Synthesis, characterization, biological evaluation, BSA binding properties, density functional theory and molecular docking study of Schiff bases

Abstract In order to make an advancement in the discovery of the more effective ways to eliminate ROS, which causes oxidative stress or to eliminate the harmful microorganisms from the organism in humans, and bearing in mind the fact that Schiff bases belong to a class of biologically active compounds, a series of Schiff bases were synthesized and tested to evaluate their antioxidant and antimicrobial activity. DPPH, superoxide anion, and reducing power assays were used in assessing the antioxidative potential of studied compounds. Among tested compounds, the B1 compound showed the largest activity in all antioxidant assays. IC50 values in DPPH radical and superoxide anion radical scavenging activities were 15.64 µg/mL and 54.72 μg/mL, respectively (even better than positive control ascorbic acid). Moreover, these compounds had effective reducing power (absorbance was in the range 2.415–1.270, depending on the concentrations tested). A high antioxidant effect was also found in B2 and C3 compounds. The remaining tested compounds showed slightly weaker antioxidant activity. Besides, the antioxidative capacity of selected compounds was studied by density functional theory (DFT). The antimicrobial activity of B1, B2 and C1–4 compounds was examined towards eight microorganisms (four species of bacteria and five species of fungi) using the microdilution method. Among tested compounds, B1 and B2 showed marked antibacterial activity (MIC values ranged from 0.15 to 1.25 mg/mL), while C4 and B1 compounds showed very strong antifungal activity (MIC values ranged from 0.07 to 1.25 mg/mL). Molecular docking simulations were performed to better understand the binding modes selected compounds with DNA and BSA, as well as to comprehend their antioxidative or antimicrobial activity.