ABSTRACT
References..............................................................................................................169
Plant resources have been emphasized worldwide as precious sources of raw
materials. They not only provide the basic needs of life such as food, feed, fiber, fuel,
and shelter, but they have always been a valuable source of prophylactic
phytochemicals, flavors, and fragrances and other industrial products. A large
number of studies provide convincing evidence of the beneficial role of plant
foods and their nutraceuticals for the maintenance of health [1,2]. Epidemiological
studies show a protective effect of fruits, vegetables, traditional plant preparations
and beverages like teas against the risk of chronic diseases such as cancer,
atherosclerosis, cardiac dysfunctions, diabetes, hypertension, and neurodegenerative
disorders [3-6]. The benefits that plant-rich diets confer are believed to be ascribed
to various antioxidants, especially carotenoids and antioxidant vitamins, including
ascorbic acid and tocopherols. However, the antioxidant capacity of a particular
fruit, vegetable or tea may originate from compounds other than b-carotene, vitamin
C or vitamin E. The significance of phenolics such as catechins, phenylcarboxylic
acids, phenylpropanoids, anthocyanins, and proanthocyanidins as dietary antiox-
idants in fruits, vegetables, medicinal plant extracts and teas is attracting
considerable attention [7-10]. The antimutagenic, antibacterial, anti-inflammatory,
antithrombotic, and vasodilatory actions of polyphenolics are well characterized
[11] and accumulating chemical, biochemical, clinical, and epidemiological
evidence supports the chemopreventive effects of phenolic antioxidants against
oxidative stress-mediated disorders [12,13]. The pharmacological actions of
phenolic antioxidants are strongly suggested to stem mainly from their free radical
scavenging and metal chelating properties, as well as from their effects on cell
signaling pathways and on gene expression [14-18].
