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Probing the Antioxidant Activity of Polyphenols by CIDNP: From Model Compounds to Green Tea and Red Wine
Author(s) -
Neshchadin Dmytro,
Levinn Rebecca,
Gescheidt Georg,
Batchelor Stephen N.
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200903238
Subject(s) - chemistry , cidnp , polyphenol , catechin , wine , antioxidant , hydrogen atom abstraction , hydrogen , organic chemistry , food science , radical
Polyphenols occur naturally in a vast variety of plants. One of their predominant properties is their antioxidant activity. To provide a deeper understanding of the antioxidant mechanism, 1 H CIDNP spectroscopy (CIDNP=chemically induced dynamic nuclear polarization) is used to study model hydrogen abstraction reactions with four catechin‐based polyphenols: catechin (CA), gallocatechin (GC), epigallocatechin (EGC), and epigallocatechin gallate (EGCG). The experiments involve photoinduced hydrogen‐atom transfer to a hydrogen abstractor (e.g., excited isopropylthioxanthone) followed under steady‐state conditions and in a time‐resolved fashion (resolution 500 ns–1 ms). It is found that hydrogen abstraction is an essentially stochastic process with a slight preference for the B rings in the catechin‐based polyphenols. Remarkably, analogous reactivity patterns could be followed in the “real systems”, green tea and red wine. We also show that CIDNP can be used as a semiquantitative tool to assess chemical reactivity.