Enzymatic production of steviol using a commercial β-glucosidase and preparation of its inclusion complex with γ-CD.

Diterpenoid steviol and its derivatives have gained a growing interest for their broad therapeutic benefits in recent years. In nature, steviol exists primarily in the form of glycosides which are subject to hydrolysis after oral injestion. The present study evaluated the production of steviol using a new commercially available β-glucosidase and its inclusion complex, namely γ-cyclodextrin/steviol (γ-CD/steviol). Firstly, steviol was prepared by sequential hydrolysis from stevioside via steviolbioside, with the highest conversion of stevioside at 100% and a total yield of 64.9% based on the results of single factor experiments. To enhance steviol's aqueous solubility, γ-CD/steviol was prepared by a co-evaporation method. Results showed that the solubility of steviol increased by a factor of 102 times using an 1:1 γ-CD/steviol inclusion complex. Physiochemical properties of the γ-CD/steviol complex were evaluated by HPLC, FT-IR, TGA, XRD, SEM and NMR. At ambient temperature, the γ-CD/steviol complex aqueous solution was extremely stable when assayed in the pH range from 4.01 to 9.18 up to 30 days. [ABSTRACT FROM AUTHOR]