The antioxidant properties of melatonin were tested in this work by EPR technique. It was found that melatonin scavenges phenylglyoxylic ketyl radicals. Its effectiveness was 10-times lower than that of vitamin C. A new method of generation of phenylglyoxylic ketyl radicals by spontaneous decomposition of D,L-2,3-diphenyltartaric acid in propan-2-ol was used.
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Angew Chem Int Ed Engl
January 2020
Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis 15771, Athens, Greece.
Direct alkylation of C(sp )-H bonds to convert an aldehyde into a ketone is a notorious transformation, due to the laborious challenge of the formation of ketyl or acyl radicals. Herein, we report a green, cheap, metal-free and efficient method for the hydroacylation of olefins in water. This photochemical protocol utilizes phenylglyoxylic acid, a commercially available small organic molecule, as the photoinitiator, water as the solvent and household fluorescent lamps as the irradiation source, leading to a broad substrate scope of products in moderate to good yields.
View Article and Find Full Text PDFFitoterapia
December 2006
Comenius University in Bratislava, Faculty of Natural Sciences, Institute of Chemistry, 842 15 Bratislava, Slovakia.
The antioxidant properties of silymarin and its flavanolignan components (silybin, silychristin and silydianin) were tested. Silymarin, silychristin and silydianin exhibit relatively good antioxidant effectiveness against phenylglyoxylic ketyl radicals and DPPH. The most effective scavengers of phenylglyoxylic ketyl radicals were silymarin and silychristin whereas silydianin was ca.
View Article and Find Full Text PDFJ Agric Food Chem
July 2005
Palacký University, Faculty of Medicine, Institute of Medical Chemistry and Biochemistry, Hnevotínská 3, CZ-77515 Olomouc, Czech Republic.
Radical scavenging and anti-lipoperoxidative effects of two organic fractions and two aqueous extracts from the leaves of a neglected Andean crop-yacon (Smallanthus sonchifolius Poepp. & Endl., Asteraceae) were determined using various in vitro models.
View Article and Find Full Text PDFGen Physiol Biophys
December 2004
Institute of Chemistry, Faculty of Natural Sciences, Comenius University, Mlynská dolina, 842 15 Bratislava 4, Slovakia.
The antioxidant properties of melatonin were tested in this work by EPR technique. It was found that melatonin scavenges phenylglyoxylic ketyl radicals. Its effectiveness was 10-times lower than that of vitamin C.
View Article and Find Full Text PDFCeska Slov Farm
May 2004
Chemický ústav Prírodovedeckej fakulty Univerzity Komenského, Bratislava.
The paper describes spontaneous decomposition of D,L-2,3-diphenyltartaric acid in propane-2-ol, which takes place via radicals at ambient temperature. The primary product of the decomposition is short-living ketyl radicals of phenylglyoxalic acid, which are captured and stabilized by means of the spin trap of N-terc-butyl-alpha-phenylnitrone. The spontaneous decomposition of D,L-2,3-diphenyltartaric acid in propane-2-ol served as the source of radicals for the determination of the antioxidative effect of known antioxidants: C-vitamin, E-vitamin, and selenomethionine.
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