Bioactivities of surface extracts from eelgrass toward marine microbial epiphytes

We identified defense compounds that are present on the surface of Zostera marina and inhibit settlement of microfoulers at natural concentration. Moderately polar eelgrass surface extract prepared with propan-2-ol inhibited the settlement of seven marine bacteria that originated from nonliving substrata and of one yeast, while five other bacterial strains that had been directly isolated from eelgrass surfaces were all insensitive (see "Data underlying figures 1 and 2"). In contrast, microbial growth was not inhibited by these extracts (see "Data underlying figure 3" and "Data underlying figure.S4"). Avter solvent evaporation propan-2-ol extract could be redissolved in methanol without activiy loss (see "Data underlying figure S2). Of six fractions prepared from propan-2-ol crude extract by HPLC three inhibited certain microorganisms (see "Data underlying figures 5 and 6"). Rosmarinic acid, luteolin-7-sulfate and diosmetin-7-sulfate or its isomer chrysoeriol-7-sulfate were identified as main components in these fractions and all three compounds prevented bacterial settlement in a dose-dependent manner (see "Data underlying figures 8 and S6" and "Data underlying figure S3").