phenolic with the flavonoids, are capable to catalyze the incorporation of 1 or more hydroxyl groups in benzene rings on the flavonoid structure [177]. Even though a greater number of hydroxyl groups within the structure of phenolics is usually related with a greater ROS-scavenging potency [179], the extent to which the CYP-hydroxylation of particular flavonoids contribute to boost the cell’s antioxidant capacity remains to be established. As described above, in relation to the ROS-scavenging properties of flavonoids, the oxidation of specific flavonoid structures (i.e., flavonols) is connected together with the formation of mixtures of metabolites whose antioxidant activities are largely retained. In view from the ubiquitous distribution and abundance on the flavonol quercetin in edible plants of 29 Antioxidants 2022, 11, x FOR PEER Evaluation 12 [32,33], and its fairly low toxicity in humans [180], particular focus has been paid towards the study of your consequences that the oxidation of this flavonoid brings on its antioxidant properties. five. Oxidation of Quercetin and Its Consequences on Its Antioxidant PropertiesAmong dietary flavonoids, Consequences on Its Antioxidant Properties five. Oxidation of Quercetin and Itsquercetin (five,7,three,4-tetrahydroxyflavonol or 3,5,7,3,4pentahydroxyflavone, incorporated in 5-LOX Source Figure two) remains one of the most studied molecules Among dietary flavonoids, quercetin (5,7,three ,four -tetrahydroxyflavonol or three,five,7,3 ,4 [181]. Its early and well-established in vitro capacity to lower ROS formation by scavengpentahydroxyflavone, integrated in Figure two) remains probably the most studied molecules [181]. ing these species [61,182], by chelating redox-active ROS-forming metals [18385], and/or Its early and well-established in vitro capacity to reduced ROS formation by scavenging by inhibiting the activity of ROS-generating enzymes for example xanthine oxidase, lipoxythese species [61,182], by chelating redox-active ROS-forming metals [18385], and/or genases, mono-aminooxidase and cyclooxygenase [18690], has continuously prompted by inhibiting the to engage in the study of its enzymes as an as xanthine Concerning its lots of scientists activity of ROS-generating possible such antioxidant. oxidase, lipoxygenases, mono-aminooxidase and cyclooxygenase [18690], has continuously prompted ROS-scavenging home, quercetin possesses crucial structural characteristics: Dopamine Receptor Formulation ortho-dihydroxy several scientists B-ring (catechol structure), which confers higher antioxidant. Concerning its substitution in to engage in the study of its prospective as an stability for the flavonoid ROS-scavenging home, quercetin possesses essential structural capabilities: ortho-dihydroxy phenoxyl radical through hydrogen bonding or by expanded electron delocalization; the C2substitutionbond (in conjugation structure), which confers higher stabilitythe coplanarity C3 double in B-ring (catechol together with the 4-oxo group) which determines towards the flavonoid phenoxyl radical through hydrogen bonding or by expanded electron delocalization; theover in the heteroring and participates in radical stabilization via electron delocalization C2 three double bond (in conjugation with the 4-oxo group)and 5-OH groups forthe coplanarity of all three ring systems; as well as the presence from the 3-OH which determines maximum radthe heteroring and participates in radical stabilization through electron delocalization over all ical scavenging capacity [191,192]. three ring systems; plus the presence on the 3-OH and 5-OH groups for maximum radical scavenging capacity [191,
