Identification, Characterization and Synthesis of Natural Parasitic Cysteine Protease Inhibitors — More Potent Falcitidin Analogs

Protease inhibitors represent a promising therapeutic option for the treatment of parasitic diseases such as malaria and human African trypanosomiasis. Falcitidin was the first member of a new class of inhibitors of falcipain 2, a cysteine protease of the malaria parasite Plasmodium falciparum. Using a metabolomics dataset of 25 Chitinophaga strains for molecular networking enabled identification of over 30 natural analogs of falcitidin. Based on MS/MS spectra, they vary in their amino acid chain length, sequence, acyl residue, and C terminal functionalization; therefore, they were grouped into the four falcitidin peptide families A-D. The isolation, characterization and absolute structure elucidation of two falcitidin-related pentapeptide aldehyde analogs by extensive MS/MS spectrometry and NMR spectroscopy in combination with advanced Marfey's analysis was in agreement with the in silico analysis of the corresponding biosynthetic gene cluster. Total synthesis of chosen pentapeptide analogs followed by in vitro testing against a panel of proteases revealed selective parasitic cysteine protease inhibition and additionally low-micromolar inhibition of α-chymotrypsin. The pentapeptides investigated here showed superior inhibitory activity compared to falcitidin.

Amended Safety Assessment of Fatty Acyl Sarcosines and Sarcosinate Salts as Used in Cosmetics

The Expert Panel for Cosmetic Ingredient Safety (Panel) assessed the safety of 5 acyl sarcosines and 9 sarcosinate salts as used in cosmetics; all of these ingredients are reported to function in cosmetics as hair conditioning agents and most also can function as surfactants—cleansing agents. The ingredients reviewed in this assessment are composed of an amide comprising a fatty acyl residue and sarcosine and are either free acids or simple salts thereof. The Panel relied on relevant new data, including concentration of use, and considered data from the previous Panel report, such as the reaction of sarcosine with oxidizing materials possibly resulting in nitrosation and the formation of N-nitrososarcosine. The Panel concluded that these ingredients are safe as used in cosmetics when formulated to be non-irritating, but these ingredients should not be used in cosmetic products in which N-nitroso compounds may be formed.

Marine alkaloids as the chemical marker for the prey–predator relationship of the sponge Xestospongia sp. and the nudibranch Jorunna funebris

The dietary relationship study between marine sponge Xestospongia sp. and its nudibranch predators Jorunna funebris based on the discovery of isoquinolinequinones has long been studied. In this study, chemical investigation of the sponge Xestospongia sp. and nudibranch J. funebris from the South China Sea yielded a new marine alkaloid neopetroside C (1), together with nine known alkaloids (2–10). The chemical structures of all the compounds were elucidated by extensive spectroscopic analysis. Neopetroside C (1) featured a riboside of nicotinic acid with a rare α-N glycosildic linkage and an acyl residue of (Z)-2-methylbut-2-enoic acid attached to C-5′. The plausible chemical ecology relationship between sponge Xestospongia sp. and its nudibranch predator J. funebris was proposed based on the biogenetic relationship of the common marine alkaloids. The observation of two structural fragments, (Z)-2-methylbut-2-enoyloxy and trigonelline groups in both sponge and nudibranch, indicated that nudibranch might uptake chemicals from sponge and then modify and transform them into chemical weapons to defend against predators.

Synthesis of 5-aryl-4-acyl-3-hydroxy- 1-carboxymethyl-3-pyrrolin-2-ones

5-Aryl-1,4-disubstituted terahydropyrrole-2,3-diones are five-membered nitrogen heterocycles containing in the first alkyl position or an aryl functionalized substituent and in the fourth position in another state of nature an acyl residue. Trahydropyrrole-2,3-diones constitute a significant class of available and stable substances. Along with this, they easily enter into reactions with various nucleophilic reagents due to the highly reactive carbonyl group in the third position of the heterocycle. The presence of the latter, as well as the carbonyl group of the side chain, makes it possible to form various condensed systems from heterocycles in reactions with binucleophilic reagents. The synthesis of biologically active substances based on 1,4,5-trisubstituted tetrahydropyrrole-2,3-diones is one of the promising ways of using this class of compounds. Previously, it was found that 1,4,5-trisubstituted 3-hydroxy-3-pyrin-2-ones have anti-inflammatory, analgesic, antimicrobial, nootropic, antiplatelet and antiviral activity. We set the task to obtain 5-aryl-4-acyl-3-hydroxy-3-pyrrolin-2-ones, in the first position of the heterocycle there is a carboxymethyl substituent. By setting up a three-component reaction of acylpyruvic acid ether with aromatic aldehydes and glycine in dioxane in dioxane. The structure of the compound was established on the basis of IR and 1H NMR spectroscopy data. Based on the data of 1H NMR spectroscopy and a positive reaction with an alcoholic solution of iron(III) chloride, the predominant presence of compounds in the enol form was established. The article presents the proposed mechanism and schemes of the formula for the synthesis of 5-aryl-4-acyl-3-hydroxy-1-carboxymethyl-3-pyrrolin-2-ones, their physicochemical and spectral characteristics, as well as the yields of the reaction products.

Hydrolysis, alcoholysis and aminolysis of N,N'-malonyldiimidazole

The achievements of molecular biology, biochemistry and bioorganic chemistry are largely due to the methods of organic chemistry, in particular chemistry N-azolides over the past twenty years. Imidazolides are not the most reactive group of compounds among heterocyclic amides, however, it is interesting for preparative purposes because of the availability of imidazole. It is known that compounds of this class are widely used as specific condensing agents in the synthesis of a number of biologically active substances. The investigation of the physicochemical properties of N-azolides is of great interest. According to well-known kinetic studies, the aminolysis and the alcoholysis of N-azolides proceed according to the addition-elimination mechanism. The hydrolysis of N-azolides of sterically hindered carboxylic acids proceeds according to the mechanism of monomolecular nucleophilic substitution. These conclusions are based on the study of the dependence of the rate constants and the activation energy of the acyl residue. Differences in the reactivity of N-azolides with different acyl residues are quite pronounced. In this work, the reactions of hydrolysis, alcoholysis and aminolysis of N,N'-malonyldiimidazole were studied by an HPLC method on an isocratic pump chromatograph, with a UV spectrophotometric detector with a wavelength range of 190–600 nm. A polar chromatographic column with a particle size of 5 μm was used. Acetonitrile eluent (CH3CN) was used as the mobile phase. The speed of the mobile phase was 1,000 ml/min. Before the experiment, air was removed from the mobile phase by degassing into an ultrasonic bath. We used the program "Open LAB" for processing the results. Chromatography was carried out in isocratic mode at a wavelength of 280 nm. After a certain period of time, chromatography was carried out and a decreasing peak area of the starting dionicid of malonic acid was noted. The kinetics of the processes of hydrolysis, aminolysis of alcoholysis was determined during the study. The relative instability of N,N'-malonyldiimidazole and high reactivity were established because of the calculated half-life data.

Sequencing and Analysis of the Biosynthetic Gene Cluster of the Lipopeptide Antibiotic Friulimicin in Actinoplanes friuliensis

ABSTRACT Actinoplanes friuliensis produces the lipopeptide antibiotic friulimicin, which is a cyclic peptide with one exocyclic amino acid linked to a branched-chain fatty acid acyl residue. The structural relationship to daptomycin and the excellent antibacterial performance of friulimicin make the antibiotic an attractive drug candidate. The complete friulimicin biosynthetic gene cluster of 24 open reading frames from A. friuliensis was sequenced and analyzed. In addition to genes for regulation, self-resistance, and transport, the cluster contains genes encoding peptide synthetases, proteins involved in the synthesis and linkage of the fatty acid component of the antibiotic, and proteins involved in the synthesis of the nonproteinogenic amino acids pipecolinic acid, methylaspartic acid, and 2,3-diaminobutyric acid. By using heterologous gene expression in Escherichia coli, we provide biochemical evidence for the stereoselective synthesis of l-pipecolinic acid by the deduced protein of the lysine cyclodeaminase gene pip. Furthermore, we show the involvement of the dabA and dabB genes in the biosynthesis of 2,3-diaminobutyric acid by gene inactivation and subsequent feeding experiments.

The Pea Nodule Environment Restores the Ability of a Rhizobium leguminosarum Lipopolysaccharide acpXL Mutant To Add 27-Hydroxyoctacosanoic Acid to Its Lipid A

ABSTRACT Members of the Rhizobiaceae contain 27-hydroxyoctacosanoic acid (27OHC28:0) in their lipid A. A Rhizobium leguminosarum 3841 acpXL mutant (named here Rlv22) lacking a functional specialized acyl carrier lacked 27OHC28:0 in its lipid A, had altered growth and physiological properties (e.g., it was unable to grow in the presence of an elevated salt concentration [0.5% NaCl]), and formed irregularly shaped bacteroids, and the synchronous division of this mutant and the host plant-derived symbiosome membrane was disrupted. In spite of these defects, the mutant was able to persist within the root nodule cells and eventually form, albeit inefficiently, nitrogen-fixing bacteroids. This result suggested that while it is in a host root nodule, the mutant may have some mechanism by which it adapts to the loss of 27OHC28:0 from its lipid A. In order to further define the function of this fatty acyl residue, it was necessary to examine the lipid A isolated from mutant bacteroids. In this report we show that addition of 27OHC28:0 to the lipid A of Rlv22 lipopolysaccharides is partially restored in Rlv22 acpXL mutant bacteroids. We hypothesize that R. leguminosarum bv. viciae 3841 contains an alternate mechanism (e.g., another acp gene) for the synthesis of 27OHC28:0, which is activated when the bacteria are in the nodule environment, and that it is this alternative mechanism which functionally replaces acpXL and is responsible for the synthesis of 27OHC28:0-containing lipid A in the Rlv22 acpXL bacteroids.

Isolation and Partial Characterization of Antagonistic Peptides Produced by Paenibacillus sp. Strain B2 Isolated from the Sorghum Mycorrhizosphere

ABSTRACT Paenibacillus sp. strain B2, isolated from the mycorrhizosphere of sorghum colonized by Glomus mosseae, produces an antagonistic factor. This factor has a broad spectrum of activity against gram-positive and gram-negative bacteria and also against fungi. The antagonistic factor was isolated from the bacterial culture medium and purified by cation-exchange, reverse-phase, and size exclusion chromatography. The purified factor could be separated into three active compounds following characterization by amino acid analysis and by combined reverse-phase chromatography and mass spectrometry (liquid chromatography-mass spectrometry and mass spectrometry-mass spectrometry). The first compound had the same retention time as polymyxin B1, whereas the two other compounds were more hydrophobic. The molecular masses of the latter compounds are 1,184.7 and 1,202.7 Da, respectively, and their structure is similar to that of polymyxin B1, with a cyclic heptapeptide moiety attached to a tripeptide side chain and a fatty acyl residue. They both contain threonine, phenylalanine, leucine, and 2,4-diaminobutyric acid residues. The peptide with a molecular mass of 1,184.7 contains a 2,3-didehydrobutyrine residue with a molecular mass of 101 Da replacing a threonine at the A2 position of the polymyxin side chain. This modification could explain the broader range of antagonistic activity of this peptide compared to that of polymyxin B.

An acyl-CoA dehydrogenase is involved in the formation of the Δcis3 double bond in the acyl residue of the lipopeptide antibiotic friulimicin in Actinoplanes friuliensis

The lipopeptide antibiotic friulimicin, produced by Actinoplanes friuliensis, is an effective drug against Gram-positive bacteria, such as methicillin-resistant Staphylococcus epidermidis and Staphylococcus aureus strains. Friulimicin consists of a cyclic peptide core of ten amino acids and an acyl residue linked to an exocyclic amino acid. The acyl residue is essential for antibiotic activity, varies in length from C13 to C15, and carries a characteristic double bond at position Δcis3. Sequencing of a DNA fragment adjacent to a previously described fragment encoding some of the friulimicin biosynthetic genes revealed several genes whose gene products resemble enzymes of lipid metabolism. One of these genes, lipB, encodes an acyl-CoA dehydrogenase homologue. To elucidate the function of the LipB protein, a lipB insertion mutant was generated and the friulimicin derivative (FR242) produced by the mutant was purified. FR242 had antibiotic activity lower than friulimicin in a bioassay. Gas chromatography showed that the acyl residue of wild-type friulimicin contains a double bond, whereas a saturated bond was present in FR242. These results were confirmed by the heterologous expression of lipB in Streptomyces lividans T7, which led to the production of unsaturated fatty acids not found in the S. lividans T7 parent strain. These results indicate that the acyl-CoA dehydrogenase LipB is involved in the introduction of the unusual Δcis3 double bond into the acyl residue of friulimicin.