Aspochracin

Three new aspochracin-type cyclic tripeptides, sclerotiotides M-O (1-3), together with three known analogues, sclerotiotide L (4), sclerotiotide F (5), and sclerotiotide B (6), were obtained from the ethyl acetate extract of the fungus Aspergillus insulicola HDN151418, which was isolated from an unidentified Antarctica sponge. Spectroscopic and chemical approaches were used to elucidate their structures. The absolute configuration of the side chain in compound 4 was elucidated for the first time. Compounds 1 and 2 showed broad antimicrobial activity against a panel of pathogenic strains, including Bacillus cereus, Proteus species, Mycobacterium phlei, Bacillus subtilis, Vibrio parahemolyticus, Edwardsiella tarda, MRCNS, and MRSA, with MIC values ranging from 1.56 to 25.0 µM.

Three new cyclic peptides including a cyclic tetrapeptide (1), an aspochracin-type cyclic tripeptide sclerotiotide L (2) and a diketopiperazine dimer (3), have been isolated from the ethyl acetate extract of a marine sponge-derived fungus Aspergillus violaceofuscus. The structures of all compounds were unambiguously elucidated on the basis of HRESIMS, 1D and 2D NMR spectroscopic data, MS/MS experiments and chemical methods. Compounds 1 and 3 showed anti-inflammatory activity against IL-10 expression of the LPS-induced THP-1 cells with inhibitory rates of 84.3 and 78.1% respectively at concentration of 10 μM.

Eleven new aspochracin-type cyclic tripeptides, sclerotiotides A-K (1-11), together with three known compounds, JBIR-15 (12), aspochracin (13), and penicillic acid, were isolated from the ethyl acetate extract of the fermentation broth of the halotolerant Aspergillus sclerotiorum PT06-1 in a hypersaline nutrient-rich medium. Their structures were elucidated by spectroscopic analysis and chemical methods. Chemical transformations of 12 and 13 proved that sclerotiotides D-K (4-11) were artifacts probably formed during the fermentation or subsequent isolation steps. All 13 cyclic tripeptides have been evaluated for their antimicrobial and cytotoxic effects. Only sclerotiotides A (1), B (2), F (6), and I (9) and JBIR-15 (12) showed selective antifungal activity against Candida albicans with MIC values of 7.5, 3.8, 30, 6.7, and 30 microM, respectively.