Hofmannolin, a cyanopeptolin from Scytonema hofmanni PCC 7110

Two depsipeptide metabolites, scyptolin A and B, were reported recently from the axenically grown terrestrial cyanobacterium Scytonema hofmanni PCC 7110. A related, novel depsipeptide was isolated from this Scytonema and designated hofmannolin. The amino acid analysis in context with infrared, mass and 1H/13C-NMR spectroscopies revealed a cyclic depsipeptide structure of M(r) 1073 belonging to the class of cyanopeptolins. Two peculiar features distinguish hofmannolin from other cyanopeptolins: O-methylated tyrosine forms the sixth moiety from the amino terminus, and the N-terminus is blocked by 2-hydroxy-3-methyl-valeric acid, a residue that has not yet been reported as a component in other cyanopeptolins. Preliminary assays of peptidase inhibitory and antimicrobial activities suggested negligible bioactivities for hofmannolin.     

Scyptolin A and B, cyclic depsipeptides from axenic cultures of Scytonema hofmanni PCC 7110.

Two novel cyclic depsipeptides were isolated from axenic cultures of the terrestrial cyanobacterium Scytonema hofmanni PCC 7110 and designated scyptolin A and B. Amino acid analyses in context with mass and 1H/13C NMR spectroscopies revealed a composition typical for heterologous cyanopeptolins but containing the uncommon residue 3'-chloro-N-methyl-Tyr (cmTyr) and a unique sidechain. Scyptolin A and B both consist of the N-acylated peptide But(1)-Ala(2)-Thr(3)-Thr(4)-Leu(5)-Ahp(6) (3-amino-6-hydroxy-2-oxo-1-piperidine)-Thr(7)-cmTyr(8)-Val(9), which forms a 19-membered ring by esterification of the carboxyl of Val(9) with the hydroxyl of Thr(4). In scyptolin B, the hydroxyl of the Thr(3) residue is additionally esterified with N-butyroyl-Ala. Both scyptolin A and B exhibit selective inhibition of porcine pancreatic elastase in vitro with IC(50) values of 3.1 microg/ml.     

Isolation and structure determination of a cholesterol esterase inhibitor from Ganoderma lucidum

Bioassay-guided fractionation of methanol extract of Ganoderma lucidum gave a pure cholesterol esterase inhibitor. On the basis of spectroscopic analysis and comparison with data from the literature, its structure was identified as 5alpha,8alpha-epidioxyergosta-6,22-dien-3beta-ol (compound I). Compound (I) inhibited cholesterol esterase with an IC50 value of 42 micronM. A Lineweaver-Burk plot revealed that the compound (I) is a noncompetitive inhibitor. Findings from this study suggest that compound (I) may be the active principle of the hypocholesterolemic effect of Ganoderma lucidum.     

Isolation and structure determination of triterpenes from Iris tectorum

Four iridal-type triterpenoids, two of which were new compounds, have been isolated from rhizomes of Iris tectorum Maxim. Their structures were determined by 1D and 2D NMR spectroscopy and ESI-MS spectrometry. The compounds were identified as the iritectols A and B, and the known iridobelamal A and isoiridogermanal. The presence of epoxide and tetrahydrofuran functions are not common in previously isolated iridal-type triterpenoids.     

Isolation and structure elucidation of isoaltenuene,a new metabolite ofAlternaria alternata

Mycotoxin Research - Isoaltenuene, a previously unknownAlternaria metabolite has been isolated from a rice culture ofAlternaria alternata and purified by semipreparative HPLC. The assigned...     

Isolation and structure determination of algicidal compounds from Ulva fasciata

Thirty-seven species of seaweeds including 10 Chlorophyta, 13 Phaeophyta, and 14 Rhodophyta collected from the coast of Nagasaki Prefecture, Japan, were screened for algicidal activity against the red-tide phytoplankton Heterosigma akashiwo. The green alga Ulva fasciata (Ulvaceae, Chlorophyta) showed the strongest algicidal activity among the seaweeds tested. Bioassay-guided fractionation of the methanol extract of U. fasciata led to isolation of three algicidal compounds whose structures were determined to be hexadeca-4,7,10,13-tetraenoic acid (HDTA), octadeca-6,9,12,15-tetraenoic acid (ODTA), and alpha-linolenic acid on the basis of spectroscopic information. These polyunsaturated fatty acids (PUFAs) showed potent algicidal activity against H. akashiwo (LC(50) 1.35 microg/ml, 0.83 microg/ml, and 1.13 microg/ml for HDTA, ODTA, and alpha-linolenic acid, respectively), and the result demonstrated the potential of these PUFAs for practical harmful algal bloom control.     

Isolation and X-ray structure determination of a neolignan from Clerodendron inerme seeds

A new neolignan, 5,8-epoxy-6,7-dimethyl 2′,3′,2″,3″-dimethylene dioxy-4′,1″-dimethoxy-1,2:3,4-dibenzo-1,3-cyclooctadiene, from the petrol extract of Clerodendron inerme seeds, was characterized by spectroscopic and X-ray crystallographic methods. This compound makes up ca 5% by wt of the seeds.     

Isolation and structure determination of a novel spiro-gamma-lactam, spiro-arogenate

The eucaryotic microorganism, Neurospora crassa, is able under specified conditions (Zamir, L.O., Jung, E., and Jensen, R.A. (1982) J. Biol. Chem. 258, 6492-6496) to synthesize a cyclohexadienyl derivative of prephenic acid having the novel structure of a spiro-gamma-lactam. This L-gamma-(spiro-4-hydroxy-2,5-cyclohexadienyl)-pyroglutamate is herein given the trivial name, spiro-arogenate, to indicate its close relationship to the amino acid, L-arogenate. Spiro-arogenate is quantitatively converted to phenylalanine at mildly acidic pH and can be converted to arogenate by boiling at basic pH. The structure of spiro-arogenate was established through the application of spectroscopic techniques (ultraviolet, 1H-NMR, 13C-NMR, and mass spectrometry). The 1H-NMR and 13C-NMR spectra of spiro-arogenate isolated as the natural product conformed to the spectrum of spiro-arogenate prepared by chemical synthesis by S. Danishefsky and co-workers (Danishefsky, S., Morris, J., and Clizbe, L.A. (1981) J. Am. Chem. Soc. 103, 1602-1604). Circular dichroism established the S configuration of the asymmetric carbon at C-8 of spiro-arogenate.     

Isolation of a growth and mitosis inhibitory peptide from mouse liver

The isolation of a liver peptide that inhibits the growth, mitosis rate and thymidine incorporation in regenerating liver is described. The peptide has the structure Pyroglu-gln-gly-ser-asn, and the deamidated forms are also active. The peptide probably belongs to a class of growth inhibitors with a high degree of tissue specificity. Two such peptides have previously been isolated from the epidermis (Reichelt et al. 1987) and from colonic tissue (Skraastad et al. 1987).     

Isolation of a growth and mitosis inhibitory peptide from mouse liver

The isolation of a liver peptide that inhibits the growth, mitosis rate and thymidine incorporation in regenerating liver is described. The peptide has the structure Pyroglu-gln-gly-ser-asn, and the deamidated forms are also active. The peptide probably belongs to a class of growth inhibitors with a high degree of tissue specificity. Two such peptides have previously been isolated from the epidermis (Reichelt et al. 1987) and from colonic tissue (Skraastad et al. 1987).     

Stereospecific synthesis of a GS 4104 metabolite: determination of absolute stereochemistry and influenza neuraminidase inhibitory activity.

The total synthesis for the determination of the absolute stereochemistry of a GS 4104 metabolite 3 is described. In addition, the influenza neuraminidase inhibitory activity of 3 and related intermediates are reported.     

4,8-anhydro-N-acetylneuraminic acid. Isolation from edible bird's nest and structure determination

A new, sialic-acid-derived compound was isolated from the acid hydrolysate of edible bird's nest by ion-exchange chromatography. Combined use of mass spectroscopy and 1H- and 13C-NMR spectroscopy established that it is the 4,8-anhydro derivative of N-acetylneuraminic acid and that in solutions it exists in two tautomeric forms. The formation of the new compound supports and earlier findings that in the glycoprotein of edible bird's nest at least a portion of N-acetylneuraminic acid is acetylated at HO-4.     

Isolation of the protein tyrosine phosphatase 1B inhibitory metabolite from the marine-derived fungus Cosmospora sp. SF-5060

In the course of bioassay-guided study on the EtOAc extract of a culture broth of the marine-derived fungus Cosmospora sp. SF-5060, aquastatin A (1) was isolated as a protein tyrosine phosphatase 1B (PTP1B) inhibitory component produced by the fungus. The compound was isolated by various chromatographic methods, and the structure was determined mainly by analysis of NMR spectroscopic data. Compound 1 exhibited potent inhibitory activity against PTP1B with IC₅₀ value of 0.19 μM, and the kinetic analyses of PTP1B inhibition by compound 1 suggested that the compound is inhibiting PTP1B activity in a competitive manner. Aquastatin A (1) also showed modest but selective inhibitory activity toward PTP1B over other protein tyrosine phosphatases, such as TCPTP, SHP-2, LAR, and CD45. In addition, the result of hydrolyzing aquastatin A (1) suggested that the dihydroxypentadecyl benzoic acid moiety in the molecule is responsible for the inhibitory activity.     

Isolation and characterization of a novel endogenous inhibitor of the proteasome

A novel endogenous inhibitor of the proteasome (high molecular weight multicatalytic protease) has been isolated and characterized from human erythrocytes. After purification by ion-exchange and sizing chromatography, the inhibitor displayed a native molecular mass of approximately 200 kDa and contained a single subunit of 50 kDa with an isoelectric point of 6.9. Although the inhibitor noncompetitively blocks proteolysis of [methyl-14C]-alpha-casein (Ki = 7.1 x 10(-8) M) and inhibits hydrolysis of Suc-Leu-Leu-Val-Tyr-AMC, it did not affect hydrolysis of other peptide substrates, such as MeOSuc-Phe-Leu-Phe-MNA and Z-Ala-Arg-Arg-MNA. To further characterize the 50-kDa inhibitor, a monoclonal antibody (MI-8) was generated that showed specific binding upon Western blot analysis of both native PAGE and SDS-PAGE. Immunoprecipitation with MI-8 specifically removed inhibitor activity against the proteasome. The 50-kDa inhibitor is distinct from a previously described 40-kDa inhibitor of the proteasome (Murakami, K., & Etlinger, J.D. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 7588-7592) on the basis of lack of cross-reactivity with MI-8 and dissimilar peptide digest patterns. It is suggested that these endogenous inhibitors may have a role in ATP/ubiquitin-dependent proteolysis and/or other cellular functions involving this protease.     

Isolation and structure determination of a paralytic peptide from the hemolymph of the silkworm, Bombyx mori.

A peptide with paralytic activity in larvae of the silkworm, Bombyx mori, was isolated from its hemolymph. Purification procedures consisted of extraction with 50% acetone, Vydac C4 reversed-phase cartridge elution and 4 steps of reversed-phase HPLC. Injection of the purified peptide into 4th instar B. mori larvae caused rapid and rigid paralysis for 2 min at a dose of 3.4 ng/larva. This paralytic peptide consists of 23 amino acid residues containing 2 cysteines with an intra-disulfide bond. The complete amino acid sequence is: H-Glu-AsnPhe-Val-Gly-Gly-Cys-Ala-Thr-Gly-Phe-Lys-Arg-Thr-Ala-Asp-G ly-Arg-Cys-Lys-Pro-Thr-Phe-OH. The relationship between structure and the biologic activity of synthetic analogs indicated that the entire amino acid sequence and the intra-disulfide bond were necessary for biological activity.     

Characterization of bioactive glycolipids from Scytonema julianum (cyanobacteria)

Cyanobacteria serve as a rich source of novel bioactive metabolites. Few studies on glycolipids reported them as having specific biological activities. In this study, total lipids of Scytonema julianum, a filamentous cyanobacterium isolated from a Greek cave, were separated into neutral and phospho- and glycolipids, and the latter were further fractionated by high-performance liquid chromatography (HPLC). Each glycolipid fraction was tested in vitro for its ability to inhibit platelet-activating factor (PAF)- and thrombin-induced washed rabbit platelet aggregation and/or to cause platelet aggregation. The structures of the most active fractions were elucidated by biological assays, by chemical determinations and identified by electrospray mass spectrometry. One fraction was a potent inhibitor of PAF-induced platelet aggregation. Structural studies of this fraction indicated the existence of a phosphoglyco-analog of acyl-sphingosine. Two fractions causing platelet aggregation were detected and identified as phosphoglycolipids. The first one was identified as a phosphoglyco-analog of acyl-acetylated sphingosine and the second one as a glyco-analog of phosphatidylglycerol. The presence of the above bioactive compounds demonstrates new types of lipids in cyanobacteria in regard to the structure and biological activity. In addition, the identified bioactive lipids may contribute to the allergic character of cyanobacteria.