| heal.abstract |
Flavonoids are strong antioxidants that prevent DNA damage. The anticancer and antiviral activities of these natural products are implicated in their mechanism of actions. We report the interactions of quercetin (que), kaempferol (kae) and delphinidin (del) with calf-thymus DNA and transfer RNA in aqueous solution at physiological conditions, using constant DNA or RNA concentration (6.25 mmol) and various drug/polynucleotide(phosphate) ratios of 1/65 to 1. Structural analysis showed quercetin, kaempferol and delphinidin intercalate RNA duplex with minor external binding to the major or minor groove and the backbone phosphate group with overall binding constants Kque=4.80 x 104 M-1, Kkae=4.65 x 104 M -1 and Kdel=9.47 x 104 M-1. The stability of adduct formation is in the order of del>que>kae>. A comparison with flavonoids-DNA adducts showed both intercalation and external bindings with stability order Kque=7.25 x104 M -1, Kkae=3.60 x104 M-1 and K del=1.66 x104 M-1. Low flavonoid concentration induces helical stabilization, whereas high pigment content causes helix opening. A partial B to A-DNA transition occurs at high drug concentration, while tRNA remains in A-family structure. |
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