This study investigates whether tomato juice can inhibit cytochrome P450 (CYP) 3A4-mediated drug metabolism. Three commercially available, additive-free tomato juices, along with homogenized fresh tomato, were analyzed for their ability to inhibit testosterone 6β-hydroxylation activity using human recombinant CYP3A4. Results were compared to that of grapefruit juice. Ethyl acetate extracts of the tomato juices moderately reduced residual activity of CYP3A4 testosterone 6β-hydroxylation activity by 19.3-26.2% with 0-min preincubation. Residual activity was strongly reduced by 69.9-83.5% at 20-min preincubation, a reduction similar to that of grapefruit juice extract, known to contain constituents of mechanism-based inhibitors. One juice extract (tomato juice C) showed irreversible dose-and preincubation time-dependent and partial nicotinamide adenine dinucleotide phosphate (NADPH)-dependent inhibition of CYP3A4 activity. Furthermore, we examined whether the CYP3A4 inhibitory effect of tomato juice was substrate dependent by examining midazolam 1′-hydroxylation activity and nifedipine oxidation activity, in addition to testosterone 6β-hydroxylation activity. Tomato juice showed a potent inhibitory effect on nifedipine oxidation activity, which was comparable to that on testosterone 6β-hydroxylation activity; however, it showed a weak inhibitory effect on midazolam 1′-hydroxylation activity. We conclude that tomato juice contains one or more mechanism-based and competitive inhibitor(s) of CYP3A4. Additionally, significant CYP3A4 inhibitory activity did not result from lycopene, a major compound in tomato. Although the active compound was uncertain, a strong CYP3A4 inhibitory activity was observed in other solanaceous plants, i.e., potato, eggplant, sweet pepper, and capsicum. Therefore, responsible compounds in tomato are likely commonly shared among solanaceous vegetables.Key words tomato juice; mechanism-based inhibition; food-drug interaction; human recombinant cytochrome P450 3A4 Many foods and/or beverages have recently been found to influence drug metabolism or transport, sometimes resulting in clinically important drug interactions. This food-drug interaction is a critical aspect of pharmacotherapy. Food-drug interaction can be viewed in terms of pharmacokinetics and pharmacodynamics. Pharmacokinetic interactions can involve enzymes and transporters that are implicated in drug absorption, distribution, metabolism, or excretion. Pharmacodynamic interactions involve the pharmacological effect of a drug or physiologic effect of a dietary constituent.
1)Foods that inhibit drug metabolism enzymes, such as cytochrome P450 (CYP), elevate the blood concentration of co-administered drugs, resulting in a food-drug interaction, which sometimes causes adverse effects. [2][3][4] In vitro screening assays with beverages and foods such as beer, red wine, black and herbal tea, garlic, spices, mace, nutmeg, fruits, and fruit juices have all shown the ability to inhibit enzyme-mediated drug metabolism. [5][6][7][8][9][10] CYP...