Isolation, purification, and identification of antialgal substances in green alga Ulva prolifera for antialgal activity against the common harmful red tide microalgae.

Ten compounds (1~10) were successfully isolated from green algae Ulva prolifera through the combination of silica gel column chromatography, Sephadex LH-20 column chromatography and repeated preparative thin-layer chromatography. These ten compounds showed antialgal activity against red tide microalgae. Among them, compounds 3, 6, and 7 showed stronger antialgal activity against red tide microalgae. Furthermore, their structure was identified on the basis of spectroscopic data. There are three glycoglycerolipids: 1-O-octadecanoic acid-3-O-ß-D-galactopyranosyl glycerol (2), 1-O-palmitoyl-3-O-ß-D-galactopyranosyl glycerol (4), and 1-O-palmitoyl-2-O-oleoyl-3-O-ß-D-galactopyranosyl glycerol (5); two monoglycerides: glycerol monopalmitate (1), 9-hexadecenoic acid, 2,3-dihydroxypropyl ester (3); two terpenoids: loliolide (6) and lsololiolide (7); one lipid-soluble pigments: zeaxanthin (8); one sterol: cholest-5-en-3-ol (9); and one alkaloid: pyrrolopiperazine-2,5-dione (10). These compounds were isolated from U. prolifera for the first time, and compounds 2, 3, 5, and 8 were isolated from marine macroalgae for the first time.

[Isolation and identification of Marinobacter adhaerens HY-3 and its allelopathy on Skeletonema costatum].

UNLABELLED: The allelopathy between bacteria and algae is a very complicated physical and ecological phenomenon. A marine bacterium was isolated from the water of a shrimp and crab mix-culturing pond. By 16S rRNA analysis, it was identified as Marinobacter adhaerens HY-3. Skeletonema costatum, a common dominant species of red-tide microorganism in China, was chosen as the other research object. The allelopathic effect of Marinobacter adhaerens HY- 3 on S. costatum was studied. Using the growth mass of Skeletonema costatum and the content of chlorophyll a as the parameters, the effects of HY-3 on the growth and photosynthesis of Skeletonema costatum were studied after co-cultivation and addition of extracellular metabolites of HY-3. The results showed that the growth of S. costatum was inhibited when the concentration of the strain HY-3 was above 10(4), and the growth mass of the 10(4), 10(6) and 10(8) HY-3 group was 70%, 23% and 22% of the control group respectively on the 10th day, with the content of chlorophyll being 88%, 62% and 60% of the control group, respectively. Therefore, the suppression increased with increasing concentration of HY-3. However, addition of extracellular metabolites of HY-3 had no effect on the growth of S. costatum. CONCLUSIONS: M. adhaerens HY-3 had certain allelopathy on S. costatum and affected its growth and photosynthesis. Moreover, interaction between M. adhaerens HY-3 and S. costatum was achieved by their direct contact and the extracellular metabolites did not contain allelopathy factors.