Comparison of Flavonoids and Isoflavonoids as Antioxidants

Abstract

The isoflavonoid genistein was found to be a better antioxidant than the isomeric flavonoid apigenin in phosphatidyl liposomes at pH 7.4. The higher antioxidation activity of genistein compared with apigenin is in agreement with its lower oxidation potential (0.73 vs 0.86 V as determined by cyclic voltammetry in aqueous solution of pH= 7.4), lower dissociation enthalpy (87.03 vs 87.88 kcal mol(-1) as calculated for the more reducing 4'-hydroxyl group), and higher radical scavenging capacity in the TEAC assay. On the basis of quantum mechanical calculations for genistein and apigenin in comparison with the flavonoid naringenin and the isoflavonoids puerarin, daidzein, and equol, a lower dipole moment and a larger deviation for the A-to-B dihedral angle from coplanarity (39.3 degrees for genistein, 18.5 degrees for apigenin) are suggested to be important for the increased antioxidant efficiency at water/lipid interfaces among (iso) flavonoids with an equal number of phenolic groups.

A comparative overview of antioxidative properties and phenolic profiles of different fungal origins: fruiting bodies and submerged cultures of Coprinus comatus and Coprinellus truncorum

“…In addition daidzein and genistein were produced in a much greater amount in submerged extracts than in FB for C. comatus. These two compounds are already well known as antioxidants (Han et al 2009) and anti-tumour agents (Birt et al 2001). Moreover, genistein was characterised as a beneficial agent for prevention of diabetes (Fraga 2009).…”

PlaNet: Combined Sequence and Expression Comparisons across Plant Networks Derived from Seven Species

“…Red MYB transcription factor PAP1 resulted in accumulation of cyanidin and quercetin derivates and led to the activation of genes associated with the anthocyanin production (Tohge et al, 2005). Figure 4C shows a schematic pathway outline of the conserved flavonoid biosynthesis pathway, including anthocyanin, flavonol, glycoflavone, and isoflavone synthesis, based on literature survey and KEGG pathways, for Arabidopsis (Tohge et al, 2005(Tohge et al, , 2007Yonekura-Sakakibara et al, 2008), barley (Nørbaek et al, 2003;Brazier-Hicks et al, 2009;Klausen et al, 2010), Medicago (Kowalska et al, 2007;Farag et al, 2008), rice (Han et al, 2009;Kim et al, 2009), soybean (Steele et al, 1999;Choung et al, 2001;Latunde-Dada et al, 2001), and wheat (Ioset et al, 2007). Subclasses of flavonoids and anthocyanins have been detected and reported in all six plant species, but none of the flavonoid subfamilies, flavonol, glycoflavone, and isoflavone, has been reported.…”

Electrochemical characterization of bioactive hydroxyxanthones by cyclic voltammetry

“…In fact, genistein, a 4 0 -hydroxyisoflavone, has a comparable oxidation peak (0.51 V) with that of XH2 and apigenin, the corresponding 4 0 -hydroxyflavone, presented the same oxidation peak (0.64 V) of XH4 at pH 7.4 versus Ag/AgCl. 20 Cyclic voltammograms of several hydroxybenzoic and hydroxycinnamic acids also presented single anodic peaks at higher potentials and the absence of a cathodic peak in the reverse scan. 21 Moreover, the rapid decrease of the oxidation peak after multiple cyclic scans, without polishing the electrode between the cycles, clearly indicates that XH2 and XH4 products adsorb on the surface, blocking the diffusion process and their oxidation in the working surface electrode.…”

“…p-Coumaric acid, a para-substituted cinnamic acid, presented a barely defined oxidation peak at 0.86 V 28,32 whereas 4 0 -hydroxyflavone and 4 0 -hydroxyisoflavone derivatives presented the same cyclic voltammogram profile. 21 In addition, the isoflavonoid genistein presented a lower potential value (E pa = 0.80 V) than the flavonoid apigenin (E pa = 0.87 V) 20 and a similar relationship is found in the anodic potentials of xanthones XH2 and XH4 (E pa = 0.84 and 0.87 V, respectively), indicating that the D-phenol oxidation is more favorable than the E-phenol, at pH 4.0 versus Ag/AgCl. The presence of two phenolic groups in the xanthone core (XH5) provides a single anodic peak, at 0.84 V (Scheme 1).…”