Zn–polyphenol chelation: complexes with quercetin, (+)-catechin, and derivatives: I optical and NMR studies

Biological Activities and Effects of Food Processing on Flavonoids as Phenolic Antioxidants

“…The flavonoids form a stable complex with transition metals (Fe 3+ , Al 3+ , Cu 2+ , Zn 2+ ); the stoichiometry of the complex and the site of chelation depend on the nature of the flavonoid mainly the presence of the catechol part (Le Nest et al, 2004) When the flavonoids have several chelating metal sites, they can be polymerized. The copolymerization of the flavonoids and iron is responsible for anemia disease observed in large consumers of tea (Damas et al 1985).…”

Effect of Zinc (II) on the interactions of bovine serum albumin with flavonols bearing different number of hydroxyl substituent on B-ring

“…So, the structural difference between them may lead to the formation of different Zn II -flavonol complexes under the same conditions. Studies showed that Gal and Kae employ the 4-CO and 3-OH groups on the C-ring to chelate Zn 2+ ion, forming mononuclear complex Zn II -Gal [22] and Zn II -Kae [31]. As for Que, a dinuclear Zn II -Que complex forms in different buffers [22,31].…”

“…The 5-OH group is usually not involved in the chelation due to its lesser proton acidity and the steric hindrance caused by the first complexation [22]. Related studies on flavonols Gal, Kae, Que and Myr have been reported previously [20][21][22][23][24][25][26][27][28][29][30][31].…”

Spectroscopic and pulse radiolysis studies of the antioxidant properties of (+)catechin: metal chelation and oxidizing radical scavenging

“…17 Different Cu-containing species (1 : 1) have been found in the 3-11 pH range, 18 whereas the Zn(II) chelation has been investigated under anaerobic conditions in hydro-organic solvents. 19,20 In order to gain further insight into the mechanism of the beneficial effects of Cat, the capability of Cat in binding Zn(II) and Cu(II) ions, and scavenging oxidizing radicals, such as ž OH, N ž 3 and NO ž 2 , was examined by different techniques. The structural characterisation of the Zn-Cat and Cu-Cat complexes was performed by UV/vis and vibrational spectroscopy, whereas the Cat reactivity towards radiation-induced radicals was investigated by pulse radiolysis.…”