Abstract: Response Surface Methodology (RSM) was used to optimize extraction parameters (including material/liquid ratio, extraction time and concentration of extracting agents) so as to achieve the maximum extraction yield of total phenolic compounds. Studies were carried out on the respective independent variables (material/liquid ratio, extraction time and concentration of extracting agents) and the interactive effects of these three factors on the total phenolic compounds according to Box-Benhnken design. A mathematical quadratic polynomial regression equation reflecting the relationship between the total phenolic compounds and the above extraction parameters was established. The optimal extraction parameters were obtained as: material/liquid ratio 1:14 (g/mL) , extraction time 31 min, and 80% acidification methanol as extracting agent. Under the optimal condition, the total phenolic content was 0.67 mg GAE/g, and the model prediction deviation was 6.9%. Meanwhile, the antioxidant activity was determined with five different methods, and the results showed that garlic had good antioxidant activity.

Key words: garlic, total phenolic compounds, antioxidant activity, response surface methodology