Glycoalkaloid content of some superior potato (Solanum tuberosum L) clones and commercial cultivars

Abstract

Glycoalkaloids are important metabolites in potato because of their toxic properties and potential harmful effects to humans. To validate a rapid assay to determine and quantify glycoalkaloid content and its distribution in potato tubers, we have characterized and quantified, by HPLC and by colorimetry with bromphenol blue, the glycoalkaloids in 15 potato cultivars and experimental clones grown in the tropical climate of Kenya. There was significant correlation of TGA by HPLC and colorimetry. Significant differences in glycoalkaloid content were detected among potato cultivars. The concentration of α-chaconine in the 15 cultivars ranged from 1.62 to 4.46 mg/100 g fresh weight (fwt), of α-solanine from 1.45 to 4.51 mg/100 g, and of solanidine from 1.58 to 5.21 mg/100 g. Total glycoalkaloid values (TGA, sum of the three compounds) for the 15 cultivars determined by HPLC ranged from 5.31 to 15.39 mg/100 g and the corresponding values determined by bromphenol blue colorimetry, from 3.51 to 17.48 mg/100 g. Dutch Robijn, a late blight susceptible cultivar under Kenyan conditions had the lowest level (3.51 mg/100 g) of total glycoalkaloids and Tigoni, a late blight resistant cultivar, had the highest amount (15.97 mg/100 g). In contrast to most previous studies, high levels of solanidine in tubers of tropical-climate adapted cultivars were recorded in our experiments. The dietary significance of a high amount of solanidine in the cultivars has not been previously reported and deserves further study.

Keywords:

• Solanum tuberosum
• late blight resistance α-chaconine
• α-solanine
• solanidine
• Kenya

Acknowledgements

This research was conducted in partial fulfillment of an M.S. degree by the first author. The study was supported by funds provided by the University of Nairobi and the International Potato Center (CIP). We thank the Kenya Plant Health Inspectorate Service (KEPHIS), Nairobi for providing the facilities for HPLC analysis. The National Potato Research Centre (NPRC), Tigoni, provided the potato cultivars and CIP potato clones. Assistance from Dr. N. Kozukue of Kenmei Junior College, Japan and Dr. Tony Musoke and Mrs. C. Nkonge of International Livestock Research Institute (ILRI)'s staff in Kenya is also very much appreciated. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture and the University of Nairobi or Agricultural Research Center.

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O. M. Olanya

This work was authored as part of O. M. Olanya's official duties as an employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105 no copyright protection is available for such works under U.S. law.