Fe2+ and Co2+ Improved the Affinities of 7-Hydroxyflavone, Chrysin and Quercetin for Human Serum Albumin In Vitro

Chrysin, 7-hydroxyflavone, and quercetin were studied for their affinities with human serum albumin (HSA) in the presence and absence of Fe²⁺ and Co²⁺. The fluorescence intensities of HSA decrease remarkably with increasing concentration of the tested flavonoids. Chrysin resulted in a blue-shift of the emission line λ _em of HSA from 336 to 330 nm whereas quercetin showed an obvious red-shift of λ _em from 336 to 347 nm. However, the extents of the λ _em shifts induced by flavonoids in the presence of mental ions are much bigger than those of the corresponding systems in the absence of mental ions. Fe²⁺ and Co²⁺ increased the quenching constants of the tested flavonoids for HSA by 12.4–48.1 and 15.0–66.7 %, respectively. The affinities of 7-hydroxyflavone, chrysin and quercetin for HSA increased by about 6.42, 7.38 and 0.62 %, respectively, in the presence of Fe²⁺. Co²⁺ increased the affinities of 7-hydroxyflavone, chrysin, and quercetin for HSA about 8.43, 7.86 and 11.73 %, respectively.