Α-pyrones and diketopiperazine derivatives from the marine-derived actinomycete Nocardiopsis dassonvillei HR10-5

Three new α-pyrones, nocapyrones E-G (1-3), and three new diketopiperazine derivatives, nocazines A-C (4-6), together with a new oxazoline compound, nocazoline A (7), were isolated from the marine-derived actinomycete Nocardiopsis dassonvillei HR10-5. The new structures of 1-7 were determined by spectroscopic analysis, X-ray single-crystal diffraction, CD spectra, and modified Mosher and Marfey methods. Compounds 1-3 showed modest antimicrobial activity against Bacillus subtilis with MIC values of 26, 14, and 12 μM, respectively.

Glionitrin B, a cancer invasion inhibitory diketopiperazine produced by microbial coculture

A new diketopiperazine, glionitrin B (1), was produced using a microbial coculture of the fungus Aspergillus fumigatus KMC-901 and the bacterium Sphingomonas sp. KMK-001 that were isolated from acidic coal mine drainage. The structure of 1 was determined to be (3S,10aS)-dithiomethylglionitrin A. This structure was determined by the analyses of extensive NMR data and the circular dichroism spectra of the natural product and a semisynthetic compound derived from glionitrin A. In contrast to glionitrin A (2), glionitrin B (1) is not cytotoxic against the human prostate cancer cell line DU145. However, compound 1 caused suppression of DU145 cell invasion, producing 46% inhibition at 60 μM.

Itaconic acid derivatives and diketopiperazine from the marine-derived fungus Aspergillus aculeatus CRI322-03

Three metabolites, pre-aurantiamine (1), (-)-9-hydroxyhexylitaconic acid (4) and (-)-9-hydroxyhexylitaconic acid-4-methyl ester (5), together with two known compounds, paraherquamide E (6) and secalonic acid D (7), were isolated from the marine-derived fungus, Aspergillus aculeatus.

Protuboxepins A and B and protubonines A and B from the marine-derived fungus Aspergillus sp. SF-5044

Two new oxepin-containing (1 and 2) and two diketopiperazine-type alkaloids (3 and 4) have been isolated from an EtOAc extract of the marine-derived fungus Aspergillus sp. SF-5044. The structures of these metabolites were determined through analysis of NMR and MS data, along with Marfey's method. Compound 1 showed weak growth inhibitory activity against a small panel of cell lines.

7-O-Methylvariecolortide A, a new spirocyclic diketopiperazine alkaloid from a marine mangrove derived endophytic fungus, Eurotium rubrum

A new spirocyclic diketopiperazine alkaloid, namely, 7-O-methylvariecolortide A (1), together with recently reported known compounds variecolortides A-C (2-4), were isolated and identified from the liquid fermentation cultures of Eurotium rubrum, an endophytic fungus that was isolated from the inner tissue of the stems of the mangrove plant Hibiscus tiliaceus. The structures of these compounds were determined by extensive analyses of their spectroscopic data.

Diketopiperazines produced by endophytic fungi found in association with two Asteraceae species

Diketopiperazine (DKP) derivatives, named colletopiperazine, fusaperazine C and E as well as four known DKPs were isolated from cultures of Colletotrichum gloeosporioides, Penicillium crustosum, both endophytic fungi isolated from Viguiera robusta, and a Fusarium spp., an endophyte of Viguiera arenaria, respectively. Their structures were established on the basis of their spectroscopic data. Conformational analysis of two known DKPs showed that folded conformations were as energetically stable as the extended one.

Thiodiketopiperazines produced by the endophytic fungus Epicoccum nigrum

Thirteen new thiodiketopiperazines, epicoccin I (1), ent-epicoccin G (2), and epicoccins J-T (3-13), together with six known diketopiperazines (14-19), have been isolated from the endophytic fungus Epicoccum nigrum. The structures of 1, 2, and 10 were confirmed by X-ray crystallography, and the absolute configurations of 2, 4, 6, and 8 were assigned using Moshers' method. Compounds 2, 6, 12, and 17 showed potent activities in vitro against the release of beta-glucuronidase in rat polymorphonuclear leukocytes induced by platelet-activating factor, with IC(50) values of 3.07, 4.16, 4.95, and 1.98 microM, respectively. None of the 19 compounds exhibited detectable cytotoxic activities toward six tumor cell lines (A549, Be-l7402, BGC-823, HCT-8, HCT-116, and A2780) in the MTT assay.

New angucyclines and antimicrobial diketopiperazines from the marine mollusk-derived actinomycete Saccharothrix espanaensis An 113

Two new angucyclines, saccharothrixmicines A (2) and B (3), together with three known diketopiperazines 4-6 were isolated from the actinomycete Saccharothrix espanaensis An 113 associated with the marine mollusk Anadara broughtoni. Their structures were determined by HRESI-MS and 1D and 2D NMR. Compounds 2 and 3 differ in aglycone and glycosidic bond type. 2 is an alpha-L-6-deoxyaltrose-phenylglycoside of a benz[a]anthraquinone aglycone, while 3 is an O-glycoside of the same sugar linked to C-7 of the known angucyclinone (1). A saccharothrixmicine-containing fraction exhibited activity towards Candida albicans and Xanthomonas sp. pv. badrii whereas the diketopiperazines showed antibiotic activities against Vibrio alginolyticus and Vibrio parahaemolyticus.

Assessing the trypanocidal potential of natural and semi-synthetic diketopiperazines from two deep water marine-derived fungi

Human African trypanosomiasis (HAT, commonly known as African sleeping sickness) is categorized as a neglected disease, as it afflicts >50,000 people annually in sub-saharan Africa, and there are few formal programs in the world focused on drug discovery approaches for this disease. In this study, we examined the crude extracts of two fungal strains (Aspergillus fumigatus and Nectria inventa) isolated from deep water sediment which provided >99% growth inhibition at 1microg/mL of Trypanosoma brucei, the causative parasite of HAT. A collection of fifteen natural products was supplemented with six semi-synthetic derivatives and one commercially available compound. Twelve of the compounds, each containing a diketopiperazine core, showed excellent activity against T. brucei (IC(50)=0.002-40microM), with selectivity over mammalian cells as great as 20-fold. The trypanocidal diketopiperazines were also tested against two cysteine protease targets Rhodesain and TbCatB, where five compounds showed inhibition activity at concentrations less than 20microM. A preliminary activity pattern is described and analyzed.

Two diketopiperazines from Acanthopanax senticosus Harms

From the dried aerial parts of Acanthopanax senticosus, two new diketopiperazines, eleutherazines A (1) and B (2), were isolated. Their structures were elucidated on the basis of chemical and spectroscopic methods.

Diketopiperazines from the Cordyceps-colonizing fungus Epicoccum nigrum

New diketopiperazines, epicoccins E-H (1-4) and diphenylalazines A (5) and B (6), have been isolated from the solid-substrate fermentation culture of the Cordyceps-colonizing fungus Epicoccum nigrum. The structures of 1-6 were determined primarily by NMR experiments, and the structure of 1 was confirmed by X-ray crystallography. The absolute configurations of 3 and 5 were assigned using the modified Mosher (3) and Marfey's (5) methods, respectively. Compounds 3-5 showed inhibitory effects on HIV-1 replication in C8166 cells.

Glionitrin A, an antibiotic-antitumor metabolite derived from competitive interaction between abandoned mine microbes

The nutrient conditions present in abandoned coal mine drainages create an extreme environment where defensive and offensive microbial interactions could be critical for survival and fitness. Coculture of a mine drainage-derived Sphingomonas bacterial strain, KMK-001, and a mine drainage-derived Aspergillus fumigatus fungal strain, KMC-901, resulted in isolation of a new diketopiperazine disulfide, glionitrin A (1). Compound 1 was not detected in monoculture broths of KMK-001 or KMC-901. The structure of 1, a (3S,10aS) diketopiperazine disulfide containing a nitro aromatic ring, was based on analysis of MS, NMR, and circular dichroism spectra and confirmed by X-ray crystal data. Glionitrin A displayed significant antibiotic activity against a series of microbes including methicillin-resistant Staphylococcus aureus. An in vitro MTT cytotoxicity assay revealed that 1 had potent submicromolar cytotoxic activity against four human cancer cell lines: HCT-116, A549, AGS, and DU145. The results provide further evidence that microbial coculture can produce novel biologically relevant molecules.

[Chemical constituents from the mycelia of Alternaria sp. YD-01]

To study the chemical constituents of the mycelia of the Endophytes YD-01, 2, 3-dihydroxy-quinoline-4-O-beta-D-glucopyranoside (1), 3-methyl-pyrrol opiperazine-2, 5-dione (2) and naringenin (3) were isolated from its acetone extracts by using silica gel column chromatography and Sephadex LH-20. Their structures were elucidated on the basis of spectroscopic analysis. Compound 1 is a new compound.

Pestalazines and pestalamides, bioactive metabolites from the plant pathogenic fungus Pestalotiopsis theae

Pestalazines A (1) and B (2), two new diketopiperazine heterodimers, and pestalamides A-C (3-5), three new amides, have been isolated from cultures of the plant pathogenic fungus Pestalotiopsis theae. The structures of these compounds were elucidated mainly by NMR spectroscopy. The absolute configurations of 1 and 2 were determined using Marfey's method on their acid hydrolysates and by comparison of their CD spectra with that of a model compound. Compounds 1, 3, and 6 displayed inhibitory effects on HIV-1 replication in C8166 cells. Compound 3 also showed potent antifungal activity against Aspergillus fumigatus.

A new diketopiperazine alkaloid isolated from an algicolous Aspergillus flavus strain

A new diketopiperazine alkaloid containing the uncommon amino acid L-7, 9-dihydroxy-8-methoxyphenylalanine (1), has been isolated from the algicolous Aspergillus flavus strain. The structure of 1 including the absolute stereochemistry was determined by spectroscopic data and chemical means. Compound 1 showed weak cytotoxicity against HL-60 cell lines with an IC50 value of 36.5 microg/ml.

Two diketopiperazines from marine fungus Gliocladium sp. YUP08

Two new diketopiperazines, PJ147 (1) and PJ157 (2), were isolated from the mycelium of a fungus, Gliocladium sp. YUP08, which was separated from sea mud collected in Rushan, Shandong, China. Their structures were elucidated by spectroscopical and chemical methods.