Dictionary of Nutraceuticals and Functional Foods

Michael Eskin, Snait Tamir

• Publisher: CRC Press
• Year: 2005
• Print ISBN: 9780849315725
• eBook ISBN: 9781135503666
• Topic: Medicine
• Subtopic: Nutrition, Dietics & Bariatrics

Health professionals are recognizing the major role that nutraceuticals play in health enhancement. As a result, there is a dramatic increase in research aimed at identifying new functional foods and nutraceuticals. There is not, however, a single source that presents this research in a thorough and accessible manner. Comprehensive and complete, th

Z

Zeaxanthin

Zeaxanthin, a hydroxylated carotenoid, is an important plant food xanthophyll. Together with lutein, they are found in the macula pigment of the central retina of the eye responsible for the yellow coloration (Snodderly et al., 1986). Since the source of the macular pigment is solely dietary-based, studies have examined the possible relationship between the pigment and dietary intake. The majority of dietary zeaxanthin and lutein (78 percent) are obtained from such vegetables as spinach and orange pepper, although they are also found in egg yolk (Summerburg et al., 1998; USDA, 1998). The importance of the macula pigment is its protection against agerelated maculopathy, one of the major causes of blindness in Western countries (Klaver et al., 1998). Modified diets that are supplemented with zeaxanthin and lutein were shown to augment or enhance the macular pigment optical density (Hammond et al., 1997; Johnson et al., 2000). Both zeaxanthin and lutein are strong antioxidants, as age-related maculopathy is due to a combination of cumulative blue-light damage or oxidative stress (Beatty et al., 2000). Thus, oxidative stress appears to play a role in such neurodegenerative diseases as age-related macular degeneration (ARMD), the primary cause of blindness in seniors in developed countries (Leibowitz et al., 1980; Klein et al., 1992).

Wrona and coworkers (2004) examined the ability of zeaxanthin to protect the outer layer of the retina containing photoreceptor outer segments and retinal pigment epithelium (RPE), possible targets of oxidative damage. Using ARPE 19 cells from the globes of a 19-year-old male donor, they showed that zeaxanthin, in the presence of ascorbic acid and α-tocopherol, significantly enhanced resistance to photo-induced oxidative stress. Compared to cells without added antioxidants, these cells had enhanced cell viability and accumulated fewer lipid hydroperoxides. A synergism was evident between zeaxanthin and vitamin E or C, which could play a role in protecting the cell membranes from oxidative damage. The reduction in the decay of zeaxanthin in the presence of either vitamin C or E, following photo-sensitized oxidation of ARPE-19 cells, pointed to their protective effects. The synergism between these antioxidants was responsible for preventing the depletion of zeaxanthin by free-radical degradation and repair of the semioxidized zeaxanthin molecules. Chen et al. (2005) recently reported the successful use of high-speed, counter-current chromatography for isolating and purifying zeaxanthin from the microalga Microcystis aeruginosa. For a further review of the relationship between serum and dietary levels of zeaxanthin, lutein, and macular pigment optical density, the article...

Table of contents

• Cover Page
• Title Page
• Copyright Page
• Preface
• The Authors
• A
• B
• C
• D
• E
• F
• G
• H
• I
• J
• K
• L
• M
• N
• O
• P
• Q
• R
• S
• T
• U
• V
• W
• X
• Y
• Z