Seasonal Variations of Eucommiol in Eucommia ulmoides Leaves and Changes in the Amounts of Eucommiol and Aucubin in the Cortexes

Methods: The amounts of eucommiol and aucubin in the leaves and barks of Eucommia ulmoides were detected by HPLC.Results: (1) The amount of eucommiol in E. ulmoides leaves peaked in mid-September (1.450%); the amount was lowest in May (0.133%). (2) Changes in the amounts of eucommiol and aucubin in the cortexes of E. ulmoides were determined. (3) A possible biotransformation pathway that converts aucubin to eucommiol in the leaves and barks of E. ulmoides was suggested.