Tea tree oil is an essential oil of Melaleuca alternifolia which has antibacterial activity. Hydrophobic properties of tea tree oil cause problem in the formulation of drug product as well as water-based cosmetics. This study aims to formulate tea tree oil into nano emulsion gel dosage form and evaluate its physical stability and antibacterial activity. Nano emulsion gel was formulated in various concentrations of tea tree oil, which were 5%, 7%, and 9% using tween 80 as surfactant and propylene glycol as co-surfactant. Tea tree oil nano emulsion gel showed stable physical appearance during 8 weeks of storage at low temperature (4°C ± 2°C) and room temperature (25° ± 2°C), cycling test, as well as mechanical test. The best formula was nanoemulsion gel F1 containing 5% of tea tree oil because it had good stability, smaller globule size, and more viscous. Results of antibacterial activity in vitro studies showed that tea tree oil nano emulsion gel had antibacterial activity against Propionibacterium acnes by the formation of inhibition zone. Higher concentration of tea tree oil in nano emulsion gel (5%, 7%, and 9%) showed greater mean inhibition zone (28.33 ± 0.88 mm; 30.33 ± 0.33 mm; and 31.67 ± 0.33 mm).

Keywords :  antibacterial activity, Melaleuca alternifolia, nano emulsion gel, Propionibacterium acnes, physical stability, tea tree oil