Secondary Metabolites Of Three Coastal Plants And Their Bioactivity

The marine red algal species of the genus Laurencia (family Rhodomalaceae, orderCeramiales, class Rhodophyceae, and phylum Rhodophyta) are mainly spread alongtropical, subtropical, and temperate coasts. The secondary metabolites of the genusLaurencia are mainly sesquiterpenes, diterpenes, triterpenes/polyethers,C15-acetogenins and steroids. Sesquiterpenes and C15-acetogenins are usually bondingto halogen. In this thesis, secondary metabolites isolated from the species as well astheir biological activities in the last10years were reviewed. The isolation, structuralelucidation, bioactivity assay of the secondary metabolites of two Laurencia speciesLaurencia okamurai collected from Shandong (northern China) and Laurenciacomposita collected from Fujian and Guangdong (southern China) was conducted.Helianthus tuberosus Linn (Asteraceae, commonly named Jerusalem artichoke) isan herbaceous plant cultivated widely around the temperature areas, widely used inindustry as a raw material to produce inulin and ethanol. The secondary metabolites ofthis species are mainly sesquiterpenes, diterpenes, triterpenes and steroids. In theworks of this thesis, secondary metabolites isolated from the species as well as theirbiological activities were reviewed, the isolation, structural elucidation, andbioactivity assay of the secondary metabolites of this species collected from Shandongwere conducted.Dried and powdered algal and H. tuberosus material was extracted with organicsolvents. Each extract was purified by repeated silica gel and Sephadex LH-20column chromatography, by preparative thin layer chromatography (PTLC), and byhigh performance liquid chromatography (HPLC) to give pure compounds, and theirstructures were elucidated mainly by1D and2D NMR, mass, infrared spectroscopictechniques. As results, a total of42compounds were isolated and identified from thetwo algals. Among them, there were11new compounds and2new natural products.Most of them were halogenated. The new compounds included10sesquiterpenes and1C12-acetogenins, and new natural products included2sesquiterpenes. Secondary metabolites of the Laurencia okamurai from Shandong province identified28compounds including7new structures and1new natural product, while25compounds with4new chemicals and1new natural product were identified fromLaurencia composita collected from Fujian and Guangdong province.12steroidscompounds were isolated and identified from the Helianthus tuberosus and there were2new compounds among them.Bioactivity assay including antibacterial against Staphylococcus aureus andEscherichia coli, antifungal against Colletotrichum lagenarium and Fusariumoxysporum, and the toxic to brine shrimp showed that some secondary metabolites,especially those halogenated structures from the Laurencia species, possessedantibacterial, antifungal and toxic to brine shrimp bioactivity. The antibacterialactivity of Laurane sesquiterpenes LO18and LO20against S. aureus and E. coli,LO13and LO15toxic to brine shrimp were notable, and chamigrane sesquiterpenesLC11and LC4possess an obviously bioactivity antibacterial, antifungal and weretoxic to brine shrimp. The2new compounds from H. tuberosus exhibited weakantibacterial activity.