Inhibition Selectivity of Grapefruit Juice Components on Human Cytochromes P450

• Published in: Archives of biochemistry and biophysics 2000-06, Vol.378 (2), p.356-363
• Main Authors: Tassaneeyakul, Wichittra, Guo, Lian-Qing, Fukuda, Katsuyuki, Ohta, Tomihisa, Yamazoe, Yasushi
• Format: Article
• Language: English
• Subjects: Aryl Hydrocarbon Hydroxylases; Beverages; Chromatography, High Pressure Liquid; Citrus - metabolism; Coumarins - pharmacology; CYP3A4; Cytochrome P-450 CYP2A6; Cytochrome P-450 CYP2C19; Cytochrome P-450 CYP3A; Cytochrome P-450 Enzyme Inhibitors; Cytochrome P-450 Enzyme System - metabolism; cytochromes P450-inhibition; Dose-Response Relationship, Drug; drug–grapefruit juice interaction; Enzyme Inhibitors - pharmacology; furanocoumarins; Furocoumarins - pharmacology; Humans; Inhibitory Concentration 50; Kinetics; Liver - drug effects; Liver - enzymology; Microsomes, Liver - drug effects; Microsomes, Liver - enzymology; Mixed Function Oxygenases - antagonists & inhibitors; Mixed Function Oxygenases - metabolism; Sesquiterpenes - pharmacology; Substrate Specificity; Time Factors
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1006/abbi.2000.1835

Five compounds including furanocoumarin monomers (bergamottin, 6′,7′-dihydroxybergamottin (DHB)), furanocoumarin dimers (4-[[6-hydroxy-7[[1-[(1-hydroxy-1-methyl)ethyl]-4-methyl-6-(7-oxo-7H-furo[3,2-g][1]benzopyran-4-yl)-4-hexenyl]oxy]-3,7-dimethyl- 2-octenyl]oxy]-7H-furo[3,2-g][1]benzopyran-7-one (GF-I-1) and 4-[[6-hydroxy-7[[4-methyl-1-(1-methylethenyl)-6-(7-oxo-7H-furo[3,2-g][1]benzopyran-4-yl)-4-hexenyl]oxy]-3,7-dimethyl-2-octenyl]oxy]-7H-furo[3,2-g][1]benzopyran-7-one (GF-I-4)), and a sesquiterpene nootkatone have been isolated from grapefruit juice and screened for their inhibitory effects toward human cytochrome P450 (P450) forms using selective substrate probes. Addition of ethyl acetate extract of grapefruit juice into an incubation mixture resulted in decreased activities of CYP3A4, CYP1A2, CYP2C9, and CYP2D6. All four furanocoumarins clearly inhibited CYP3A4-catalyzed nifedipine oxidation in concentration- and time-dependent manners, suggesting that these compounds are mechanism-based inhibitors of CYP3A4. Of the furanocoumarins investigated, furanocoumarin dimers, GF-I-1 and GF-I-4, were the most potent inhibitors of CYP3A4. Inhibitor concentration required for half-maximal rate of inactivation (KI) values for bergamottin, DHB, GF-I-1, and GF-I-4 were calculated, respectively, as 40.00, 5.56, 0.31, and 0.13 μM, whereas similar values were observed on their inactivation rate constant at infinite concentration of inhibitor (kinact, 0.05–0.08 min−1). Apparent selectivity toward CYP3A4 does occur with the furanocoumarin dimers. In contrast, bergamottin showed rather stronger inhibitory effect on CYP1A2, CYP2C9, CYP2C19, and CYP2D6 than on CYP3A4. DHB inhibited CYP3A4 and CYP1A2 activities at nearly equivalent potencies. Among P450 forms investigated, CYP2E1 was the least sensitive to the inhibitory effect of furanocoumarin components. A sesquiterpene nootkatone has no significant effect on P450 activities investigated except for CYP2A6 and CYP2C19 (Ki = 0.8 and 0.5 μM, respectively).