Variation of bioactive furocoumarins and flavonoids in different varieties of grapefruits and pummelo

Grapefruit juice has been shown to increase the oral bioavailability of many therapeutic drugs. Certain citrus bioactive compounds such as furocoumarins and flavonoids have potent inhibitory effects on cytochrome P450 3A4 (CYP 3A4) enzyme and P-glycoprotein. The levels of these bioactive compounds in the grapefruit juice may affect the magnitude and mechanism of grapefruit juice-induced drug interaction. The levels of three furocoumarins such as dihydroxybergamottin (DHB), paradisin A and bergamottin and flavonoids have been separated and quantified using high-performance liquid chromatography (HPLC) in seven varieties of grapefruits and its parent pummelo. Considerable differences were observed in the levels of these bioactive compounds in different grapefruit varieties. Ray Red showed the lowest (0.492 ± 0.027 DHB μg/ml, 0.059 ± 0.001 μg/ml paradisin A and 0.344 ± 0.030 μg/ml bergamottin) levels of all three furocoumarins and Duncan contain the highest amount of DHB (2.587 ± 0.432 μg/ml) and bergamottin (1.004 ± 0.068 μg/ml), where as Star Ruby contain the highest levels of paradisin A. Pummelo contain the highest levels of naringin (4.587 ± 0.061 mg/ml), while Rio Red showed the lowest level (1.986 ± 0.145 mg/ml) of naringin.