Catechol-O-methyltransferase and monoamine oxidase B inhibitory activities of Australian bee pollen

Bee pollen is an apicultural product collected by honeybees from flower stamens and used as a functional food worldwide. In the present study, we aim to elucidate the functions of Australian bee pollen. Australian bee pollen extracts and their main components were tested for catechol-O-methyltransferase (COMT) and monoamine oxidase B (MAOB) inhibitory activities. These enzymes are key neurotransmitters involved in Parkinson's disease and depression. Myricetin (5), tricetin (6), and luteolin (7) exhibited high COMT inhibitory activities (half maximal inhibitory concentration [IC50] = 23.3, 13.8, and 47.4 µM, respectively). In contrast, 5, 7, and annulatin (8) exhibited MAOB inhibitory activities (IC50= 89.7, 32.8, and 153 µM, respectively). Quantitative analysis via high-performance liquid chromatography revealed that 5was abundant in Australian bee pollen extracts. Our findings suggest that 5contributes to the COMT and MAOB inhibitory activities of Australian bee pollen.Graphical AbstractMyricetin, the major component in Australian bee pollen, possesses COMT and MAOB inhibitory activities.