Agriculture Reference
In-Depth Information
has yet to be determined. However, for select groups of phytochemicals, such as
non-provitamin A carotenoids, glucosinolates, and phytoestrogens, the active com-
pound or compounds have been identified and rigorously studied. Epidemiologic
studies have suggested a potential benefit of the carotenoid lycopene in reducing the
risk of prostate cancer, particularly the more lethal forms of this cancer. Five stud-
ies support a 30% to 40% reduction in risk associated with high tomato or lycopene
consumption in the processed form in conjunction with lipid consumption, although
other studies with raw tomatoes were not conclusive (Giovannucci 2002). Since carot-
enoids are lipid soluble and cooking breaks down carotenoid binding proteins, this
is not an unexpected outcome. A study by Mehta et al. (2002) to modify polyamines
to retard tomato ripening found an unanticipated enrichment in lycopene with lev-
els up by 2 to 3.5-fold compared with conventional tomatoes. This approach may
work in other fruits and vegetables. Flavonoids meanwhile are soluble in water, and
foods containing both water-soluble and fat-dissolved antioxidants are considered to
offer the best protection against disease. Anthocyanins offer protection against cer-
tain cancers, cardiovascular disease, and age-related degenerative diseases. There
is evidence that anthocyanins also have anti-inflammatory activity, promote visual
acuity, and hinder obesity and diabetes. Both Gonzali et al. (2009) and Butelli et al.
(2008) used snapdragon transcription factors to achieve high-level expression of the
reactive oygen scavengers, anthocyanins, in tomatoes. In a pilot test, the life span of
cancer-susceptible mice (p53 mutants) was significantly extended when their diet was
supplemented with the purple tomatoes compared to supplementation with normal
red tomatoes.
Other phytochemicals of interest include related polyphenolics such as resveratrol,
which has been demonstrated to inhibit platelet aggregation and eicosanoid synthe-
sis in addition to protecting the sirtuins, genes implicated in DNA modification and
life extension; flavonoids, such as tomatoes expressing chalcone isomerase that show
increased contents of the flavanols rutin and kaempferol glycoside; glucosinolates
and their related products such as indole-3 carbinol (I3C); catechin and catechol; iso-
flavones, such as genistein and daidzein; anthocyanins; and some phytoalexins. Table
3.1 summarizes activities in improving nutritional characteristics of various crops
worldwide. A comprehensive list of phytochemicals is provided Table 3.2. To reiterate,
although there is a growing knowledge base indicating that elevated intakes of specific
phytochemicals may reduce the risk of diseases, such as certain cancers, cardiovascular
diseases, and chronic degenerative diseases associated with aging, further research and
epidemiological studies are still required to prove definitive relationships.
Fighting Plants Fighting Back
Plants deploy many defense strategies to protect themselves from predators. Many, such
as resveratrol and glucosinate, which are primarily pathogen-protective chemicals, also
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