Transport of the flavonoid chrysin and its conjugated metabolites by the human intestinal cell line Caco-2

• Published in: Biochemical pharmacology Vol. 58; no. 3; pp. 431 - 438
• Main Authors: Walle, U.Kristina, Galijatovic, Alema, Walle, Thomas
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.08.1999; Elsevier Science
• Subjects: AIDS/HIV; Anti-HIV Agents - metabolism; bioflavonoids; Biological and medical sciences; Biological Transport; Caco-2 Cells; Cell physiology; chrysin; cMOAT; efflux; flavonoids; Flavonoids - metabolism; Fundamental and applied biological sciences. Psychology; General pharmacology; glucuronidation; Humans; Intestinal Absorption; Intestinal Mucosa - metabolism; Medical sciences; Membrane and intracellular transports; Molecular and cellular biology; MRP2; Pharmacokinetics. Pharmacogenetics. Drug-receptor interactions; Pharmacology. Drug treatments; sulfation; Time Factors; Caco-2 cells; MRP2; bioflavonoids; sulfation; intestinal absorption; chrysin; flavonoids; efflux; glucuronidation; cMOAT; Human; Flavones; Enzyme; Digestive system; Metabolite; Biological transport; Gut; Enzyme inhibitor; Glucuronic acid conjugation; Metabolism; Flavonoid; In vitro; Sulfatation; Absorption; Membrane transport; Established cell line; Drug-metabolizing enzyme; Colon; Conjugated compound; Tumor cell
• ISSN: 0006-2952; 1873-2968
• DOI: 10.1016/S0006-2952(99)00133-1

Chrysin (5,7-dihydroxyflavone), a natural product present in our daily diet, is a potent inhibitor of drug-metabolizing enzymes. However, its oral bioavailability is not known. This study examined the intestinal epithelial transport of chrysin (20 μM), using the human colonic cell line Caco-2 as a model of human intestinal absorption. The apical to basolateral flux of chrysin, with an apparent permeability coefficient ( P app) during the first hour of 6.9 ± 1.6 × 10 −6 cm · sec −1 (mean ± SEM), was more than 10-fold higher than for the paracellular transport marker mannitol, 0.42 ± 0.12 × 10 −6 cm · sec −1. Interestingly, the reverse, basolateral to apical flux of chrysin, P app = 14.1 ± 1.6 × 10 −6 cm · sec −1, was about 2-fold higher than the apical to basolateral flux ( P < 0.01). In transport studies beyond 1 hr, there was a rapid decline in P app. This correlated with the appearance of two metabolites, M1 (chrysin glucuronide) and M2 (chrysin sulfate), identified by enzymatic hydrolysis procedures and HPLC. Following apical loading of chrysin, as much as 90% of M1 + M2 appeared on the apical side, thus indicating clear efflux of the chrysin metabolites. The addition of the anion transport inhibitor MK-571 (50 μM) on the apical side produced a 71% ( P < 0.0001) and 20% ( P < 0.05) inhibition of the efflux of M1 and M2, respectively, suggesting the involvement of the multidrug resistance protein MRP2 pump. Indeed, using specific antibodies, MRP2 was in fact detected by western blotting in Caco-2 plasma membranes, whereas MRP1 was not. These observations suggest that chrysin has favorable membrane transport properties but that its intestinal absorption may be seriously limited by surprisingly efficient glucuronidation and sulfation by the enterocytes and almost quantitative efflux by MRP2 of the metabolites formed.