Investigation Of Meroterpenoids Constituents From Two Marine-derived Fungi Strains

Analyses of the fungal model strain Aspergillus. nidulans genome revealed that fungi have many secondary metabolism pathways including polyketide biosythetic pathway (PKS), isoprene pathway, nonribosomal peptiede biosynthetic pathway (NRPS), shikimate pathway and other multiple biosynthetic pathways. Compounds that generated from mixed biosynthetic pathways were termed as hybrid origin products. Meroterpenoid is a class of natural products which are partially derived from isoprene pathway. Meroterpenoids produced by fungi showed a broad distribution of biological activities grouped into a variety of areas such as antimicrobial, antiviral, antitumoral, immunomodulatory, enzyme inhibitors and activators, phytotoxins, mycotoxins and antiinsect.The present work on the chemical investigation of two marine-derived bioactive fungal strains Emericella nidulans (HK-ZJ) and Alternaria sp.JJY-32 leads to 30 meroterpenoids, which can be sub-classified into three groups: isoindolone- farnesyls, austin-like meroterpenoids and alternarenes.A large scale fermentation of E. nidulans (HK-ZJ) was performed and the crude organic solvent extract was subjected to silica gel column, Sephadex LH20, PHPLC and etc to yield 20 compounds including six new isoindolone- farnesyls (4-9), seven astin-like meroterpenoids (10-16), three new isoindolones (1-3), two xanthones (17-18) and two dimethyldiphenyl ethers (19-20).Fermented under the origin culture condition, Alternaria sp.JJY-32 have been proved to produce 9 novel alternarenes and in the present work , by means of applying the OSMAC (One Strain Many Compounds) method, the meroterpenoid production capacity of Alternaria sp.JJY-32 was developed and potentialized. through manipulating culture medium components and addition of enzyme inhibitor, the secondary metabolites profile of Alternaria sp.JJY-32 was drastically shifted and resulted in another 11 new alternarenes (30-36, 38 and 44-46). Additionally, compounds 44 and 45 shared a natural rare skeleton of cyclohexenone ring beard with a triprenyl group.The stereochemistry of the monocyclo- alternarenes (45-56), bicyclo-alternarenes (21-24, 26-27), tricyclo- alternarenes (30-33) and sipro-tricyclo- alternarene (25) were investigated by means of 2-D NOESY experiment, CD method, conformational analysis as well as approach of chemical derivation. Further more, the biogenetic relationships and the stereochemistry of the skeleton transformation among the alternarenes were rationally proposed on the basis of their planar and stereochemical structure.Compounds 1-8 were tested for in vitro activity against H1N1 replication in MDCK cells. However, only compounds 1-3 showed moderate inhibitory effects with IC50 values of 42.07μg/mL and 62.05μg/mL (ribavirin as a positive control, IC50 24.60μg/mL). Compouns10-16 were experimentally confirmed to have obvious lethal toxicity to brine shrimp and especially for compound 14, the IC50 was 7.2 ppm.Using LPS-induced RAW264.7 cell activation and MALP-2 induced macrophages and 293T cells expressing TLR receptor as model systems, the molecular mechanism of anti-inflammatory activity exhibited by compound 37 has been demonstrated. The data indicate that anti-inflammatory properties of 37 resulted from the inhibition of proinflammatory cytokines and enzymes production via TLR2/MyD88/NF-κB signaling pathway.with compound 37 as a control, the anti-inflammatory activities of compounds 25, 28, 30-34, 38-39 and 41-42 were also evaluated by NF-κB-luciferase reporter gene transfect 293T cells model. Compounds 31-34, 39, and 41-42 exhibited the equal activities to compound 37 at the same concentration of 100μmol/L.In this study, 30 metroterpenods were isolated and identified from two marie-derived fungal strains E. nidulans (HK-ZJ) and Alternaria sp.JJY-32. Among them, 17 compounds were identified as new ones and the possible biogenetic pathways of the alternarenes (30-46) were given on the basis of their planar and stereochemical structure. Furthermore, a series of new compounds with anti-inflammatory activities were discovered, which to some extent enlighten the developing of new drug for curing diseases such as asthma, SLE and rheumatoid arthritis.