[Flavonoids--bioactive compounds in fruits juice]

Since 1989, grapefruit juice is reported to modify, with clinical implications, the pharmacokinetic of a series of drugs such as calcium channel blockers that are dihydropyridine derivates and/or some HMGCoA reductase inhibitors. All these drugs are metabolized to a large extent by the most abundant human isoform of cytochrome P450, CYP3A4. Grapefruit inhibits the cytochrome P450 3A4 enzyme system responsible for the oxidative metabolism of many orally administered drugs. The most important compounds of GFJ considered to be involved in the pharmacokinetic interaction are flavonoids (naringin, naringenin, narirutin, quercetin, kaempferol, hesperidin, neohesperidin, didymin, and poncirin), furanocoumarins (6',7'-dihydroxy-bergamottin, bergamottin, bergamottin-6',7'-epoxide, bergapten, epoxy-bergamottin) and sesquiterpens (noot-katone).

The experimental researches had as object the comparative study of total content of flavonoidic compounds, like naringin in different fruit juices: citric fruit (white, pink and red grapefruit), apples, pears--industrial or laboratory prepared juices (by squeezing). They praised a different content in flavonoidic compounds for citric and for the rest of analyzed fruits.

For grapefruit juices the concentrations in flavonoidic compounds are higher in total fruit juice: 143.86 mg/100 mL in red, 131.47 mg/100 mL in pink and 84.21 mg/100 mL in white grapefruit juice. In juice prepared from fruit pulp, the concentrations were 81.92 mg/100 mL, 108.23 mg/100 mL and 65.76 mg/100 mL, respectively. The content in naringin, the most important flavanone in citrus fruit, varied between 1.98 and 51.2 mg/100 mL juice.