Studies Of The Active Constituents Of Secondary Metabolites Produced By Three Marine Fungal Strains

As an important member of marine microorganism, marine fungus have been considered an important source of bioactive leading compounds, due to their unique living environment. A study on three strains of marine fungal strains was carried out to investigate the potential anti-tumor compounds.By combinatory use of brine shrimp bioassay testing, cytometric bioassay against MCF7,SF-268,NCI-H460 cell line, and chemical analysis, 9 bioactive strains have been screened from 21 strains isolated from six marine samples.Monitoring by bioassay-guided isolation, the active fraction is chromatographed on silica gel, Sephadex LH-20 and prepared TLC, and preparative reversed phase HPLC, respectively, forty-two compounds were isolated from the three active strains. Twenty compounds (1-20) were isolated from fungus PR19N-1 (Penicillium sp.), eighteen compounds (21-38)) from fungus c-f-3 (Aspergillus flavus), six compounds (39-44) from fungus v-3-1.By means of modern spectral analysis (UV, IR, NMR, MS, CD) and physico-chemical properties, the structures (see Fig. 1) of forty pure compounds were respectively determined. Among them there are fourteen new compounds, including eleven eremophilane-type sesquiterpenes (1-6,8-12), which were deduced the relative structure by NOESY spectrum and the coupling constants, and some of which were proposed the absolute stereochemistry by analysis their biosynthesis route; one new diketopiperazine (21),which was deduced the relative structure by NOE and determined the absolute stereochemistry by chiral HPLC analysis; two new 2-pyrons (24, 25). Additionally, two compounds (13,28) were isolated from nature source for the first time.In addition, the chemical structure types of compounds are mainly involved in Steroides (32,33,40,41), sesquiterpenes (7,14-16), Benzene derivates (17,18,19,26), Alkaloids (20,22,23,27,28), 2-Pyrone (29,30), etc.These compounds were evaluated for their cytotoxicities against several cancer cell lines such as HL-60, A549 etc, by the MTT or SRB method. The results indicated that new compounds 1 and 8 showed stronge cytotoxicities on A549 cell lines; new compounds 9 and 10 showed moderate cytotoxicities on A549 cell lines; new compounds 8, 10, 11 showed a certain cytotoxicities on HL-60 cell lines; new compound 21 showed slightly cytotoxicities on HL-60 cell lines; and compound 28 showed cytotoxicities on the three cell lines of A549,HL-60及MOLT-4.New compounds 24, 25 were tested the GPR12 receptor binding activity by cAMP assay. The results showed that 24 could promote a small but significant cAMP increase in a dose-dependent manner on both GPR12-CHO cells and GPR12-HEK293 cells, while no significant difference on their vector controls.Summarily, this work obtained nine important active strains from six marine alga samples, and forty compounds from three active strains. Among them, fourteen compounds were identified new. Six new compounds with antitumor activities in vitro were discovered, and one new compound with GPR12 receptor binding activity. Studies mentioned above provided novel structures for searching leading compounds and strain resources of great value for further study and development of marine fungus.