Study of interactions of flavonoids with DNA using acridine orange as a fluorescence probe

The interactions of flavonoids, such as quercetin, kaempferide and luteolin, with fish sperm deoxyribonucleic acid (DNA) were explored by using acridine orange (AO) as a fluorescence probe. The variations in the spectroscopic characteristics of DNA–AO in an aqueous medium upon addition of the three drugs were observed. Measurements of ultraviolet absorption and fluorescence spectra, determination of binding constants for flavonoids–double stranded DNA (dsDNA) or flavonoids–single stranded DNA (ssDNA), studies on competitive bindings among these drugs interacting with DNA–AO systems, melting temperature (Tm) curves and viscosity measurements were carried out to investigate binding mechanism of these flavonoids with DNA. The binding mode of quercetin, kaempferide and luteolin with DNA was evaluated to be groove binding. The binding constants of quercetin, kaempferide and luteolin with dsDNA (or ssDNA)–AO complex were 3.19 × 104 (or 1.19 × 104), 5.63 × 104 (or 4.58 × 104) and 2.33 × 104 (or 1.03 × 104) L mol−1, respectively.