Antioxidant Activity of Flavonoids of Different Polarity, Assayed by Modified ABTS Cation Radical Decolorization and EPR Technique

Abstract

Modified ABTS cation radical decolorization assay and EPR technique were applied to screen the antioxidant activity of three flavonoids with different polarity: 7-O-β-[2-O-feruloyl-β-glucuronopyranosyl (1→2) glucuronopyranoside] (tricine), 4'-methoxy-5,7-dihydroxyflavone 6-C-β-glucopyranoside (isocytisoside) and I 3' II 8 biapigenine (amentoflavone), with nonpolar all-trans β-carotene used as standard carotenoid molecule. The ABTS [2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid] cation radical decolorization assay was modified as follows: (1) measurements extended up to 8 days after preparation, (2) method adapted for flavonoids with different polarity and β-carotene, (3) concentrations in the 0.01-10 μM range of both trolox and antioxidants in order to use the same experimental conditions for both this technique and EPR measurement.

Antioxidant Activity of Phyllanthus niruri Extract, Rutin and Quercetin

“…Those factors are including ortho-dihydroxy structure in the B ring, 2,3-double bond in conjugation with a 4-oxo function in the C-ring, hydroxy groups in positions 3 and 5 in the A ring, or the angle between the rings in the compound structure. (37)(38)(39)(40) In summary, P. niruri extract and quercetin have great potential as a natural antioxidant source.…”

Antiradical and antioxidant activity of flavones fromScutellariae baicalensis radix

“…Antioxidant activity of flavones from Scutellariae radix depends on structural attributes such as the number and position of hydroxyl and methoxyl groups as well as glycosylation (Yokozawa et al 1997;Pawlak et al 2010). Baicalein and baicalin can form stable free radicals in alkaline solution, probably with active position in 6-OH group (Gao et al 1999).…”

A semi-empirical study of flavone compounds with antioxidant efficiency

“…The earlier result suggests that binding at the 3-4 site is stronger than at the 3'-4' site. The complexation of iron with one Fe, Fe-quercetin binding strength at different sites has the order 3-4 > 4-5 >3'-4', while for complexes containing two Fe atoms, the complex with one Fe bound at the 3-4 site and the second Fe at the 3'-4' site (Pawlak et al, 2010). Figure 1 (Figure 2) shows that most of the electron densities are in the B ring and C-2, C-3 double bonds only.…”

“…These compounds are found at relatively high concentrations in the human diet and comprise several classes of molecules including flavonols, flavonones and flavones. A variety of properties have been found on several recent reports such as metal bind capacity and antioxidant activity (Pawlak et al, 2010;LaChman et al, 2010).…”