Molecular aspects on the specific interaction of homoisoflavonoids to DNA

Homoisoflavonoids (3-benzylidenechroman-4-ones) are related to flavonoids and occur as natural products and exhibit biological activity. These compounds have been reported to possess antioxidant, antifungal, hypocholesterolemic, antimutagenic and antiviral activities. This study was designed to examine the interactions of four synthetic homoisoflavonoids (BMC, BPC, HBC and HBMC) with calf-thymus DNA in aqueous solution at physiological conditions, using constant DNA concentration (6.25 mM) and various homoisoflavonoids/polynucleotide (phosphate) ratios of 1/120, 1/80, 1/40, 1/20, 1/10 and 1/5. Fourier transform infrared (FTIR) and UV–Visible spectroscopic methods were used to determine the ligand binding modes, the binding constants and the stability of homoisoflavonoids–DNA complexes in aqueous solution. Spectroscopic evidence showed major binding of homoisoflavonoids to DNA with overall binding constants of KBMC–DNA = 9.37(±0.34) × 103 M−1, KBPC–DNA = 1.8(±0.09) × 104 M−1, KHBC–DNA = 1.3(±0.19) × 103 M−1 and KHBMC–DNA = 4.7(±0.41) × 103 M−1. The affinity of homoisoflavonoids–DNA binding is in the order of BPC > BMC > HBMC > HBC. No biopolymer secondary structural changes were observed upon homoisoflavonoids interaction and DNA remains in the B-family structure in these complexes.