Kinetics of nitroxide radical trapping. 2. Structural effects

1992 ◽  
Vol 114 (13) ◽  
pp. 4992-4996 ◽  
Author(s):  
V. W. Bowry ◽  
K. U. Ingold
Keyword(s):  
Nitroxide Radical ◽  
Structural Effects ◽  
Radical Trapping ◽  
Kinetics Of

ChemInform Abstract: Kinetics of Nitroxide Radical Trapping. Part 1. Solvent Effects.

ChemInform ◽  
2010 ◽  
Vol 23 (39) ◽  
pp. no-no
Author(s):  
A. L. J. BECKWITH ◽  
V. W. BOWRY ◽  
K. U. INGOLD
Keyword(s):  
Solvent Effects ◽  
Nitroxide Radical ◽  
Radical Trapping ◽  
Kinetics Of

Kinetics of nitroxide radical trapping. 1. Solvent effects

1992 ◽  
Vol 114 (13) ◽  
pp. 4983-4992 ◽  
Author(s):  
A. L. J. Beckwith ◽  
V. W. Bowry ◽  
K. U. Ingold
Keyword(s):  
Solvent Effects ◽  
Nitroxide Radical ◽  
Radical Trapping ◽  
Kinetics Of

Structural effects on epimerization of bacteriochlorophyll a and chlorophyll a revealed using 3-acetyl chlorophyll a

2020 ◽  
Vol 24 (04) ◽  
pp. 499-504 ◽  
Author(s):  
Yoshitaka Saga ◽  
Shiori Nakagawa
Keyword(s):  
Physicochemical Properties ◽  
Chlorophyll A ◽  
Photosynthetic Reaction Center ◽  
Molecular Structures ◽  
Structural Factors ◽  
Structural Effects ◽  
Photosynthetic Organisms ◽  
Acetyl Group ◽  
Kinetics Of

Chlorophyll (Chl) and bacteriochlorophyll (BChl) pigments, which are crucial cyclic tetrapyrroles in photosynthesis, generally have a chiral center in their exo-cyclic five-membered E-ring. Although [Formula: see text]-epimers (primed-type) of (B)Chl pigments are rarely present in photosynthetic organisms, they play key roles in photosynthetic reaction center complexes. The epimerization mechanism of (B)Chl pigments in vivo has not been unraveled. The structural effects on the physicochemical properties of (B)Chl epimerization reactions provide useful information to tackle this question. We analyzed epimerization of three pigments, BChl [Formula: see text], Chl [Formula: see text], and 3-acetyl Chl [Formula: see text], to elucidate the structural factors that are responsible for epimerization reactions. We compared the epimerization kinetics of the three pigments and concluded that the bacteriochlorin skeleton (7,8,17,18-tetrahydroporphyrin) significantly retarded the epimerization kinetics. Thus, BChl [Formula: see text] exhibited slower epimerization kinetics than Chl [Formula: see text] in spite of the presence of the electron-withdrawing 3-acetyl group that accelerates epimerization. In contrast to the large structural effects of (B)Chl molecules on epimerization kinetics, the thermodynamic properties at equilibrium in the epimerization of the three pigments were barely influenced by their molecular structures. This study also demonstrates that a semi-synthetic pigment, 3-acetyl Chl [Formula: see text], is appropriate for comparative analyses of the structural effects of BChl [Formula: see text] and Chl [Formula: see text] on their physicochemical properties.

In vivo temporal EPR imaging for estimating the kinetics of a nitroxide radical in the renal parenchyma and pelvis in rats

2002 ◽  
Vol 20 (1) ◽  
pp. 77-82 ◽  
Author(s):  
Atsushi Ueda ◽  
Hidekatsu Yokoyama ◽  
Sohji Nagase ◽  
Aki Hirayama ◽  
Akio Koyama ◽  
...  
Keyword(s):  
Nitroxide Radical ◽  
Renal Parenchyma ◽  
Kinetics Of

scholarly journals Absolute Antioxidant Activity of Five Phenol-Rich Essential Oils

Molecules ◽  
2021 ◽  
Vol 26 (17) ◽  
pp. 5237
Author(s):  
Yafang Guo ◽  
Romeo Pizzol ◽  
Simone Gabbanini ◽  
Andrea Baschieri ◽  
Riccardo Amorati ◽  
...  
Keyword(s):  
Essential Oils ◽  
Antioxidant Activities ◽  
Oxygen Uptake Kinetics ◽  
Butylated Hydroxytoluene ◽  
Thymus Vulgaris ◽  
Origanum Vulgare ◽  
Cinnamomum Zeylanicum ◽  
Radical Trapping ◽  
Chain Breaking ◽  
Kinetics Of

Essential oils (EOs) have promising antioxidant activities which are gaining interest as natural alternatives to synthetic antioxidants in the food and cosmetic industries. However, quantitative data on chain-breaking activity and on the kinetics of peroxyl radical trapping are missing. Five phenol-rich EOs were analyzed by GC-MS and studied by oxygen-uptake kinetics in inhibited controlled autoxidations of reference substrates (cumene and squalene). Terpene-rich Thymus vulgaris (thymol 4%; carvacrol 33.9%), Origanum vulgare, (thymol 0.4%; carvacrol 66.2%) and Satureja hortensis, (thymol 1.7%; carvacrol 46.6%), had apparent kinh (30 °C, PhCl) of (1.5 ± 0.3) × 104, (1.3 ± 0.1) × 104 and (1.1 ± 0.3) × 104 M−1s−1, respectively, while phenylpropanoid-rich Eugenia caryophyllus (eugenol 80.8%) and Cinnamomum zeylanicum, (eugenol 81.4%) showed apparent kinh (30 °C, PhCl) of (5.0 ± 0.1) × 103 and (4.9 ± 0.3) × 103 M−1s−1, respectively. All EOs already granted good antioxidant protection of cumene at a concentration of 1 ppm (1 mg/L), the duration being proportional to their phenolic content, which dictated their antioxidant behavior. They also afforded excellent protection of squalene after adjusting their concentration (100 mg/L) to account for the much higher oxidizability of this substrate. All investigated EOs had kinh comparable to synthetic butylated hydroxytoluene (BHT) were are eligible to replace it in the protection of food or cosmetic products.

Thermal Decomposition Mechanisms oftert-Alkyl Peroxypivalates Studied by the Nitroxide Radical Trapping Technique

2000 ◽  
Vol 65 (1) ◽  
pp. 16-23 ◽  
Author(s):  
Tomoyuki Nakamura ◽  
W. Ken Busfield ◽  
Ian D. Jenkins ◽  
Ezio Rizzardo ◽  
San H. Thang ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Nitroxide Radical ◽  
Radical Trapping ◽  
Decomposition Mechanisms
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