Antioxidant Change in Biosynthesis from Naringenin Chalcone to Flavonoid Apingenin

Naringenin chalcone (NAC) can undergo biosynthesis to convert into dihydroflavonoid naringenin and then to flavonoid apigenin. To explore the antioxidant change during this biosynthesis, the three were comparatively analyzed using several methods. Ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry analysis gave a dimer MS peak and an adduct MS peak when each of them mixing the 1,1'-diphenyl-2-picrylhydrazyl radical. In antioxidant colorimetric analyses, the IC50 values increased in the order NAC < apigenin < naringenin. Thus, the three can scavenge free radicals via a chain reaction including propagation and termination steps. The propagation step involves a hydrogen-atom-abstraction (or electron-transfer plus H+-transfer) antioxidant mechanism. From NAC to naringenin, the antioxidant potential decreases, possibly due to enzymatic cyclization, which eliminates a phenolic -OH and saturates a C=C bond. From naringenin to apigenin, the antioxidant potential increases because the 2,3-dehydrogenation reaction cause extended - conjugation. In the termination step, each of them forms a dimer product and an adduct-with-radical product.