Growth Inhibition of Phaeocystis Globosa Induced by Luteolin-7-O-glucuronide from Seagrass Enhalus acoroides.

() is one of the most common species in seagrass meadows. Based on the application of allelochemicals from aquatic plants to inhibit harmful algal blooms (HABs), we used aqueous extract against harmful algae species (). The results showed that aqueous extract could significantly inhibited the growth of , decrease the chlorophyll-a content and photosynthetic efficiency (Fv/Fm) values of , followed by vacuolization, plasmolysis, and the destruction of organelles. Twelve types of major chemical constituents were identified in aqueous extracts by ultraperformance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS), including six flavonoids, two homocyclic peptides, two long-chain aliphatic amides, one tannin, and one nitrogen heterocyclic compound. Flavonoids were the characteristic chemical constituents of aqueous extract. Furthermore, the antialgal activity of luteolin-7-O-glucuronide (68.125 μg/mL in 8 g/L aqueous extract) was assessed. The EC value was 34.29 μg/mL. In conclusion, the results revealed that luteolin 7-O-glucuronide was one of the antialgal compounds of aqueous extract, with potential application as novel algaecide.