Naringenin is a flavanone, a type of flavonoid, that is considered to have a bioactive effect on human health as antioxidant, free radical scavenger, anti-inflammatory, carbohydrate metabolism promoter, and immune system modulator. It is the predominant flavanone in grapefruit.

Naringenin can be found in grapefruits, oranges and tomatoes (skin). This bioflavonoid is difficult to absorb on oral ingestion. In the best-case scenario, only 15% of ingested Naringenin will get absorbed in the human gastrointestinal tract. A full glass of orange juice will supply about enough naringenin to achieve a concentration of about 0.5 micromoles per liter. The Naringenin-7-Glucoside form seems less bioavailable than the aglycol form. Grapefruit juice can provide much higher plasma concentrations of naringenin than orange juice. Also found in grapefruit is the related compound Kaempferol, which has a hydroxyl group next to the ketone group. Naringenin can be absorbed from cooked tomato paste.

Naringenin shown to reduce oxidative damage to DNA in vitro. Scientists exposed cells to 80 micromoles of naringenin per liter, for 24 hours, and found that the amount of hydroxyl damage to the DNA was reduced by 24% in that very short period of time. Naringenin found in grapefruit juice has been shown to have an inhibitory effect on the human cytochrome P450 isoform CYP1A2, which can change pharmacokinetics in a human (or orthologous) host of several popular drugs in an adverse manner, even resulting in carcinogens of otherwise harmless substances.

Naringenin has also been shown to reduce hepatitis C virus production by infected hepatocytes (liver cells) in cell culture. This seems to be secondary to Naringenin's ability to inhibit the secretion of very-low-density lipoprotein by the cells. The antiviral effects of naringenin are currently under clinical investigation. Naringenin seems to protect LDLR-deficient mice from the obesity effects of a high-fat diet.

Naringenin lowers the plasma and hepatic cholesterol concentrations by suppressing HMG-CoA reductase and ACAT in rats fed a high-cholesterol diet. Like many other flavonoids, naringenin has been found to possess activity at the opioid receptors. It specifically acts as a non-selective antagonist of all three opioid receptors, albeit with somewhat weak affinity.