Abstract:

A method for studying the effect of some organic compounds, which are neither soluble in water nor to be made into soluble salts in water, on DNA has been investigated by a series of experiments. The solubility experiments have shown that dimethyl sulphoxide (DMSO) and its aqueous solution are excellent solvents for the hydrophobic multicycles compounds with nitrogen atoms. The data of UV (298 K), CD (298 K), ~(31)P-NMR (323 K) spectra and molar enthalpy changes (298 K) for the effect of DMSO on DNA have not shown that DMSO has an effect on DNA when the pH of solution is equal to 7.0 and its concentration is less than 0.15 mol·L~(-1). This has further proved it is safe when DMSO is used as a carrier of medicinal compounds and enters into human bodies. Under the fixed experimental conditions, no differences were found out from the results of viscous tests (298 K) and UV spectra (298 K) for the effect of harmine hydrochloride on DNA in the presence and absence of DMSO even if the concentration of DMSO reached 0.5 mol·L~(-1). It has indicated that the existence of DMSO in aqueous solutions doesn't disturb the effect of compounds on DNA. The data of UV (298 K), CD(298 K), ~(31)P-NMR (323 K) spectra and molar enthalpy changes (298 K) for the effect of some multicycles compounds with nitrogen atoms on DNA in aqueous solutions of DMSO have also given a clear explanation to the intercalation bindings of these organic compounds to DNA, and a method to study the effect of these compounds on DNA can be developed from these experiments. By analying all the data for the effect of the above compounds on DNA, both the mechanism of interaction between the compounds and DNA and the relationship between the rule of intercalation binding of a series of compounds with same multicycles structures to DNA and their microstructures have been discussed. Since the two multicycles compounds with nitrogen atoms including harmine have high bioactivity, the further experiments inside animal bodies and clinical trial on patients as anticancer drugs should be carried out.

Key words: Dimethyl sulphoxide, Multicycles compounds, Selective solvation, Intercalation binding, Anticancer efficacy