Quantitative profiling of polyacetylenes in tissue cultures and plant parts of three species of the Asteraceae

Polyacetylenes are a group of fatty-acid derived specialized metabolites with several C–C-triple bonds and derived compounds which are widely distributed in the plant kingdom, but are especially abundant and structurally diverse in the Asteraceae family. Despite their interesting structural and biological properties, the biosynthesis of polyacetylenes is only poorly understood. We have used three species of the Asteraceae (Carthamus tinctorius, Tagetes patula, and Arctium lappa) to compare their suitability for studies of polyacetylene biosynthesis when used after cultivation on soil or as tissue culture. The polyacetylene profiles detected in different plant parts together with information from the literature indicate that C. tinctorius seedlings and flowers as well as T. patula roots and flower buds are major sites of polyacetylene biosynthesis. Highest levels of polyacetylenes were detected in T. patula about 30 µmol/g dry weight (d.w.) thiophenes in roots] while A. lappa contained less than 1 µmol/g d.w.. Methyljasmonate (MeJ)-induced T. patula hairy root cultures proved to be an excellent source of butenynyl-bithiophene (200 µmol/g d.w., 43 mg/g d.w.) while T. patula flower buds could serve as a source of pentenynyl-bithiophene and α-terthienyl (5–10 µmol/g d.w.) and C. tinctorius flowers or seedlings as a source of polyacetylenic C₁₃ hydrocarbons, the biosynthetic precursors of thiophenes (5–10 µmol/g d.w.). Upon addition of elicitors to tissue cultures, highest elicitation factors (between four and seven) were reached for 1,11-tridecadiene-3,5,7,9-tetrayne in C. tinctorius cell suspension cultures with 40 µM MeJ and α-terthienyl in T. patula hairy root cultures with 100 µM MeJ.