| Abstract
| - The catechol functionality present in the catechins is responsible for the protective effects exertedby green tea against a wide range of human diseases. High-level electronic structure calculations andcanonical variational transition-state theory including multidimensional tunneling corrections have allowedus to understand the key factors of the antioxidant effectiveness of the catechol group. This catechol groupforms two hydrogen bonds with the two oxygen atoms of the lipid peroxyl radical, leading to a very compactreactant complex. This fact produces an extremely narrow adiabatic potential-energy profile correspondingto the hydrogen abstraction by the peroxyl radical, which makes it possible for a huge tunneling contributionto take place. So, quantum-mechanical tunneling highly increases the corresponding rate constant value,in such a way that catechins become able to trap the lipid peroxyl radicals in a dominant competition withthe very damaging free-radical chain-lipid peroxidation reaction.
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