Binding affinity of p-PD-based schiff-bases towards human serum albumin; in-vitro and in-silico assessment

Abstract

The Schiff-bases {N,N′-Bis(2-hydroxybenzylidene)-benzene-1,4-diamine (L1), N,N′-Bis(5‑bromo-2-hydroxybenzylidene) -benzene-1,4-diamine (L2), N,N′-Bis(2‑hydroxy-3‑methoxy-benzylidene)-benzene-1,4-diamine (L3), and N,N′-Bis(2-hydroxynaphthylidene)-benzene-1,4-diamine (L4)} have been synthesised by the reaction of 1,4-phenylenediamine (p-PD) with the necessary aldehydes and characterised by UV–Vis, FT-IR, 1H NMR, and mass spectroscopy. Their solubilities, at room temperature, were determined according to the USP and BP classification. Quantum chemical calculations of the compounds L1 to L4 have been carried out by DFT at the B3LYP/6–311++G(d,p) level; these show the results of the calculations to be in accordance with the experimental ones. A comparative analysis of the experimental and calculated vibrational frequencies was performed and significant bands were identified.The binding affinity between our Schiff-bases and human serum albumin (hsa) was studied under simulated physiological conditions, using absorbance titration experiments, fluorescence spectroscopy, circular dichroism (CD), and molecular docking (MD). Interaction results revealed one molecule of synthesised Schiff-bases to bind to the protein. MD results suggested that the binding site of L1 and L3 was site IA and that of L2 and L4 were sites IIIB and IIA, respectively. In vitro anticancer activity of the synthesised compounds was evaluated against the human hepatocellular carcinoma (HepG2) and human breast (MCF-7) cancer cells using MTT assays. Among the compounds, L4 (containing a naphthyl substituents) exhibited the highest anticancer activity with IC50 values of 12.90 ± 8.91 and 13.90 ± 7.88 against the HepG2 and MCF-7 cell lines after an incubation of 24 h.