Long-chain alkenes and alkadienes of eight lichen species collected in Japan

The hydrocarbons of eight lichen species isolated in Japan were analyzed, and diverse mono-, di-, and triunsaturated alkenes were detected. The positions of the double bonds of C17 alkadienes (heptadecadiene) and C17-C20 alkenes were determined by mass spectrometry of their dimethyl disulfide adducts. We found that the six lichens containing green algal photobionts were distinguished by the presence of 1,8-heptadecadiene, 6,9-heptadecadiene, and 8- and 7-heptadecenes. On the other hand, 1-octadecene, 4-octadecene, and 5-nonadecene were the major alkene components of the two lichens with cyanobacterial photobionts. These alkadienes and alkenes were present in large quantities in the lichen samples. In particular, 1,8-heptadecadiene accounted for more than 90% of the total alkenes in all four lichens containing it. Our results provide new insights into the origin of C17 alkadienes and C17-C20 alkenes in environmental and geological samples, and these alkenes can potentially be applied as lichen biomarkers.

Automated summary

The hydrocarbons of eight lichen species isolated in Japan were analyzed, revealing diverse mono-, di-, and triunsaturated alkenes. Mass spectrometry was used to determine the locations of double bonds in C17 alkadienes and C17-C20 alkenes. Lichens with green algal photobionts were distinguished by specific alkenes, while those with cyanobacterial photobionts had different major alkene components.