Research On Secondary Metabolites Of Marine-derived Fungi:Structures And Anti-influenza H1N1 Viral Activities

Marine-derived microorganisms can produce novel bioactive secondary metabolites through their unique metabolic pathways, and have become the great important resource for natural products research. Marine fungal secondary metabolites as a hot research field, is an important resource for finding new lead compounds. The isolation of bioactive compounds and determination of absolute configuration are two important aspects in the study of natural products. This paper has two main research ascepts, one is research on active compounds with anti-H1N1 influenza virus from marine fungal secondary metabolites; another one is research on stereoconfiguration-determination of the novel complex natural products by quantum chemistry ECD calculationStudy on fungal metabolites with Anti-H1N1 activity:48 fungi without cytotoxic activity was get from the strains library in the laboratory. Using the H1N1 virus canine kidney epithelial cells (MDCK) screening model, followed by chemical screening (HPLC-UV-MS) and strains identificational screening, as a result 5 fungi as target strains was obtained.Their fermentation was performed under the optimal conditions, and then the fermented products were isolated using conventional column chromatography and semi-preparative high performance liquid chromatography method. As a result,38 compounds were got, including 15 compounds isolated from the mangrove Cladosporium sp. PJX41; 4 compounds from Penicillin chrysogenum PJX17; 6 compounds from Paraphaeosphaeria sp. PJXM5; 13 compounds from other two fungal strains Penicillium crustosum PJXJ23 and Aspergillus fumigatus PJXZ72.Basing on various spectrum analysis methods, X-Ray diffraction and quantum chemical ECD calculation methods, the structures of 38 compounds (1-38) were determined. The structural types of the 10 new compounds, includeing six novel quinazolinone indole alkaloids (1-5,15), two polyketides with a new skeleton type (16-17), two novel tetrahydronaphthalene ketone compound (20,22); and a new natural alkaloid compound (12); together with the first report about the absolute configurations of three known indole alkaloids quinazolinone (6-8) and a a-tetralone compound (21). Other structure types of known compounds include:9 indole alkaloids quinazolinone derivatives (6-14),2 polyketide sorbicillin derivatives (18-19), 3 palmarumycins derivatives (23-25),10 diketopiperazine compounds (26-35),3 viridicatin derivatives (36-38).Through H1N1 virus infection using dog kidney epithelial cells (MDCK) model, the anti-influenza virus activity of compounds 1-22 was evaluated, among them 18 showed active, including 8 novel new compounds (2b,5,7-9,11,16,20) showed potent anti-H1N1 influenza virus activity (activity results quite positive drug ribavirin). The indole alkaloids quinazolinone derivatives, sorbicillin derivatives and a-tetralone derivatives were first reported to have significant anti-H1N1 influenza virus activity.Determination the stereochemistry of complex novel natural products by quantum chemistry ECD calculations:marine microbial secondary metabolites with varied structure and unique activity, is an important source for discoverying lead compounds. As marine natural product usually characterised by complicated structure, low amount, typically containing a plurality of chiral centers, there are greater difficulties in the determination of absolute configuration structure. In recent years, the use of circular dichroism (CD) and a combination of modern quantum chemical calculations, identification technology of absolute configuration of the new organic agents in theory and practice has made a major breakthrough, and quickly became an effective means to solve this problem. But the technology is currently has not yet widely used in domestic natural products research group. By learning quantum chemistry ECD calculation to solve the absolute configuration of the complex structure of marine natural products, and identified the absolute configuration of many marine compounds isolated by our group, including the novel alkaloids, terpenoids, sorbicillin, citrinin derivatives, to solve the absolute configuration of some complex natural products while using conventional NMR and chemical methods cannot make it.In summary,5 fungi with anti-influenza virus activity were obtained by integrated activity-chemical-biological screening mode from laboratory strains library as research subjects; 38 compounds including 10 new compounds were isolated from the extracts, herein first reported the anti-H1N1 influenza virus activity of quinolone-ketone alkaloids, sorbicillin derivatives and a-tetralone derivatives. In this paper, these research provide new active marine-derived fungi; add new structure types to natural product research; at the same time also provide one new chemical structure for anti-H1N1 research. In addition, by quantum chemistry ECD calculations, the absolute configurations of 19 novel compounds from marine microorganisms were identified, and the absolute configuration of them is difficult to determine using conventional methods.