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Composition of tomatoes and tomato products in antioxidants (WG1) page 51
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1.4 mg/kg fresh matter (yellow stage) then decreased to 1 mg/kg fresh matter (red stage) due
to a high antioxidative activity in the fruit and thus for food protection, but it is biologically
inactive as vitamin E in the human body.
6.4. Phenolic compounds
6.4.1. Introduction
Citing the U.S. Department of Agriculture (1997), Beecher (1998) gave estimates of
tomato content in quercetin (8 mg/kg fresh matter), one of the flavonoids that has very high
antioxidant activity relative to alpha-tocopherol.
Senter et al.(1988) have shown that in tomato fruit the quantities of total phenols in the
epidermial tissue, the placental tissue, the radial and inner wall of the pericarp and the outer
wall of the pericarp were 30.2*10 3 , 25.2*10 3 , 20.8*10 3 and 19.4*10 3 mg/kg dry tissue
respectively. Since the greater quantities of these compounds are concentrated predominantly
in the epidermial tissue of the tomato, they might function as natural barriers to microbial
invasion.
6.4.2. Influence of light
In a review, Herrmann (1976) reported that nearly the total flavonol content was in the
outer parts of the tissues, which were 4-5% of the fruit. Since the formation of flavonol (e.g.
kaempferol and quercetin) glycosides depends on light, it is not surprising that they are found
mainly in the skins of fruit. For the tomato cv. “Ronald V” cultivated in open air and in
glasshouse, values of kaempferol and quercetin glycoside (estimated and calculated as mg
aglycon per kg of fresh matter) fruit contents are given respectively : 0.2 and 0.2 mg/kg
kaempferol, 7 and 2.5 mg/kg quercetin; leaf contents are respectively : 20 and 4 mg/kg
kaempferol, 420 and 155 mg/kg quercetin.
Hunt and Baker (1980) have identified chalconaringenin, naringenin, naringenin-7glucoside,
and m- and p-coumaric acids as phenolic constituents of tomato fruit cuticles of
three cultivars (Aisa Craig, Alicante and Grower’s Pride). The composition of the flavonoid
fraction was controlled by the spectral quality of incident radiation, red light favouring the
formation of chalconaringerin.