Quantitative variation in Brazilian vegetable sources of flavonols and flavones

Reliable data on the levels of flavonoids in foods are necessary to identify sources and establish better the association between consumption and incidence of diseases. The objective of this work was to determine the flavonols and flavones of major vegetable sources in Brazil, compare with data obtained in different countries and evaluate possible seasonal and processing effects. Quercetin was the most widely distributed flavonol in the vegetables analysed, onions, kale and rucula being the richest sources. Kaempferol had the highest level in rucula. Apigenin was found only in parsley, at high concentration. The flavonoid contents tended to be higher in the summer, but the difference was statistically significant only for quercetin in curly lettuce and kale. Dehydrated onion had widely varying within-brand and between-brand quercetin contents, indicating lack of quality control in the processing plants. Dehydrated parsley, on the other hand, did not have significant difference in the apigenin content among four brands.