Abstract
The peels of citrus fruits (Pericarpium Citri Reticulatae, PCR) have long been used in traditional Chinese medicines (TCMs). Polymethoxylated flavonoids (PMFs) were found to be the main components present in PCR extracts, but their metabolism remains unclear which restrain the utilization of this TCM. In the present work, rat liver microsomes were immobilized on magnetic nanoparticles (LMMNPs) for in vitro metabolic study on the whole PMFs of PCR. LMMNPs were characterized by transmission electron microscope and Fourier-transform infrared spectrum. The relative enzyme binding capacity of LMMNPs was estimated to be about 428 μg/mg from thermogravimetric analysis. Incubation of LMMNPs with PMFs produced demethylated metabolites of PMFs, six of which were identified by ultrahigh pressure liquid chromatography–mass spectrometry (UPLC–MS/MS). The 3′-hydroxylated tangeretin (T3) was detected from the metabolites of tangeretin for the first time, which suggested that 4′-demethylated and 3′-hydroxylated derivative of tangeretin (3′-hydroxy-5,6,7,8,4′-pentamethoxyflavone, T4) was not only derived from 4′-demethylated tangeretin (T2) as previously reported, but also from T3. This is the first investigation of the metabolism of the whole PMFs, which may shed light on the mechanism of action of PCR.
Highlights
The health benefits and economic values of peels from citrus fruits have been known for over a thousand years, and they have been widely used in pharmaceutical, food and cosmetic industries
We investigated the metabolism of the whole extracts of Pericarpium Citri Reticulatae (PCR) by a highly active nanobioreactor prepared by immobilizing rat liver microsomes onto magnetic nanoparticles (LMMNPs)
Compared with Fe3O4@SiO2 and Fe3O4@SiO2@polydiallyldimethylammonium chloride (PDDA), the absorption peaks at 2924, 2853, 1647, 1542 and 1457 cm−1 for liver microsomes were immobilized on magnetic nanoparticles (LMMNPs) are ascribable to the vibrations of the methylene and amide groups, which belong to side chains of the enzyme on the surface of the magnetic nanoparticles [23, 24]
Summary
The health benefits and economic values of peels from citrus fruits have been known for over a thousand years, and they have been widely used in pharmaceutical, food and cosmetic industries. We investigated the metabolism of the whole extracts of PCR by a highly active nanobioreactor prepared by immobilizing rat liver microsomes onto magnetic nanoparticles (LMMNPs). We improved the relative enzyme loading capacity of the microsomal nanobioreactors that greatly facilitated metabolic study on the whole extract of PCR.
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