Free radical scavenging potency of physiologically active equol molecule, derived by gut microbiota from soy isoflavone daidzein, was investigated by using M06-2X/6-311++G(d,p) level of theory, accompanied with the TST and Eckart tunneling corrections for the estimation of rate constants. Phenolic hydrogens of equol are recognized as much more abstractable than C-ring hydrogens. This finding is opposite to the one very recently suggested, but in accordance with well-known facts related to the flavonoid chemistry and phenolic O−H vs C−H reactivity.
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