Rosmarinic acid modified chitosan oligosaccharide as well as preparation method and application thereof

The invention discloses rosmarinic acid modified chitosan oligosaccharide as well as a preparation method and application thereof. Rosmarinic acid is utilized to modify natural chitosan oligosaccharide, the rosemary modified chitosan oligosaccharide (COS-RA) is prepared, and the compound has antioxidant activity far higher than that of the natural chitosan oligosaccharide, has a remarkable improvement effect on anthocyanin in fruits, and further promotes fruit coloring. After the water-soluble preparation prepared from the compound is sprayed to fruits, the total anthocyanin content of the fruits is increased by 40.2%-54.5%, and the content of various monomer anthocyanin is remarkably increased. Compared with natural chitosan oligosaccharide, the compound is better in effect, smaller in dosage, more uniform in coloring and higher in anthocyanin content accumulation during maturation in the application of promoting fruit coloring, and also has the characteristics of non-toxicity, easiness in biodegradation and