Preparation of tea tree oil gel and its pharmacodynamic study and irritation evaluation / 中草药

ABSTRACT

Objective To study the prescription and preparation technology of tea tree oil gel, and evaluate its anti-inflammatory efficacy, antibacterial effect and the irritation. Methods The tea tree oil gel was prepared using the carbomer-940 as gel matrix, Cremophor RH-40 and 1,2-propylene glycol as solvents. The appearance characters, pH value, viscosity, moisture retention, drug content, and the stability were observed. The anti-inflammatory efficacy, the antibacterial effect and the irritation of tea tree oil gel were evaluated. Results The prescription of tea tree oil gel was selected as following tea tree oil (1.0%), Cremophor RH-40 (5.0%), 1,2-propylene glycol (5.0%), Carbomer-940 (0.6%), glycerol (8.0%), with distilled water 100 g, adjusting pH to 5.0 by triethanolamine. The gel exhibited transparent, well uniformity, appropriate viscosity and fine coating expansion performance, with pH value of 5.52 ± 0.03, viscosity at (48 782 ± 25) mPa•s, the moisture retaining rate of (93.32 ± 0.38)% for 24 h test, containing tea tree oil of (9.55 ± 0.10) mg/g. The inhibition rate of tea tree oil gel on the mouse auricle swelling was 46.15%, which was significantly different as compared to the negative control group (P < 0.01). The diameters of inhibition zone of the gel against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa respectively was (15.50 ± 0.96), (15.25 ± 2.36), and (15.75 ± 1.91) mm. The half hemolysis rate (LC50) and the hemoglobin degeneration index (DI) respectively were 456 157 mg/L and 157.98%. The tea tree oil gel had no eye irritation in rabbits based on the value of LC50/DI 2 887.44. Fourteen consecutive’days administration indicated that the tea tree oil gel had no skin irritation in rabbits. The illumination score of irritative reaction to the rabbit skin was 0.125 after a single administration, while that was 0.036 after successive administration experiment. The results of high speed centrifugalization cold- resistance and heat-resistance tests showed that the preparation exhibited good stability, which needed to be kept tightly in a cool place and protected from light. Conclusion The formulation design was reasonable, while the preparation technology was simple, corresponding to the main index of the gel for topical application, with good anti-inflammatory efficacy, antibacterial effect and safety, which offered the basis for further research and development of tea tree oil.