Tomatoes are an excellent source of the
carotenoid lycopene, a compound that is thought to be protective against
prostate cancer. They also contain small amounts of
flavonoids in their peel ( approximately 5-10 mg/kg fresh weight), mainly
naringenin chalcone and the
flavonol rutin, a
quercetin glycoside.
Flavonols are very potent
antioxidants, and an increasing body of epidemiological data suggests that high
flavonoid intake is correlated with a decreased risk for
cardiovascular disease. We have upregulated
flavonol biosynthesis in the tomato in order to generate fruit with increased
antioxidant capacity and a wider range of potential health benefit properties. This involved transformation of tomato with the Petunia chi-a gene encoding
chalcone isomerase. Resulting transgenic tomato lines produced an increase of up to 78 fold in fruit peel
flavonols, mainly due to an accumulation of
rutin. No gross phenotypical differences were observed between high-
flavonol transgenic and control lines. The phenotype segregated with the transgene and demonstrated a stable inheritance pattern over four subsequent generations tested thus far. Whole-fruit
flavonol levels in the best of these lines are similar to those found in onions, a crop with naturally high levels of
flavonol compounds. Processing of high-
flavonol tomatoes demonstrated that 65% of
flavonols present in the fresh fruit were retained in the processed
paste, supporting their potential as raw materials for tomato-based functional food products.