The benzophenanthridine alkaloid chelerythrine binds to DNA by intercalation: Photophysical aspects and thermodynamic results of iminium versus alkanolamine interaction

Cytotoxicity and DNA interaction of brucine and strychnine—Two alkaloids of semen strychni

“…Binding of the alkaloid harmalol to DNA was also shown to be through intercalation, with a binding constant of 4.5 × 10 5 M −1 [33]. To the best of our knowledge, the binding constants estimated for alkaloid-DNA associations have been found to range from 10 3 to 10 7 M −1 [34][35][36][37]. The present study showed that brucine interacted with DNA via both intercalation and electrostatic interaction, similar to most alkaloids.…”

Entropy driven binding of the alkaloid chelerythrine to polyadenylic acid leads to spontaneous self-assembled structure formation

“…Quenching studies were carried out with the anionic quencher KI as described in details previously [21]. The data were plotted as Stern-Volmer plots of relative fluorescence intensity (F o /F) versus I À concentration.…”

“…We measured the binding of chelerythrine to poly(A) at first by isothermal titration calorimetry at T = 293.15 K. The alkaloid can exist in the charged iminium and neutral alkanolamine forms with a pKa of 8.58 [21]. Therefore, the measurements were performed at pH 6.25 that ensured practically the presence of charged iminium form only.…”

“…Chelerythrine has strong peaks in the visible absorption region (spectrum 1 of figure 5A) [21,23], but poly(A) has no absorbance above 300 nm. Hence a titration study of a fixed concentration of the alkaloid with increasing concentration of poly(A) was initially performed to understand the nature of the interaction; figure 5A depicts the results of spectral titration of the alkaloid with poly(A) at T = 293.15 K. Noteworthy spectral features that were observed in this study are: (i) hypochromic effect, suggesting strong intermolecular interaction involving apparently the overlap of the p electron clouds of the alkaloid and the poly(A) base pairs, (ii) bathochromic shift of the absorbance maxima due to a change in environmental conditions of the chromophore, for example, a change in polarity, (iii) isosbestic points in the series of spectra that testified for a two state system consisting of bound and free alkaloids at any wavelength in this region and, (iv) hypochromic and bathochromic effects leading to saturation of the binding sites.…”

“…It also stimulates the production of reactive oxygen species, which may deplete cellular antioxidants, provide a signal for rapid execution of apoptosis [18], and provoke cell death in a variety of tumour cells leading to potential application as an anticancer agent [16,19,20]. The DNA binding activity of chelerythrine was studied recently in our laboratory [21,22] to show that the binding occurs by intercalation with remarkable guanine-cytosine base pair specificity. A few other studies on its DNA binding have also been reported [23][24][25].…”