Optimum Parameters for Extracting Three Kinds of Carotenoids from Pepper Leaves by Response Surface Methodology

To determine the optimum parameters for extracting three carotenoids including zeaxanthin, lutein epoxide, and violaxanthin from pepper leaves by response surface methodology (RSM), a solvent of acetone and ethyl acetate (1:2) was used to extract carotenoids with four independent factors: ultrasound time (20-60 min); ratio of sample to solvent (1:12-1:4); saponification time (10-50 min); and concentration of saponification solution (KOH-methanol) (10-30%). A second-order polynomial model produced a satisfactory fitting of the experimental data with regard to zeaxanthin (R-2 = 75.95%, p < 0.0197), lutein epoxide (R-2 = 90.24%, p < 0.0001), and violaxanthin (R-2 = 73.84%, p < 0.0809) content. The optimum joint extraction conditions of zeaxanthin, lutein epoxide, and violaxanthin were 40 min, 1:8, 32 min, and 20%, respectively. The optimal predicted contents for zeaxanthin (0.823022 mu g/g DW), lutein epoxide (4.03684 mu g/g dry; DW-dry weight), and violaxanthin (16.1972 mu g/g DW) in extraction had little difference with the actual experimental values obtained under the optimum extraction conditions for each response: zeaxanthin (0.8118 mu g/g DW), lutein epoxide (3.9497 mu g/g DW), and violaxanthin (16.1590 mu g/g DW), which provides a theoretical basis and method for cultivating new varieties at low temperatures and weak light resistance.