Photo‐oxidation of some flavonoids with photochemically generatedt‐BuO^•radicals in at‐BuOH water system using a kinetic approach

Abstract

As a dietary component, flavonoids are thought to have a variety of pharmacological and health‐promoting properties in both in vivo and in vitro systems. This variety is attributed to their high antioxidant capacity, which in turn is associated with their free radical scavenging properties. In order to understand the mechanism of t‐BuO• radical scavenging properties of some flavonoids, viz, quercetin (QU), apigenin (AP), daidzein (DA), genistein (GE), myricetin (MY), and kaempferol (KA), a kinetic study of photo‐oxidation of these flavonoids with photochemically generated t‐BuO• radicals in a t‐BuOH water (2:1 v/v) system was carried out. The oxidation of flavonoids by t‐BuO• radicals was performed spectrophotometrically by measuring the absorbance of quercetin (375 nm), apigenin (340 nm), daidzein (250 nm), genistein (263 nm), myricetin (255 nm), and kaempferol (375 nm) at their respective λmax. The initial rates of oxidation of flavonoids increased with [flavonoid], [t‐BuOOH], and light intensity. The quantum yields (φ) were considered from the initial rate of oxidation of flavonoids by t‐BuO• radicals and measured light intensity at 254 nm. The order on [flavonoid] and [t‐BuOOH] was found to be fractional, whereas the order on light intensity was found to be one. The products of the oxidation of flavonoids by t‐BuO• radicals were identified using LC–MS and FTIR analysis.

Scavengome of an Antioxidant

“…In view of the scavengome concept, this is an interesting example for the chemical environment significantly affecting the product profile connected to ROS/RNS scavenging by a smallmolecule antioxidant. The dimer IV/2 was observed as a main oxidation product in a photooxidation experiment, in which quercetin was oxidized by in situ formed tert-butoxyl radicals (t-BuO • ) in a solvent mixture of t-BuOH water (2:1 v/v) containing t-BuOOH (Mallepu et al, 2018). Since the excess t-BuOH supposedly scavenged the • OH radicals also formed from the photolysis, results of this experiment suggest that such a dimerization of quercetin may also take place when it reacts with alkoxyl radicals.…”

Scavengome of an Antioxidant

“…In view of the scavengome concept, this is an interesting example for the chemical environment significantly affecting the product profile connected to ROS/RNS scavenging by a smallmolecule antioxidant. The dimer IV/2 was observed as a main oxidation product in a photooxidation experiment, in which quercetin was oxidized by in situ formed tert-butoxyl radicals (t-BuO • ) in a solvent mixture of t-BuOH water (2:1 v/v) containing t-BuOOH (Mallepu et al, 2018). Since the excess t-BuOH supposedly scavenged the • OH radicals also formed from the photolysis, results of this experiment suggest that such a dimerization of quercetin may also take place when it reacts with alkoxyl radicals.…”

Application of graphene oxide in the adsorption and extraction of bioactive compounds from lemon peel

“…On the other hand, rutin and naringin are the plentiful flavonoids in citrus fruits (Wang et al., 2008). These flavonoids were generally applied as antioxidant (El‐desoky et al., 2018; Mallepu et al., 2018). Moreover, a huge number of reports have been presented about the medical activities of naringin and rutin (El‐desoky et al., 2018; Gullón et al., 2017).…”

“…were generally applied as antioxidant (El-desoky et al, 2018;Mallepu et al, 2018). Moreover, a huge number of reports have been presented about the medical activities of naringin and rutin (El-desoky et al, 2018;Gullón et al, 2017).…”