Β-resorcylic Acid Research Articles

Studies on phenolic acids variation in Central European Pinus species 1. Five Polish populations of Pinus mugo Turra and some related forms

Phenolic acids were investigated in the needles of eight different pine populations, five of which were <em>Pinus mugo</em>, two -- <em>P. silvestris</em> and one a critical form described by Neumann as <em>P. uliginosa</em>. Twenty different phenolic acids were detected. Six were discovered in pine needles for the first time (salicylic acid, gentisic acid, γ-resorcylic acid, o-hydroxyphenylacetic acid, β-resorcylic acid, p-hydroxyphenylacetic acid). Each of the investigated taxons was shown to exhibit a characteristic spectrum of phenolic acids. The critical form from the locus classicus of <em>Pinus uliginosa</em> is of intermediate character.

Plant-derived antimicrobials reduce E. coli O157:H7 virulence factors critical for colonization in cattle gastrointestinal tract in vitro.

This study investigated the effect of subinhibitory concentrations (SIC) of five plant-derived antimicrobials (PDAs), namely, trans cinnamaldehyde, eugenol, carvacrol, thymol, and β-resorcylic acid, on E. coli O157:H7 (EHEC) attachment and invasion of cultured bovine colonic (CO) and rectoanal junction (RAJ) epithelial cells. In addition, PDAs' effect on EHEC genes critical for colonization of cattle gastrointestinal tract (CGIT) was determined in bovine rumen fluid (RF) and intestinal contents (BICs). Primary bovine CO and RAJ epithelial cells were established and were separately inoculated with three EHEC strains with or without (control) SIC of each PDA. Following incubation, EHEC that attached and invaded the cells were determined. Furthermore, the expression of EHEC genes critical for colonization in cattle was investigated using real-time, quantitative polymerase chain reaction in RF and BICs. All the PDAs decreased EHEC invasion of CO and RAJ epithelial cells (P < 0.05). The PDAs also downregulated (P < 0.05) the expression of EHEC genes critical for colonization in CGIT. Results suggest that the PDAs could potentially be used to control EHEC colonization in cattle; however follow-up in vivo studies in cattle are warranted.

Efficacy of Plant‐Derived Antimicrobials as Antimicrobial Wash Treatments for Reducing Enterohemorrhagic Escherichia Coli O157:H7 on Apples

This study investigated the efficacy of 3 GRAS-status, plant-derived antimicrobials (PDAs), trans-cinnamaldehyde (TC), carvacrol (CR), and β-resorcylic acid (BR) applied as an antimicrobial wash for killing Escherichia coli O157:H7 on apples. "Red delicious" apples inoculated with a 5 strain mixture of E. coli O157:H7 were subjected to washing in sterile deionized water containing 0% PDA (control), 0.15% TC, 0.35% TC, 0.15% CR, 0.30% CR, 0.5% BR, or 1% BR for 1, 3, and 5 min at 23 °C in the presence and absence of 1% soil, and surviving pathogen populations on apples were enumerated at each specified time. All PDAs were more effective in reducing E. coli O157:H7 compared to the water wash treatment (P < 0.05) and reduced the pathogen by 4- to 5-log CFU/apple in 5 min. Chlorine (1%) was the most effective treatment reducing the pathogen on apples to undetectable levels in 1 min (P < 0.05). Moreover, the antimicrobial effect of CR and BR was not affected by the presence of soil, whereas the efficacy of TC and BR was decreased in the presence of soil. Further, no bacteria were detected in the wash solution containing CR and BR; however, E. coli O157:H7 was recovered in the control wash water and treatment solutions containing TC and chlorine, in the presence of 1% soil (P < 0.05). Results suggest that the aforementioned PDAs, especially CR and BR could be used effectively to kill E. coli O157:H7 on apples when used as a wash treatment. Studies on the sensory and quality characteristics of apples treated with PDAs are needed before recommending their usage.

Gentiobiosylation of β-Resorcylic Acid Esters and Lactones: First Synthesis and Characterization of Zearalenone-14-β,d-Gentiobioside

The development of an optimized protocol for the gen­tiobiosylation of β-resorcylic acid esters and lactones (β-RAL) is presented. Different gentiobiosyl donors were prepared and used for regioselective and diastereoselective glycosylation affording a reliable synthetic strategy towards this class of natural product glycosides. The improved procedure was finally used for the preparation of the masked Fusarium mycotoxin zearalenone-14-β, d -gentiobioside.

Sulfation of β-resorcylic acid esters—first synthesis of zearalenone-14-sulfate

Abstract The chemical sulfation of β-resorcylic acid esters was investigated by applying state of the art procedures for the synthesis and deprotection of 2,2,2-trichloroethyl protected sulfates as appropriate intermediates. The selectivity of monosulfation was studied and reaction optimization was performed considering the effect of the solvent, different bases as well as the sulfation reagent itself. Finally the obtained protocols were applied for the first synthesis of zearalenone-14-sulfate (ammonium salt), an important conjugated (masked) mycotoxin, as reference material for further investigations in the field of bioanalytics as well as toxicology.

Zearalenone Mimics: Synthesis of (E)-6-(1-Alkenyl)-substituted β-Resorcylic Acid Esters

Two versatile strategies for the synthesis of mimics of the Fusarium mycotoxin zearalenone (1) have been developed. Optimized preparation of (E)-6-(1-alkenyl) substituted β-resorcylic acid esters was realized via ortho-directed lithiation of variable substrates combined with allylation/isomerization or via formylation/Schlosser–Wittig olefination using different protective group patterns. Spontaneous decarboxylation of (E)-6-(1-alkenyl) substituted β-resorcylic acids indicated the influence of this substituent on the chemical behavior of these compounds. These mimics were already used for the development of optimized standard protocols for the synthesis of phase II metabolites of ZEN (glucosides, glucuronides), and further applications (i.e., sulfate conjugates) are still under investigation. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.

Paecilomycins J–M, four new β-resorcylic acid lactones from Paecilomyces sp. SC0924

Four new β-resorcylic acid lactones, paecilomycins J–M, all possessing an oxygen bridge between C-2′ and C-5′ to form a tetrahydrofuran ring, were isolated from the mycelial solid culture of Paecilomyces sp. SC0924. Their structures were elucidated on the basis of extensive NMR analysis, single-crystal X-ray diffraction, and chemical means. Paecilomycin M exhibited weak antifungal activity against Peronophythora litchii.

Inactivation of Escherichia coli O157:H7 on Cattle Hides by Caprylic Acid and β-Resorcylic Acid

Two naturally occurring, generally recognized as safe compounds, namely, caprylic acid (CA) (1%) and β-resorcylic acid (BR) (1%), and their combination, applied at 23 and 60°C were evaluated for their antimicrobial effects against Escherichia coli O157:H7 on cattle hides in the presence and absence of bovine feces. Fresh cleaned cattle hides were cut into pieces (5 cm2), air dried, and inoculated with a five-strain mixture of nalidixic acid--resistant (50 μg/ml) E. coli O157:H7 (∼8.0 log CFU). The hide samples were air dried under a biosafety hood for 2 h and sprayed with 95% ethanol, 1% CA, 1% BR, or a mixture of 1% CA and 1% BR at 23 or 60°C. The hide samples were kept at 23°C, and E. coli O157:H7 populations were determined at 2 and 5 min after treatment. Both CA and BR were effective in decreasing E. coli O157:H7 populations on hides by 3 to 4 log CFU/cm2 (P < 0.05). Sterile bovine feces had no effect on the decontaminating property of CA and BR on cattle hides (P > 0.05). Results of this study indicate that CA and BR could potentially be used to decontaminate cattle hides, but follow-up research under slaughterhouse conditions is warranted.

Inactivation of Listeria monocytogenes on frankfurters by plant-derived antimicrobials alone or in combination with hydrogen peroxide

Listeria monocytogenes is a significant foodborne pathogen associated with outbreaks involving contaminated ready-to-eat (RTE) products, including frankfurters. The USDA-FSIS has established a zero tolerance policy for L. monocytogenes in RTE products, thereby warranting effective post-processing interventions to control the pathogen on these foods. In the present study, the antilisterial activity of GRAS (generally recognized as safe)-status plant-derived antimicrobials (PDAs), namely β-resorcylic acid (BR), carvacrol (CR), and trans-cinnamaldehyde (TC) either alone or in combination with hydrogen peroxide (HP) as post-processing dip treatments on frankfurters was investigated. Frankfurters were surface inoculated with a five-strain mixture of L. monocytogenes (~6.0logCFU per frankfurter), followed by dip treatment at 55°C for 60s or 65°C for 30s in sterile deionized water, or water containing BR (1.5%), CR (0.75%), or TC (0.75%) either alone or in combination with HP (0.1%). Treated frankfurters were vacuum-packaged, and stored at 4°C for 70days. Representative samples were analyzed on days 0, 1, 3, 7, 14, 28, 42, 56, and 70 of refrigerated storage for enumerating surviving L. monocytogenes on frankfurters. Six frankfurters were sampled at each time point for each treatment. On day zero, all PDAs reduced L. monocytogenes counts by >2logCFU/frankfurter at both temperatures (P<0.05), compared to controls. From days 1 to 70, L. monocytogenes counts on PDA-treated frankfurters were consistently lower (P<0.05) and after 70days of storage, the pathogen counts were reduced to undetectable levels on frankfurters treated with PDA-HP combinations at 65°C, and by combinations of BR and TC with HP at 55°C. Results suggest that PDAs alone, or in combination with HP could be effectively used as post-processing dips to reduce L. monocytogenes on frankfurters, although follow-up studies on sensory and quality characteristics of PDA-treated frankfurters are necessary.

Intensification of slow reversible chemical transformation: carboxylation of resorcinol as a case study

Conjugated kinetic and thermodynamic modeling is suggested as a suitable approach to identify a novel process window (NPW) for the intensification of slow reversible reactions. The aqueous Kolbe-Schmitt synthesis of β-resorcylic acid is taken as a model. The potential of operating at high pressure (P) and temperature (T) is evaluated in order to reduce the characteristic reaction time (tr) and increase the specific productivity. For the first time, a reliable kinetic model for this reaction is derived from batch experiments. Based on this model, an NPW of P=10 bars, T=453 K is determined for a continuous reactor operated at a residence time of 28 s. It is predicted that the specific productivity can be increased by a factor of 100 with a 4.2 times less concentrated KHCO3 solution, as compared to a conventional batch process, if the reaction is kinetically controlled. The model prediction is experimentally validated with a continuously operated milli-reactor equipped by SMXS mixer elements (Sulzer Chemtech, Switzerland) ensuring a fast mixing (characteristic mixing time ~4.10-2 s). The milli-reactor renders exclusively β-resorcylic acid (selectivity 100%) and confirms process intensification (PI) of two orders of magnitude as compared to conventional batch operation.

Fast and reproducible chemical synthesis of zearalenone-14-β,D-glucuronide

The Fusarium mycotoxin zearalenone (ZEA) is mainly converted to the conjugate zearalenone-14-β,D-glucuronide (ZEA-14-GlcA) during phase II detoxification in humans and animals. This metabolite - previously described as zearalenone-4-O-β,D-glucuronide - is excreted via urine and could therefore serve as possible biomarker for ZEA exposure to estimate its intake. Direct determination of this substance is limited by the availability of a reference substance. So far, only the production of small amounts by enzymatic synthesis has been described. In this work, a fast and reproducible protocol for the chemical synthesis of ZEA-14-GlcA was developed, using substituted β-resorcylic acid esters as mycotoxin mimics and different glucuronyl donors for optimising the glycosylation (Königs-Knorr, trifluoroacetimidate method) and the deprotection step. This cost-effective procedure should be easily reproducible in other labs using standard equipment and common reagents.

Kinetic and thermodynamic study of the aqueous Kolbe–Schmitt synthesis of beta-resorcylic acid

Detailed thermodynamic and kinetic study of the aqueous Kolbe–Schmitt synthesis of beta-resorcylic acid has been carried out in a laboratory-scale batch reactor operated under ambient pressure. The dependence of the conversion on partial pressure of carbon dioxide (4×10−4−1bar), initial concentration of resorcinol (0.4–0.8M), initial concentration of potassium bicarbonate (0.4–6M) and temperature (348–428K) was studied. The reaction was found to be reversible and exothermic (ΔH=−30.4kJ/mol). Partial pressure of carbon dioxide does not influence the reaction kinetics when carried out in the excess of potassium bicarbonate (CKHCO3,0/CR,0>1). Increase of the initial concentration of potassium bicarbonate accelerates drastically the rate and shifts the equilibrium conversion to higher values. For the first time a reliable kinetic model has been proposed based on two reversible reactions of pseudo first order towards resorcinol and beta-resorcylic acid. The kinetic constants showed Arrhenius dependencies on the reaction temperature with the apparent energies of activation 105 and 125kJ/mol for the forward and the reversed reactions, respectively. Pre-exponential factors increased with the initial concentration of potassium bicarbonate indicating a complexity of the reaction mechanism involved. The kinetic model was successfully validated against experimental data obtained under high pressure and temperature using a micro-plant. Finally, the model was found consistent with the literature data available for this reaction.

Correction to β-Resorcylic Acid Lactones from a Paecilomyces Fungus

Correction to β-Resorcylic Acid Lactones from a <i>Paecilomyces</i> Fungus

Catechol metabolites of zeranol and 17β-estradiol: A comparative in vitro study on the induction of oxidative DNA damage and methylation by catechol-O-methyltransferase

α-Zearalanol (α-ZAL, zeranol) is a highly estrogenic macrocyclic β-resorcylic acid lactone, which is used as a growth promotor for cattle in various countries. We have recently reported that α-ZAL and its major metabolite zearalanone (ZAN) are hydroxylated at the aromatic ring by microsomes from human liver in vitro, thereby forming two catechol metabolites each. Thus, the oxidative metabolism of α-ZAL and ZAN resembles that of the endogenous steroidal estrogens 17β-estradiol (E2) and estrone (E1), which also give rise to two catechols each. As these catechol metabolites are believed to mediate the carcinogenicity of E2 and E1 by causing oxidative DNA damage and DNA adducts, their methylation by catechol-O-methyltransferase (COMT) is an important inactivation pathway. Here we report that hepatic microsomes from five species generate catechol metabolites of α-ZAL and ZAN, the highest amounts being formed by human liver microsomes, followed by rat, mouse, steer and swine. The microsomal extracts and the individual catechols of α-ZAL, ZAN, E2 and E1 were found to induce oxidative DNA damage, as measured by the formation of 8-oxo-7,8-dihydro-2′-deoxyguanosine in a cell-free system. The ranking of pro-oxidant activity was 15-HO-ZAN>15-HO-α-ZAL≈4-HO-E2/E1≈2-HO-E2/E1>13-HO-ZAN>13-HO-α-ZAL. With respect to the rate of methylation by human hepatic COMT, the ranking was 2-HO-E2/E1>>4-HO-E2/E1>15-HO-α-ZAL/ZAN>>13-HO-α-ZAL/ZAN. Thus, some catechol metabolites of α-ZAL and ZAN are better pro-oxidants and poorer substrates of COMT than the catechols of E2 and E1. These findings warrant further investigations into the genotoxic potential of α-ZAL, which may constitute another biological activity in addition to its well-known estrogenicity.

Monocillin II Inhibits Human Breast Cancer Growth Partially by Inhibiting MAPK Pathways and CDK2 Thr160 Phosphorylation

Twenty-two β-resorcylic acid lactones (RALs) were evaluated for cytotoxicity against human breast cancer cells to find their structure-activity relationship (SAR). Monocillin II, a trans-enone RAL without epoxy and conjugated dienone, was found to have higher activity in inhibiting tumor cell growth in both in vitro experiment and in vivo nude xenografted mice model than its analogue radicicol, an anticancer lead compound. We demonstrated for the first time that monocillin II could arrest breast cancer cell cycle in G1 phase, which might partially be the result of its inhibition effect on the phosphorylation of the Thr160 residue of cyclin dependent kinase 2 (CDK2), a key enzyme in cell-cycle regulation. Moreover, monocillin II exhibited inhibition of heat shock protein 90 (Hsp90) and depleted its target proteins, Raf-1 and A-Raf, which are involved in Ras/Raf/MEK/ERK mitogen-activated protein kinase (MAPK) pathway. Remarkably, we found that monocillin II could inhibit activation of MAPKs including ERK, JNK and p38, which might be involved in the inactivation of CDK2. These results suggest that monocillin II has potential therapeutic benefits in breast cancer prevention and intervention.

Three New Phenolic Compounds from the LichenThamnolia vermicularisand Their Antiproliferative Effects in Prostate Cancer Cells

Three new phenolic compounds, thamnoliadepsides A (1), B (2), and thamnolic acid A (3), and seven known compounds, everninic acid (4), baeomycesic acid (5), β-orcinol (6), β-resorcylic acid (7), ethyl orsellinate (8), squamatic acid (9), and vermicularin (10), were isolated from the lichen Thamnolia vermicularis (Sw.) Ach. ex Schaerer. Their structures were determined based on spectroscopic analysis, including 2D-NMR experiments and HR-MS techniques. Compound 1 inhibited growth of prostate cancer cells and bonded to G-quadruplex DNA based on NMR determination.

Solid-State Forms of β-Resorcylic Acid: How Exhaustive Should a Polymorph Screen Be?

A combined experimental and computational study was undertaken to establish the solid-state forms of β-resorcylic acid (2,4-dihydroxybenzoic acid). The experimental search resulted in nine crystalline forms: two concomitantly crystallizing polymorphs, five novel solvates (with acetic acid, dimethyl sulfoxide, 1,4-dioxane, and two with N,N-dimethyl formamide), in addition to the known hemihydrate and a new monohydrate. Form II°, the thermodynamically stable polymorph at room temperature, was found to be the dominant crystallization product. A new, enantiotropically related polymorph (form I) was obtained by desolvation of certain solvates, sublimation experiments, and via a thermally induced solid−solid transformation of form II° above 150 °C. To establish their structural features, interconversions, and relative stability, all solid-state forms were characterized with thermal, spectroscopic, X-ray crystallographic methods, and moisture-sorption analysis. The hemihydrate is very stable, while the five solvates and the monohydrate are rather unstable phases that occur as crystallization intermediates. Complementary computational work confirmed that the two experimentally observed β-resorcylic acid forms I and II° are the most probable polymorphs and supported the experimental evidence for form I being disordered in the p-OH proton position. These consistent outcomes suggest that the most practically important features of β-resorcylic acid crystallization under ambient conditions have been established; however, it appears impractical to guarantee that no additional metastable solid-state form could be found.

Inactivation of Salmonella spp. on tomatoes by plant molecules

The efficacy of carvacrol (CAR), trans-cinnamaldehyde (TC), eugenol (EUG) and β-resorcylic acid (BR) as a wash treatment for reducing Salmonella spp. on tomatoes was investigated. Plum tomatoes inoculated with a six-serotype mixture of Salmonella (108CFU) were subjected to washing in sterile deionized water (control) or deionized water containing chlorine (100ppm), CAR (0.25 and 0.75%), TC (0.5 and 0.75%), EUG (0.25 and 0.75%), or BR (0.75 and 1.0%) for 15sec, 1min, and 3min. The plant molecules were more effective (P<0.05) in reducing Salmonella on tomatoes compared to washing in water and chlorine. Both concentrations of CAR and TC, and 0.75% EUG decreased Salmonella counts on tomatoes by~6.0 log CFU/ml at 1min. Both concentrations of BR decreased the pathogen on tomatoes to undetectable levels at 3min of exposure. Washing of tomatoes in deionized water and chlorine for 3min reduced Salmonella by ca. 2.0 and 4.0 log CFU/ml, respectively. No Salmonella was detected in the wash water containing the plant molecules or chlorine, whereas a substantial population of the pathogen survived in the control wash water. Moreover, none of the dipping treatments had any effect on the red color of tomatoes (P>0.05). Results indicate that CAR, TC, EUG and BR could effectively be used to kill Salmonella on tomatoes, but additional studies on sensory and quality characteristics of tomatoes treated with plant molecules are warranted.

Zearalenone and its metabolites as endocrine disrupting chemicals

Zearalenone (ZEA) is a macrocyclic β-resorcylic acid lactone produced by numerous species of Fusarium. It frequently contaminates corn and cereal products in many regions of the world. The biological activity of ZEA is dominated by its pronounced oestrogenicity, which is even enhanced in certain reductive metabolites. This review updates the metabolism in fungi, plants and mammalian systems, as well as the pharmacokinetics of ZEA. The present evidence for the hormonal effects of the parent mycoestrogen and some of its metabolites in vitro and in farm and experimental animals in vivo is reviewed, together with its association with endocrine-disruptive effects in humans. Possible mechanisms of the oestrogenic and carcinogenic activity of ZEA are discussed and future areas of research proposed.

Effect of Subinhibitory Concentrations of Plant-Derived Molecules in Increasing the Sensitivity of Multidrug-Resistant Salmonella enterica Serovar Typhimurium DT104 to Antibiotics

This study investigated the efficacy of plant-derived antimicrobials, namely, trans-cinnamaldehyde, β-resorcylic acid, carvacrol, thymol, and eugenol or their combination, in increasing the sensitivity of Salmonella Typhimurium DT104 to five antibiotics. The subinhibitory concentrations of each antimicrobial or their combination containing concentrations lower than the individual subinhibitory concentrations were added to tryptic soy broth supplemented with antibiotics at their respective break points for resistance. Salmonella Typhimurium DT104 was inoculated into tryptic soy broth at ~6 log CFU/mL, and growth (optical density at 600 nm) was determined before and after incubation at 37° C for 24 hours. Appropriate controls were included. Duplicate samples were assayed and the experiment was replicated three times. Trans-cinnamaldehyde increased the sensitivity of Salmonella Typhimurium DT104 (p<0.05) toward all five antibiotics, namely, ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline, thereby making the pathogen susceptible to drugs. Thymol made the pathogen susceptible to all four antibiotics except ampicillin, whereas carvacrol increased the sensitivity to two antibiotics (chloramphenicol and sulfamethoxazole for strain H3380, and streptomycin and sulfamethoxazole for strain 43). The combination of five molecules was more effective than individual ones (p<0.05) in rendering the pathogen susceptible to the antibiotics. Results indicate that these natural molecules individually and synergistically increased the sensitivity of Salmonella Typhimurium DT104 to all the five antibiotics, and justify future studies to control antibiotic resistance of the pathogen in food animals using these plant molecules.