Research at Washington State University supported by The Organic Center has led to the first-ever assessment of the bioavailability of the chiral flavonoids hesperetin, naringenin, and eriodictyol — important antioxidants in citrus fruits and juices. Dr. Neal Davies leads the research team at WSU.
Using sensitive techniques, they measured the levels of three flavonoids and their enantiomers in conventional and organic fruit and tomato juices, and for the first time ever, quantified both the glycoside (molecule with attached sugars) and agylcone (molecule stripped of sugars) forms of the enantiomers of these three flavonoids. Organic lemonade had ten-times the total eriocitrin (glycoside form of eriodictyol) compared to conventional lemonade, and the agylcone form had over three-times the level in conventional juice.
Organic lime juice also had three-times the level of eriocitrin, compared to conventional lime juice. Organic apple juice had over three times the total hesperidin (glycoside), and almost twice the hesperetin (agylcone form). Organic grapefruit juice had about 20% less total hesperidin (glycoside), but 77% more hesperetin (agylcone). The importance of measuring both the glycoside and agylcone form of flavonoids (and other nutrients) is clear in the grapefruit juice findings.
Based on the data for just the glycoside form of hesperidin, it would appear that conventional grapefruit juice contains more of this flavonoid than the organic juice that was tested. But by focusing on the more bioavailable agylcone form, the opposite conclusion would be reached.
Source: J.A. Yanez et al., “Pharmacokinetics of Selceted Chiral Flavonoids: Hesperetin, Naringenin, and Eriodictyol in Rats and their Content in Fruit Juices,” Biopharmaceutics Drug Disposition, Vol. 29, pp. 63-82, September 2007