Effect of Different Proportions of Phenolics on Antioxidant Potential: Pointers for Bioactive Synergy/Antagonism in Foods and Nutraceuticals

Phenolic compounds include a broad variety of antioxidant plant substances such as flavonoids that have in common an aromatic ring with one or more hydroxyl groups. Nutraceuticals and health food supplements are designed from flavonoids as well as pure phytochemicals, often in isolation. However, studies on synergistic and antagonistic effects of such compounds are relatively few. In the current study, dual combinations prepared from five phenolic compounds (flavonoid and non-flavonoid) including rutin hydrate, quercetin dihydrate, hydroquinone, kaempferol, and resveratrol were tested for their antioxidant activities using DPPH(·) radical scavenging assay. The synergistic antioxidant interactions among these phenolics were evaluated by comparing their individual antioxidant effect with that obtained by a mixture of two compounds in various ratios. Quercetin dihydrate showed the highest antioxidant activity. Many combinations were found statistically synergistic in particular ratios. Rutin hydrate and resveratrol showed maximum synergy (1:1, 2:1, and 3:1 ratio). Antagonistic interactions were also identified. The results of this study could be used by industries to develop more potent nutraceutical supplements or guide the researchers for further bioactivity validation using in vivo assays.