Synthesis of oxidized β-cyclodextrin with high aqueous solubility and broad-spectrum antimicrobial activity

Oxidized β-cyclodextrins with different oxidation levels were prepared using hydrogen peroxide as the oxidant and copper sulfate as the catalyst. The physicochemical, antimicrobial and antifungal properties of oxidized β-cyclodextrin were systematically studied. The results showed that the oxidation level of oxidized β-cyclodextrin was successfully controlled by adjusting the dosage of hydrogen peroxide. The aqueous solubility of oxidized β-cyclodextrin was highly improved as expected. However, oxidation changed the morphology and partly reduced the crystallinity of oxidized β-cyclodextrin due to the introduced carbonyl and carboxyl groups. It is interesting that oxidized β-cyclodextrin presented a broad-spectrum antimicrobial activity, which was efficiently improved with the increasing oxidation level. Growth of A. niger spores was efficiently inhibited in the presence of oxidized β-cyclodextrin. Moreover, oxidized β-cyclodextrin could effectively extend the storage time of apple. In summary, oxidized β-cyclodextrin shows potential as antimicrobial and antifungal agents in food industry.