Binding Affinity And In Vitro Cytotoxicity Of Harmaline Targeting Different Motifs Of Nucleic Acids: An Ultimate Drug Designing Approach

The work focuses towards interaction of harmaline, with nucleic acids of different motifs by multispectroscopic and calorimetric techniques. Findings of this study suggest that binding constant varied in the order single-stranded (ss) poly(A) > double-stranded calf thymus (CT) DNA > double-stranded poly(G)poly(C) > clover leaf tRNA(Phe). Prominent structural changes of ss poly(A), CT DNA, and poly(G) poly(C) with concomitant induction of optical activity in the bound achiral alkaloid molecule was observed, while with tRNA(Phe), very weak induced circular dichroism perturbation was seen. The interaction was predominantly exothermic, enthalpy driven, and entropy favored with CT DNA and poly(G)poly(C), while it was entropy driven with poly(A) and tRNA(Phe). Intercalated state of harmaline inside poly(A), CT DNA, and poly(G)poly(C) was shown by viscometry, ferrocyanide quenching, and molecular docking. All these findings unequivocally pointed out preference of harmaline towards ss poly(A) inducing self-structure formation. Furthermore, harmaline administration caused a significant decrease in proliferation of HeLa and HepG(2) cells with GI(50) of 28M and 11.2M, respectively. Nucleic acid fragmentation, cellular ultramorphological changes, decreased mitochondrial membrane potential, upregulation of p53 and caspase 3, generation of reactive oxygen species, and a significant increase in the G(2)/M population made HepG(2) more prone to apoptosis than are HeLa cells.