Comprehensive analysis of polymethoxyflavone metabolism in orange peel using an animal model

Polymethoxyflavones (PMFs) are a unique class of flavonoids naturally present without attached sugar molecules and with a lack of exposed hydroxyl groups. This structural difference results in higher bioavailability. This study investigated the metabolism and tissue distribution of PMFs following oral administration of orange peel extract to mice. Tissue samples were subsequently analyzed using liquid chromatography-mass spectrometry (LC-MS). Our findings indicate that PMFs are efficiently absorbed and distributed, with their accumulation patterns directly related to their chemical structures. Specifically, a less bulky A-ring structure was found to be crucial for PMF distribution in different tissues. The absence of a methoxy group at the C-5 position enhanced penetration into the brain, while the presence of methoxy groups near the hydrogen bond region (C-4/5) decreased the accumulation of hydroxylated PMFs in the liver. Based on key-ion filtering strategies, a total of 87 PMF metabolites, including demethylated forms and conjugates with glucuronate and sulfate were identified using UHPLC-Orbitrap-HRMS. This study is the first to report on the practical distribution of PMFs in various tissues after the administration of a natural orange peel extract.