xact direction nor the magnitude of a modify in such activity is usually precisely predicted around the sole basis of the chemical nature of a flavonoid [98], theoretically, it may be expected that nu blocking by means of methylation, sulfation or glucuronidation, one or additional of its redox-active mAChR2 supplier phenolic groups, as an illustration, a single phenolic, catechol or Akt3 web galloyl in ring B, would compromise the flavonoid’s original antioxidant properties [61,99,100]. InAntioxidants 2022, 11,6 ofAntioxidants 2022, 11, x FOR PEER REVIEW6 offact, most studies indicate that when such a type 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 through the portal vein, they circulate in systemic blood just about exclusively as O-glucua substantial achieve of such activity [74,96,10112]. Primarily, comparable in vitro outcomes have ronide, O-sulphate and/or O-methyl ester/ether metabolites (typically in this order of lately been reported concerning the capacity of some flavonoids’ phase II-conjugation abundance) [69,90]. metabolites to upregulate (by means of an indirect action) the cell’s endogenous antioxidant capacity [80,11315] (Table 1). It really should be noted, on the other hand, that in some certain cases, Table 1. Phenol-compromising reactions. As exemplified for quercetin (Q), the key reactions that affect the redox-active phase I and/or II biotransformation metabolites have already been shown to exert a variety of phenol moieties of quercetin are listed. Furthermore, the chemical nature of a number of the formed metabolites along with the influence other, not necessarily the antioxidant properties biological actions that could that the phenol-compromising reactions can have onantioxidant-dependent, of your metabolites are described. significantly contribute for the health-promoting effects of their precursor flavonoids [79,116,117]. Phenol Effect on Metabolites Compromising Reactions Table 1. Phenol-compromising reactions. As exemplified for quercetin (Q), the primary reactions that Antioxidant Potency affect the redox-active phenol moieties of quercetin are basic, these metabolites have less of Glycosides (e.g. Q-3-O-glucoside; Q-4-OIn listed. Furthermore, the chemical nature O-Glycosylation a number of the formed metabolites Q-5-O-glucoside the ROS-scavenging potency than their on and also the effect that phenol-compromising reactions can have glucoside; 3,4-O-diglucoside; (in plants) the antioxidant properties in 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 Effect on Compromising Metabolites deglycosylated metabolites is, in most Antioxidant Potency (in human intestine/colon) C7 Reactions situations, significantly greater These Normally, these metabolites have significantly less metabolites have, in general, significantly 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) 3,4 -O-diglucoside; Q-5-O-glucoside and Q-7-O-glucoside) ROS scavenging/reduction potency but in Biotransformation corresponding aglycones glucuronides) some specific instances are in a position 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
