Preliminary analysis of allelochemicals produced by the diatom Phaeodactylum tricornutum

• Substances from the filtrate of Phaeodactylum tricornutum were separated by high-performance liquid chromatography (HPLC).
• Active compounds from P. tricornutum were screened using activity-guided fraction methods.
• Anti-algal compounds from P. tricornutum were isolated and analyzed mainly by HPLC–MS.
• The isolated allelochemical was preliminary identified as TYR-PRO-PHE-PRO-GLY-NH2, a type of glycinamides.

Marine diatom Phaeodactylum tricornutum is known to exude allelochemicals with negative effects on Heterosigma akashiwo according to our previous study, while the information about the allelochemical compounds remains unknown. The present study dealt with isolation and analysis of the active substances released by P. tricornutum into the culture medium. Filtrate of P. tricornutum was extracted using ethyl acetate and chloroform respectively. The anti-algal fractions were isolated using high performance liquid chromatography (HPLC) and screened using activity-guided fraction methods. Results demonstrated that fraction Ⅱ and Ⅵ showed significant allelopathic effect on H. akashiwo growth. Then the anti-algal activity fractions were analyzed preliminary using gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography-electrospray time-of-flight mass spectrometry (HPLC-ESI-TOF-MS). An active compound was derived from fraction Ⅵ with the molecular weight of 578 and possible molecular formula of C30H38N6O6, which was speculated to be TYR-PRO-PHE-PRO-GLY-NH2. a kind of glycinamides.