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It is possible to improve the antioxidant action of tomatoes by a directed
change in the production of flavonoids by means of genetic modification.
This has been shown in doctoral research by Elio Schijlen on the basis of
which he hopes to take his degree on Thursday 8 February at the University
of Amsterdam, February 2007.

Schijlen demonstrated that this approach enables tomatoes to produce
larger amounts of specific flavonoids and to let tomatoes produce flavonoids
they cannot produce by nature. The results show that genetic modification is
a possible approach to further increase the health promoting value of
vegetables and fruit.

Flavonoids are frequently occurring and important metabolites in plants.
About 6000 different flavonoids are known to be involved in various natural
processes. The colour of flowers and ripe fruits, e.g., are often caused by
flavonoids. But flavonoids also play an important role in other plant
processes such as pollen production, disease resistance, and protection
against UV radiation.

Because flavonoids are so frequently occurring in plants, they are a
permanent component of our food. Part of the health promoting effects of
vegetables and fruit is attributed to flavonoids. It may therefore be
attractive to increase the amount of flavonoids and/or change their
composition.

This was why Schijlen, working at Plant Research International of Wageningen
UR, studied the possibilities of steering the production of flavonoids by a
directed change of the biosynthesis route via genetic modification. He
followed various approaches to achieve this. One approach was to investigate
the possibility of increasing the amount of flavonoids in tomato by means of
so-called transcription factors, proteins involved in regulating gene
activity.

Schijlen also investigated the possibility to produce new flavonoids in
tomatoes which might increase the health promoting properties of tomatoes.
For this purpose he used genes form other crops such as grape and alfalfa,
genes that are involved in certain steps in the biosynthesis of flavonoids
in these crops.

Both approaches were found to be successful. Through genetic modification
Schijlen succeeded in developing tomatoes not only with more flavonoids but
also with new flavonoids.

Via biochemical analysis Schijlen demonstrated an increased antioxidant
action of tomatoes with flavones and more flavonoles, two specific groups of
flavonoids. In cooperation with scientists of BASF Plant Science and TNO,
the potential health promoting effects of these tomatoes were tested in
feeding studies with mice. Blood analyses showed that that the tomatoes with
increased flavonoids had a stronger positive effect on blood properties that
are characteristic of a reduced risk of cardiovascular disorders.

[www.plantsciencesgroup.nl]