In vitro interaction of a benzodiazepine group of drugs Alprazolam (Alp), a hypnotic and tranquilizer, with DNA was studied by various methods. Absorption spectrophotometric study showed that Alp binds strongly with supercoiled pUC 19 DNA and the calculated binding constant is 8.245 × 10³ M^-1 in 10 mM Tris-Cl buffer, pH 7.4. Spectrofluorometric study showed that ethidium bromide induced DNA fluorescence intensity was reduced completely after addition of Alp. But Alp did not interfere with the interaction of Hoechst 33258, a DNA minor groove binder, with plasmid DNA. Circular dichroic spectroscopic study showed that with the gradual increase in Alp concentrations, both the positive and the negative peaks of DNA were gradually decreased and at higher concentrations of Alp (60 μM and 80 μM), the negative peaks became positive indicating the intercalation and the conformational change in the DNA. Binding of Alp with DNA increased the thermal stability of DNA by 6 °C with respect to the mock treated sample. Gel electrophoresis study of supercoiled pUC 19 DNA showed more compact structure as a result of Alp binding. Transmission electron microscopic observations also confirmed this compactness. Thus, our observations suggest the strong interaction of Alp with DNA, which may raise serious questions about the random uses of Alprazolam.

Key words: Alprazolam; DNA; Spectroscopic study; Intercalation; Gel electrophoresis; Transmission electron microscopy.