Laurencia filiformis: phytochemical profiling by conventional and HPLC-NMR approaches

Chemical investigation of the southern Australian marine alga Laurencia filiformis forma heteroclada resulted in the isolation of two new compounds, cycloisoallolaurinterol (16) and isoallolaurinterol (23), along with the previously reported sesquiterpenes filiformin (1), filiforminol (2), allolaurinterol (3) and bromolaurenisol (10). All structures were secured by detailed spectroscopic analysis since no previous 2D NMR studies had been described for compounds 1, 2 and 10. As a result of this study, the first single X-ray diffraction study for 1 was secured. The investigation of the chemical conversion of allolaurinterol (3) to filiformin (1) was monitored by on-flow HPLC-NMR, which also resulted in the identification of 23. We propose that both compounds 16 and 23 are formed as artefacts from allolaurinterol (3). HPLC-NMR was used to profile the crude extract of a marine organism, as well as for monitoring on-line compound chemical conversions. Both on-flow and stop-flow HPLC-NMR were successfully applied in the chemical profiling and compound chemical conversion studies of L. filiformis forma heteroclada. Compounds 2 and 3 displayed antimicrobial activities.