Pithohirolide, an antimicrobial tetradepsipeptide from a fungus Pithomyces chartarum.

Pithohirolide (1), a new depsipeptide, was isolated from an ascomycetous fungus Pithomyces chartarum TAMA 581. The planar structure of 1 was elucidated on the basis of NMR and MS analyses and the absolute configuration was determined by the advanced Marfey's analysis, chiral-phase HPLC analysis, and synthesis of degradation product. Compound 1 possesses a cyclic structure comprising (S)-2-hydroxy-3-phenylpropanoic acid, (S)-3-hydroxy-3-phenylpropanoic acid, (S)-2-hydroxyisovaleric acid, and N-methyl-L-alanine, connected via three ester and one amide linkages. Compound 1 exhibited antimicrobial activity against Staphylococcus aureus and Saccharomyces cerevisiae at MIC 3.1 µg ml-1.

Cordycepamides A-E and cordyglycoside A, new alkaloidal and glycoside metabolites from the entomopathogenic fungus Cordyceps sp.

Five new alkaloidal metabolites cordycepamides A-E (1-5), and one glycoside metabolite cordyglycoside A (6), together with six known compounds (7-12) were isolated from the entomopathogenic fungus Cordyceps sp. (LB1.18060004) from unidentified insect collected in Baoshan City, Yunnan Province, People's Republic of China. The structures were characterized by NMR and HRESIMS spectroscopic analyses. Cordycepamides A and B (1 and 2) were mixtures of two isomers in 5:4 ratio by integration of 1H NMR spectra. In additional, the structure of cordycepamide A (1) was further confirmed by X-ray crystallography as a pair of enantiomers. Absolute configurations of sugar moiety of cordyglycoside A (6) was confirmed by the acid hydrolysis and subsequent HPLC analysis. The isolated metabolites were evaluated for antimicrobial, cytotoxicity, and the DPPH scavenging assay, only 4 showed modest antioxidant effects in the DPPH scavenging assay (IC50 = 51.42 ± 3.08 µM).

Genome mining and biosynthesis of the Acyl-CoA:cholesterol acyltransferase inhibitor beauveriolide I and III in Cordyceps militaris.

Ascomycete fungi Cordyceps are widely used in traditional Chinese medicine, and numerous investigations have been carried out to uncover their biological activities. However, primary researches on the physiological effects of Cordyceps were committed using crude extracts. At present, there are only a few compounds which were comprehensively characterized from Cordyceps, partial owing to the low production. In order to scientifically take advantage of Cordyceps, we used the strategy of genome mining to discover bioactive compounds from Cordyceps militaris. We found the putative biosynthetic gene cluster of the acyl-CoA:cholesterol acyltransferase inhibitor beauveriolides in the genome of C. militaris, and produced the compounds by heterologous expression in Aspergillus nidulans. Production of beauveriolide I and III also was detected in both ferment mycelia and fruiting bodies of C. militaris. The possible biosynthetic pathway was proposed. Our studies unveil the active compounds of C. militaris against atherosclerosis and Alzheimer's disease and provide the enzyme resources for the biosynthesis of new cyclodepsipeptide molecules.

Secondary metabolites from endophytic fungus Chaetomium sp. induce colon cancer cell apoptotic death.

A rare depsipeptide, chaetomiamide A (1), together with two known diketopiperazines (2, 3) were isolated from the cultures of endophytic fungus Chaetomium sp., which was isolated from the root of Cymbidium goeringii. Compound 1 represents a rare skeleton with a 13-membered ring system. It structure was established on the basis of spectroscopic data interpretation. The configuration of 1 was determined by NOESY and Marfey's analysis. These isolates were evaluated for anticancer activity and 3 displayed more potent cytotoxicity than the positive control cisplatin associated with G2/M cell cycle arrest. In addition, 3 induced apoptosis via caspase-3 induction and PARP cleavage, concomitantly with the increase of Bax and decrease of Bcl-2.

Beauvericin K, a New Antifungal Beauvericin Analogue from a Marine-derived Fusarium sp.

Chemical investigation of a Chinese collection of a marine-derived fungus, Fusarium sp., led to the characterization of beauvericin.K, a new analogue of beauvericin. The structure of the new compound was elucidated by detailed spectroscopic analysis, including ID and 2D NMR methods, and HRMS. Beauvericin K showed significant activity against the yeast Candida albicans with an IC50 value of 6.25 üg/mL..

Development of a QuEChERS-based extraction method for the determination of destruxins in potato plants by UHPLC-MS/MS.

Ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) with electrospray ionization has been proposed for the determination of fifteen natural destruxins (A, B, C, D, E, Ed, Ed1, A2, B2, D2, E2, Cl, DesmA, DesmB, and DH-A), secondary metabolites with insecticidal and phytotoxic activities produced by Metarhizium species fungus, which are being studied as biological agents in pest control. Therefore, procedures to control them in the food chain are required, starting with crops. As a consequence, in this study, a simple QuEChERS-based destruxin (dtx) extraction procedure has been developed and validated in four different parts of potato plant (tuber, root, stem and leaves) for the first time. For dtx A, the limits of detection obtained, ranged between 0.5 and 1.3 µg/kg, and for quantification, ranged between 1.7 and 4.2 µg/kg. Precision values were below 8.5%; and in all cases, recoveries were higher than 91%. Finally, the method has been applied in potato samples inoculated by EAMa 01/58-Su strain, where dtxs A and B were detected and quantified. In all cases, dtx B concentration was higher than dtx A.

Potent anti-calmodulin activity of cyclotetradepsipeptides isolated from Isaria fumosorosea using a newly designed biosensor.

Seven cyclotetradepsipeptides, namely beauverolides C (1), F (2), I (3), Ja (4), L (5), M (6), and N (7), were isolated from the entomopathogenic fungus Isaria fumosorosea. The beauverolides were evaluated as potential calmodulin (CaM) inhibitors using the newly designed CaM biosensor hCaM M124C-AF350; these peptides displayed high affinity to the protein with dissociation constants (Kd) ranging from 0.078 µM to 3.44 µM. Beauverolide Ja, the only one containing a tryptophan residue in its structure, showed the highest affinity. The docking study predicted that beauverolides could bind to CaM in the same site of interaction as chlorpromazine, a well-known calmodulin ligand.

Cyclodepsipeptides from the ascocarps and insect-body portions of fungus Cordyceps cicadae.

A new cyclodepsipeptide cordycecin A (1), together with four known ones beauvericin E (2), beauvericin J (3), beauvericin (4), and beauvericin A (5) was isolated from the ascocarps and insect-body portions of fungus Cordyceps cicadae. Their structures were identified by NMR and MS analyses. The absolute configuration of 1 was confirmed by crystal X-ray diffraction. Compounds 2-5 exhibited a significant inhibitory effect on HepG2 and HepG2/ADM cells with IC50 values ranging from 2.40±0.37 to 14.48±1.68 µM. Interestingly, compounds 3-5 showed cytotoxic activity against multiple drug resistant HepG2 cell line (HepG2/ADM) with IC50 value 25-fold more sensitive to doxorubicin.

Discovery and biological activity of new chondramides from Chondromyces sp.

Myxobacteria have proven to be highly valuable sources of natural products, as they produce a variety of secondary metabolites with unique structures and often new modes of action. In this study, high-content screening is demonstrated to be a convenient tool for bioactivity-guided isolation of natural products from crude bacterial extracts. By the application of focused, image-based screens we were able to identify over 30 novel chondramide derivatives from Chondromyces sp. MSr9030, some of which were present in only minute amounts. These cyclic depsipeptides were shown to target actin filaments with a similar binding mode to that of the mushroom toxin phalloidin. Fermentations of the myxobacterial strain were carried out under improved cultivation conditions, and supplementation of the culture broth with potassium bromide afforded the production of brominated analogues that are superior (in terms of biological activity) to all chondramides described to date. Initial biological profiling of 11 new derivatives in comparison to the reference compounds (chondramides A-C) showed that bromo-chondramide C3 and propionyl-bromo-chondramide C3 are the most active in cell-based studies, with GI50 values on human cancer cell lines in the low nanomolar range. Given that these brominated C3 analogues were also less potent on noncancerous human cells (by a factor of 2 to 4 in comparison to cancer cell lines), our results can aid further structure-activity relationship-guided development of chondramides, either as molecular probes or pharmaceutical agents.

Inhibition of hepatitis B virus gene expression & replication by crude destruxins from Metarhizium anisopliae var. dcjhyium.

BACKGROUND & OBJECTIVES: Destruxin A, destruxin B and destruxin E isolated from entomopathogenic fungus Metarhizium anisopliae showed a strong suppressive effect on the replication of hepatitis B virus (HBV) in human hepatoma cells. In this study, the anti-HBV effects of the crude destruxins extracted from M. anisopliae var. dcjhyium were detected both in vitro and in vivo. METHODS: HepG2.2.15 cells were cultured to observe the inhibitory effects of the crude destruxins on the gene expression and replication of HBV by radioimmunoassay detection and real-time quantitative PCR. In vivo, duck HBV (DHBV)-infected ducks were treated with the crude destruxins at 2.0, 4.0, 6.0 µg/kg once a day for 15 days, DHBV DNA was examined by real-time quantitative PCR. RESULTS: The crude destruxins suppressed the replication of HBV-DNA and the production of HBsAg and HBeAg with IC 50 of about 1.2 and 1.4 µg/ml. Transcript of viral mRNA was significantly suppressed by the crude destruxins in HepG2.2.15 cells. In vivo, the duck serum DHBV-DNA levels were markedly reduced in the group of the crude destruxins. INTERPRETATION & CONCLUSIONS: The crude destruxins inhibited the gene expression and replication of HBV both in vitro and in vivo, and their anti-HBV effect was stronger than that with destruxin B. Our results indicate that the crude destruxins from M.anisopliae var. dcjhyium may be potential antivirus agents. Further studies need to be done to confirm these findings.

Beauvericin from the endophytic fungus, Fusarium redolens, isolated from Dioscorea zingiberensis and its antibacterial activity.

From the fungal endophyte, Fusarium redolens Dzf2, isolated from rhizomes of the Chinese medicinal plant Dioscorea zingiberensis, beauvericin was obtained by TLC in combination with bioautographic antibacterial assay. The compound was identified by spectroscopic and physicochemical means. The median effective inhibitory concentration (IC50) values of beauvericin against six test bacteria (Bacillus subtilis, Staphylococcus haemolyticus, Pseudomonas lachrymans, Agrobacterium tumefaciens, Escherichia coli and Xanthomonas vesicatoria) were between 18.4 and 70.7 microg/mL. The beauvericin content of F. redolens Dzf2 mycelia was 9.60 mg/g dw, and beauvericin yield 62.4 mg/L. The obtained results show the potential use of the endophytic fungus for its biological role in providing its host plant with protection, as well as the possible development of beauvericin as an antibacterial.

Hantupeptins B and C, cytotoxic cyclodepsipeptides from the marine cyanobacterium Lyngbya majuscula.

Hantupeptins B (2) and C (3) were isolated, along with the previously reported hantupeptin A (1), from the marine cyanobacterium, Lyngbya majuscula, collected from Pulau Hantu Besar, Singapore. Their structures were elucidated by interpretation of extensive 1D and 2D NMR spectroscopic data. Compounds 2 and 3 are cyclic depsipeptides consisting of five alpha-amino/hydroxy acid residues, including phenyllactic acid, proline, N-methyl-valine, valine, N-methyl-isoleucine, and a beta-hydroxy acid unit with different degrees of unsaturation at the terminal end of each molecule. The absolute configurations of the common amino acids and phenyllactic acid were determined by the advanced Marfey's and chiral HPLC analyses, respectively. The complete stereochemistry of 3-hydroxy-2-methyl-7-octynoic acid moiety in hantupeptin A was elucidated by a combination of homonuclear J-resolved 2D NMR experiments and by Mosher's method. Hantupeptins B and C showed moderate in vitro cytotoxicity when tested against MOLT-4 (leukemic) and MCF-7 (breast cancer) cell lines.

Largamides A-C, tiglic acid-containing cyclodepsipeptides with elastase-inhibitory activity from the marine cyanobacterium Lyngbya confervoides.

Three unusual tiglic acid-containing cyclodepsipeptides, possessing the revised regioisomeric structures for largamides A-C (1-3), have been isolated from the marine cyanobacterium Lyngbya confervoides collected from southeastern Florida. The two-dimensional structures were determined by NMR spectroscopy and the absolute configurations by chiral HPLC analysis of degradation products. Compounds 1-3 are moderate inhibitors of mammalian elastase activity in vitro with IC(50) values ranging from 0.53 to 1.41 microM.

Depsipeptides from microorganisms: a new class of antimalarials.

Depsipeptides are a large group of natural products produced by fungi, actinomycetes, cyanobacteria, higher plants and marine organisms. This family of compounds is known to exhibit a wide range of biological activities, and thanks to the progress of isolation techniques and the advances of methods for structure determination, the numbers of depsipeptides having both unique structures and attractive biological activities are increasing. Many of these compounds have shown a wide range of biological activities, and some are in clinical use or have entered human clinical trials as antibiotic or anticancer agents. However, only a handful of them have been evaluated for their antimalarial activity. This paper aims to review the recent advances in depsipeptides as potential antimalarial compounds.