents of water, proteins, lipids, carbohydrates, and ash were the same as those of other cultivar berries. The sugar-acid ratio in the berries was low; these were acidulous. By sensory evaluation, the main factors were vivid red colour, aroma, and acidity. The berries were rich in phenols, flavonoids, vitamin C, and anthocyanins. The anthocyanins of the berries became unstable by heat treatment and light exposures such as visible rays. On the other hand, the extracts prepared from the berries showed the functionalities such as antioxidant activity, active oxygen species scavenging activities, and antihypertensive activity.  Conclusions: The strawberry cultivar, ‘Summertiara’ berries were the most suitable for processing ingredient of strawberry-derived products with superior health promoting functionalities.Keywords: Summertiara, everbearing strawberry cultivar, characterization, sensory evaluation, color and storage, functional property

Intramolecular Hydrogen Bonding Facilitates Electrocatalytic Reduction of Nitrite in Aqueous Solutions

2019 ◽  
Vol 58 (14) ◽  
pp. 9443-9451 ◽  
Author(s):  
Song Xu ◽  
Hyuk-Yong Kwon ◽  
Daniel C. Ashley ◽  
Chun-Hsing Chen ◽  
Elena Jakubikova ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Aqueous Solutions ◽  
Intramolecular Hydrogen Bonding ◽  
Electrocatalytic Reduction ◽  
Intramolecular Hydrogen
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