A Quantum Chemical Study on the Free Radical Scavenging Activity of Tyrosol and Hydroxytyrosol

Theoretical Chemistry Accounts (Impact Factor: 2.14). 01/2012; 131:1173. DOI: 10.1007/s00214-012-1173-3

ABSTRACT The free radical scavenging activity of
hydroxytyrosol (HTyr) and tyrosol (Tyr) has been studied
in aqueous and lipid solutions, using the density functional
theory. Four mechanisms of reaction have been considered:
single electron transfer (SET), sequential electron proton
transfer (SEPT), hydrogen transfer (HT), and radical
adduct formation. It was found that while SET and SEPT
do not contribute to the overall reactivity of HTyr and Tyr
toward �OOH and �OCH3 radicals, they can be important
for their reactions with �OH, �OCCl3, and �OOCCl3. The
�OOH-scavenging activity of HTyr and Tyr was found to
take place exclusively by HT, and it is also predicted to be
the main mechanism for their reactions with �OCH3. HT is
proposed as the main mechanism for the scavenging
activity of HTyr and Tyr when reacting with other �OR and
�OOR radicals, provided that R is an alkyl or an alkenyl
group. The major products of reaction are predicted to be
the phenoxyl radicals. In addition, Tyr was found to be less
efficient than HTyr as free radical scavenger. Moreover,
while HTyr is predicted to be a good peroxyl scavenger,
Tyr is predicted to be only moderately for that purpose.

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