Antioxidant Activities and in-silico Evaluation of Selected Active Biomolecules from Syzygium aromaticum and Kalanchoe pinnatum on Target Bacterial Proteins

Abstract

Syzygium aromaticum and Kalanchoe pinnatum possess relevant bioactive compounds rich in antioxidant and antimicrobial potentials. This study evaluates the antioxidant activities and in-silico identification of potential compounds against target proteins (OmpA and CitA) in Acinetobacter baumannii and Klebsiella pneumoniae. Crude extracts from S. aromaticum and K. pinnatum were obtained by hot and cold aqueous extraction method and concentrated with a rotary evaporator. The antioxidant activities of the crude extracts were evaluated using DPPH free radical scavenging and H₂O₂ assay at different concentrations. Selected compounds from GC-MS analysis were subjected to in-silico ADMET prediction to determine their pharmacokinetic properties. Docking was performed to evaluate binding interactions between ligands and bacterial proteins (OmpA and CitA) from A. baumannii and K. pneumoniae. Data obtained were analyzed using SPSS version 26.0 and mean and standard deviation was calculated and accepted at P≥0.05. The DPPH assay showed that S. aromaticum had the best inhibition at 25% concentration with 65.95% and 63.33% in hot and cold extract respectively while highest inhibition in K. pinnatum was observed at 60.02 % in the cold extract. S. aromaticum increased from 30.07%–60.35% and 38.63%–50.49%, while K. pinnatum increased from 23.55% to 53.31% with increasing concentration. Selected compounds showed Caco-2 permeability ranging from 1.423–1.734×10⁻⁶ cm/s, blood brain barrier penetration and CYP safety. Tannin had the strongest binding affinity at −8.0 kcal/mol against the target proteins. These plants possess notable antioxidant and antibacterial activities, thus suggesting their promising option for safer and effective therapeutic agent development against rising multidrug-resistant bacteria.