Characterization and content of stilbenes and other polyphenols in tomato plants transformed with the stilbene synthase gene

There is a growing interest in producing food plants with increased amounts of antioxidants because of their potential health benefits. In particular polyphenolic secondary metabolites, such as flavonoids and stilbenes, have a great antioxidant activity, important both for plant physiology and human nutrition. Tomato fruit contains only small amounts of flavonoids, and normally do not produce any stilbenes. With the aim of generating plants and fruits with increased antioxidant capacity and a wider range of potential health benefits, the tomato flavonoid route was modified through the over-expression of the grape stilbene synthase cDNA under a constitutive 35S and a fruit specific TomLoxB, promoters. In order to verify the metabolic impairment, the amounts of soluble phenolics (i. e. chlorogenic acid) and flavonoids (i. e. naringenin and rutin), in both transgenic and wild type fruits were compared. Moreover the synthesis of stilbenes was evaluated in tomato flesh, peel and whole red fruit. The stilbenes found in transgenic plants are present as piceids. The degree of glycosilation may have an impact on the ability of these compounds to be absorbed at the intestinal level. Hence the structure of the stilbenes synthesized in the transformed tomato plants is of considerable interest from a nutritional point of view.