Antibacterial Activity of Compounds Identified from the Active Fractions of Secang Wood (Caesalpinia sappan)

Sappan wood, also known as ‘Secang’ wood (Caesalpinia sappan), has traditionally been used as an antimicrobial agent. This study aimed to identify the chemical composition of sappan wood extract and evaluate its antibacterial activity. Sappan wood was extracted by maceration in methanol, followed by Vacuum Liquid Chromatography (VLC), resulting in five primary fractions (A – E) which were further analyzed using Liquid Chromatography-Mass Spectrometry (LC-MS/MS). The antibacterial activity of the fractions was evaluated against Escherichia coli and Staphylococcus aureus using the microdilution method. Molecular docking was performed by docking ligands identified in Fraction E against target proteins; β-ketoacyl-acyl carrier protein synthase (β-ketoacyl-ACP synthase) from E. coli (PDB ID: 1FJ4) and tyrosyl-tRNA synthetase (TyrRS) from S. aureus (PDB ID: 1JIJ) using AutoDock Tools v1.5.6.  LC-MS/MS analysis of the fractions identified various compounds belonging to the terpenoid, steroid, phenolic, and alkaloid groups of phytochemicals. All the fractions exhibited strong antibacterial activity against the test pathogenic bacterial (E. coli and S. aureus) with minimum inhibitory concentration (MIC) ranging from 2 – 8 µg/mL. Of all the fractions, Fraction E showed the highest antibacterial activity against the two organisms tested, with MIC values of 2 µg/mL against both organisms. Molecular docking study showed that the compound isosalsoline from Fraction E of sappan wood extract has the most promising antibacterial activity against S. aureus and E. coli. These findings indicate that sappan wood has the potential as alternative source of natural antibacterial compounds that can be used for the treatment of bacterial infections, especially those caused by antibiotics-resistant bacteria.