Characterization of allelochemicals of the diatom Chaetoceros curvisetus and the effects on the growth of Skeletonema costatum

Abstract

Allelopathy has been regarded as chemical weapons for marine phytoplankton that enhanced competition ability in stressful conditions, especially during blooms. In a previous study, Chaetoceros curvisetus achieved growth advantage to Skeletonema costatum by producing allelochemicals. However, C. curvisetus allelochemicals have never been isolated and characterized until now. In this study the extraction and purification conditions were systematically optimized and C. curvisetus filtrate extracts were used to assess bioactive effects on the growth of S. costatum. The preliminary results showed that filtrates of C. curvisetus in exponential phase extracted under a temperature lower than 50°C could ensure a stronger activity of allelochemicals. Ethyl acetate extraction showed significant allelopathic effect and the wavelength of characteristic absorption was 255–260nm. Then C. curvisetus allelochemicals were isolated by Si-SPE, Sephadex-25 columns and C18 column and identified by HPLC-electrospray time-of-flight mass spectrometry (ESI TOFMS). It was found that the molecular weight of C. curvisetus allelochemicals was 314 and the allelochemical was supposed to be 2- ((2-cyanophenyl) amino)-2-oxoethyl,3-cyclohexyl propanoate.