Study On Secondary Metabolites Of Six Microorganisms And Their Activity

Microorganisms widely exist in the nature, they far outnumber plants and ani-mals. They can produce a great number of secondary metabolites with interesting bi-oactivity. For this reason, microorganisms are considered to be an important resource of natural bioactive substances. The research of their secondary metabolites has im-portant implications for the finding of new drugs. This dissertation is composed of four chapters. In chapter 1, two fungi PH30461 and PH30434 from Panax noto-ginseng (Burk.) F. H. Chen were characterized as Cheatomium globosum and Xylaria bambusicola, then the structures and bioactivity of their secondary metabolites were investigated. In chapter 2, a strain PH30583 from soil of Tibet characterized as Stachybotrys sp., was selected to study the structures and bioactivity of its secondary metabolites. Chapter 3 described the separation and bioactivity studies of secondary metabolites from three endophytic actinomycetes:Streptomyces sp. YIM66403 from Isodon eriocalyx (Dunn) Hara, Nocardia alba YIM64630 from Tripterygium wilfordii Hook. f. and Streptomyces sp. YIM65033 from D. viscosa (Linn.) Jacq.. In the last chapter, the recent progresses on the cholinesterase inhibitors from microorganisms were reviewed.Eighty nine compounds with 81 different compounds, including 11 new ones, were isolated by a variety of chromatographic methods and their structures were elu-cidated on the basis of extensive spectroscopic methods. The structure types of com-pounds were diverse, including alkaloid, polyphenols, anthraquinone, terpenes, ster-ides, cyclopeptides, nucleosides and so on. Some of them were evaluated for antimi-crobial activity, cytotoxic activity, antioxidant activity and the anti-AChe activity and there appeared several compounds with prominent activities.Specially, the flavipin derivatives separated from fungus Cheatomium sp. PH30461, and all of them were known compounds but were firstly reported as anti-oxidants and acetylcholinesterase inhibitors. Three new substances 22-hydroxy-24-glucoergosta-4,6,8(14)-22-tetraen-3-one, PH30434-2 and 16-β-D- glucopyranosyloxyisopimar-7-en-19-oic acid were isolated from fungus PH30434 and the crystal structure of oxacyclotetradeca-3,6,9-trien-2-one,5,8-dihydroxy-14-methyl-(3E,5S,6Z,8S,9E,14S) was firstly reported in this dissertation. Three polyphenols and their three dimers were separated from fungus PH30583, they were all novel com-pounds except anishidiol and three dimers indicated moderate anti-AChe activity. A new anthracyclines, misamycin, and a new cyclic tetrapeptide cyclo (L-Val-Try-L-Ile-Try) were isolated from Streptomyces sp. YIM66403, and misamycin showed moderate inhibition for four tumor cell lines in vitro.