Study on the interaction between ginsenoside Rh2 and calf thymus DNA by spectroscopic techniques

The interaction between ginsenoside Rh2 (G‐Rh2) and calf thymus DNA (ctDNA) was investigated by spectroscopic methods including UV–vis absorption, fluorescence and circular dichroism (CD) spectroscopy, coupled with DNA melting techniques and viscosity measurements. Stern–Volmer plots at different temperatures proved that the quenching mechanism was a static quenching procedure. The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS) were calculated to be –22.83 KJ · mol^–1and 15.11 J · mol^–1 · K^–1by van ’t Hoff equation, suggesting that hydrophobic force might play a major role in the binding of G‐Rh2 to ctDNA. Moreover, the fluorescence quenching study with potassium iodide as quencher indicated that the K_SV (Stern–Volmer quenching constant) value for the bound G‐Rh2 with ctDNA was lower than the free G‐Rh2. The relative viscosity of ctDNA increased with the addition of G‐Rh2 and also the ctDNA melting temperature increased in the presence of G‐Rh2. Denatured DNA studies showed that quenching by single‐stranded DNA was less than that by double‐stranded DNA. The observed changes in CD spectra also demonstrated that the intensities of the positive and negative bands decreased with the addition of G‐Rh2. The experimental results suggest that G‐Rh2 molecules bind to ctDNA via an intercalative binding mode. Copyright © 2015 John Wiley & Sons, Ltd.