Revision of the structure of isochaetoglobosin Db based on NMR analysis and biosynthetic consideration.

Isochaetoglobosin Db is a new chaetoglobosin possessing a unique 3,4-substituted pyrrole ring isolated and named by Qiu et al., and it is different from any one of the 14 sub-types in the macrocyclic ring of chaetoglobosins classified in our previous work. Its chemical shift values, coupling constants and biosynthetic consideration implied that the proposed structure of isochaetoglobosin Db was incorrect. In this report, based on detailed NMR data analysis together with biosynthetic consideration, the structure of isochaetoglobosin Db is suggested to be revised to that of penochalasin C. The NMR spectra of penochalasin C measured in the same solvent (DMSO-d 6) as that of isochaetoglobosin Db supported the above conclusion. The results imply that reasonable biosynthetic consideration could complement spectroscopic structural determination, and also support that the 1H-NMR rule of chaetoglobosin summarized in our previous work can provide help for dereplication and rectification.

[Chemical constituents from endophyte Chaetomium globosum in Imperata cylindrical].

Isolation and purification of chemical constituents from solid culture of endophyte Chaetomium globosum in Imperata cylindrical was performed through silica gel column chromatography, gel filtration over Sephadex LH-20 and preparative HPLC. Nine compounds were obtained and their structures were determined as chaetoglobosin F(1), chaetoglobosin Fex(2), chaetoglobosin E(3) cytoglobosin A(4), penochalasin C(S), isochaetoglobosin D (6), N-benzoylphenylalaninyl-N-benzoyphenylalaninate(7), uracil(8) and 5-methyluracil(9), respectively, based on HR-MS and NMR data and comparison with literatures. Compound 7 was isolated from Chaeeomium sp. for the first time. In vitro cytotoxicity of compounds was evaluated using MTT mothed and 1,3,4 and 5 showed inhibition activity to the human cervical carcinoma cell HeLa with IC50 values of 99.43, 23.77, 97.92, 86.25 micromol x L(-1), while positive cotolocisnin Ad apno1ch alse IC50 24.33 micromol x L(-1).

A new cytochalasin from endophytic Phomopsis sp. IFB-E060.

AIM: To study the chemical constituents of the solid culture of the endophyte Phomopsis sp. IFB-E060 in Vatica mangachapoi. METHOD: Isolation and purification were performed through silica gel column chromatography, gel filtration over Sephadex LH-20, ODS column chromatography, and HPLC. Structures of the isolated compounds were elucidated by a combination of spectroscopic analyses (UV, CD, IR, MS, 1D, and 2D NMR). The cytotoxicity of the isolates was evaluated in vitro by the MTT method against the human hepatocarcinoma cell line SMMC-7721. RESULTS: Five compounds were isolated from the solid culture of the endophyte Phomopsis sp. IFB-E060 and their structures were identified as 18-methoxy cytochalasin J (1), cytochalasin H (2), (22E, 24S)-cerevisterol (3), ergosterol (4), and nicotinic acid (5). Compound 1 had an inhibition rate of 24.4% at 10 µg·mL(-1) and 2 had an IC50 value of 15.0 µg·mL(-1), while a positive control 5-fluorouracil had an inhibition rate of 28.7% at 10 µg·mL(-1). CONCLUSION: 18-Methoxy cytochalasin J (1), produced by endophytic Phomopsis sp. IFB-E060, is a new cytochalasin with weak cytotoxicity to the human hepatocarcinoma cell line SMMC-7721.