Integrated Experimental and Computational Investigation of Salicylaldehyde-Derived Imine/Amine Derivatives as Antioxidant and Cytotoxic Agents

In plain language

Researchers synthesised two series of salicylaldehyde-derived phenolic compounds, comprising six imines and six reduced secondary amines, to investigate their antioxidant and cytotoxic characteristics. Antioxidant testing across five laboratory assays demonstrated contrasting activity profiles between the groups. Imine derivatives performed better in electron-transfer assays, while reduced amines demonstrated greater radical-scavenging activity. Among all tested compounds, amine derivative A6 showed the strongest overall antioxidant potency, surpassing standard reference antioxidants such as BHT and BHA. Theoretical calculations revealed that sequential proton loss electron transfer is the primary mechanism driving the antioxidant activity of A6. Cytotoxicity evaluations against breast cancer cells and healthy control cells indicated that chlorinated imines, notably compound I5, possess moderate anticancer properties while maintaining minimal toxicity towards healthy cells. Computational docking and dynamic simulations confirmed stable binding interactions with target cancer-related proteins, including EGFR, tubulin, and topoisomerase II beta.

Key takeaways

Amine derivative A6 demonstrated superior overall antioxidant activity across multiple assays, outperforming standard reference antioxidants including BHT and BHA.
Density functional theory calculations confirmed that the antioxidant reactivity of compound A6 occurs predominantly via a sequential proton loss electron transfer mechanism.
Imine derivatives excelled in electron-transfer assays, whereas the reduced amine counterparts exhibited stronger radical-scavenging efficacy.
Chlorinated imine derivative I5 demonstrated moderate cytotoxicity against breast cancer cells alongside low toxicity toward non-tumour cells.

Why it matters

Excessive oxidative stress and cancer remain critical biomedical challenges. Discovering molecules that selectively combat oxidative damage or inhibit malignant cell growth without harming healthy tissue is vital for drug discovery. This investigation shows how subtle chemical modifications, such as reducing imines to secondary amines, can finely tune biological reactivity, offering new insights for designing safer therapeutic agents and effective antioxidants.

Commercialisation angle

This work presents early-stage laboratory research of potential interest to pharmaceutical and chemical formulation developers seeking novel antioxidant or oncology lead compounds. Candidates such as A6 and I5 offer starting points for antioxidant additives or anticancer therapeutics with low off-target toxicity. However, because findings are restricted to in vitro assays and computational modelling, significant further preclinical testing, safety profiling, and in vivo validation will be required before any commercial application.

AI-generated from the published abstract. Always read the original work before citing.

Abstract

Imines, commonly known as Schiff bases, are widely investigated compounds because of their structural versatility and biological properties. In this study, we aimed to evaluate the antioxidant potential of salicylaldehyde-derived imines and to determine how their reduction to the corresponding secondary amines affects their radical-scavenging activity and mechanism of action. Two series of phenolic derivatives, imines I1–I6 and amines A1–A6, were synthesized and assessed using an integrated experimental and theoretical strategy combining five in vitro antioxidant assays with density functional theory calculations. Antioxidant evaluation by DPPH, ABTS, FRAP, phenanthroline, and CUPRAC assays revealed distinct activity profiles for the two series. The imine derivatives were more effective in electron-transfer-based assays, whereas the reduced amines showed stronger DPPH radical-scavenging activity. Compound A6 exhibited the highest overall antioxidant activity, with IC₅₀ values (e.g., DPPH IC₅₀ = 26.7 ± 0.97 µM; ABTS IC₅₀ = 11.69 ± 0.43 µM) lower than BHT (DPPH IC₅₀ = 85.85 ± 3.69 µM) and BHA (DPPH IC₅₀ = 59.39 ± 1.9 µM) in most assays. DFT calculations in aqueous medium indicated that the phenolic OH groups govern antioxidant reactivity and identified SPLET as the dominant mechanism for A6, supported by a remarkably high rate constant (k = 1.40 × 10 5 M⁻¹s⁻¹) and a 100% branching ratio (G), completely outcompeting the HAT mechanism (k = 2.28 × 10 -2 M⁻¹s⁻¹). In addition to the antioxidant investigation, cytotoxicity was assessed in MDA-MB-231 breast cancer cells and Vero normal cells, revealing that the chlorinated derivatives such as I5 combine moderate anticancer activity (MDA-MB-231 IC₅₀ = 122.6 ± 2.23 µM) with lower toxicity toward non-tumor cells (Vero IC₅₀ > 400 µM). Molecular docking studies were conducted to elucidate the binding modes of the active derivatives within the active sites of EGFR, Tubulin, and Topoisomerase IIβ, while subsequent 100 ns molecular dynamics simulations validated the structural stability and sustained interaction energies of these predicted complexes.