Bioconversion of antifungal viridin to phytotoxin viridiol by environmental non-viridin producing microorganisms.

Biotransformation of viridin, an antifungal produced by biocontrol agent, with non-viridin producing microorganisms is studied. The results show that some environmental non-targeted microorganisms are able to reduce it in the known phytotoxin viridiol, and its 3-epimer. Consequently, this reduction, which happens in some cases by detoxification mechanism, could be disastrous for the plant in a biocontrol of plant disease. However, a process fermentation/biotransformation could be an efficient approach for the preparation of this phytotoxin.

Molecular insights into how SHBG dimerization exerts changes on ligand molecular recognition.

Sex hormone binding globulin (SHBG) is a homodimeric glycoprotein and is the major carrier protein for sex steroids in plasma, regulating sex hormone availability in most vertebrate groups. Although it was initially thought that human dimeric SHBG bound a single ligand at the homodimer interface, studies demonstrated that dimeric SHBG binds a ligand to each subunit with similar affinity. In fact, the findings from recent experimental studies suggest that ligand binding to the SHBG dimer involves a complex allosteric mechanism involving conformational changes that limit observations of the presence of allosteric regulation. Therefore, we combined structural data with molecular dynamics simulations using Molecular Mechanics Generalized-Born Surface Area (MMGBSA) to dissect the structural and energetic basis for molecular recognition between five ligands whose affinities and binding positions on SHBG are known, i.e., 3ß,17α-diol; 3ß,17ß-diol; DHT; norgestrel (NOG); and estradiol (E2), and monomeric and dimeric SHBG. Protein-ligand complexes, involving dimeric SHBG saturated with two ligands on each subunit, reproduce the experimental affinity tendency and allow the observation that dimerization exerts disparate effects on binding affinity, characteristic of negative cooperativity for E2, DHT, and NOG, whereas 3ß-17α-diol and 3ß-17ß-diol lack allostery.

Hyfraxinic Acid, a Phytotoxic Tetrasubstituted Octanoic Acid, Produced by the Ash (Fraxinus excelsior L.) Pathogen Hymenoscyphus fraxineus Together with Viridiol and Some of Its Analogues.

A new tetrasubstituted octanoic acid, named hyfraxinic acid (1), was isolated together with known 1-deoxyviridiol (2), viridiol (3), nodulisporiviridin M (4), and demethoxyviridiol (5) from the organic extract of Hymenoscyphus fraxineus responsible for ash (Fraxinus excelsior L.) dieback in Europe. Hyfraxinic acid (1) was characterized, using spectroscopic methods, as 2,4-dihydroxy-7-methyl-6-methyleneoctanoic acid. Furthermore, the advanced Mosher method was used to determine the absolute configuration (3R) of 1-deoxyviridiol. Nodulisporiviridin M (4) was isolated for the first time from H. fraxineus. The phytotoxicity of each compound was tested by a leaf puncture assay on Celtis australis L., Quercus suber L., Hedera elix L., Juglans regia L., and Fraxinus angustifolia L. leaves. Compounds 1, 3, and 5 exhibited remarkable phytotoxicity on all plants tested, inducing necrotic lesions at concentrations of 1.0 and 0.5 mg/mL, while compounds 2 and 4 were found to be inactive in this bioassay. These results could contribute to a deeper understanding of the pathogenicity of H. fraxineus.

Overexpression of cytochrome p450 125 in Mycobacterium: a rational strategy in the promotion of phytosterol biotransformation.

Androst-4-ene-3, 17-dione (AD) and androst-1, 4-diene-3, 17-dione (ADD) are generally produced by the biotransformation of phytosterols in Mycobacterium. The AD (D) production increases when the strain has high NAD+/NADH ratio. To enhance the AD (D) production in Mycobacterium neoaurum TCCC 11978 (MNR M3), a rational strategy was developed through overexpression of a gene involved in the phytosterol degradation pathway; NAD+ was generated as well. Proteomic analysis of MNR cultured with and without phytosterols showed that the steroid C27-monooxygenase (Cyp125-3), which performs sequential oxidations of the sterol side chain at the C27 position and has the oxidative cofactor of NAD+ generated, played an important role in the phytosterol biotransformation process of MNR M3. To improve the productivity of AD (D), the cyp125-3 gene was overexpressed in MNR M3. The specific activity of Cyp125-3 in the recombinant strain MNR M3C3 was improved by 22% than that in MNR M3. The NAD+/NADH ratio in MNR M3C3 was 131% higher than that in the parent strain. During phytosterol biotransformation, the conversion of sterols increased from 84 to 96%, and the yield of AD (D) by MNR M3C3 was increased by approximately 18% for 96 h fermentation. This rational strain modification strategy may also be applied to develop strains with important application values for efficient production of cofactor-dependent metabolites.

Enantioselective Chemical Syntheses of the Furanosteroids (-)-Viridin and (-)-Viridiol.

Herein we describe concise enantioselective chemical syntheses of (-)-viridin and (-)-viridiol. Our convergent approach couples two achiral fragments of similar complexity and employs an enantioselective intramolecular Heck reaction to set the absolute stereochemical configuration of an all-carbon quaternary stereocenter. To complete the syntheses of these base- and nucleophile-sensitive natural products, we conduct carefully orchestrated site- and diastereoselective oxidations and other transformations. Our work is the first to generate these targets as single enantiomers.

Identification and characterization of novel long-term metabolites of oxymesterone and mesterolone in human urine by application of selected reaction monitoring GC-CI-MS/MS.

The search for metabolites with longer detection times remains an important task in, for example, toxicology and doping control. The impact of these long-term metabolites is highlighted by the high number of positive cases after reanalysis of samples that were stored for several years, e.g. samples of previous Olympic Games. A substantial number of previously alleged negative samples have now been declared positive due to the detection of various long-term steroid metabolites the existence of which was unknown during the Olympic Games of 2008 and 2012. In this work, the metabolism of oxymesterone and mesterolone, two anabolic androgenic steroids (AAS), was investigated by application of a selected reaction monitoring gas chromatography-chemical ionization-triple quadrupole mass spectrometry (GC-CI-MS/MS) protocol for metabolite detection and identification. Correlations between AAS structure and GC-CI-MS/MS fragmentation behaviour enabled the search for previously unknown but expected AAS metabolites by selection of theoretical transitions for expected metabolites. Use of different hydrolysis protocols allowed for evaluation of the detection window of both phase I and phase II metabolites. For oxymesterone, a new metabolite, 18-nor-17ß-hydroxymethyl-17α-methyl-4-hydroxy-androst-4,13-diene-3-one, was identified. It was detectable up to 46 days by using GC-CI-MS/MS, whereas with a traditional screening (detection of metabolite 17-epioxymesterone with electron ionization GC-MS/MS) oxymesterone administration was only detectable for 3.5 days. A new metabolite was also found for mesterolone. It was identified as 1α-methyl-5α-androstan-3,6,16-triol-17-one and its sulfate form after hydrolysis with Helix pomatia resulted in a prolonged detection time (up to 15 days) for mesterolone abuse. Copyright © 2017 John Wiley & Sons, Ltd.

Synthesis and antiproliferative evaluation of some novel B-nor-D-homosteroids.

Using 3ß-hydroxy-5-androsten-17-one as a starting material, a series of novel nitrogen-containing B-nor-D-homosteroids were designed and synthesized by the oximation, Beckman rearrangement, ozonation, cyclization and condensation reaction. The structures of all new compounds were determined by analysis of their NMR, MS and IR spectra. The antiproliferative activity of compounds was evaluated against HT-29 (colonic carcinoma), HeLa (human cervical carcinoma) and Bel 7404 (human liver carcinoma) cells.

17ß-carboxamide steroids--in vitro prediction of human skin permeability and retention using PAMPA technique.

In this paper, twenty-two 17ß-carboxamide steroids were synthesized from five corticosteroids (hydrocortisone, prednisolone, methylprednisolone, dexamethasone and betamethasone) in two steps. The first step was periodic acid oxydation of these corticosteroids to corresponding cortienic acids and the second step was amidation of thus obtained cortienic acids with esterified l-amino acids. These compounds are potential soft corticosteroids with local anti-inflammatory activity in the skin. Parallel artificial membrane permeability assay (PAMPA) was applied in order to predict permeability and retention of these compounds in human skin. Comparison of permeability and retention parameters between 17ß-carboxamide steroids and corresponding corticosteroids was performed. Compounds with significantly higher retention were identified and the derivative that does not have significantly higher permeability was underlined. Molecular structures of all compounds were optimized by use of Gaussian semiempirical/PM3 method. Geometrical, thermodynamic, physicochemical and electronical molecular parameters of the optimized structures were calculated and quantitative structure-property relationship (QSPR) analysis was performed in order to explain permeability and retention of these compounds. ANN-, PLS- and MLR-QSPR models were created. Quality of these models was evaluated by commonly used statistical parameters and the most reliable models were selected. Analyzing descriptors in the selected models, main molecular properties that influence permeability and retention in the PAMPA artificial membrane were identified. Based on these data, further structural modifications could be applied in order to increase retention without significant increase of permeability, which can positively affect potential local anti-inflammatory activity of these compounds. Selected QSPR models could be used as in silico tool for predicting human skin permeability and retention of novel 17ß-carboxamide steroids without performing PAMPA experiments.

B-norsteroids from Hymenoscyphus pseudoalbidus.

Two viridin-related B-norsteroids, B-norviridiol lactone (1) and B-norviridin enol (2), both possessing distinct unprecedented carbon skeletons, were isolated from a liquid culture of the ash dieback-causing fungus Hymenoscyphus pseudoalbidus. Compound 2 was found to degrade to a third B-norsteroidal compound, 1ß-hydroxy-2α-hydro-asterogynin A (3), which was later detected in the original culture. The proposed structure of 1 is, regarding connectivity, identical to the original erroneous structure for TAEMC161, which was later reassigned as viridiol. Compound 2 showed an unprecedented ¹H-¹³C HMBC correlation through an intramolecular hydrogen bond. The five-membered B-ring of compounds 1-3 was proposed to be formed by a benzilic acid rearrangement. The known compound asterogynin A was found to be formed from 3 by a ß-elimination of water. All compounds were characterized by NMR spectroscopy, LC-HRMS and polarimetry.

Synthesis and biological evaluation of 16E-arylidenosteroids as cytotoxic and anti-aromatase agents.

Taking into consideration the structural requirements for cytotoxicity and aromatase inhibition, several new 16E-arylidenosteroidal derivatives have been prepared and evaluated for their cytotoxic and aromatase inhibitory activity. The new steroidal analogues 3, 5-8 and 11 exhibited significant cytotoxic effects when screened against three cancer cell lines, MCF-7 (breast), NCl-H460 (lung) and SF-268 central nervous system (CNS) at 100 µM and sensible cytotoxic effects subsequently in sixty cancer cell lines derived from nine cancers types (leukemia, lung, colon, CNS, melanoma, ovarian, renal, prostate and breast cancers). The imidazolyl substituted steroidal derivatives 5 and 7 exhibited strong inhibition of the aromatase enzyme with 16-[4-{3-(imidazol-1-yl)propoxy}-3-methoxybenzylidene]-5-androstene-3ß,17ß-diol (7) displaying 13 times more potency in comparison to aminoglutethimide.

Microbial side-chain degradation of ergosterol and its 3-substituted derivatives: a new route for obtaining of deltanoids.

The strain of Mycobacterium sp. VKM Ac-1815D was found to convert ergosterol and its 3-acetate mainly to androst-4-ene-3,17-dione (AD) thus demonstrating ability to reduce 7(8)-double bond and hydrolyze sterol ester in addition to oxidation of 3beta-hydroxy group, Delta(5)-Delta(4) isomerization and side-chain degradation. Ergosterol bioconversion in the presence of isoflavones and ions of some bivalent metals - known inhibitors of 3beta-hydroxysteroid dehydrogenase, did not alter products composition. Protection of ergosterol 3beta-hydroxyl with methoxymethyl group allowed the formation of bioconversion products retaining the Delta(5,7)-configuration. The major product was identified by mass-spectrometry and proton NMR as 3-methoxymethoxy-androsta-5,7-diene-17-one (MA). The MA producing activity was found to be inducible with sterols, cholestenone or lithocholic acid, but not with dehydroepiandrosterone, AD, androsta-1,4-ene-3,17-dione or organic acids. Under the optimized conditions, the yield of MA reached 5g/l from 10g/l O-methoxymethyl-ergosterol (approx. 60% molar conversion) for 120h. The results might be applied at the production of novel vitamin D derivatives.

9-epi-Viridiol, a novel cytotoxic furanosteroid from soil fungus Trichoderma virens.

A novel furanosteroid named 9-epi-viridiol (1), along with viridiol (2) and mevalonic acid (3), was isolated from Trichoderma virens. The structure of 1 was verified by combined spectroscopic data (COSY, HSQC, HMBC and NOESY) to be a C-9 epimer of viridiol. 9-epi-Viridiol exhibited cytotoxicity towards HeLa and KB cells with IC50 values of 19 and 50 microg mL(-1), respectively.

Multidimensional statistical analysis applied to electron ionization mass spectra to determine steroid stereochemistry.

The differentiation of stereoisomers on the basis of their mass spectra only is usually a difficult challenge even when an informative ionization technique such as electron ionization is used; this is particularly the case for steroids. In this study, multivariate statistical techniques have been applied to the mass spectra of derivatized 5xi-androstane-3xi,17xi-diols (xi = alpha,beta) in order to investigate the possibility of discrimination among the different isomers. After collection of the data from the mass spectra (20 replicates for each of the 8 isomers), each ion was considered as a statistical variable and each mass spectrum as an observation. The more discriminative variables (42 out of the 160 initial ones) were selected using the analysis of variance technique (ANOVA). Thereafter, a linear discriminant analysis (LDA) allowed us to set up a predictive model for stereochemistry determination. The two-dimensional graphical display of the 160 observations on the basis of the canonical variables derived from LDA made it possible to separate the eight isomers. The discrimination of 5alpha and 5beta isomers as well as 3alpha and 3beta was unambiguous, whereas, the discrimination of 17alpha and 17beta epimers was less obvious. The robustness of the model was checked with 40 mass spectra recorded over a 6-month period on different quadrupole mass spectrometers and under different signal acquisition conditions. The percentage of correct assignment of these 'unknown' stereoisomers was 92%; only three 17alpha and 17beta epimers were not correctly plotted in the expected zone. Nevertheless, the performance score was better than those observed with traditional mass spectral libraries. Furthermore, this statistical approach allowed us to identify the main fragment ions involved in the discrimination between isomers: m/z 256 and 421 for isomers 5a-5b; m/z 241 and 331 for isomers 5alpha3alpha-5alpha3beta; m/z 143 and 162 for isomers 5beta3alpha-5beta3beta; and m/z 255 for epimers 17alpha-17beta.

Structure reassignment of the fungal metabolite TAEMC161 as the phytotoxin viridiol.

Two-dimensional NMR analyses including HMBC, NOESY, and ROESY as well as 1D NOE experiments led to a reassignment of the structure of the recently identified Trichoderma hamatum metabolite TAEMC161 (1) as the previously known viridiol (2). In addition, GIAO-calculated (13)C NMR chemical shifts of 1 and 2 provided strong support for the revised structure.

Role of hydrophilic interaction in binding of hydroxylated 3-deoxy C(19) steroids to the active site of aromatase.

As part of our investigation into the structure-activity relationship of a novel class of aromatase inhibitors, C(19) steroids having no oxygen function at C-3, we tested aromatase inhibition activity of polar diol compounds 4,19-dihydroxyandrost-5-en-17-ones (25 and 27) and 6,19-dihydroxyandrost-4-en-17-ones (36 and 37). 4alpha,19-Diol 25 was synthesized from tert-butyldimethylsilyoxyandrost-4-ene steroid (9) through its OsO(4) oxidation, giving the 4alpha,5alpha-dihydroxy derivative 12, as a key reaction. Acetylation of 5beta,6alpha-dihydroxy-19-acetate 30 and its 5alpha,6beta-analogue 31 followed by dehydration with SOCl(2) and alkaline hydroxysis gave 6alpha,19-diol 36 and its 6beta-isomer 37, respectively. The stereochemistry of a hydroxy group at C-4 of compound 25 and that at C-6 of compounds 36 and 37 were determined on the basis of (1)H NMR spectroscopy in each case. 4beta,19-Diol 27, previously synthesized, was identified as an extremely powerful competitive inhibitor of aromatase (K(i) = 3.4 nM). In contrast, its 4alpha,19-dihydroxy isomer 25 and other series of diol compounds, 6,19-dihydroxy-4-en-17-one steroids, were moderate to poor competitive inhibitors (K(i) = 110-800 nM). Through this series of analyses, it was concluded that hydrophilic interaction of a 4beta,19-diol function with the active site of aromatase plays a critical role in the tight binding of 3-deoxy-5-ene steroids.

Regioselective O-alkylation of cortienic acid and synthesis of a new class of glucocorticoids containing a 17 alpha-alkoxy, a 17 alpha-(1'-alkoxyethyloxy), a 17 alpha-alkoxymethyloxy, or a 17 alpha-methylthiomethyloxy function.

The synthesis of a new class of glucocorticoids, to be evaluated as anti-inflammatory agents with expected low systemic toxicity, is described. The new steroids possess a 17 beta-chloromethyl carboxylate function and a 17 alpha-alkoxy, a 17 alpha-(1'-alkoxyethyloxy), a 17 alpha-alkoxymethyloxy, or a 17 alpha-methylthiomethyloxy function. A 17 alpha-alkoxy function is a new feature in cortisol analogs.