| 摘要 |
A method is disclosed for making the 3R-3'R stereoisomer of zeaxanthin as a sole detectable or heavily dominant (more than about 90%) stereoisomer, for human ingestion. Zeaxanthin, a yellowish pigment which is naturally present in macular cells in the center of the human retina, absorbs blue and near-ultraviolet light radiation, thereby protecting the retinal cells against phototoxic damage. Zeaxanthin preparations which contain only the desired R-R isomer can be produced by a strain of Flavobacterium multivorum cells (ATCC accession number 55238). These cells (and other cells transformed with their zeaxanthin-producing genes) do not create any detectable quantities of the undesired S-S or S-R isomers of zeaxanthin, and they do not synthesize significant quantities of other carotenoids which might compete against zeaxanthin for alimentary uptake after oral ingestion. After synthesis using cell fermentation, the zeaxanthin can be concentrated to about 5-20% by simple and inexpensive steps such as solvent extraction, and can be purified to much higher levels by other methods if desired. The isomerically pure preparations can be taken orally, either as a therapeutic drug by patients suffering from macular degeneration, or as a nutritional supplement by anyone who wants to reduce his or her risk of suffering from age-related macular degeneration, which is widespread among people over the age of about 50 or 60.
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