Cytotoxic Trichothecene Macrolides Produced by the Endophytic Myrothecium roridum.

Six new macrolides named myrothecines D-G (1-4), 16-hydroxymytoxin B (5), and 14'-dehydrovertisporin (6), including four 10,13-cyclotrichothecane derivatives, in addition to 12 known compounds (7-18), were isolated from three endophytic Myrothecium roridum, IFB-E008, IFB-E009, and IFB-E012. The isolated compounds were characterized by MS, NMR, CD, and single-crystal X-ray crystallography. The isolated macrolides exhibited an antiproliferation effect against chronic myeloid leukemia K562 and colorectal carcinoma SW1116 cell lines. Compounds 1-6 were cytotoxic, with IC50 values ranging between 56 nM and 16 µM. Since slight structural changes led to obvious activity differences, the CoMFA (comparative molecular field analysis) and CoMSIA (comparative molecular similarity indices analysis) methods were then used to explore the 3D QSAR (three-dimensional quantitative structure-activity relationship) of these macrolides. The result showed that the steric, electrostatic, hydrophobic, and H-bond acceptor factors were involved in their cytotoxicity and provided an in-depth understanding of the structure-activity relationships of these metabolites.

Cytotoxic Tricycloalternarene Compounds from Endophyte Alternaria sp. W-1 Associated with Laminaria japonica.

The chemical investigation of the culture filtrate of endophyte Alternaria sp. W-1 associated with Laminaria japonica provided a new tricycloalternarene compound, 2H-(2E)-tricycloalternarene 12a (1), together with five known analogs: (2E)-tricycloalternarene 12a (2), tricycloalternarene 3a (3), tricycloalternarene F (4), 15-hydroxyl tricycloalternarene 5b (5), and ACTG-Toxin D (6). In vitro cytotoxicity against the human hepatocellular carcinoma cell line SMMC-7721 and the human gastric carcinoma cell line SGC-7901 was evaluated by the MTT method. Compounds 1, 3, and 4 inhibited the growth of SMMC-7721 cells with IC50 values of 49.7 ± 1.1, 45.8 ± 4.6, and 80.3 ± 3.8 µg/mL, respectively, while the IC50 value of the positive control cisplatin was 6.5 ± 0.5 µg/mL. Compounds 3 and 6 also showed moderate anti-proliferation activity against SGC-7901 cells with IC50 values of 53.2 ± 2.9 and 35.1 ± 0.8 µg/mL, respectively, while the IC50 value of cisplatin was 4.5 ± 0.6 µg/mL. Further studies revealed that the in vitro anticancer activity of compound 3 to SMMC-7721 cells was related to G1 phase cell cycle arrest and cell apoptosis, and the induced apoptosis was involved in both the mitochondrial pathway and the death receptor pathway. This is the first report on the anticancer mechanism of tricycloalternarene compounds.

[Chemical constituents of liquid culture of symbiotic Chaetomium globosum ML-4 of oyster and their in vitro antitumor activity].

Isolation and purification of chemical constituents of liquid culture of symbiotic Chaetomium globosum ML-4 of oyster was performed through silica gel column chromatography, gel filtration over Sephadex LH-20, preparative TLC and HPLC. Five compounds were obtained and their structures were determined as chaetoglobosin V(1), chaetoglobosin Vb(2), tyrosol(3), 5-methyluracil(4)and uracil(5), respectively, based on HR-MS and NMR data and comparison with literatures. In vitro cytotoxicity of compounds against human hepatocellular carcinoma cell line SMMC-7721 were measured byMTT method, and results showed that compound 1 could obviously inhibit the proliferation of SMMC-7721 cells with an IC50 value of 60.5 mg•L⁻¹, while the IC50 value of positive control cisplatin was 19.96 mg•L⁻¹. Further studies discovered that compound 1 could lead to G2 phase arrest in SMMC-7721 cells and induce SMMC-7721 cells apoptosis. The ratio of Bcl-2/Bax in SMMC-7721 cells was decreased. The expression of protein Caspases-3,-8,-9 was improved and the expression and phosphorylation level of Akt were reduced. Aforementioned results revealed that in vitro antitumor activity of compound 1 against SMMC-7721 cells were related to G2 phase cell cycle arrest and induced-apoptosis. The induced-apoptosis was involved in both the mitochondrial pathway and the death receptor pathway and connected with activity decline of PI3K/Akt signaling pathway.

A new trichothecene from Myrothecium roridum QDFE005, a symbiotic fungus isolated from Mactra chinensis.

A new trichothecene, 12'-episatratoxin H (1), together with three known analogs: roridin A (2), 16-hydroxyroridin E (3), and roridin E (4), was isolated from the culture broth of the symbiotic fungus Myrothecium roridum QDFE005, which was isolated from Mactra chinensis. Their structures were elucidated on the basis of spectroscopic methods, including 1D and 2D NMR (COSY, HMQC, and HMBC) techniques. Compound 1 exhibited significant cytotoxicity against the human tumor cell lines KB and HepG2 with IC50 values of 1.42 and 2.27 µM, respectively.

Bioactive metabolites from Guignardia sp., an endophytic fungus residing in Undaria pinnatifida.

AIM: To isolate new and/or bioactive constituents from EtOAc extract of liquid culture of endophyte Guignardia sp. from the leaves of Undaria pinnatifida (Harv.) Sur. METHODS: Isolation and purification were performed through silica gel column chromatograph, Sephadex LH-20 and reversed-phase ODS column and the structures of the compounds obtained were identified through a combination of spectral and chemical methods (IR, MS, (1)H and (13)C NMR). In vitro bioactive assays including antifungal activity against three human pathogenic fungi Microsporum canis, Tricophyton rubrum and Epidermophyton floccosom and cytotoxic activity against the human nasopharyngeal epidermoid tumor KB cell line were evaluated. RESULTS: Seven compounds have been obtained from the liquid culture of the title endophyte: ergosterol peroxide (6, 22-diene-5, 8-epidioxyergosta-3-ol) (1), ergosterol (2), cyclo-(Tyr-Leu) (3), cyclo-(Phe-Phe) (4), cyclo-(Val-Leu) (5), cyclo-(Phe-Pro) (6) and cyclo-(Leu-Ile) (7). Compounds 1-3 and 6 inhibited the growth of M. canis with MICs of 10.0, 20.0, 50.0 and 5.0 µg·mL(-1), respectively and compounds 1, 2 and 6 against T. rubrum with MICs of 15.0, 20.0 and 10.0 µg·mL(-1), respectively and 1 and 6 against E. floccosom with MICs of 20.0 and 50.0 µg·mL(-1), respectively. In addition, compounds 1, 3 and 6 exhibited cytotoxic activity against KB cell line with IC(50) of 20.0, 10.0, 10.0 µg·mL(-1), respectively. CONCLUSION: Compounds 1-7 were obtained from Guignardia sp. of U. pinnatifida for the first time, and compounds 1 and 6 had potent cytotoxic and antifungal activity.

Benzophenones from Guignardia sp. IFB-E028, an endophyte on Hopea hainanensis.

The first natural S-containing benzophenone dimer, named guignasulfide (3), was isolated from the culture of Guignardia sp. IFB-E028, an endophytic fungus residing in healthy leaves of Hopea hainanensis. Its structure was determined through correlative analyses of its MS, 1D- and 2D-NMR spectroscopic data. Two other known benzophenone derivatives, monomethylsulochrin and rhizoctonic acid (1 and 2, resp.) were also isolated. Guignasulfide (3) was more active against the human liver cancer cell line HepG2 (IC(50) value: 5.2+/-0.4 microM) than metabolites 1 and 2 (IC(50) values: 63.5+/-0.6 and 60.2+/-0.5 microM); compounds 1-3 showed also moderately inhibitory effects on the human bacterial pathogen Helicobacter pylori with MIC values of 28.9+/-0.1, 60.2+/-0.4, and 42.9+/-0.5 microM, respectively.