Glycoside production by in vitro <em>Rhodiola rosea</em> cultures

Abstract Rhodiola rosea is a medicinal plant, mainly used in Asia and Scandinavia. It is characterized as an adaptogen and is reported to have many pharmacological properties, which are ascribed to the glycosides of cinnamyl alcohol and tyrosol. As natural habitats are already overharvested and the cultivation of this plant needs 4–6 years, the production of the pharmacologically important compounds in in vitro cultures could be an alternative. In the work presented here, the production of these glycosides in compact callus aggregate cultures of roseroot was addressed. Biotransformation of exogenously added cinnamylalcohol and tyrosol was studied. Glucosylation of the precursors yielded high amounts of rosin and salidroside and low amounts of rosavin. During the course of this work, four new glycosides of cinnamyl alcohol were found and identified. The optimal concentration of the precursors and the time needed for the biotransformation was also determined. For enhancing the biotransformation rate, glucose was added to the culture medium alongside with sucrose, which doubled the production of cinnamyl alcohol glycosides but did not affect the production of salidroside. A pilot experiment using air-lift bioreactor was performed. A cDNA fragment encoding tyrosine decarboxylase was isolated and described. The expression of this gene was analysed in the leaves and roots of two chemotypes. The results demonstrate the important role of tyrosine decarboxylase in the production of salidroside. The results revealed production of the pharmacologically important glycosides of Rhodiola rosea; however the successful pilot bioreactor experiment remains to be scaled-up. New information was obtained on the biosynthesis of salidroside, which substantiate the metabolic engineering of roseroot