Edwards D J, Bellevue F H, Woster P M
Department of Pharmacy Practice, College of Pharmacy and Allied Health Professions, Wayne State University, Detroit, MI 48202, USA.
Drug Metab Dispos. 1996 Dec;24(12):1287-90.
Grapefruit juice inhibits the metabolism of substrates for enzymes of the CYP3A subfamily. However, the identity of the inhibitor has not been established. Grapefruit juice was extracted into methylene chloride and chromatographed by HPLC, and the effect of the HPLC eluent on CYP3A activity was assessed by measuring 6beta-hydroxytestosterone formation in rat liver microsomes. Significant inhibition was associated with a fraction of HPLC eluent containing a single peak, with a retention time of 16 min. The substance producing this peak was isolated using TLC and identified, using NMR and MS, as 6',7'-dihydroxybergamottin (C21H2406; molecular weight, 372), a furanocoumarin (psoralen) compound. The concentration of 6',7'-dihydroxybergamottin required to inhibit 6beta-hydroxytestosterone formation by 50% was 25 microM. Grapefruit juice reduced CYP3A activity to a significantly greater extent (p < 0.05) than did orange juice, which contained no measurable 6',7'-dihydroxybergamottin (28.6% vs. 62.2% of control activity). The addition of 6',7'-dihydroxybergamottin (30 microM) to orange juice decreased CYP3A activity to values comparable to those observed with grapefruit juice. 6',7'-Dihydroxybergamottin is a potent inhibitor of CYP3A activity, accounts for the difference in inhibition between grapefruit juice and orange juice in vitro, and may be primarily responsible for the effects of grapefruit juice on cytochrome P450 activity in humans.
葡萄柚汁可抑制细胞色素P450 3A亚家族酶底物的代谢。然而，抑制剂的具体成分尚未明确。将葡萄柚汁用二氯甲烷萃取后进行高效液相色谱（HPLC）分析，并通过测定大鼠肝微粒体中6β-羟基睾酮的生成来评估HPLC洗脱液对细胞色素P450 3A活性的影响。显著抑制作用与HPLC洗脱液中一个保留时间为16分钟的单峰部分相关。使用薄层色谱法（TLC）分离出产生该峰的物质，并通过核磁共振（NMR）和质谱（MS）鉴定为6',7'-二羟基佛手柑内酯（C21H24O6；分子量372），一种呋喃香豆素（补骨脂素）化合物。抑制6β-羟基睾酮生成50%所需的6',7'-二羟基佛手柑内酯浓度为25微摩尔。与不含可测6',7'-二羟基佛手柑内酯的橙汁相比，葡萄柚汁使细胞色素P450 3A活性降低的程度显著更大（p < 0.05）（分别为对照活性的28.6%和62.2%）。向橙汁中添加6',7'-二羟基佛手柑内酯（30微摩尔）可使细胞色素P450 3A活性降低至与葡萄柚汁相当的值。6',7'-二羟基佛手柑内酯是细胞色素P450 3A活性的强效抑制剂，解释了葡萄柚汁和橙汁在体外抑制作用的差异，可能是葡萄柚汁对人体细胞色素P450活性产生影响的主要原因。
