Antioxidant interactions between hydrophilic and lipophilic phytochemicals are influenced by their ratios and total concentrations

Lipophilic (lycopene, β-carotene) and hydrophilic (caffeic acid, p -coumaric acid) phytochemicals were mixed in molar mass at different concentrations/ratios to explore the antioxidant interactions on H 2 O 2 -treated H9c2 cells. Reactive oxide species (ROS), expression of antioxidant enzymes , and oxidation products were analyzed and evaluated by synergistic rate (SR) and combination index (CI). At constant concentrations, antioxidant interactions were influenced by ratios. Group contained more hydrophilic compounds (eg., p -coumaric acid:β-carotene=9:1) showed antioxidant synergism (SR=22.33±1.23, SR>0) at 3.0 μM, while groups that contained more lipophilic compounds (eg., p -coumaric acid:β-carotene=1:9) showed antioxidant antagonism (SR=-11.68±1.25, SR<0) at 3.0 μM. Antioxidant interactions were also influenced by concentrations. From results, ROS generation of group ( p -coumaric acid:β-carotene=1:9) changed from synergism (SR=12.27±2.34, SR>0) to antagonism (SR=-11.68±1.25, SR<0) as their total concentrations increased from 1.5 μM to 3.0 μM. Therefore, this study discussed the possible mechanism of ratio and concentration on the antioxidant interaction among hydrophilic and lipophilic phytochemicals. It also suggested that proper concentrations/ratios of hydrophilic and lipophilic phytochemicals should be considered in diet and formulation of functional foods.