Two New Isomers of Palmityl-4-hydroxycinnamate from Flowers of Taraxacum Species.

Two isomers, (Z)- and (E)-palmityl 4-hydroxycinnamate [hexadecyl(2Z)-3-(4-hydroxyphenyl)prop-2-enoate and hexadecyl(2E)-3-(4-hydroxyphenyl)prop-2-enoate] were isolated for the first time from ligulate flowers of Taraxacum linearisquameum Soest (sect. Taraxacum). The highest amount of these compounds was detected in pollen grains; 0.26 mg/100 mg DW of the (E)-isomer and 0.096 mg/100 mg DW of the (Z)-isomer. The structures of these compounds were elucidated by a combination of HPLC-ESI-Qtof-MS and 1D and 2D NMR spectroscopy. Their presence was confirmed in other species of Taraxacum, but they were not found in the male - sterile triploid agamospermous taxon T. parnassicum.