Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2003
Publication Date: 6/1/2003
Citation: FRIEDMAN, M., ROITMAN, J.N., KOZUKUE, N. GLYCOALKALOID AND CALYSTEGINE CONTENTS OF EIGHT POTATO CULTIVARS. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY. 2003. v. 51. p. 2964-2973. Interpretive Summary: Potatoes are a widely consumed food but are part of a plant family (Solanaceae) known for producing nitrogenous substances called alkaloids. Numerous reports of human and livestock poisoning from potatoes have been attributed to steroidal alkaloid glycosides. These have often been associated with the consumption of green, moldy or sprouting potatoes whose alkaloid content was much higher than in normal potatoes. More recently an entirely new class of alkaloids, termed calystegines, have been found in potatoes and some other foods belonging to the same plant family. These are inhibitors of glycoprotein processing enzymes necessary for normal health of all mammals and it is thus important to measure the levels of these and the steroidal alkaloids especially in new potato varieties before they are introduced as foodstuff. Eight varieties of commercially grown potatoes were analyzed for their content of both steroidal glycoalkaloids and calystegines. Amounts of alkaloids were found to vary considerably amongst the different cultivars and the information should prove valuable to developers of new potato varieties.
Technical Abstract: Diverse procedures have been reported for the separation and analysis by HPLC of the two major glycoalkaloids present in potatoes, a-chaconine and a-solanine. To further improve the usefulness of the HPLC method, we have carried out studies on the influence of several salient parameters on the analysis of the two potato glycoalkaloids. We studied effects on retention (elution, separation) times of the (a) composition and pH of the mobile phase (acetonitrile and phosphate buffer); (b) the concentration of the phosphate buffer (c) the capacity values of column packing of four commercial HPLC amino columns; and (d) column temperature. Except for pH, all of the variables significantly influenced the retention times. The results make it possible to select analysis conditions that produce well separated as well as symmetrical peaks of the two glycoalkaloids. This improved HPLC method (limit of detection of about 150 ng) was evaluated with extracts from the cortex of one whole potato variety (May Queen) grown in Japan and freeze-dried peel and flesh from the following eight cultivars grown in the United States: Atlantic, Dark Red Norland, Ranger Russet, Red Lasoda, Russet Burbank, Russet Norkota, Shepody, and Snowden. In addition, the same samples were analyzed by GC-MS for the presence of two water-soluble nortropane alkaloids, calystegine A3 and calystegine B2, reported to be potent glycosidase inhibitors. The following ranges for the eight varieties of total glycoalkaloid and calystegine levels (in mg/kg) were observed: dry flesh, 5-592 and 6-316; dry peel, 84-2226 and 218-2581; dry whole potatoes, 40-883 and 34-326; wet flesh, 1-148 and 1-68; wet peel, 12-429 and 35-467; wet whole potatoes, 7-187 and 5-68. The possible significance of the results to plant and food sciences are discussed.