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 lambda (em) of HSA from 336 to 330 nm whereas quercetin showed an obvious red-shift of lambda (em) from 336 to 347 nm. However, the extents of the lambda (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.