Potential of UV-Vis Spectroscopy for Determining the Mechanism of the Synergistic Antioxidant Process of Kaempferol with Three Other Flavonoids and β-Carotene

The antioxidant activities of flavonoid mixtures can be used to investigate the synergistic antioxidant mechanism of flavonoids. The antioxidant capacities of three flavonoids (quercetin, baicalein, and daidzein) and β-carotene in binary and ternary mixtures with kaempferol were analyzed using a 2,2-diphenyl-1-picrylhydrazyl (DPPH) inhibition assay by means of absorption spectroscopy. The results showed that the number of hydroxyl groups and o-hydroxyl groups had a significant effect on the antioxidant activity of the flavonoids, and the mixture of kaempferol, quercetin, and baicalein showed optimal synergistic antioxidant activity. Compared with quercetin and baicalein, kaempferol had the fastest inhibition rate, and multiple prolonged kinetic processes associated with the scavenging of DPPH radicals occurred in mixtures of kaempferol with the other flavonoids and β-carotene. Kaempferol has a potential synergistic antioxidant effect when mixed with daidzein and β-carotene, and the results suggested that this may be due to the regeneration of kaempferol after antioxidation. By means of classic UV-Vis spectroscopy, reaction details of the synergistic antioxidant process of DPPH radical scavenging by flavonoids can be obtained.