Characterization of the metabolic network of bioactive phenolic compounds in potato (Solanum tuberosum L.)

Abstract

Potato is the main non-cereal food crop worldwide and a significant contributor to daily dietary antioxidants. We have demonstrated that polyphenol extracts from Andean potato (Solanum tuberosum L. ssp. andigena) tubers have antioxidant, bactericidal and cytotoxic activities in vitro. In order to determine the compounds responsible for those activities, we analyzed the composition of skin and flesh tubers from three Andean potato cultivars (Santa María, Waicha and Moradita) by HPLC-ESI-MS/MS. We confirmed the annotation of 30 compounds by comparison with databases, literature and authentic standards. We propose the identification of two miscellaneous (sinapine, salicylic acid glucoside, one remains unknown), four polyamines (caffeoyl putrescine, feruloyl putrescine, bis dihydrocaffeoyl spermidine, tris dihydrocaffeoyl spermine), four HCCs (3-CGA, 4-CGA, 5-CGA, cis-5-CGA), ten anthocyanins (four peonidin derivatives, one cyanidin derivative, five pelargonidin derivatives, plus two pelargonidin hexoses without identification), two non-anthocyanin flavonoids (eriodictyol hexose, rutin, plus three putative flavonoids with phenolic acids), and two glycoalkaloids (solanine, chaconine). Among families, we observed that HCCs, polyamines and glycoalkaloids were found in higher concentrations than flavonoids in potato tubers. In general, HCCs presented higher concentrations in the skin than in the flesh. Among polyamines, caffeoyl and feruloyl putrescine levels were similar between skin and flesh. On the contrary, bis dihydrocaffeoyl spermidine was more abundant in the skin than in the flesh, and tris dihydrocaffeoyl spermine was only found in skin. Miscellaneous metabolites were generally more abundant in flesh than skin. Among anthocyanins, peonidin and pelargonidin derivatives were found in both skin and flesh of Santa María, and in skin of Waicha and Moradita. Non-anthocyanin flavonoids were principally found in Santa María skin and flesh. Among glycoalkaloids, solanine and chaconine levels were more abundant in the skin than flesh, and absent in Waicha flesh. We then aimed to identify the isoforms of the genes involved in the biosynthesis of those bioactive compounds. To study the tuber transcriptome, transcript profiles are being generated by high-throughput RNA sequencing services in tuber flesh and skin. We will establish correlations between transcripts and metabolites. This systemic approach contributes to the development of a model of metabolic regulation of bioactive phenolic compounds and to the identification of novel targets for the breeding of valuable potato cultivars.