Structural optimization of natural product fusaric acid to discover novel T3SS inhibitors of Salmonella.

Type III secretion system (T3SS) plays a critical role in host cell invasion and pathogenesis of Salmonella. We recently identified the mycotoxin fusaric acid (FA) as a T3SS inhibitor of Salmonella. Herein, twenty-two diphenylsulfane derivatives were designed and synthesized using FA as a lead compound through scaffold hopping. Among them, SL-8 and SL-19 possessing strong anti-T3SS and anti-invasion activity were identified as T3SS inhibitors with improvement in potency as compared to FA. The inhibitory mechanisms on SPI-1 did not depend on the HilD-HilC-RtsA-HilA or PhoP-PhoQ pathway or the assembly of T3SS needle complex. Accordingly, we proposed that the inhibitory effects of SL-8 and SL-19 on SPI-1 probably influence the formation of SicA/InvF-effector complex or other related proteins.

Fusaricates H-K and fusolanones A-B from a mangrove endophytic fungus Fusarium solani HDN15-410.

Seven compounds including four undescribed fusaric acid derivatives, namely fusaricates H-K, and two undescribed γ-pyrone derivatives, named fusolanones A-B, as well as a known compound fusaric acid, were isolated from a mangrove endophytic fungus Fusarium solani. Fusaricates H-K represent the first cases of fusaric acid butanediol esters and are diastereoisomers. Their structures including absolute configurations were elucidated based on NMR, MS, chemical synthesis, chiral HPLC analysis and ECD calculations. The antibacterial activity of all undescribed compounds were tested and fusolanone B showed the best activity with MIC value 6.25 µg/mL on Vibrio parahaemolyticus.

Methyl Fumarate-Derived Iron Carbonyl Complexes (FumET-CORMs) as Powerful Anti-inflammatory Agents.

Autoimmune diseases are characterized by dendritic cell (DC)-driven activation of pro-inflammatory T cell responses. Therapeutic options for these severe diseases comprise small molecules such as dimethyl fumarate, or "gasotransmitters" such as CO. Herein we describe the synthesis of bifunctional enzyme-triggered CO-releasing molecules (ET-CORMs) that allow the simultaneous intracellular release of both CO and methyl fumarate. Using bone-marrow-derived DCs the impressive therapeutic potential of these methyl fumarate-derived compounds (FumET-CORMs) is demonstrated by strong inhibition of lipopolysaccharide-induced pro-inflammatory signaling pathways and blockade of downstream interleukin-12 or -23 production. The data also show that FumET-CORMs are able to transform DCs into an anti-inflammatory phenotype. Thus, these novel compounds have great clinical potential, for example, for the treatment of psoriasis or other inflammatory conditions of the skin.

Two separate key enzymes and two pathway-specific transcription factors are involved in fusaric acid biosynthesis in Fusarium fujikuroi.

Fusaric acid (FSA) is a mycotoxin produced by several fusaria, including the rice pathogen Fusarium fujikuroi. Genes involved in FSA biosynthesis were previously identified as a cluster containing a polyketide synthase (PKS)-encoding (FUB1) and four additional genes (FUB2-FUB5). However, the biosynthetic steps leading to FSA as well as the origin of the nitrogen atom, which is incorporated into the polyketide backbone, remained unknown. In this study, seven additional cluster genes (FUB6-FUB12) were identified via manipulation of the global regulator FfSge1. The extended FUB gene cluster encodes two Zn(II)2 Cys6 transcription factors: Fub10 positively regulates expression of all FUB genes, whereas Fub12 is involved in the formation of the two FSA derivatives, i.e. dehydrofusaric acid and fusarinolic acid, serving as a detoxification mechanism. The major facilitator superfamily transporter Fub11 functions in the export of FSA out of the cell and is essential when FSA levels become critical. Next to Fub1, a second key enzyme was identified, the non-canonical non-ribosomal peptide synthetase Fub8. Chemical analyses of generated mutant strains allowed for the identification of a triketide as PKS product and the proposition of an FSA biosynthetic pathway, thereby unravelling the unique formation of a hybrid metabolite consisting of this triketide and an amino acid moiety.

Phytotoxicity of fusaric acid and analogs to cotton.

We developed a cotton cotyledonary leaf bioassay to test the phytotoxicity of fusaric acid (5-butylpicolinic acid), picolinic acid and related analogs. The compounds were dissolved in aqueous Tween 80, and 20 µL of the test solution was placed at three positions on the leaf, and a needle was used to puncture the leaf through each drop; the results were evaluated after 48 h. In contrast to previous studies, we found the carboxylic acid group is essential for phytotoxicity. Nicotinic acid was considerably less phytotoxic than picolinic acid and conversion of picolinic acid to the amide or N-oxide decreased phytotoxicity. Increasing the alkyl chain length at the 5-position on picolinic acid from two up to five carbons atoms increased phytotoxicity. Fusaric acid methyl ester, the most phytotoxic compound tested, is a naturally occurring compound; as such it has potential as a herbicide in organic farming.

Cu(II): a "signaling molecule" of the mangrove endophyte Fusarium oxysporum ZZF51?

We previously reported the isolation of Cu-fusaric acid (Cu-FA) complex from the mangrove endophyte Fusarium oxysporum ZZF51. In this study, we explored the mechanism of Cu-FA production in the strain ZZF51 by comparing with that of another endophyte Fusarium sp. B2, which produced FA but not Cu-FA in the same culture condition. The results allowed us to hypothesize that Cu(2+) may act as a "signaling molecule" to awaken the silent FA biosynthetic genes in ZZF51, inducing intracellular production of FA followed by chelation with Cu(2+). This signaling network was triggered specifically by Cu(2+) and may be interfered by other metal ions.

HPLC analysis of fusaric acid, 9,10-dehydrofusaric acid and their methyl esters, toxic metabolites from weed pathogenic Fusarium species.

A simple and rapid HPLC method, using a high-density C18 column, has been developed for the quantitative analysis of fusaric and dehydrofusaric acids and their methyl esters in the methanol extract of lyophilised culture filtrates of species of Fusarium. The method has been used to determine the content of these metabolites in two strains of Fusarium oxysporum and in strains of F. nygamai and F. udum. Fusaric acid has been isolated and identified from a strain of F. udum for the first time.

Degradation and transformation of a potential natural herbicide in three soils.

The methyl ester of fusaric acid (ME) is one of four toxins produced by the fungus Fusarium nygamai, which could be used as a natural herbicide against Striga hermonthica, a parasitic weed of sorghum and corn in a vast zone of West and Central Africa. A laboratory study was performed to measure the degradation of ME in three soil types and under different temperature and soil moisture conditions, so as to ascertain whether a single ME treatment would protect the crops against this weed during the critical phases of growth. The results show that the persistence in all soils and under all incubation conditions is long enough to protect the crops for the first week of growth, excluding the trial at 30 degrees C in the humic soil, where the half-life of 6 days would require more than one treatment. A degradation product of ME (butylpyridine, BP) was identified by gas chromatography/mass spectrometry and its degradation measured. The sum of ME and BP residues for the first 7 days was almost 100% of the applied compound in all soils and incubation conditions, thus indicating that BP may be the only transformation product of ME at this stage.

[Comparative effectiveness of the beta-(N,N-diethylamino)ethylamide hydrochloride of fusaric acid, obzidan and atenolol in experimental adrenaline-induced cardiac arrhythmia]. / Sravnitel'naia éffektivnost' gidrokhlorida beta-(N,N-diétilamino)étilamida fuzarinovoi kisloty, obzidana i atenolola pri éksperimental'noi adrenalinovoi aritmii serdtsa.

Hydrochloride beta-(N,N-diethylamino)ethylamide of fusaric acid (DAEA) exerted an antiarrhythmic activity in adrenaline-induced arrhythmia in rats. DAEA single pretreatment in doses of 1-5 mg/kg prevented the disorders of rhythm and conductivity in most animals. A pronounced antiarrhythmic effect was manifest at doses of 2 and 4 mg/kg of DAEA. The comparison of efficacy of DAEA, obzidan and atenolol showed that atenolol exhibited only a low antiarrhythmic activity, DAEA prevented the development of arrhythmia in 50% of animals in a dose of 1.7 mg/kg (1/42 of LD50) and obzidan--1 mg/kg (1/40 of LD50), respectively. The antiarrhythmic effect of DAEA was not followed by marked suppression of cardiac conductivity.

Isolation and characterization of two new fusaric acid analogs from Fusarium moniliforme NRRL 13,163.

Fusarium moniliforme NRRL 13,163 produced two new fusaric acid analogs, a 10,11-dihydroxyfusaric acid and a diacid of fusaric acid in which the C-11 methyl was oxidized to a carboxyl. Several hundred milligrams of the 10,11-dihydroxyfusaric acid were routinely recovered from a kilogram of corn grit medium. It crystallized as white, irregularly shaped rectangles that melted at 153 to 154 degrees C. The diacid analog of fusaric acid crystallized as white rods that melted at 210 to 211 degrees C. Unlike the consistent recovery experienced with the 10,11-dihydroxyfusaric acid, the diacid analog proved difficult to purify after the initial discovery and was detectable in subsequent fermentations only by mass spectrometry.

Physiologic mechanisms of bupicomide- and hydralazine-induced increase in plasma renin activity in hypertensive patients.

A study was made of the possible mechanisms underlying bupicomide- and hydralazine-induced increase of plasma renin activity. Six patients with mild to moderate hypertension were treated with both bupicomide and hydralazine on separate occasions in random order. Bupicomide lowered mean arterial pressure from 124.2 +/- 3.7 mm Hg (mean +/- SE) to 107.2 +/- 3.9 mm Hg (P less than 0.001). The associated increase in plasma renin activity was 1.27 ng/ml per hour and the increase in heart rate was 16.5 beats/min. Hydralazine reduced mean arterial pressure from 124.2 +/- 3.7 mm Hg to 107.0 +/- 2.0 mm Hg (P less than 0.01). The associated increase in plasma renin activity was 2.20 ng/ml per hour and the increase in heart rate was 22.4 beats/min. Plasma renin activity during bupicomide and hydralazine administration correlated positively with control plasma renin activity (r = 0.98, P less than 0.001). The log of plasma renin activity correlated positively with heart rate (r = 0.51, P less than 0.02) and negatively with mean arterial pressure (r = -0.62, P less than 0.005). We conclude that control plasma renin activity is a major determinant of change in plasma renin activity during administration of bupicomide or hydralazine. Both an increase in sympathetic activity and a decrease in perfusion pressure may contribute to the bupicomide- and hydralazine-induced increase in plasma renin activity, possibly by a baroreceptor-mediated increase in adrenergic tone.

Systemic and renal hemodynamic effects of bupicomide: a new vasodilator.

The systemic and renal hemodyanmic effects of bupicomide were studied in 10 male patients with uncomplicated essential hypertension of moderate severity. Bupicomide significantly reduced systolic, diastolic, and mean arterial pressure and peripheral vascular resistance and this hypotensive effect was associated with a reflexive increase in heart rate, left ventricular ejection rate, and cardiac index; it had no effect upon other reflexive sympathetic adjustments induced by upright tilt and the Valsalva maneuver. Bupicomide also increased renal blood flow and decreased renal vascular resistance, but it had no effect upon the glomerular filtration rate. The hypotensive mechanism of bupicomide therefore is mediated by peripheral arteriolar dilation, through vascular smooth muscle relaxation. The more immediate clinical side effects of bupicomide are related to its strong vasodialting action and include headaches, cutaneous flushing, and tachycardia.