In vitro Evaluation and Molecular Docking Study of the Antibacterial Potential of Macaranga hullettii King ex Hook.f. Leaf Extract

Due to the resistance of bacteria to antibiotics, there has been increasing interest in the use of plant extracts to combat infections. Plants in the genus Macaranga contain secondary metabolites such as flavonoids with antibacterial properties. Macaranga hullettii King ex Hook.f. are particularly noteworthy due to their widespread distribution in East Kalimantan. This study aimed to investigate the antibacterial potential of M. hullettii leaf extract through in vitro and molecular docking studies. The antibacterial activity of the methanol extract, n-hexane, and ethyl acetate fractions from M. hullettii leaves was evaluated against three bacterial species, Staphylococcus aureus, Streptococcus mutans, and Propionibacterium acnes using the disc diffusion assay. Molecular docking of eleven flavonoid derivatives presents in four Macaranga species was performed against selected bacterial proteins (PDB ID: IJIJ, 3IPK, and 7LBU). The results showed that both the methanol extract and ethyl acetate fraction displayed antibacterial activity against the three bacteria strains, with minimum inhibitory concentrations (MICs) < 0.15%, except for the methanol extract, which had MIC of 0.15-0.31% against Propionibacterium acnes. In addition, molecular docking study showed that four flavonoids possessing prenyl or geranyl groups (6-isoprenyleriodictyol, nymphaeol A, nymphaeol B, and solophenol D) showed the highest binding affinity and dominant hydrogen bonding interactions with key amino acid residues in the binding sites of three bacterial proteins. The findings suggest that the methanol extract and its ethyl acetate fraction from Macaranga hullettii leaves could be a potential source of new antibacterial agents. Further studies are needed to isolate and evaluate the bioactive compounds.