xact direction nor the magnitude of a adjust in such activity is often precisely predicted

xact direction nor the magnitude of a adjust in such activity is often precisely predicted on the sole basis of the chemical nature of a flavonoid [98], theoretically, it can be expected that nu blocking by way of methylation, sulfation or glucuronidation, one particular or far more of its redox-active phenolic groups, for example, a single phenolic, catechol or galloyl in ring B, would compromise the flavonoid’s original antioxidant properties [61,99,100]. InAntioxidants 2022, 11,six ofAntioxidants 2022, 11, x FOR PEER REVIEW6 offact, most studies indicate that when such a sort of metabolites are assayed in vitro for their ROS-scavenging/reducing activity, these have either drastically lost or only marginally retained the antioxidant activity of their precursors, but that in no case have they undergone liver via the portal vein, they circulate in systemic blood nearly exclusively as O-glucua substantial obtain of such activity [74,96,10112]. Primarily, similar in vitro benefits have ronide, O-sulphate and/or O-methyl ester/ether metabolites (commonly in this order of lately been reported relating to the capacity of some flavonoids’ phase II-conjugation abundance) [69,90]. metabolites to upregulate (through an indirect action) the cell’s endogenous antioxidant capacity [80,11315] (Table 1). It really should be noted, however, that in some unique situations, Table 1. DYRK4 Accession phenol-compromising reactions. As exemplified for quercetin (Q), the primary reactions that influence the redox-active phase I and/or II biotransformation metabolites have been shown to exert a number of phenol moieties of quercetin are listed. Additionally, the chemical nature of a few of the formed metabolites along with the MC4R supplier impact other, not necessarily the antioxidant properties biological actions that could that the phenol-compromising reactions can have onantioxidant-dependent, on the metabolites are described. substantially contribute towards the health-promoting effects of their precursor flavonoids [79,116,117]. Phenol Influence on Metabolites Compromising Reactions Table 1. Phenol-compromising reactions. As exemplified for quercetin (Q), the principle reactions that Antioxidant Potency impact the redox-active phenol moieties of quercetin are basic, these metabolites have much less of Glycosides (e.g. Q-3-O-glucoside; Q-4-OIn listed. Moreover, the chemical nature O-Glycosylation some of the formed metabolites Q-5-O-glucoside the ROS-scavenging potency than their on plus the influence that phenol-compromising reactions can have glucoside; three,4-O-diglucoside; (in plants) the antioxidant properties from the metabolites are described. and Q-7-O-glucoside) corresponding aglycones The ROS-scavenging potency of OPhenol O-Deglycosylation Quercetin O-deglycosylated in C3, C4 C5 or Influence on Compromising Metabolites deglycosylated metabolites is, in most Antioxidant Potency (in human intestine/colon) C7 Reactions circumstances, significantly greater These In general, these metabolites have much less metabolites have, generally, much less O-Glycosylation Glycosides (e.g., Q-3-O-glucoside; Q-4 -O-glucoside; ROS-scavenging potency than their Glucuronides (e.g. Q-3-O- and Q-7-O(in plants) three,four -O-diglucoside; Q-5-O-glucoside and Q-7-O-glucoside) ROS scavenging/reduction potency but in Biotransformation corresponding aglycones glucuronides) some particular cases are capable to up(in human intestine/ O-Deglycosylation The ROS-scavenging potency of Sulphates (e.g. Q-3-O-andin C3, C4 , C5 or C7 Q-3′-O-sulphates) (in human Quercetin O-deglycosylated O-deglycosylated meta