Studies On The Structures And Bioactivities Of Secondary Metabolites From Fout Hainan

Infectious diseases and foodborne illnesses can cause severe health effects and can even lead to death among the residing population, especially in the developing regions of the world. The continual emergence of antibiotic-resistant microorganisms and the possible side effects of using chemical-based antimicrobial agents have forced researchers to identify and explore natural plant-based antimicrobial agents (or preservatives) that are toxicologically safe and more effective against the resistant microbial pathogens.Natural products are both fundamental sources of new chemical diversity and integral components of today's pharmaceutical compendium. In order to find antifungal and antibacterial agents as natural preservatives for foods or applications in the pharmaceutical industries and to develop new and economical herbal-based products for treating various diseases, we studied the aerial parts of Kopsia hainanensis, Araucaria cunninghamii, Winchia calophylla, and Dicranopteris linearis, collected in the Hainan Province of China.From the above plants,114compounds were obtained, including14labdane diterpenoids,4clerodane glycosides,27indole alkaloids,25triterpenoids,5flavonoid glycosides,41ignans,2biflavonoids,3isoflavonoids,3steroids,4ionones,9benzene derivatives, and other types of compounds. Among of them,11compounds were identified to be new ones including6indole alkaloids (compounds1,19,20,21,22, and27),2diterpenoids (compounds28and29), and3other types of compounds (compounds56,62, and64).Some of these compounds were tested for their antibacterial activities against six bacteria(Bacillus cereus, Staphylococcus aureus, Bacillus subtilis, Escherichia coil, Pseudomonas aeruginosa, Erwinia caratovora) by micro-broth dilution method, antifungal activities against four plant pathogenic fungi (Helminthosporium tritici-rulgaris Nishik, Rhizoctonia solani, Fusarium oxysporum f. sp. niveum, and Fusarium oxysporum f. sp. cubense race4) using the growth rate method, toxicity on Xenopus embryos, and cytotoxic activities against HL-60and SMMC-7721cancer cell lines using the sulforhodamine B (SRB) method.Within the series of compounds tested, alkaloids10,15,19,23, and24were most active in the antimicrobial activities screening with MIC value from15.5-62.5μg/mL, and all of them exhibited no toxicity on Xenopus embryos at50μg/mL. The comparative data revealed that the alkaloids can be good candidates for further clinical studies to develop new antimicrobial dugs.Compound28exhibited modest inhibitory activities against E. coli with a MIC of15.5μg/mL, and it was more effective in cytotoxic study with IC50values of8.90and11.53μM.Compounds66,79,80,82, and83showed modest antifungal activities against six plant pathogenic fungi with EC50value from62.7to150μg/mL, and antibacterial activities against five bacteria with MICs value in the rage31.5-125μg/mLIn this dissertation, natural metabolites with potentially useful antimicrobial activities have been reported in the period2002-2011were reviewed.The thesis would be a supplement for the research on bioactivities of chemical constituents as well as structure-activities relationship in traditional Chinese medicine, helpful reference for pharmacology, chemotaxonomy, and screening new medicines, and may benefit utilizing and developing the natural resources of our country.