Vitamin C and flavonoid levels of fruits and vegetables consumed in Hawaii

Food levels of vitamin C and flavonoids not only vary greatly depending on species and variety, growing location, harvesting time, storage, processing, and other conditions, but also with respect to methodological differences. For accurate dietary exposure determination and in support of future studies on the effects of dietary vitamin C and flavonoids, we determined ascorbic acid, and the major dietary flavones (apigenin, luteolin), flavonols (kämpferol, quercetin, myricetin), flavanones (hesperetin, naringenin and their glycosides), and anthocyanidins (pelargonidin, cyanidin, delphinidin) in fruits and vegetables commonly consumed in Hawaii. After optimization of extraction procedures to avoid loss of these sensitive analytes, high-pressure liquid chromatography with electrochemical, diode-array and/or mass spectrometric detection revealed concentrations ranging in foods as eaten from 4 to 801 mg/kg for ascorbic acid and 172 to 905 mg/kg for citrus flavanones to as high as 259 mg/kg for flavones/flavonols and 1168 mg/kg for anthocyanidins. Storage and processing, especially when heat was applied, led to significant losses of all analytes. The high variability in the levels of these antioxidants, in part caused by culturally diverse food preparation techniques, indicates that food level determinations are a prerequisite for accurate human diet studies.