The influence of different drying methods on bioactive components of Eucommia ulmoides Oliver male flower and the comprehensive assessment for industrial application

This study investigated the impact of different drying methods on Eucommia ulmoides Oliver male flowers (EUOMF), which were separately dried by hot air drying (HAD), microwave drying (MWD), and vacuum freeze drying (VFD) methods under different conditions. The results of HPLC showed that the geniposide (GP), and VB2 in the stamens were higher than those in the whole flowers. The contents of CGA, GPA, and GP in the stamens treated by MWD were 1.68, 1.52, and 5.88 times of those treated by HAD. However, compared with HAD, the destroy degree of free amino acid in MWD is up to 80%. VB2 and VE are the most damaged by VFD. The contents of VB2 and VE in the stamens treated by HAD were 11.5 and 1.85 times of those treated by VFD. Emphatically, principal component analysis indicated that the optimal drying conditions was MWD. Based on the economic efficiency, MWD is more suitable to produce the EUOMF tea than other methods for industrialization process.