Astaxanthin diferulate as a bifunctional antioxidant
摘要:
Astaxanthin when esterified with ferulic acid is better singlet oxygen quencher with k(2) = (1.58 +/- 0.1) 10(10) L mol(-1)s(-1) in ethanol at 25 degrees C compared with astaxanthin with k(2) = (1.12 +/- 0.01) 10(9) L mol(-1)s(-1). The ferulate moiety in the astaxanthin diester is a better radical scavenger than free ferulic acid as seen from the rate constant of scavenging of 1-hydroxyethyl radicals in ethanol at 25 degrees C with a second-order rate constant of (1.68. 0.1) 10(8) L mol(-1)s(-1) compared with (1.60. 0.03) 10(7) L mol(-1)s(-1) for the astaxanthin: ferulic acid mixture, 1:2 equivalents. The mutual enhancement of antioxidant activity for the newly synthetized astaxanthin diferulate becoming a bifunctional antioxidant is rationalized according to a two-dimensional classification plot for electron donation and electron acceptance capability.
Radical Trifluoromethoxylation of Arenes Triggered by a Visible‐Light‐Mediated N−O Bond Redox Fragmentation
作者:Benson J. Jelier、Pascal F. Tripet、Ewa Pietrasiak、Ivan Franzoni、Gunnar Jeschke、Antonio Togni
DOI:10.1002/anie.201806296
日期:2018.10.15
method enables non‐directed functionalization of C−H bonds on a range of substrates, providing access to aryl trifluoromethyl ethers. This light‐driven process is distinctly different from conventional procedures and occurs through an OCF3 radical mechanism mediated by a photoredox catalyst, which triggers an N−O bond fragmentation. The pyridinium‐based trifluoromethoxylation reagent is bench‐stable and
α-Chromanoxyl radical formed by the interaction of α-tocopherol (vitamin E) with alkoxyl radical or DPPH was found by electron spin resonance spectroscopy to react with glutathione and vitamin C to regenerate α-tocopherol.
The GC/MS(MC) technique was shown to be applicable to identify various kinds of freeradicals trapped by α-aryl N-t-butyl nitrones. When spinadducts are unstable under the conditions for measurement, they were trimethylsilylated on the nitroxyl oxygen atom, which makes GC/MS measurement possible.
Substituent Effect on the Rate of the Hydroxyl and Phenyl Radical Spin Trapping with Nitrones
作者:Yoshimi Sueishi、Chiharu Yoshioka、Claudio Olea-Azar、Lester A. Reinke、Yashige Kotake
DOI:10.1246/bcsj.75.2043
日期:2002.9
and spintrapping was performed in benzene. Spintrapping rate constants were calculated using EPR signal intensity ratios for the DMPO spin adducts vs PBN-type spin adducts. The rate constants were strongly dependent on the kind of substituent in the spintrap; the magnitude of the substituent effect was also dependent on the kind of free radicalstrapped, i.e., hydroxyl or phenyl radicals. For example
Pre-incubation with 2 g/L chitosan followed by filtration had a better effect than adding 50 mg/L sulphurdioxide to the experimental Chardonnay wine on the release of 4-POBN adducts after 6 days of incubation with 100 μM iron(II). In a relevant photooxidative system acetaldehyde formation was significantly reduced after 6 days of incubation. Parallel EPR tests were performed to assess the importance
通过电子顺磁共振(EPR)研究了两种商业上不溶的壳聚糖(一种被批准用于酿酒)在模型酒和不含亚硫酸盐的白葡萄酒中对氧化降解的功效。两种化合物在不同剂量下均显着抑制α-(4-吡啶基-1-氧化物)-N - t的形成正常葡萄酒储存条件下的丁基丁基亚硝基(4-POBN)-1-羟乙基加合物。与100μM铁(II)孵育6天后,与2 g / L脱乙酰壳多糖进行预温育然后过滤比将50 mg / L二氧化硫添加到实验霞多丽酒中对4-POBN加合物的释放有更好的效果。在相关的光氧化系统中,孵育6天后乙醛的形成显着减少。进行了并行的EPR测试,以评估金属螯合(铁和铜)相对于直接清除羟基自由基对壳聚糖的影响的重要性。本数据支持使用生物相容性壳聚糖作为更健康的补充和/或替代二氧化硫对抗白葡萄酒氧化变质的潜力。