High efficiency preparation method of burdock leaf natural antioxidant

The invention relates to a high efficiency preparation method of a burdock leaf natural antioxidant. The preparation method comprises the following characteristic steps: 1, crushing dry burdock leaves, adding water, carrying out composite enzyme process extraction to obtain an aqueous extract of the antioxidant, and concentrating to obtain a concentrate 1; 2, adding an ethanol solution to burdock leaf residues subjected to enzymatic hydrolysis, carrying out ultrasonic microwave synergistic extraction, and filtering to obtain an ethanol extract; 3, carrying out reduced pressure concentration on the ethanol extract until no solvent exists to obtain a concentrate a; 4, dispersing the concentrate a in water, adding the concentrate 1, extracting by solvents of hexane, ether, petroleum ether and the like, removing impurities of pigments and the like, and reserving the obtained water phase; and 5, adding n-butanol, ethyl acetate and the like to the water phase, extracting to obtain an extract, concentrating, and drying to obtain the burdock leaf natural antioxidant. According to the invention, the ultrasonic microwave synergistic extraction technology and the biological enzyme technology are utilized to extract, so the extraction time is substantially shortened, and the extraction rate is improved. The antioxidant activity of the antioxidant prepared in the invention is stronger than the antioxidant activity of TBHQ (tertiary butylhydroquinone).