*2.2. Preparation of Standard Solutions*

Standard stock solutions of gelsemine, koumine and humantenmine were prepared with methanol at a concentration of 1 mg/mL and stored at −20 ◦C. The working solution of gelsemine, koumine and humantenmine was compounded by diluting the standard stock solution with methanol. Moreover, working solutions of gelsemine, koumine and humantenmine were added to blank honey to compound quality control (QC) samples. All QC samples were stored at −20 ◦C.
