Preparation of a Nanoscale Garlic Oil Microemulsion and Its Antioxidant Activity

Garlic oil has been shown to have many pharmacological and biological activities. However, its poor solubility in water, volatility and instability limit its extensive application in the fields of medicine, cosmetics and food. In this work, nanoscale garlic oil microemulsions were prepared with canola oil, a canola oil/garlic oil mixture or pure garlic oil as the oil phase, Tween-80 as the surfactant and ultrapure water as the aqueous phase, and the microemulsions were characterized. The influence of the co-surfactant type (glycerol, ethanol and n-butanol) and the mass ratio of the surfactant to the co-surfactant (K-m ) in the oil-in-water (O/W), water-in-oil (W/O), and binary continuous phase (BC) microemulsion regions in pseudoternary phase diagrams were investigated. Moreover, the antioxidant activity of the prepared garlic oil microemulsion was evaluated. The results showed that when ethanol was used as a co-surfactant, a canola oil monophase microemulsion area of 42.03% can be obtained at a K-m of 2: 1 with a particle size of 88.44 nm, and the monophase microemulsion area was approximately 18.55% and 52.54% for the canola oil/garlic oil mixture as the oil phase at the mass ratios of 10: 1 and 5: 1, respectively, with a mean particle diameter of 13.33 similar to 14.00 nm. The results also suggested that when using ethanol as the co-surfactant at a K-m of 3: 1, the garlic oil monophase microemulsion area of 52.54% and an O/W microemulsion area of 16.62% could be produced with a size of approximately 15.0 nm. Furthermore, the results showed that a microemulsion of garlic oil/Tween-80/ethanol/water exhibited remarkable antioxidant activity against the superoxide anion, hydroxide radical and hydrogen peroxide using chemiluminescence methods, with IC50 values of 17.98 mg/mL, 4.17 mg/mL and 8.47 mg/mL, respectively. This study suggested that garlic oil microemulsions may be a promising dispersion for use in food and pharmaceutical products.