Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 25, 2004
Publication Date: April 15, 2005
Citation: Brown, C.R. 2005. Antioxidants in potato. American Journal of Potato Research. 82:163-172. Interpretive Summary: Foods rich in antioxidants are considered to be an important part of the human diet. Antioxidants counteract the destructive activities of oxidative chemicals in human metabolism. Oxidative chemicals have been shown to be important in development of heart disease, certain cancers, macular degeneration, and cataracts. Within the diversity of potato varieties there is great variation in the content of natural compounds that serve as antioxidants. Some of these are colored compounds, like anthocyanins which are red to purple in color. The carotenoids are generally yellow to red in color. All potatoes have some level of carotenoids. The content matches the intensity of the yellow color. Deeply yellow or orange flesh potatoes, which are relatively unknown in the US, have levels of carotenoid similar to winter squash. Carotenoids are fat soluble and stay in the body over a number of days. Anthocyanins of potato may be both in the skin and flesh. Red skin potatoes are familiar to U.S. consumers. Less familiar, however, are potato varieties that have red or purple flesh. Solidly pigmented flesh in potatoes is a source of abundant anthocyanins which are themselves potent antioxidants. They are water soluble and pass through the human body within hours of ingestion, much like vitamin C. Consumers in the US eat relatively large amounts of potato compared to other vegetables and fruits. Therefore, the inclusion of high antioxidant potatoes in the diet is a good way of substantially increasing antioxidants in the diet.
Technical Abstract: The content of compounds in potato that may act as antioxidants in the human diet is not widely appreciated. Carotenoids are present in the flesh of all potatoes. The contents mentioned in the literature range from 50 to 100 micrograms per 100 grams Fresh Weight (g FW) in white flesh varieties to 2000 micrograms per 100 g FW in deeply yellow to orange flesh cultivars. The carotenoids in potato are primarily lutein, zexanthin and violaxanthin, all of which are xanthophylls. There is just a trace of either alpha- or beta-carotene, meaning that potato is not a source of pro-vitamin A carotenes. In potatoes with total carotenoids ranging from 35 to 795 micrograms per 100 g FW, the lipophilic extract of potato flesh presented oxygen radical absorbance capacity (ORAC) values ranging from 4.6 to 15.3 nmoles alpha-tocopherol equivalents per 100 g FW. Potatoes contain phenolic compounds and the predominant one is chlorogenic acid which comprises about 80% of the total phenolic acids. Up to 30 micrograms per 100 g FW of flavonoids are present in the flesh of white flesh potatoes with roughly twice the amount present in red and purple flesh potatoes. The predominant flavonoids are catechin and epicatechin. Red and purple potatoes derive their color from anthocyanins. The skin alone may be pigmented, or the flesh may be partially or entirely pigmented. Whole unpeeled with complete pigmentation in the flesh may have up to 40 milligrams per 100 g FW of total anthocyanins. Red flesh potatoes have acylated glucosides of pelargonidin while purple potatoes have, in addition, acylated glucosides of malvidin, petunidin, peonidin and delphinidin. The hydrophilic antioxidant activity of solidly pigmented red or purple potatoes is comparable to Brussels sprouts of spinach. In red and purple potatoes with solidly pigmented flesh with levels of total anthocyanin ranging from 9 to 38 mg per 100 g FW, ORAC ranged from 7.6 and 14.2 umole per g FW of Trolox equivalents. Potato contains on average 20 mg per 100 g FW of vitamin C which may account for up to 13% of the total antioxidant capacity. Potatoes should be considered vegetables that may have high antioxidant capacity depending on the flesh composition.