Formulation of Microemulsions Containing Rambutan Peel Extract and Their Antibacterial Activities

Nowadays, numerous pathogens have become increasingly resistant to antibiotics. To address this issue, it is important to undertake additional research to develop alternative antibacterial agents. The goal of this investigation was to fabricate microemulsions from rambutan (Nephelium lappaceum L.) peel extract and test their antibacterial activity. The cytotoxicity of the rambutan peel extract was studied. The other assessments were conducted on the visual, physical, and electrical properties of microemulsions, which include their appearance, phase separation, viscosity, and conductivity. Moreover, the research also examined the potential antibacterial effects of microemulsions against both gram-negative (Escherichia coli) and gram-positive (Staphylococcus aureus) bacteria by exploring their ability to inhibit bacterial growth. The findings indicated that even when the extract was used at the highest concentration (100 µg/mL), there were no cytotoxic effects on skin keratinocyte cells. Using the pseudoternary phase diagram, a blend of rosemary oil, water, and a combination of surfactant (Tween® 80) and co-surfactant (Ethanol) were employed to create microemulsions containing different quantities of rambutan peel extract. According to the results, a stable microemulsion was observed as the ratio of Tween® 80 and ethanol was higher than 38%. The microemulsions containing extract at concentrations of 1% w/w, 5% w/w, and 10% w/w were clear and transparent, with no phase separation. All formulations were physiochemically acceptable. Microemulsions containing 1% w/w – 10% w/w rambutan peel extracts were shown to be efficient in suppressing only gram-positive S. aureus.