The photostability of flavanones, flavonols and flavones and evolution of their antioxidant activity

The objective of this paper is to study the effect the light on the stability of 6 flavonoids with different structures under different oxygen amounts. The evolution of their antioxidant activity and the identification of degradation products were also investigated. The results obtained indicated that the kinetics of flavonoid degradation are not only influenced by the light intensity and the oxygen amount but also by the flavonoid structure. The 6 flavonoids can be ranked below according to their stability: naringin, eriodictyol then rutin, luteolin, luteolin-7-O-glucoside and mesquitol. The presence of a hydroxyl group in position 3 and a double bond C2-C3 decrease flavonoid stability. Moreover, it was also observed that despite the total degradation of some flavonoids, the treated solutions still have an antioxidant activity. The identification of the degraded products by LC-MS showed that the degradation pathways are different according to the flavonoid studied.