Interação entre compostos biologicamente ativos e ctDNA (Calf Thymus): uma abordagem espectroscópicaI

Abstract

DNA interactions studies with small molecules such as drugs, organic dyes and metal complexes have been a wide-ranging research theme during the last decades. Since those interactions can lead to a better comprehension at molecular level processes. The elucidation of drug action mechanisms and new drugs conception that are DNA-target designed can be achieved. So, the aim of this work was to evaluate the ctDNA (Calf thymus) interaction with three derivative classes of β-carboline, aldimine and acridine compounds, using spectrophotometric techniques and theoretical studies, leading to the evaluation of biding mode and magnitude for the ctDNA/ligand complex, as well as the correlation with their biological activities. According to the results, for the derivative β-carboline and acridine compounds there was formation of a non-fluorescent supramolecular complex, characterized by static quenching mechanism. The binding constants (Kb) ranged from 3.30x102 to 1.82x106 L mol-1 for β-carboline compounds where it was observed that the alkaloids with the N,N-dimethylaniline radical (radical b) shown greater Kb values (3.98x105-1.82x106 L mol-1). For the acridine compounds, it was verified that the Kb values ranged from 2.09 to 7.76x103 L mol-1, corroborating with predicted energy binding values obtained by the molecular docking studies. For the aldimines compounds, it was observed that the Kb values ranged from 0.37 to 3.07x105 L mol-1, being the hydroxylated compounds (orto and para positions) the ones with greatest Kb values. Additionally, the potassium iodide and competition with ethidium bromide assays, thermal denaturation profile and contact energy transfer were executed to determine the preferential biding mode of the DNA-ligand complexes. These studies have shown that the preferential binding mode for the derivate β-carboline and acridine compounds occur by intercalation, while that for aldimine compounds were preferentially by groove. Furthermore, once the Kb values were determined, the linear correlation for the biological activities of the evaluated compounds was established. An inverse linear profile for β-carboline, acridine compounds and a few derivative aldimine compounds (class 1, only hydroxyl substituted), indicating that the greater Kb values, smaller are the GI50 or IC50, being selective for resistant ovarian (NCI-ADR/RES), ovarian (OVCAR-03) and prostate (PC-3) cell lines, while class 2 aldimine compounds (radical nitro substituted) had a direct linear trend for anti-proliferative activity, where the Kb and GI50 values increase proportionally, being selective to resistant ovarian cell lines. Moreover, the anti-malaria activity for acridine compounds was evaluated towards P. falciparum W2, showing an inverse profile; that is, the greater the Kb values the smaller IC50 and binding energy obtained by molecular docking. In conclusion, the set of results suggests that the mechanism of action for the evaluated compounds in both anti-proliferative and anti-malaria activity can be associated with the DNA interaction as a pharmacological target.