Research On Secondary Metabolites Of Five Sponge-derived Fungi: Structures And Bioactivities

As simple multicellular invertebrates and filter feeders, sponge are rich of a largenumber of microorganisms on the surface and in the body. Due to unique livingenvironment, sponge fungi which form unique and variety biosynthetic pathway inthe long-term natural selection process, can generate many secondary metaboliteswith structural novelty and biological activities. Therefore, sponge-derived fungibecome an important resource for lead compounds of drugs and hot spot in theresearch of marine bioactive substances. In order to search for new lead compounds,secondary metabolites of5fungal strains from sponge were studied, and thesymbiotic relationship between sponges and associated fungi was also discussed.302fungi were isolated from16marine sponge samples collected from watersnear Nazhou Island of Guangdong Province and Xisha Islands. Using cytotoxicityassay and P388cell line as bioactive screen model,29fungal strains were detected thecytotoxic activity. Together with applying the TLC and HPLC chemical screen assays,five bioactive strains, Stachybotrys chartarum HDN10-123, Aspergillus flavusHDN10-125, Aspergillus sp. HDN10-108, Penicillium sp. HDN10-173, and Aspergillusterreus HDN10-109were chosen as aimed strains for further study.In all,72compounds were isolated and purified, from the EtOAc extracts of the5aimed strains, by using solvent extraction, silica gel column, ODS, Sephadex LH20,MPLC, HPLC and etc. Basing on their physicochemical properties and spectral data(IR, UV, MS, NMR, CD, and X-ray), combined with quantum chemical CDcalculation and marfey’s and mosher mothod, structures of the72pure compoundswere respectively determined. Among them there are26new compounds, including7new phenylspirodrimane meroterpenoids (1-7), one new chromene derivative (13),4new CPA analogs (22-25),1new polycyclic compound containing oxo-adamantaneskeleton (35),3new benzoic derivates (36-38),3new cyclohexenes (49-51) and5new cyclopentenones (52-54,56-57), one new butyrolactone analog (62), as well as two types of new structures, one new cyclized iminoisoindoline (12) and two CPAanalogs with six fused rings (22-23). The other known compounds containedstructural types like amides, pyrones, diketopiperazines, aspergillus acid analogs,meroterpenoids, and sesterterpenes and etc.The HIV-1replication inhibition activities were evaluated on compounds1-14and22-25by recombinant VSVG/HIV-1pseudovirions. The results showed that onlycompound1has obvious activity with EC508.4μM. Further study on the mechanismdisclosed compound1inhibited RNA reverse transcriptase and five non-nucleosidereverse-transcriptase inhibitors (NNRTIs) resistant HIV-1strains with EC50valuesranging from0.7-to2.8-fold of the value against the wild type strain. Severalcompounds were evaluated for their cytotoxicities against several cancer cell linessuch as HL-60, K562, A-549, P-388and etc., by the MTT or SRB method. Amongthem, compound13showed different levels of cytotoxicities.Extracts of5sponge-derived fungi and original sponges were analysis by HPLCand LC-MS, and the same component, cytotoxic compound13was detected in theextracts of both sponge XS-28and associated fungus HDN10-123.Summarily,72compounds were isolated and identified from5sponge-derivedfungal strains, including26new compounds. Two types of new structures, one newsulfate meroterpenoid contained rare decahydropyrrolo[1,2-a][1,3]diazocine skeleton(12) and CPA derivatives with multiple fused rings (22-23) were firstlydiscovered. One new non nucleoside reverse transcriptase inhibitor (1) was firstlydiscovered. And one new chromene derivative detected in the extracts of both spongeand associated fungus was also firstly found. The study provides a chemotype fornatural product research and the search for lead compounds of antitumor and anti-HIVdrugs,and some scientific basis for the relationship between sponge and symbioticmicrobes.