Yan Binlun

Green alga Ulva pertusa—a new source of bioactive compounds with antialgal activity

We tested the effects of solvent fractions (FA, FB, FC, and FD), which partitioned by liquid-liquid extraction from the methanol extract of Ulva pertusa, on the growth of red tide microalgae (Karenia mikimitoi, Skeletonema costatum, Alexandrium tamarense, Heterosigma akashiwo, Prorocentrum donghaiense), and FA, FB, and FC exhibited significantly antialgal activity. The chemical constituent analysis showed the existence of bioactive compounds such as phenols and alkaloids. Further, four solvent fractions were applied to silica gel column and repeated preparative TLC to produce 13 samples and their purity qualified as thin-layer chromatographic grade. Among these purified samples, FA111, FB411, FC411, FD111, and FD211 exhibited stronger antialgal activity. Furthermore, their functional groups were analyzed by colorimetric methods and UV spectra data. FD111 and FD211 were temptatively identified as alkaloids; the others were initially identified as phenolic acids. This is a preliminary study and the structure identification of these purified samples requires further investigation. While concentration of these purified samples in this algae was very small, they showed excellent effects against red tide microalgae.

The growth inhibition of the four species of red tide microalgae by the extracts from Porphyra yezoensis

A kind of aqueous extracts of Porphyra yezoensis was extracted with distilled water,and its inhibitory activity against four species of red tide microalgae,Amphidinium hoefleri,Karenia mikimitoi, Skeletonema costatum and Alexandrium tamarense was tested. The extracts were extracted with five solvents (methanol,acetone,ethyl acetate,chloroform and petroleum ether),respectively,to probe their inhibitory effects on the growth of those microalgae. Based on the observation of microalgal morphology and density,cell size and the contents of some key physiological indicators (chlorophyll,proteins and polysaccharides),the inhibitory effect of the solvent extract that had strongest inhibition on all tested microalgae was investigated. Thereafter,the extracts mentioned above were separated again with petroleum ether phase,ethyl acetate phase,n-butanol phase and distilled water phase by the method of liquid-liquid fractionaction. The results showed that the growth of the four microalgae was significantly inhibited by the aqueous extracts of P. yezoensis at the concentration of 16 g/L. The inhibitory effect of the aqueous extracts of P. yezoensis for A. hoefleri and K. mikimitoi was stronger than that for A. tamarense and S. costatum. The methanol extracts of P. yezoensis dry powder had the strongest effect,and at the concentration of 16 g/L its growth inhibitory effect on A. hoefleri,K. mikimitoi,A. tamarense and S. costatum was 70. 5% ,79. 9% ,67. 1% and 65. 1% on day 12, respectively. At the same time,the cell size and athletic ability of the cells decreased,and cavities,pieces and pigment faded in cells were caused. The further investigation found that under the effect of the methanol extracts the contents of chlorophyll,proteins and polysaccharides in the cells of those microalgae significantly decreased. The methanol extracts were partitioned to petroleum ether phase,ethyl acetate phase,n-butanol phase and distilled water phase by liquid-liquid fractionaction,among which those extracted with petroleum ether and ethyl acetate had the strongest effect.