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

Abstract

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(-1) and 15.11 J · mol(-1) · K(-1) by 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 KSV (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.