Inhibitory Effects Of Kandelia Candel And Bruguiera Gymnorrhiza Leaf Extracts On Red Tide Algae

The research conducted on biological remediation with regard to the inhibition of HABs is becoming a major focus in marine ecology.The present study used two mangrove species,namely Bruguiera gymnorrhiza and Kandelia candel and two harmful algae species Phaeocystis globosa and Karenia mikimotoi as experimental organisms.In the mangrove community,young(grow out 1-5 days),mature(growth within 15-30 days),and senescent(growing time for more than 45 days)leaves were separately collected from the mangrove plants of the same age,the present study determined the inhibitory effects from mangrove leaves and Superoxide dismutase(SOD),glutathione(GSH),malondialdehyde(MDA),protein content of harmful algae,and analyzed the main chemical composition of the aqueous extracts by Ultra-Perfomance Liquid Chromatography coupled to high resolution mass spectrometry(UPLC-QTOF-MS).The results indicated that :(1)The leaf extracts from different leaf ages of B.gymnorrhiza and K.candel leaves exhibited apparent inhibitory effects on the growth of harmful algae.The inhibitory effects of B.gymnorrhiza and K.candel leaves extracts on the growth of harmful algae were in the following order: senescent > mature > young leaves.(2)The levels of the parameters SOD activity,GSH and MDA content in harmful algae following treatment with B.gymnorrhiza and K.candel leaves extracts were increased as follows: senescent > mature > young leaves.(3)14metabolites were found in the aqueous extracts from B.gymnorrhiza leaves and were identified as follows: 5 norsesquiterpenes compounds 3,4,8,9 and 10;4 phenolic glycoside compounds 2,5,6 and 7;1 carbohydrate compound1;And 4 fatty acid compounds11,12,13 and 14.A total of11 types of major chemical constituents were detected in the leaf aqueous extracts of K.candel and were identified as follows: 3 norsesquiterpenes compounds 4,8 and 9;3 phenolic glycoside compounds 5,6 and 7;1 carbohydrate compound 1 and 4 fatty acid compounds 11,12,13 and14.the intensity of the ion peaks of the specific secondary metabolites assigned 4,7,8,9 and 10 in the aqueous extracts from the B.gymnorrhiza leaves were increased.The intensities of the ion peaks of the secondary metabolites 7,8 in the aqueous extracts from the K.candel leaves were also increased.Therefore,we considered that the norsesquiterpenes compounds 4,8,9 and 10 and a phenolic glycoside compound 7 were the active constituents in the aqueous extracts of themangrove leaves responsible for the inhibition of algae growth.This evidence provided theoretical guidance for the development of biological methods to control red tides.