One new cytochalasin metabolite isolated from a mangrove-derived fungus Daldinia eschscholtzii HJ001

One new cytochalasin metabolite [11]-cytochalasa-5(6),13-diene-1,21-dione-7,18-dihydroxy-16,18-dimethyl-10-phenyl-(7S*,13E,16S*,18R*) (1), together with three known compounds (2–4) were obtained from the EtOAc extract of the endophytic fungus Daldinia eschscholtzii HJ001 isolated from the mangrove Brguiera sexangula var. rhynchopetala collected in the South China Sea. Their structures were elucidated by the detailed analysis of comprehensive spectroscopic data. Compounds 1 and 2 were evaluated for their antibacterial and cytotoxic activities.     

The isolation and structure of a toxic metabolite from Diplodia maydis (Berk.) Sacc.

Diplodiatoxin is a toxic metabolite of Diplodia maydis (Berk.) Sacc. Studies are described which have led to the structure as shown in 1a.     

Abyssomicin E, a highly functionalized polycyclic metabolite from Streptomyces species

Abyssomicin E (1), a new polycyclic metabolite with a C19 skeleton, was isolated from Streptomyces sp. (HKI0381). Its chemical structure was determined by comprehensive NMR and MS spectroscopic analyses. For the first time in this recently discovered class of compounds, the absolute stereochemistry was directly established by subsequent single-crystal X-ray diffraction study using anomalous dispersion with copper radiation.     

Cephalimysin A, a potent cytotoxic metabolite from an Aspergillus species separated from a marine fish

Cephalimysin A (1) was isolated from a strain of Aspergillus fumigatus originally separated from the marine fish Mugil cephalus, and its absolute stereostructure was elucidated on the basis of spectroscopic analyses using 1D and 2D NMR techniques and some chemical transformations including the modified Mosher’s method. This compound exhibited significant cytotoxicity against cultured P388 cells and HL-60 cells.     

The structure of the major urinary metabolite of prostaglandin E2 in man

This letter reports the structure of the major urinary metabolite formed from prostaglandin E2 (PGE2) in humans. Radiolabeled PGE2 was injected intravenously into male subjects. 50% of the radioactivity was recovered in urine during the first 5 hours and less than 3% during the following 12 hours. The urine was acidified, and this extract was subjected to reversed-phase partition chromatography. Formation of the major metabolite (depicted stereochemically in the text) from PGE2 involved 4 steps of reactions: 1) dehydrogenation of the alcohol group in the side chain; 2) reduction of the trans double bond; 3) 2 steps of beta oxidation; and 4) delta oxidation.     

Ultrasound-assisted conversion of toxic beta-asarone into nontoxic bioactive phenylpropanoid: isoacoramone, a metabolite of Piper marginatum and Acorus tararinowii

Ultrasound-assisted synthesis of bioactive isoacoramone (1), a metabolite of Piper marginatum and Acorus tararinowii, has been achieved by oxidation of toxic beta-asarone (2) with potassium permanganate/copper sulphate/alumina into asaronaldehyde (3) followed by treatment with ethylmagnesium iodide to provide 1-(2,4,5-trimethoxy)phenyl-1-propanol (4) which upon further oxidation with potassium permanganate/copper sulphate afforded 1 in 64% yield (overall 32%). Toxicological evaluation of 1 reveals it to be nontoxic up to 60 mg/kg b.w.     

Structure and absolute stereochemistry of phormidolide,a new toxic metabolite from the marine cyanobacterium Phormidium sp

The extract from a laboratory culture of an Indonesian isolate of the cyanobacterium Phormidium sp. displayed inhibitory activity in a Ras-Raf protein interaction assay. Assay-guided fractionation led to the isolation of both active and inactive materials of novel structure. The major inactive metabolite, phormidolide, was nevertheless highly toxic to brine shrimp (LC(50) = 1.5 microM), and hence, its structure was elucidated using various spectroscopic methods, primarily NMR. A series of partial structures were developed from standard experiments and then assembled using GHMBC, 2D INADEQUATE, and ACCORD-ADEQUATE data obtained on a (13)C-enriched sample. The relative stereochemistry at phormidolide's 11 chiral centers was established using the J-based configuration analysis method in concert with the G-BIRD(R)-HSQMBC NMR experiment. Absolute stereochemistry was determined on a bis-acetonide derivative using the variable temperature Mosher ester method. The robust number of NMR restraints provided from determination of most homonuclear and heteronuclear coupling constants in phormidolide, along with an abundance of NOE information, allowed construction of a refined lowest energy three-dimensional structure in Macromodel. Phormidolide is one of only a few macrolide-type natural products to be reported from marine cyanobacteria.     

Extracellular synthesis of silver bionanoparticles from Aspergillus clavatus and its antimicrobial activity against MRSA and MRSE

New enzymatic approaches using bacteria and fungi for the synthesis of nanoparticles in both intra- and extracellular are playing an advanced key role in pharmacotherapeutics. In the present study we have reported on the use of fungus Aspergillus clavatus for the extracellular synthesis of bionanoparticles from silver nitrate (AgNO₃) solution. The bionanoscale particles were characterized by UV–visible spectroscopy, thin layer chromatography, atomic force microscopy (AFM) and FTIR. The synthesized bionanoscale particle showed a maximum absorption in the visible region of 420 nm. The AFM study of bionanoscale particle ranged in the size of 550–650 nm. The analysis was carried out by TLC and FTIR to identify the biomolecules responsible for the bioreduction of silver ion and capping of the bioreduced silver nanoparticles. The present study analyzes the antimicrobial activity of the silver nanoparticles synthesized from A. clavatus against MRSA and MRSE, which showed the maximum activity against MRSA, followed by MRSE.     

Homarine, a common metabolite in edible Mediterranean molluscs: occurrence, spectral data and revision of a related structure

Homarine was isolated from nine edible species of marine molluscs belonging to classes Gastropoda, Bivalvia, and Cephalopoda. A thorough chromatographic, NMR and MS study provided evidence that homarine is a common and abundant metabolite of all these species. This study casts doubt on a previous assertion that 1,1'-dimethyl-[2,2']-bipyridinium is a metabolite of the Bivalve Callista chione.     

Design and efficient synthesis of novel haptens and complete antigens for the AOZ, a toxic metabolite of furazolidone

A good strategy was brought forward for designing efficient haptens and complete antigens for 3-amino-2-oxazolidinone (AOZ). Haptens designed newly were achieved facilely in good yield by using LiCI-N(Et)_3 as new catalysis system,the structure of which was elucidated by spectroscopy analysis,such as NMR and MS.Novel antigens for AOZ were prepared successfully by convenient active ester method.The ratios of haptens 3 and 4 to carrier proteins were proven respectively as 41:1(5a),39:1(6a),11:1(5b) and 9:1(6b) by trinitrobenzene sulfonic acid(TNBS) method.The results of indirect competitive ELISA (ic-ELISA) of antiserums indicated that the haptens with a short unsaturated side chain can evoke specific immune response effectively.