CONTENT OF POTENTIALLY ANTICARCINOGENIC FLAVONOIDS OF 28 VEGETABLES AND 9 FRUITS COMMONLY CONSUMED IN THE NETHERLANDS

The content of the potentially anticarcinogenic flavonoids quercetin, kaempferol, myricetin, apigenin, and luteolin of 28 vegetables and 9 fruits was determined by RP-HPLC with UV detection. Fresh foods were purchased in a supermarket, a grocery, and a street market and combined to composites. Processed foods were purchased additionally. Sampling was carried out in spring, summer, winter, and spring of the following year. Quercetin levels in the edible parts of most vegetables were generally below 10 mg/kg except for onions (284-486 mg/kg), kale (110 mg/kg), broccoli (30 mg/kg), French beans (32-45 mg/kg), and slicing beans (28-30 mg/kg). Kaempferol could only be detected in kale (211 mg/kg), endive (15-91 mg/kg), leek (11-56 mg/kg), and turnip tops (31-64 mg/kg). In most fruits the quercetin content averaged 15 mg/kg, except for different apple varieties in which 21-72 mg/kg was found. The content of myricetin, luteolin, and apigenin was below the limit of detection (<1 mg/kg) except for fresh broad beans (26 mg/kg myricetin) and red bell pepper (13-31 mg/kg luteolin). Seasonal variability was low for most vegetables except for leafy vegetables with highest flavonoid levels in summer. These collective data provide a base for an epidemiological evaluation of possible anticarcinogenic effects of flavonoids.