Changes in Phytochemical Content During Different Growth Stages in Tubers of Five Varieties of Potato (Solanum Tuberosum L.)

Geoffrey Kipkoech Kirui*, Saifuddin Fidahussein Dossaji, Nelson Onzere Amugune

School of Biological Sciences, University of Nairobi P.O. Box 30197-00100, Nairobi, Kenya.

Corresponding Author Email: gkirui@uonbi.ac.ke

Potato (Solanum tuberosum L.) synthesizes a variety of bioactive metabolites including phenolic compounds and glycoalkaloids that protects against insects and diseases, and may influence its nutritional quality. Phenolics provide valuable health promoting antioxidants, whereas glycoalkaloid concentrations exceeding the upper safety limit of 20 mg/100 g fresh weight (Fwt) are potential neurotoxins. Therefore, efficient selection for tuber nutritional quality is dependent upon safe and reliable analytical methods. The aim of this study was to determine the changes in the concentration of glycoalkaloids and phenolic compounds during different growth stages in tubers of five selected potato varieties grown in Kenya. α-chaconine and α-solanine were separated and identified by HPLC. Total glycoalkaloids (TGA) and phenolics were determined by UV spectrophotometry. Recovery efficiencies for validation of analytical methods ranged from 85.9-93.5%. Significant differences in TGA and phenolic contents were detected among potato varieties. Tuber TGA content ranged from 6.80 to 10.56 mg/100g Fwt in vars. Dutch Robijn and Tigoni, respectively, and were within the upper safety limit. The corresponding values for chlorogenic acid contents in the examined varieties ranged from 46.39 to 58.04 mg/100 g Fwt. Total phenolic concentration in the examined tuber extracts varied ranged from 129.24 to 192.52 mg CGA/g Fwt. Glycoalkaloid and phenolic production were significantly reduced from time of initiation to maturity at 55 and 125 days, respectively, after planting (DAP). These results demonstrate that tuber phytochemicals were strongly influenced by variety and level of maturity. For nutritional safety and quality purposes, harvesting of mature potato tubers after 125 DAP is recommended.

Chlorogenic acid; Glycoalkaloids; Phenolic acids; Maturity stage; Solanum tuberosum

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