quinones with BCysM based on DFT calculations. Quinones are known to have both oxidative and electrophilic addition reactivities, and thiols have reductive and nucleophilic addition reactivities, which shape their functional expression in foods and living cells. Regardless of the type of reactions, both reactivities of substituted quinones generally increase with the electron-withdrawing capacity of the substituent groups. In the studied polyphenols, the only differing substituent attached to the quinone structure is the alkyl group adjacent to the 8position. Specifically, CA has a simple methylene group, ROS and epiROS have a hydroxymethylene group, and CAR and isoCAR have an acyloxymethylene group, as shown in Figure . The most electronwithdrawing group is the acyloxymethylene group, which explains the high reactivity of the quinone derivatives of CAR and isoROS (CARQ and isoROSQ respectively) with the thiol compound BCysM. These considerations, based on the electronic theory of classical organic chemistry, were confirmed by ab initio calculations. Table shows the DFT calculation results for the following redox reaction between BCysM and the quinone derivatives of rosemary polyphenols. that the reactions yield the products more efficiently. Although a comparison of transition states is necessary to accurately determine reaction rates, if the Bell-Evans-Polany principle or Marcus theory can be adapted, the high negative ∆G values of the reactions from isoROSQ and CARQ would suggest that these reactions occurred more rapidly.