Changes in plasma concentration of flavonoids after ingestion of a flavonoid-rich meal prepared with basic foodstuffs

Abstract

Background: As flavonoids have a variety of functions, such as antioxidant activity, there is growing interest in the development of flavonoid supplements. However, there have been reports of DNA damage due to exposure to flavonoids at high concentrations in rats, which could suggest that a habitual intake of flavonoid supplements may cause toxicity. Therefore, we considered that ingesting flavonoids from a typical meal combined basic foodstuffs are safe because of unlikely to result high concentrations like supplements, and focused on the intake of flavonoids from a typical meal. Thus, this study investigated the absorption of flavonoids in humans after the consumption of a typical meal.

Methods: On the first 2 days of the study, seven healthy volunteers were provided with low-flavonoid meals (flavonoid content below the detection limit by HPLC: less than 0.24 mg/meal) three times a day as a washout. A flavonoid-rich meal (40.44 ± 1.49 mg/meal) was then provided for breakfast on the third day. Blood was collected from all volunteers 0, 2, 3, 7, 8, and 9 h after the flavonoid-rich meal was consumed. After enzyme hydrolysis of the plasma, the plasma concentrations of flavonoids aglycone of quercetin, daidzein and genistein were measured using LC-MS. Urine was also collected and pooled 24 h after the flavonoid-rich meal was consumed. Thereafter, the urine was treated with enzyme hydrolysis, and the measurement of urinary flavonoids was performed.

Results: Plasma flavonoid peaks were observed 8 h after consumption of the flavonoid-rich meal (quercetin: 4.29 ± 1.46 μM, daidzein: 0.51 ± 0.41 μM, genistein: 0.91 ± 0.73 μM). Furthermore, flavonoids were confirmed to be present in plasma even at 9 h after the intake meal. The urinary recovery of flavonoids was 3.43 ± 1.50% for quercetin, 13.87 ± 6.68% for daidzein, and 16.89 ± 11.40% for genistein.

Conclusion: These results suggest that consuming a typical meal that combines a variety of basic foodstuffs delays attainment of the plasma flavonoid peak compared with consuming a single type of food or supplements as previously reported. In addition, the flavonoid urinary recovery were also reduced compared with those previously reported.