Grapefruit is a hybrid fruit made from mixing pomelo and sweet orange.
There are three common varieties available: red, pink, and white. The names are based on the color of the fruit's pulp.
Effects on Estradiol 17beta-dehydrogenase Type 2
1-2 cups of white grapefruit juice potently inhibits Estradiol 17beta-dehydrogenase Type 2 (17bHSD2). Inhibition lasts approximately 4-8 hours.
Grapefruit juice contains the following inhibitors of 17bHSD2:
- naringenin (31.2 mg/L ) is an potent inhibitor.
- quercetin (4.9 mg/L ) is an potent inhibitor.
Blocking Psychedelic Action of Allylbenzenes
Anecdotal reports indicate that 2 cups of white grapefruit juice consumed 30 minutes before taking allylbenzenes will greatly reduce the psychedelic effects of allylbenzenes and delay their onset by up to 8 hours. The enzyme 17bHSD2 is required for allylbenzenes to produce psychedelic effects. Grapefruit juice potently inhibits this enzyme for 4-8 hours. See the article Oilahuasca Activation for more information.
Effects on the Cytochrome P450 Enzyme System
Among the varies types of grapefruit, white grapefruit has the strongest effect on P450 enzymes.
1 cup of grapefruit taken 3 times a day by human volunteers was found to inhibit CYP3A4 in small intestine (small bowel) epithelia (enterocytes) by 62%, but had no detectable effect on liver CYP3A4 activity, colon levels of CYP3A5, or small intestine concentrations of P-glycoprotein, CYP1A1, or CYP2D6.
Cytochrome P450 Enzyme Inhibitors in Grapefruit
P450 enzyme inhibitors found in grapefruit include:
- 6', 7'-dihydroxybergamottin
- naringenin (31.2 mg/L )
- naringin (628 mg/L )
- quercetin (4.9 mg/L )
Effects on Individual P450 Enzyme Levels From Juice
|Enzyme||Interaction||Dosage||Verified In Humans|
|CYP1A1||No Effect||3 cups||Yes|
|CYP1A2||23% Inhibition||1-2 cups||Yes|
|CYP2A6||Potent Inhibition ||1 Liter||Yes|
|CYP2B6||Potent Inhibition||1-2 cups||?|
|CYP2C9||No Effect||1-2 cups||Yes|
|CYP2C19||No Effect||300 ml||Yes|
|CYP2D6||No Effect||3 cups||Yes|
|CYP2E1||No Effect||1-2 cups||Yes|
|CYP3A4 ||62% Inhibition||3 cups||Yes|