Crystal structure and DNA binding properties of khellin oxime

The dried fruits of Ammi visnaga were subjected to Soxhlet extraction with water, followed by hexane and purified by column chromatography to yield Khellin (1). Oximation of 1 yielded khellin oxime (2), crystallized by slow evaporation from CH₂Cl₂:EtOAc (6:3), characterized by single-crystal X-ray diffraction method for the first time. The DNA binding affinities of the 1 and 2 have been appraised by examining their ability to bind to dsFSDNA with ultraviolet-visible and fluorescence spectroscopies, thermal denaturation and square wave voltammetry techniques. The binding constants of the both compounds with dsFSDNA are calculated by UV-vis measurements. The square wave voltammograms proved that both compounds bind to dsFSDNA by intercalative binding mode. Competitive studies with ethidium bromide (EB) have shown that 1 and 2 exhibit the ability to displace the DNA-bound EB indicating 1 and 2 bind to DNA with intercalation with EB for the intercalative binding site as a challenging displacement.