Study of Nucleic Acid Binding of Aloe emodin and Emodin by Spectroscopic Techniques

Abstract

Anthraquinone compounds attain huge significance as new anticancer agents, because of their distinguishing binding with nucleic acids. In the present study, Aloe-emodin and Emodin were selected to study the complexation with sequence-specific DNA oligomers and RNAs. The interaction study of both anthraquinones were carried out by absorption, fluorescence, electrochemical and molecular docking techniques. Hypochromic effect with bathochromic shift was observed in absorption and emission spectra of drugs depicted the intercalation mode of binding between anthraquinone and nucleic acids. Aloe-Emodin showed the binding in the range of 104 - 105 M-1 with DNA and 103 - 104 M-1 with RNA by absorption and emission study. Emodin showed the binding in 103 - 105 M-1 for DNA and RNA complexation. Iodide quenching, EtBr and Electrochemical results confirmed the intercalation mode of binding of anthraquinone with nucleic acids. Thermodynamic parameters like and#8710;G, and#8710;E and and#8710;S were calculated by temperature study and also confirmed by molecular docking studies. The thermodynamic results were clearly indicated that the complexation sustained the H-bonds, van der Waals and electrostatic forces for and#960; and#960; stacking. The obtained binding energy and binding constant confirmed the GC preference of drugs with nucleic acids. On comparison of data with experimental values, it was revealed that both values are complementing with each other and confirmed the intercalation binding of both the drugs. Both drugs showed complementary binding with all nucleic acids. It was also found that both compounds showed better binding with duplex DNA as compared to RNAs. The reason for the better affinity of anthraquinone compound for DNA is due to base stacked double-helical DNA structure which facilitates intercalation by and#61552; - and#61552; stacking interaction. Relatively less amount of double-helical structure present in the RNA structure allowed relatively weaker binding with natural RNAs employed in the study. The binding values also revealed that both RNAs showed almost similar binding strength with anthraquinone compounds. newline