Dihydrocaffeoyl polyamines (kukoamine and allies) in potato (Solanum tuberosum) tubers detected during metabolite profiling

Four related phenolic amides previously undescribed from the species were revealed during metabolic profiling of potato (Solanum tuberosum) tubers. N-1,N-12-Bis(dihydrocaffeoyl)spermine (kukoamine A) and N-1,N-6-bis(dihydrocaffeoyl)spermidine were positively identified by comparison with authentic standards, while the structures N-1,N-4,N-12-tris(dihydrocaffeoyl)spermine and N-1,N-4,N-8-tris(dihydrocaffeoyl)spermidine are proposed for the other two metabolites. Each amide was present at several tens of micrograms per gram of dry matter. Several of these compounds were subsequently detected in other solanaceous species, such as tomato (Lycopersicon esculentum) and Nicotiana sylvestris. They appeared not to be present in Arabidopsis thaliana or Beta vulgaris. Bis(dihydrocaffeoyl)spermine isomers have previously been identified in only a single plant, the Chinese medicinal species Lycium chinense (Solanaceae), where they may account for some of the described biological activity. The other compounds have not until now been reported in vivo, though some of the equivalent hydroxycinnamoyl derivatives are known. The surprising discovery of kukoamine and allies in a range of solanaceous species including potato, a common food crop that has a long history of scientific investigation, provides exemplary evidence for the potential of the nontargeted techniques of metabolomics in studying plant metabolites.