Abstract: The pH of pure water was adjusted with sulfuric acid to provide a solvent for the extraction of limonin from citrus peels. Limonin quantification was performed by HPLC. Based on one-factor-at-a-time experiments, a three-variable quadratic rotary unitization design combined with response surface methodology was used to optimize three conditions for acidic water extraction of limonin from citrus peels, and a mathematical model describing limonin yield versus the three extraction conditions was built. The optimal extraction conditions of limonin from citrus peels were 2.6 h extraction at 61.2 ℃, pH 4 and a solid-to-liquid ratio 1:19.2 (g/mL). Under the optimized conditions, a limonin yield of 0.117 mg/g was achieved.

Key words: citrus peels, limonin, extraction, quadratic rotary unitization design, high performance liquid chromatography