Synthesis and quantitation of six phenolic amides in Amaranthus spp.

Cinnamoylphenethylamines are phenolic amides in which cinnamic acid provides the acid moiety and phenethylamine the amine moiety. Single ion monitoring (SIM) in LC-MS was performed on amaranth leaf extracts. Masses corresponding to sets of regioisomers, including previously reported compounds, were examined. Six peaks were detected and their corresponding standards synthesized for a quantitative LC-MS/MS investigation of cinnamoylphenethylamines in amaranth. Four cinnamoylphenethylamines (caffeoyltyramine, feruloyldopamine, sinapoyltyramine, and p-coumaroyltyramine) are reported in the Amaranthaceae for the first time; also, one rare compound, feruloyl-4-O-methyldopamine, appeared to be quite common in the genus Amaranthus. Feruloyldopamine showed moderate antifungal activity toward an isolate of Fusarium culmorum. Our LC-MS approach, in conjunction with the straightforward synthesis, provides a simple, reliable way of quantitatively investigating cinnamoylphenethylamines in plants. Concentrations of cinnamoylphenethylamines vary widely: feruloyltyramine was present in quantities of 5.26 to 114.31 microg/g and feruloyldopamine in quantities of 0.16 to 10.27 microg/g, depending on the plant sample.