Gum Arabic-Based Microencapsulation of Delonix regia Extract and Its In Vitro Antibacterial Activity

Delonix regia is a plant species that can be easily found in Indonesia. The bioactive compounds in Delonix regia leaves have potential medicinal properties but face limitations, such as instability, which may affect their biological activity. This study aimed to microencapsulate the ethanol extract from Delonix regia leaves using gum arabic as the coating material, employing a freeze-drying process. The effect of pH, coating material concentration, and stirring duration on encapsulation efficiency was evaluated to identify optimal conditions for microcapsule formation. The antibacterial activity of the microcapsules was assessed in vitro against Escherichia coli and Salmonella typhimurium using the disc diffusion method (Kirby-Bauer). The optimum conditions for microcapsule formation were achieved at pH 5, with a coating material concentration of 4% and 30 min of stirring time, resulting in an encapsulation efficiency (%EE) of 55.00%. FTIR analysis showed shifts in wave numbers and changes in peak intensity, indicating an interaction between the core material from Delonix regia extract and the gum arabic polymer. SEM characterisation showed the microcapsules to be mostly round but irregular, with a consistent size distribution of 3-5 μm in diameter. The microcapsules exhibited antibacterial activity at 100% concentration, producing inhibition zones of 6.06 mm against Escherichia coli and 6.77 mm against S. typhimurium.