Use of isoquinoline alkaloids as markers for identification of honey and pollen from Macleaya cordata (Willd.) R. Br

Macleaya cordata (Willd.) R. Br. (McRB) is utilized in traditional medicine and is mainly distributed in North America, Europe, Japan, and China. McRB honey known as “mad honey” produced by honey bees from the nectar of McRB contains isoquinoline alkaloids that give rise to potential consumer risk. In this study, a QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) extraction procedure followed by ultra-high performance liquid chromatography–quadrupole time-of-flight mass spectrometry (UHPLC–MS/MS) was developed and optimized for the determination of seven isoquinoline alkaloids in McRB bee pollen and honey. The results revealed the presence of seven alkaloids in McRB bee pollen, four of which were also detected in McRB honey. Protopine and allocryptopine were the two predominant alkaloids, with concentrations of 0.17–0.66 mg/kg and 0.068–0.19 mg/kg in McRB honey and 1.25*10^3–3.07*10^3 mg/kg and 1.12*10^3–2.52*10^3 mg/kg in McRB bee pollen, respectively. None of the seven alkaloids were detected in commercial honey (n = 130) or pollen samples (n = 30). This study shows that protopine and allocryptopine could serve as potential markers of honey and pollen specifically from McRB.