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PubMed2002

Diels-Alder cycloadditions of 3,5-dibromo-2-pyrone: a new ambident diene.

D-A cycloadditions of 3,5-dibromo-2-pyrone were investigated with a series of electronically and sterically distinct dienophiles. Our results showed that it is a highly potent ambident diene, being more reactive and stereoselective than monobromo-2-pyrones, and thus capable of generating a variety of bicycloadducts in much higher chemical yields and endo/exo ratios than monobromo-2-pyrones. Another interesting feature of this study is that the two bromine groups on the cycloadducts could be independently manipulated to produce other synthetically useful bicyclolactones.

Alkadienes↗
PubMed2001

Synthesis and in vitro studies of pyrone derivatives as scavengers of active oxygen species.

The antioxidant properties of eleven alpha-pyrones and four gamma-pyrones were evaluated by means of three different tests: reduction of the stable free radical, 1,1-diphenyl-2-picrylhydrazyl (DPPH), superoxide anion scavenging assay and lipid peroxidation assay. In the DPPH test, 6-aryl-5,6-dihydro-4-hydroxypyran-2-ones (3) and 4-hydroxypyran-2-one (5f) were the most active derivatives with IC50 values ranging from 36.7 to 394 mumol/l. Potent superoxide anion scavenging properties appeared in derivatives possessing phenol moieties. Thus phenolic pyrones 5e and 5f exhibited a noteworthy activity (IC50 = 0.180 and 0.488 mmol/l, respectively) when reference compound, ascorbic acid, demonstrated only 24% inhibition at a concentration of 1 mg/ml. In addition derivative 5f significantly inhibited the Fe2+/ADP/ascorbate-induced lipid peroxidation of rat liver microsomes with an IC50 value of 0.069 mmol/l. Due to its multiple mechanism of protective action, compound 5f may be useful for the treatment of oxidative tissue injury in human disease.

Animals↗
PubMed1991

Observation of the light-triggered binding of pyrone to chymotrypsin by Laue x-ray crystallography.

Crystals of gamma-chymotrypsin inhibited with the photodissociable group trans-p-diethylamino-o-hydroxy-alpha-methylcinnamate were irradiated with a 1-msec flash from a high-energy xenon flashlamp in the presence of the mechanism-based inhibitor 3-benzyl-6-chloro-2-pyrone. The ensuing reaction was monitored by collection of sequential, single-exposure Laue x-ray diffraction patterns. The experiment was also performed in solution to verify the regeneration of catalytic activity and the subsequent inhibition of the enzyme by pyrone after photolysis. The resulting crystallographic structures show the presence of covalently bound cinnamate prior to photolysis, the generation of "free" enzyme after irradiation of the crystal, and the slow formation of a pyrone-inhibited complex several hours after photolysis. The structure of the free enzyme shows a significant proportion of the active sites in the crystal to contain a naturally occurring, noncovalently bound tetrapeptide inhibitor [Dixon, M.M. & Matthews, B.W. (1989) Biochemistry 28, 7033-7038], even after cinnamate acylation and photolysis. Data collected simultaneously with irradiation show the crystal to be slightly disordered during photolysis, leading to streaked x-ray photos. The resulting maps are suggestive of a bicyclic coumarin species produced by photolysis and deacylation; however, the electron density is difficult to model unambiguously by one unique chemical state. Nevertheless, Laue crystallography is shown to be capable of visualizing time-dependent chemical changes in the active site of an enzyme.

Binding Sites↗
PubMed1992

Kava pyrones and resin: studies on GABAA, GABAB and benzodiazepine binding sites in rodent brain.

Kava, an intoxicating beverage prepared from the pepper plant Piper methysticum, is widely consumed by the indigenous peoples in the islands of the South Pacific. As the first of a series of studies on the neuropharmacological interactions of kava with CNS receptors we tested purified pyrones and kava resin for activity on GABA and benzodiazepine binding sites in rat and mouse brain membranes. Only weak activity was observed on GABAA binding sites in washed synaptosomal membranes prepared from rat brain and this was abolished by extraction of the membranes with Triton X-100, suggesting that lipid soluble components were involved. No effects were observed on GABAB binding sites in rat brain membranes in vitro. Kava resin and pyrones exerted some weak effects on benzodiazepine binding in vitro but this did not correlate with pharmacological activity. In addition, in ex vivo studies, no effects were observed on [3H]diazepam binding to brain membranes prepared from mice in which selected kava constituents were injected intraperitoneally, whereas similarly administered diazepam (5 mg/kg) inhibited [3H]diazepam binding by greater than 95%. Similar lack of activity was observed in in vivo binding studies; injection of kava resin failed to influence the CNS binding of the benzodiazepine-receptor ligand [3H]Ro15-1788 injected into mice prior to sacrifice. The pharmacological activities of kava resin and pyrones do not appear to be explained by any significant interaction with GABA or benzodiazepine binding sites.

Animals↗
PubMedDate not supplied

Antitumor activity of novel tricyclic pyrone analogs in murine leukemia cells in vitro.

New tricyclic pyrone derivatives were synthesized and tested for their ability to prevent L1210 leukemic cells from synthesizing DNA and growing in vitro. At 50 microM, a pyripyropene analog has no effect, whereas four pentahydro-3-aryl-1-oxopyrano[4,3-b][1]benzopyrans all inhibit DNA synthesis by 79-91% and tumor cell growth by 93-100%. These inhibitory effects are concentration dependent with IC50 around 8.5 microM for DNA synthesis at 2 hours and 1.1 microM for tumor cell growth at 4 days. The aryl groups of these antitumor agents are either 3,4-dimethoxyphenyl or 3-pyridyl. Introduction of a methyl group at C5a and a formyloxy or hydroxy group at C6 does not alter the antitumor effects of the 3,4-dimethoxyphenyl benzopyrans but reduces those of the 3-pyridyl benzopyrans, which, at 50 microM, inhibit DNA synthesis by only 32-49% and fail to alter tumor cell growth. The 4-hydroxy-6-(3-pyridyl)-2-pyrone has no effect and the tricyclic pyrones lacking aryl groups have very little inhibitory effects on DNA synthesis, suggesting that a greater conjugation is required for the antitumor activity. These molecules have never been reported and might be valuable to develop a new class of anticancer drugs.

Animals↗
PubMed1977

The influence of various benzo-pyrones on acid and neutral protease activity levels, the cells from which they may arise and their importance in the resolution of lymphoedema.

The availability of digestable material to a phagocyte determines not only the rapidity and completeness of digestion but the amount of lysosomal enzyme which reaches the extracellular compartment and the circulation. The measurement of enzyme activities in thermally injured limbs has shown the benzo-pyrones to enhance acid protease activity. There is much evidence to suggest this activity originates from macrophages which enter the thermally injured regions in great numbers. In this paper the administration of benzo-pyrones to animals with lymphoedema is reported to enhance neutral protease activity levels. This activity is not associated with mononuclear cells but with the neutrophils. Although additional histological work must be done to confirm the presence of neutrophils in lymphoedematous tissues there is evidence to suggest the increases in neutral protease levels arise from neutrophils and that in lymphoedema it is these cells which are acted upon by the benzo-pyrones. They then cause the removal of protein by enhancing its lysis either within the cells or in the extracellular compartment.

Animals↗
PubMed1985

The effects of diosmin (a benzo-pyrone) upon some high-protein oedemas: lung contusion, and burn and lymphoedema of rat legs.

Oral diosmin (a benzo-pyrone) was used to treat rats with contused lungs, in doses of 50 or 200 mg/kg/day. The contusion was produced by direct trauma. The lungs were examined with the electron microscope, both qualitatively and quantitatively, at 1, 2 and 4 days. It was found that diosmin considerably reduced interstitial oedema and tissue disorganization. The concentration of protein, both in the interstitial tissue and in the air spaces, was also much reduced. There was a greater effect at the higher dosage than at the lower one. In two other experiments, this drug was used in the usual models of burn oedema of the rat foot and acute lymphoedema of the rat leg - estimating the amount of oedema by weighing the parts. A low dose (50 mg/kg) reduced the burn oedema; a high dose (200 mg/kg) did not. Both doses reduced the acute lymphoedema of the whole leg, or thigh. The high dose did not do this in the foot, but the low one did. At high doses, diosmin has the usual benzo-pyrone property of releasing mediators in the rat-foot. In other tissues (and, no doubt, species) this drug reduces many forms of high-protein oedema, like the other benzo-pyrones.

Acute Disease↗
PubMed1993

Treatment of filarial lymphoedema and elephantiasis with 5,6-benzo-alpha-pyrone (coumarin).

OBJECTIVE: To study efficacy of treatment of filarial lymphoedema and elephantiasis with 5,6-benzo-alpha-pyrone. DESIGN: Randomised, double blind, placebo controlled study with matching for grade and duration of disease, age, and sex. Treatment was given for 367 days, and subjects were followed up for another year. SETTING: A town in Shandong Province, China. SUBJECTS: 104 men and women with chronic unilateral filarial lymphoedema or elephantiasis of the leg: 64 were randomised to benzopyrone and 40 to placebo. By the end of the study 19 patients had dropped out of the treatment group and two out of the placebo group. INTERVENTIONS: Two 200 mg tablets of 5,6-benzo-alpha-pyrone or two placebo tablets given daily. MAIN OUTCOME MEASURES: Volumes of the affected and normal legs estimated every three months, and daily listing of any side effects. RESULTS: Benzopyrone reduced oedema for all grades of lymphoedema during the year of treatment (pW0.001) and the follow up year (p = 0.026). During treatment the mean monthly reductions in leg volume were 0.62% (95% confidence intervals 0.4% to 0.85%), 1.1% (0.71% to 1.6%), and 1.6% (0.89% to 2.3%) of the volume of the normal leg for grades 1, 2, and 3-5 (elephantiasis) of lymphoedema respectively. During follow up the mean monthly reductions were 0.18% (0.01% to 0.35%), 0.54% (0.27% to 0.82%), and 0.87% (0.51% to 1.2%). At the end of the trial the total reduction in oedema was 100%, 95%, and 45% for grades 1, 2, and 3-5. Symptoms and complications were considerably reduced, including attacks of secondary acute inflammation, while side effects were minor and disappeared after one month. In the placebo group there were no changes in the severity of lymphoedema. CONCLUSIONS: 5,6-benzo-alpha-pyrone reduces the oedema and many symptoms of filarial lymphoedema and elephantiasis. It has few side effects, and its relatively slow action makes it ideal for use without compression garments.

Coumarins↗
PubMed1988

The pathophysiology of lymphedema and the action of benzo-pyrones in reducing it.

The pathogenesis of lymphedema is briefly reviewed. Swelling secondary to lymphostasis shares the common deleterious effects of other edemas, especially those of chronic high protein edema, namely chronic inflammation with excess tissue fibrosis. Benzo-pyrones are the only known drugs which reduce the excess protein in the tissues with high protein edema including lymphedema. Once excess tissue protein is resorbed, edema subsides and the fibrosis slowly resolves by remodeling. Two of these benzo-pyrone drugs have been shown to reduce postmastectomy and primary lymphedema in randomized, double-blind, cross-over, placebo-controlled trials. One of these drugs (which is also inexpensive) has also been shown to reduce filaritic lymphedema and elephantiasis in a similar trial in India. The bigger the leg initially, the more rapid is the reduction. In this extreme condition about a 20% lessening of the excess volume occurs each year. The benzo-pyrones do not work rapidly, but they do convert a rapidly worsening condition into a slowly improving one. In addition, they have extremely low toxicity and are effective orally. They also seem to reduce the incidence of secondary acute inflammation.

Clinical Trials as Topic↗
PubMed1997

Chemical modification and structure-activity relationships of pyripyropenes. 3. Synthetic conversion of pyridine-pyrone moiety.

Structure-activity relationships of the pyridine-pyrone moiety in pyripyropene A (1), a potent acyl-CoA: cholesterol acyltransferase (ACAT) inhibitor of fungal origin, were studied. Several kinds of aromatic or hetero ring substituents for the pyridine moiety were synthesized using unique degradation reaction, following by gamma-acylation. All the six synthesized analogs decreased the inhibitory activity with 20 to 200 times larger IC50 values than that of 1. Furthermore, the pyridine-pyrone substituent also dramatically decrease the inhibitory activity. Thus, the pyridine-pyrone moiety is important for eliciting potent ACAT inhibition.

Enzyme Inhibitors↗
PubMed1997

Chemical modification and structure-activity relationships of pyripyropenes. 3. Synthetic conversion of pyridine-pyrone moiety

Structure-activity relationships of the pyridine-pyrone moiety in pyripyropene A (1), a potent acyl-CoA : cholesterol acyltransferase (ACAT) inhibitor of fungal origin, were studied. Several kinds of aromatic or hetero ring substituents for the pyridine moiety were synthesized using unique degradation reaction, following by gamma-acylation. All the six synthesized analogs decreased the inhibitory activity with 20 to 200 times larger IC50 values than that of 1. Furthermore, the pyridine-pyrone substituent also dramatically decrease the inhibitory activity. Thus, the pyridine-pyrone moiety is important for eliciting potent ACAT inhibition.

Journal Article↗
PubMed1999

High performance liquid chromatography for the analysis of fusapyrone and deoxyfusapyrone, two antifungal alpha-pyrones from Fusarium semitectum.

A simple, very sensitive and rapid HPLC method was developed for the simultaneous quantitative analysis of both fusapyrone (FP) and deoxyfusapyrone (DFP), the two antifungal 3-substituted-4-hydroxy-6-alkyl-2-pyrones isolated from rice culture of Fusarium semitectum, in crude extracts. Such method was optimized on C-18 reverse phase column, using the isolated metabolites as standards, with a sequence of linear elution steps with a MeOH-H(2)O mixture and using an ultraviolet detector fixed at 285 nm, where both alpha-pyrones showed a characteristic absorption maximum. This method was used to quantify the bioactive metabolites in crude organic extracts from two F. semitectum strains. The recovery of FP and DFP was measured in a crude extract from a poor metabolite producer F. semitectum strain. The recovery values ranged from 84% to 99% for FP and from 99% to 101% for DFP, indicating that the method was close to quantitative recovery. Furthermore, an efficient medium pressure column chromatography and TLC combined method was developed for the isolation and purification of FP and DFP from fungal culture extracts.

Antifungal Agents↗
PubMed2000

Study on the production of 6-pentyl-alpha-pyrone using two methods of fermentation.

The lactone 6-pentyl-alpha-pyrone has a characteristic coconut aroma and is produced by Trichoderma species. A study on the fermentative production of 6-pentyl-alpha-pyrone in both surface and submerged conditions by Trichoderma harzianum was carried out. Maximum concentrations of 455 mg/l and 167 mg/l after 96 h and 48 h of fermentation in surface and submerged conditions, respectively, were obtained without using any additional recovery operations. The resultant yields are higher than those previously reported in the literature, which may be attributable to strain characteristics in combination with the choice of fermentation conditions employed in the present study. Enough scope exists for further improvement in the yields by optimizing the cultural and nutritional parameters.

Biomass↗
PubMed2003

Antileishmanial activity of two gamma-pyrones from Podolepsis hieracioides (Asteraceae).

Two gamma-pyrones isolated from the seeds of Podolepsis hieracioides (Asteraceae) have been tested for their in vitro leishmanicidal activity against the promastigote form of Leishmania donovani, L. major, L. infantum and L. enriettii (IC(50)=3.76-5.43 microg/ml), and against the amastigote form of L. donovani residing within RAW 264.7 macrophage-like host cells (IC(50)=8.29-8.59 microg/ml). General toxicity of the gamma-pyrones was investigated in parallel against three mammalian cell lines (RAW 264.7, SKMel, and KB; IC(50)=11.5->25.0 microg/ml). Both compounds were not active against Trypanosoma cruzi or Trypanosoma br. brucei (IC(50)>30 microg/ml).

Animals↗
PubMed2001

Pyrone and pyridone compounds in the liquid culture of Physisporinus sanguinolentus.

Chromatographic separation of the liquid culture filtrate of the basidiomycete fungus Physisporinus sanguinolentus has yielded three new compounds viz., 2-methyl-4-pyrone, 2-methyl-5,6-dihydro-4-pyrone and the pyridone form of 4-hydroxy-2-methylpyridine, together with the known triacetic acid lactone, the sesquiterpene dialdehyde merulidial and a derivative of merulidial. Their structures were elucidated by spectroscopic analysis and by comparison to literature data and a synthetic sample. One of the compounds, merulidial, was shown to inhibit the germination of spores and the hyphal growth of the wood-rotting basidiomycete Heterobasidion annosum and the saprophytic mould Cladosporium cucumerinum.

Chromatography, High Pressure Liquid↗
PubMed1994

An antifungal gamma-pyrone and xanthones with monoamine oxidase inhibitory activity from Hypericum brasiliense.

A new gamma-pyrone (hyperbrasilone), three known xanthones (1,5-dihydroxyxanthone, 5-hydroxy-1-methoxyxanthone and 6-deoxyjacareubin) and betulinic acid have been isolated from a dichloromethane extract of stems and roots of Hypericum brasiliense. Their structures were established by spectroscopic methods (UV, EI-MS, 1H and 13C NMR) and that of the gamma-pyrone was confirmed by X-ray crystallography. Hyperbrasilone and the xanthones were all antifungal against Cladosporium cucumerinum, while the three xanthones showed differing degrees of inhibition of monoamine oxidase A and B.

Animals↗
PubMed2001

Isolation, characterization, and systematic significance of 2-pyrone-4,6-dicarboxylic acid in Rosaceae.

2-Pyrone-4,6-dicarboxylic acid was isolated from Potentilla anserina. Until now this substance was only found in bacteria and not in higher plants. By sterile cultivation it was verified that this compound is genuine also in plants. In addition the systematic relevance of 2-pyrone-4,6-dicarboxylic acid within the Rosaceae was tested. The compound seems to be a chemotaxonomic marker for the Rosoideae sensu stricto proposed by Morgan et al. (Morgan, D.R., Soltis, D.E., Robertson, K.R., 1994. Systematic and evolutionary implications of rbcL sequence variation in Rosaceae. American Journal of Botany 81, 890-903).

Chromatography, High Pressure Liquid↗
PubMed2002

Coumarins and gamma-pyrone derivatives from Prangos pabularia: antibacterial activity and inhibition of cytokine release.

The n-hexane and ethyl acetate extracts of the stems and the ethyl acetate extracts of roots from Prangos pabularia afforded an gamma-pyrone derivative and furanocoumarin derivatives with three glucose and gamma-pyrone (pabularin A, B and C), along with 26 previously known compounds (18 coumarins, six terpenoids and two glycosides). Their structures were established on the basis of spectroscopic studies. Of these, 16 coumarin derivatives isolated from P. pabularia were tested for antibacterial activity and inhibition of cytokine release.

Anti-Bacterial Agents↗