Improved low water solubility of fisetin by enzymatic encapsulation reaction using cycloamylose produced by cyclodextrin glucanotransferase

Fisetin was encapsulated with cycloamylose (CA), an intermediate product of cyclodextrin glucanotransferase (CGTase; EC 2.4.1.19), which is known to produce cyclodextrin (CD). The molecular weight measurement of the cycloamylose-fisetin inclusion complex (CA-FST) confirmed that it contained fisetin and CA with a degree of polymerization (DP) of 9–18. The aqueous solubility of CA-FST was approximately 3700 times higher than that of fisetin, with a solubility of 37.1 mg/mL. CA-FST showed a stability of 97.9 % at 4 °C over 1 week. CA-FST dissolved in water exhibited about 80 % antioxidant activity compared to the same amount of fisetin dissolved in methanol. In the analysis of anti-inflammatory effects, CA-FST decreased cytokine expression more effectively than fisetin, indicating that CA encapsulation using CGTase could be an effective method for overcoming the limited solubility of fisetin. [Display omitted] •Inclusion complex with fisetin (FST) was prepared via CGTase-mediated cyclization.•Encapsulation increased the aqueous solubility of FST approximately 3,700-fold.•The cycloamylose-FST complex exhibited similar activities as an equal amount of FST in DMSO.•With this encapsulation method, the limited solubility of FST can be overcome.