Fig 1.
Basic structure of flavonoids and general chemical structure of different flavonoids.
Fig 2.
Chemical structures of quercetin, rutin, (+)-catechin and of the four polymethylated analogues of quercetin (the thick grey colour points out the potential bidentate binding sites).
Fig 3.
Absorption spectrophotometric titration of 3,5,7-tri-O-methyl-quercetin (quercetin3’4’OH).
(A) Absorption spectra, (B) absorption electronic spectra, and (C) complex formation evolution as a function of the [FeNTA]0 of the FeNTA complex with quercetin3’4’OH. Solvent: CH3OH/H2O (80/20 by weight); pH = 7.4 (Hepes buffer); T = 25.0(2°C; l = 1 cm. [Quercetin 3’4’OH]0 = 2.89 × 10−5 M. (D) Electrospray mass spectra of quercetin3’4’OH ferric complex (noted LH2) in the presence of NTA. Solvent: CH3OH, capillary voltage = 4000 V. [L.FeNTA]tot = 5 × 10−5 M; Negative mode; Fragmentor = -100 V.
Table 1.
Stability constants of the FeNTA, Cu and Zn complexes with rutin, (+)-catechin and quercetin and its O-methylated analoguesa.
Table 2.
Effective concentration (EC50±SD) of the investigated flavonoids and standard (i.e., ascorbic acid).
SD: Standard Deviation.
Fig 4.
DPPH scavenging activity of studied flavonoids and the standard: ○-Quercetin, ■-Rutin, ▲-Quercetin 3’,4’OH,▼-Catechin, □-Ascorbic acid, ◄-Quercetin 3 OH, ►-Quercetin 3,5 OH, ●-Quercetin 5 OH.
The average error on the inhibition percentage was estimated to be 4% for all the examined concentrations.
Fig 5.
Hemolysis of a 5% human RBCs treated with metal ions (400 μM) in the absence or the presence of flavonoids (200 μM and 100µM) under air atmosphere at 37°C.
The significance of the differences between treated RBCs and control was determined by the Student t-test: *P < 0.05. **P < 0.01.
Fig 6.
Oxidant status of a 5% human RBCs treated with metal ions (400 μM) in the absence or the presence of flavonoids (200 μM and 100µM) under air atmosphere at 37°C.
The significance of the differences between treated RBCs and control was determined by the Student t-test: *P < 0.05. **P < 0.01.
Fig 7.
Antioxidant status of a 5% human RBCs treated with metal ions (400 μM) in the absence or the presence of flavonoids (200 μM and 100 μM) under air atmosphere at 37°C.
The significance of the differences between treated RBCs and control was determined by the Student t-test: *P < 0.05. **P < 0.01.