Investigation Of Secondary Metabolites Of Two Mangrove-derived Endophytic Fungi

In this dissertation,15marine-derived fungal strains which isolated frommangrove were screened under different culture conditions. The crude extracts ofthese fungi were comprehensively evaluated by antimicrobial assay together withTLC and HPLC chemical assay as the careen model. Two fungal strains, Alternariatenuissima EN192(isolated from mangrove plant Rhizophora Stylosa) andPenicillium commune MA11(isolated from mangrove plant Sonneratia alba), werechosen as the aimed strains. They were fermented on MH2medium with static flaskculture respectively for further investigation of their secondary metabolites. Most ofthe isolated compounds were evaluated for their bioactivities.The compounds were isolated by a combination of column chromatography (CC)including silica gel, Sephadex LH-20, RP-18preparative thin layer chromatography(pTLC) as well as preparative HPLC (pHPLC) and recrystallization. The structures ofthese compounds were elucidated by means of spectroscopic methods including UV,IR, MS, NMR, as well as by comparison with authentic standards or with literaturereports. As a result,19compounds (AT1～AT19) were isolated and structurallydetermined from the extract of Alternaria tenuissima EN192fermented on static MH2medium, including4indole-diterpenoids (AT1～AT4). Besides, this is the first reportof indole-diterpenoids from the fungal genus alternaria.21compounds (PN1～PN21)were isolated and structurally determined from the extract of Penicillium communeMA11fermented on static MH2medium, including3new indole-diterpoids (PN1～PN3). In addition, the proposed biosynthetic pathways of indole-diterpoids isolatedfrom Penicillium commune MA11were also discussed.Some pure compounds were screened for their antimicrobial activity and brineshrimp (A. alternate) lethality activity. In the antibacterial assay, compounds AT1～AT9exhibited selective inhibitory activity against S. Aureus, E. Coli, B. Subtlis, V.anguillarum. Compounds PN5, PN6and PN16showed moderate inhibitory activity toward E. Coli with inhibition zone diameter of10,12,13mm. Compounds PN12and PN16displayed weak inhibitory activity against S. Aureus. In the antifungal assay,compounds PN5and PN9showed weak activity against A. alternate. In addition,compound PN1, PN2, PN5～PN8, PN10, PN16exhibited brine shrimp lethalityactivity. Compounds PN7and PN10showed significant toxicity against Artemiasalina with LD50value of45.48and7.16μg/mL.In summaray, we have thoroughly studied the chemical and biological diversityof two mangrove endophytic fungi, which has enriched the chemical structures ofmarine natural products. These results may be helpful to the exploration andutilization of marine microorganisms.