Abstract:Different concentration methanol-, acetone-, ether-, and chloroform extracts of Corallina pilulifera were used to study their growth inhibitory effects on red tide microalgae Heterosigma akashiwo. The results showed that methanol extract at relatively higher concentrations had the highest growth inhibitory activity and killed all H. akashiwo cells, while the other three kinds of organic solvent extracts had no apparent inhibitory effects, suggesting that the growth inhibitory substances in C. pilulifera had relatively high polarity. The methanol extract was partitioned to petroleum ether phase, ethyl acetate phase, butanol phase, and distilled water phase by liquid-liquid fractionation, and the bioassays on the activity of each fraction were carried out on H. akashiwo. It was found that petroleum ether phase and ethyl acetate phase had strong algicidal effects on H. akashiwo, suggesting that the fatty acids in C. pilulifera tissues might be one of the main allelochemicals.