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At least 847 records · Page 47Linked to original sources
PubMed1990

Chlamydosporol, a new metabolite from Fusarium chlamydosporum.

Extracts of rice on which an isolate of Fusarium chlamydosporum had been cultured were toxic to brine shrimps. The toxic fraction was purified by flash chromatography to give two compounds which were identified by UV, IR, NMR and mass spectroscopy at the 6 alpha and 6 beta isomers of 5-hydroxy-4-methoxy-6,8a-dimethyl-6,7-dihydro-2H, 8aH-pyrano[2,3-b]pyran-2-one. These lactones for which the name chlamydosporol is proposed have not been reported previously. When tested in brine shrimp and HeLa cell assays, the LC50 concentration for a mixture of the isomers was approximately 400 micrograms/ml in both systems.

Animals↗
PubMed1985

Aflatoxin formation and the dual phenomenon in Aspergillus flavus Link.

Trials were performed with three aflatoxin-forming isolates of Aspergillus flavus from formic acid-treated materials containing aflatoxin, one A. flavus strain isolated from mouldy barley kept for two months in an anaerobic jar and one non-toxic A. flavus strain from the culture collection at our Department. The non-toxic strain and one aflatoxin producer were cultured in salts-sugar-asparagine substrate (SLM) for aflatoxin production and in a specially prepared grass substrate (GS). Formic acid and ammonium formate were added to both substrates, and sucrose in a low amount was added to the grass substrate. The aflatoxin-forming isolate segregated on the grass substrate into two different lines, one with high aflatoxin production and one with very low aflatoxin-forming ability, higher growth rate and reduced sporulation, on the SLM substrate. When exposed to sucrose in grass substrate and ammonium formate in SLM, one toxic and one non-toxic strain were provoked to increased aflatoxin formation. The A. flavus isolate from the anaerobic jar also segregated on the grass substrate, and these segregants were more sensitive to a high dose of formic acid. In these A. flavus strains three seems to be a continuous variation between different lines, depending on cultivation conditions. In the two aflatoxin-forming isolates left, such segregation tendencies were not very marked on any substrate.

Aflatoxin B1↗
PubMed1986

Substrate depletion during formation of aflatoxin and kojic acid on corn inoculated with Aspergillus flavus.

Depletion of sugar and starch carbon sources and concomitant formation of secondary fungal metabolites, aflatoxin and kojic acid, were examined in growing corn inoculated with Aspergillus flavus. Kernels from control and inoculated ears were removed and analyzed after 16, 24, 48, 96 and 168 hrs. Reducing sugars were not significantly different for inoculated and control non-inoculated samples, but after 168 hrs (seven days) starch content was 20% lower in inoculated than in control samples. Kojic acid was detected before aflatoxins formed. Kojic acid, the oxidized product of kojic acid, and aflatoxin were all present in samples two days from inoculation. The formation of this oxidation product may influence toxin levels.

Aflatoxins↗
PubMed1992

Isolation, identification and biological activity of chlamydosporol from Fusarium culmorum HM-8.

An isolate of Fusarium culmorum (W. G. Smith), Sacc. HM-8 from a scabby wheat kernel sample from England produced a novel toxin when grown in culture on rice. This toxin, which was given the trivial name of HM-8, was purified, its toxic properties demonstrated and its structure determined by spectroscopic methods. Subsequent to preliminary reports of our findings, two other laboratories have independently isolated the same substance from F. chlamydosporum and F. acuminatum, and demonstrated the same structure by spectroscopic methods and X-ray crystallography. Identity of the metabolite from F. culmorum HM-8 with the published structure is based on (1) identical elemental composition derived from both elemental analysis and high resolution mass spectrometry in electron impact and fast atom bombardment modes, (2) comparable melting point and chromatographic properties, and (3) the presence of characteristic absorption bands in the infrared, ultraviolet, and nuclear magnetic resonance (proton and carbon-13) spectra. Because both laboratories which subsequently isolated this metabolite have used the name chlamydosporol, it is being adopted here. The mass spectral properties of chlamydosporol are described. The derivative 8-O-acetylchlamydosporol was prepared and characterized. Chlamydosporol caused food refusal and weight loss in rats, cytotoxic effects to cultured mouse and human fibroblast cells at concentrations of 2.5 micrograms/ml and 7.5 micrograms/ml, respectively, and mortality to chick embryos (10 to 70%) over a concentration range from 0.5 mg to 4 mg per egg.

Animals↗
PubMed1985

Mycotoxins producing fungi and mycoflora of air-dust from Taif, Saudi Arabia.

Using the dilution plate method, 70 species and 31 genera were collected from 20 dust samples on glucose (28 genera and 64 species) and cellulose Czapek's agar (22 genera and 46 species) at 28 degrees C. The most common fungi were Aspergillus niger, A. flavus, A. flavus var. columnaris, Phoma glomerata, Fusarium oxysporum, Penicillium chrysogenum and Mucor racemosus; and A. nidulans, Phoma humicola, Drechslera spicifera and Stachybotrys chartarum on the two media, respectively. Toxicity test showed that about 85% of the isolates tested were toxic to brine shrimp (Artemia salina). Thin layer chromatographic analysis revealed that 13 out of 23 toxic isolates produced known mycotoxins. Toxins identified were: aflatoxins B1 and B2, Kojic acid and trichodermine.

Aflatoxin B1↗
PubMed1984

Pharmacological analysis of the central cardiovascular effects of four GABA analogues.

The central cardiovascular effects of 4 structural analogues of GABA were investigated. The drugs were injected intracerebroventricularly (i.c.v.) in cumulative doses into pentobarbital-anaesthetized normotensive rats. Muscimol (0.01-10 micrograms/kg), THIP (0.01-100 micrograms/kg), kojic amine (0.1-100 micrograms/kg) and isoguvacine (0.1-100 micrograms/kg) produced dose-dependent hypotension and bradycardia. The maximal fall in the mean blood pressure was of about 35% of the initial values. These effects appears to be of central origin since the intravenous (i.v.) injection of the same doses of the drugs did not produce any similar cardiovascular modifications. The hypotensive effects of muscimol and kojic amine were antagonized partly by i.c.v. bicuculline. The combination of bicuculline and kainic acid almost completely prevented the blood pressure lowering effects of muscimol, kojic amine and isoguvacine. THIP however was only slightly antagonized by bicuculline and kainic acid. Atropine i.v. also prevented partly the cardiovascular effects of all these drugs. Thus, the mechanisms of the central cardiovascular actions of GABA analogues appear to be more complex than expected and variable from one drug to another. The involvement of GABA receptors of the A and B types and of cholinergic mechanisms in the hypotensive effect of the drugs is discussed.

Animals↗
PubMed1991

Lack of cross-resistance to fostriecin in a human small-cell lung carcinoma cell line showing topoisomerase II-related drug resistance.

Cells exhibiting decreased topoisomerase II (Topo II) activity are resistant to several drugs that require Topo II as an intermediate. These drugs are cytotoxic due to the formation of a cleavable complex between the drug, Topo II and DNA. Fostriecin belongs to a new class of drugs that inhibit Topo II without inducing the formation of this cleavable complex. We tested fostriecin in three human small-cell lung carcinoma cell lines. GLC4 is the parent line. GLC4/ADR is the P-glycoprotein-negative multidrug-resistant subline, which is resistant to several Topo II inhibitors due to its decreased Topo II activity. GLC4/cDDP is the cisplatin-resistant subline, which displays increased Topo II activity. Topo II activity proved to be 100% in GLC4, 35% in GLC4/ADR and 130% in GLC4/cDDP. The fostriecin concentration causing inhibition of the growth of 50% of the cells (IC50) in the microculture tetrazolium assay following continuous incubation was 11.2, 4.1 and 14.9 microM, respectively. After 1-h incubations, the IC50 was 117.8, 101.3 and 219.8 microM, respectively. Our results indicate a relationship between Topo II activity and fostriecin sensitivity in these closely related cell lines. At least in vitro, fostriecin displayed the capacity to kill cells showing resistance to drugs due to decreased Topo II activity. There was no relationship between this capacity and an increase in the activity of the reduced-folate carrier system, the proposed mechanism for cellular entry of fostriecin, since we found no correlation between the cytotoxicity of fostriecin and that of methotrexate.

Alkenes↗
PubMed1991

Kojic acid scavenges free radicals while potentiating leukocyte functions including free radical generation.

The effects of kojic acid, a compound that suppresses melanogenesis and is widely consumed in the Japanese diet with the belief that it is beneficial to health, were investigated on several aspects of leukocyte function. Kojic acid significantly decreased the levels of reactive oxygen species (ROS) (O2-, H2O2, OH.) generated by neutrophil and by a cell-free ROS-generating system. In contrast, it significantly enhanced neutrophil phagocytosis and ROS generation, and lymphocyte proliferation stimulated by phytohemagglutinin. In addition, calcium concentration, [Ca2+]i in human neutrophils was increased in the presence of kojic acid. These results suggest that kojic acid is a favorable agent in terms of host defense in that it enhances a number of activities of leukocytes, but scavenges ROS excessively released from cells or generated in the tissues or blood vessels that are potentially injurious to host tissues.

Calcium↗
PubMed1994

Isolation and characterization of new chlamydosporol related metabolites of Fusarium chlamydosporum and Fusarium tricinctum.

Fusarium chlamydosporum strain T-826 isolated from corn in the USA produced chlamydosporol and two analogs which have been identified by various spectroscopic techniques as: 7,8-dihydro-5-hydroxy-4-methoxy-trans-7,8-dimethyl-2H,5H-pyrano(4, 3-b)pyran-2-one (or isochlamydosporol) and 4-methoxy-5-hydroxymethyl-6-(3-butan-2-ol)-2H-pyran-2-one (or chlamydospordiol). Chlamydosporol (compound a + b) chlamydospordiol (compound c) and isochlamydosporol (compound d) were produced together (up to 6000 micrograms/g) by 3 out of 11 isolates of F. chlamydosporum and by 3 out of 24 isolates of F. tricinctum from various substrates and geographic origin. Three isolates of F. chlamydosporum and one isolate of F. tricinctum produced only chlamydospordiol and 2 isolates of F. tricinctum produced chlamydosporol (a + b), and chlamydospordiol (c).

Chromatography, High Pressure Liquid↗
PubMed1994

Secondary metabolites of Penicillium bilaii strain PB-50.

A phosphate-solubilizing strain of Penicillium bilaii was tested for the production of gliotoxin and other toxic compounds. The strain was fermented under five different conditions to allow the expression of various metabolites, including gliotoxin. These included Czapek-yeast extract medium under both shaken and still conditions as well as Czapek-yeast extract/malt extract/peptone medium and sucrose/glycerol medium in shake flasks. In addition, culture filtrate from an industrial fermentation of the fungus was examined. No gliotoxin was produced in any of the media. No other expected P. bilaii metabolites were found. Three compounds were identified in all samples: dibutyl phthalate, 1-(4-hydroxy-phenyl)ethanone and 4-hydroxy-3,6-dimethyl-2H-pyran-2-one. The production of other metabolites was dependent on the culture conditions. Two hyalodendrin derivatives were found in some fermentations and two related compounds were tentatively identified. None of the compounds found have been reported as toxic. The identity of the culture was confirmed by comparison with the ex-type culture of P. bilaii.

Acetophenones↗
PubMed1978

[Diphenols and caramel compounds in roasted coffees of different varieties. II. (author's transl)].

Eleven diphenols and seven caramel compounds were extracted from roasted coffee with pentane/ether (1 + 1), silylated with BSTFA, characterized, and semiquantified by GC-MS. Seven phenols and five caramel components were identified for the first time in roasted coffee. Robusta coffee contained the highest amounts of phenols and maltol. Arabica showed higher amounts of furaneol (2.5-dimethyl-4-hydroxy-3(2H)-furanone), isomaltol, 5-hydroxymaltol, and 5-hydroxy-5.6-dihydromaltol.

Chromatography, Gas↗
PubMed1996

Haloenol lactones as inactivators and substrates of aldehyde dehydrogenase.

Human aldehyde dehydrogenase (EC 1.2.1.3) isozymes E1 and E2 were irreversibly inactivated by stoichiometric concentrations of the haloenol lactones 3-isopropyl-6(E)-bromomethylene tetrahydro-pyran-2-one and 3-phenyl-6(E)-bromomethylene tetrahydropyran-2-one. No inactivation occurred with the corresponding nonhalogenated enol lactones. Both the dehydrogenase and esterase activities were abolished. Activity was not regained on dialysis or treatment with 2-mercaptoethanol. The inactivation was subject to substrate protection: NAD afforded protection which increased in the presence of the aldehyde-substrate competitive inhibitor chloral. Saturation kinetics gave positive gamma-axis intercepts, allowing the determination of binding constants. Inactivation stiochiometry determined with 14C-labeled 3-(1-naphthyl)-6(E)-iodomethylene tetrahydropyran-2-one was found to correspond to the active-site number. The nonhalogenated lactone, 3-(1-naphthyl)-6(E)-methylene tetrahydropyran-1-one was shown to be a substrate for aldehyde dehydrogenase via its esterase function. Inactivation and enzymatic hydrolysis occurred within a similar time frame. Opening of the lactone ring to form enzyme-acyl intermediate with active site cysteine appears to be a necessary prerequisite to inactivation, since halogen in the lactone ring is nonreactive. Thus, the inactivation of aldehyde dehydrogenase by haloenol lactones is mechanism-based. Inactivation by haloenol lactones occurs in a manner analogous to that of chymotrypsin with which aldehyde dehydrogenase shares esterase activity and binding of haloenol lactones at the active site.

Aldehyde Dehydrogenase↗
PubMed1991

Intracellular free zinc and zinc buffering in human red blood cells.

Zn2+ has been allowed to equilibrate across the red cell membrane using two agents that increase membrane permeability to this ion: the ionophore A23187 and the specific carrier ethylmaltol. Extracellular free Zn2+ was controlled with EGTA (1,2-di(2-aminoethoxy)ethane-NNN'N'tetra-acetic acid] buffers, except in the case of ethylmaltol, which itself acts as a buffer. Measurement of cellular zinc content at different levels of free Zn2+ facilitated the study of intracellular Zn2+ binding. It was also possible to estimate intracellular free Zn2+ concentration in untreated cells using a "null-point" technique. Intracellular zinc was found to consist of an inexchangeable component of about 129 mumol/10(13) cells and an exchangeable component of 6.7 +/- 1.5 mumol/10(13) cells, with a free concentration of about 2.4 x 10(-11) M. The main component of Zn2+ buffering is hemoglobin, with a dissociation constant of about 2 x 10(-8) M.

Binding Sites↗
PubMed1994

Kavapyrone enriched extract from Piper methysticum as modulator of the GABA binding site in different regions of rat brain.

Regional differences in the modulation of [3H] muscimol binding to GABAA receptor complexes by kavapyrones, compounds of the rhizome of the plant Piper methysticum which possess sedative activity, were demonstrated using membrane fractions obtained from target brain centers of kavapyrone action: hippocampus (HIP), amygdala (AMY) and medulla oblongata (MED), and from brain centers outside the main kavapyrone effects as frontal cortex (FC) and cerebellum (CER). The kava extract enhanced the binding of [3H] muscimol in a concentration-dependent manner with maximal potentiation of 358% over control in HIP followed by AMY and MED (main target brain centers). Minimal stimulation was observed in CER followed by FC. In contrast, apart from CER, the potency of kavapyrones was similar in the brain areas investigated with EC50 values ranging between 200 and 300 microM kavapyrones. Scatchard analysis revealed that the observed effects of kavapyrones were due to an increase in the number of binding sites (Bmax), rather than to a change in affinity. At a kavapyrone concentration of 500 microM the order of enhancement in Bmax was HIP = AMY > MED > FC > CER. When kavapyrones are included together with pentobarbital or HPO the two classes of compounds produced a more than additive, i.e., synergetic effect on [3H] muscimol binding. Our findings suggest that one way kavapyrones might mediate sedative effects in vivo is through effects on GABAA receptor binding.

Animals↗