Chemical Profiles of Korean Bee Pollens and Their Catechol-O-methyltransferase Inhibitory Activities

Bee pollen is an apicultural product collected by honeybees from flower stamens and is consumed to help maintain a healthy diet. In this study, the chemical profiles of 11 Korean bee pollens were investigated using molecular networking analysis. This analysis elucidated the presence of two major clusters, hydroxycinnamoyl acid amides (HCAAs, molecular network 1 (MN₁)) and flavonoid glycosides (MN₂), in the bee pollen samples. The inhibitory properties of the bee pollens and the isolated HCAAs toward human catechol-O-methyltransferase (COMT), a key neurotransmitter involved in Parkinson's disease and depression, were determined. N¹,N⁵,N¹⁰-(E)-tricaffeoylspermidine ((E,E,E)-1) exhibited the highest activity of the four compounds isolated, with an IC₅₀ value 16 μM, and inhibited COMT competitively. Quantitative analysis of HCAAs showed that the amounts of N¹,N¹⁰-dicaffeoyl-N⁵-p-coumaroylspermidine (2) and N¹⁰-caffeoyl-N¹,N⁵-di-p-coumaroylspermidine (3) contributed to the observed differences in the COMT inhibitory activities of Korean bee pollens. This study may lead to the prevention and treatment of Parkinson's disease and depression using bee pollens.