Β-resorcylic Acid Research Articles

Antifungal and Cytotoxic β-Resorcylic Acid Lactones from a Paecilomyces Species.

Eight new β-resorcylic acid lactones (RALs), including the hypothemycin-type compounds paecilomycins N-P (1-3) and the radicicol-type metabolites dechloropochonin I (4), monocillins VI (5) and VII (6), 4'-hydroxymonocillin IV (7), and 4'-methoxymonocillin IV (8), along with nine known RALs (9-17), were isolated from the cultures of Paecilomyces sp. SC0924. Compounds 1 and 2 feature a novel 6/11/5 ring system, and 3 is the first 5'-keto RAL. The structures of 1-8 were elucidated on the basis of extensive spectroscopic analysis, X-ray diffraction analysis, and theoretical calculations of ECD spectra. Compounds 3, 5, and 6 exhibit cytotoxicity against MCF-7, A549, and HeLa cells, and compounds 5 and 7 display antifungal activity against Peronophythora litchii.

Formation of Supramolecular Structures in the β-Cyclodextrin–β-Resorcylic Acid System

It was found with the help of spectrophotometry, IR spectroscopy, X-ray phase analysis, and thermogravimetry, that new supramolecular structures in the β-cyclodextrin–β-resorcylic acid system are generated as a result of a spontaneous exothermic process. It was proven that the inclusion complexes of the host–guest type with a 1:1 ratio between β-cyclodextrin and the molecular form of β-resorcylic acid (or its monovalent anion) are formed through van der Waals interactions of the aromatic ring of β-resorcylic acid with the inner hydrophobic cavity of β-cyclodextrin. It was shown that partial displacement of water molecules from the inner cavity of the cyclic oligosaccharide and complete immersion of β-resorcylic acid molecule inside it occur in this case; thermal stability of β-resorcylic acid increases.

Application of β-Resorcylic Acid as Potential Antimicrobial Feed Additive to Reduce Campylobacter Colonization in Broiler Chickens.

Campylobacter is one of the major foodborne pathogens that result in severe gastroenteritis in humans, primarily through consumption of contaminated poultry products. Chickens are the reservoir host of Campylobacter, where the pathogen colonizes the ceca, thereby leading to contamination of carcass during slaughter. A reduction in cecal colonization by Campylobacter would directly translate into reduced product contamination and risk of human infections. With increasing consumer demand for antibiotic free chickens, significant research is being conducted to discover natural, safe and economical antimicrobials that can effectively control Campylobacter colonization in birds. This study investigated the efficacy of in-feed supplementation of a phytophenolic compound, β-resorcylic acid (BR) for reducing Campylobacter colonization in broiler chickens. In two separate, replicate trials, day-old-chicks (Cobb500; n = 10 birds/treatment) were fed with BR (0, 0.25, 0.5, or 1%) in feed for a period of 14 days (n = 40/trial). Birds were challenged with a four-strain mixture of Campylobacter jejuni (∼106 CFU/ml; 250 μl/bird) on day 7 and cecal samples were collected on day 14 for enumerating surviving Campylobacter in cecal contents. In addition, the effect of BR on the critical colonization factors of Campylobacter (motility, epithelial cell attachment) was studied using phenotypic assay, cell culture, and real-time quantitative PCR. Supplementation of BR in poultry feed for 14 days at 0.5 and 1% reduced Campylobacter populations in cecal contents by ∼2.5 and 1.7 Log CFU/g, respectively (P < 0.05). No significant differences in feed intake and body weight gain were observed between control and treatment birds fed the compound (P > 0.05). Follow up mechanistic analysis revealed that sub-inhibitory concentration of BR significantly reduced Campylobacter motility, attachment to and invasion of Caco-2 cells. In addition, the expression of C. jejuni genes coding for motility (motA, motB, fliA) and attachment (jlpA, ciaB) was down-regulated as compared to controls (P < 0.05). These results suggest that BR could potentially be used as a feed additive to reduce Campylobacter colonization in broilers.

Antioxidant and antimicrobial activity of linseed lignans and phenolic acids

In this study, we present antioxidant and antimicrobial activity of isolated lignans freed of other bioactive compounds in comparison with dominant phenolic acids. The combinations of screw pressing, solvent extractions, acid-catalysed hydrolysis and flash chromatography were used to describe and isolate linseed phenolic compounds. Secoisolariciresinol, ferulic, p-coumaric and caffeic acids were the most abundant ones while salicylic, gentisic, dihydro-p-coumaric, phenylacetic, vanillic, p-hydroxybenzoic and β-resorcylic acids were the minor secondary metabolites. Anhydrosecoisolariciresinol (ANHSECO) and levulinic acid were an artefacts formed during exhaustive hydrolysis. The effective concentration (EC50), antiradical power (1/EC50), stoichiometry (2·EC50) values and second order rate constants k 2 were determined to classify antioxidants according to reaction kinetics as slow (p-coumaric acid derivatives), medium (ferulic acid derivatives, secoisolariciresinol and ANHSECO; k 2 ranges from 1.85 to 2.29 μmol−1 dm3 s−1) and fast (caffeic acid derivatives; k 2 = 6.91 μmol−1 dm3 s−1) ones. Rancimat method was simulating lipid peroxidation and its inhibition. Linseed lignans and phenolic acids could be classified according to protection of unsaturated triacylglycerols in the following order: p-coumaric acid < ANHSECO < methyl p-coumarate < ferulic acid < secoisolariciresinol < methyl ferulate < crude extract < caffeic acid < methyl caffeate. The mechanism and the formation of secoisolariciresinol oxidation products were discovered by mass spectrometry. The effect of crude linseed extract, ANHSECO, caffeic, ferulic and p-coumaric acid on the growth of Gram-negative bacteria, Gram-positive bacteria, yeasts and moulds was also determined.

A new seco-pimarane diterpene and four new β-resorcylic acid lactones from a fungicolous Hypomyces subiculosus

One new seco-primarane diterpene and four new β-resorcylic acid lactones were isolated and identified from the fungicolous Hypomyces subiculosus.

Lasiodiplactone A, a novel lactone from the mangrove endophytic fungus Lasiodiplodia theobromae ZJ-HQ1.

Lasiodiplactone A (1), an unprecedented lactone, was obtained from the mangrove endophytic fungus Lasiodiplodia theobromae ZJ-HQ1. The structure of 1 was established by analysis of NMR spectroscopic data and electronic circular dichroism (ECD) spectra. Lasiodiplactone A (1) was the first example of lactone that possesses a unique tetracyclic system (12/6/6/5) of RAL12 (12-membered β-resorcylic acid lactone) with a pyran ring and a furan ring. A possible biogenetic pathway for 1 was proposed. Compound 1 showed anti-inflammatory activity by inhibiting nitric oxide (NO) production in lipopolysaccharide activated in RAW264.7 cells with IC50 value of 23.5 μM and exhibited potential α-glucosidase inhibitory activity with IC50 values of 29.4 μM.

In Russian

in Russian

Efficacy of Plant-Derived Antimicrobials in Controlling Enterohemorrhagic Escherichia coli Virulence In Vitro

Escherichia coli O157:H7 is a major foodborne pathogen that can cause serious human illness characterized by hemorrhagic diarrhea and kidney failure. The pathology of enterohemorrhagic E. coli O157:H7 (EHEC) infection is primarily mediated by verotoxins, which bind to the globotriaosylceramide receptor on host cells. Antibiotics are contraindicated for treating EHEC infection because they lead to increased verotoxin release, thereby increasing the risk of renal failure and death in patients. Thus, alternative strategies are needed for controlling EHEC infections in humans. This study investigated the effect of subinhibitory concentrations of five plant-derived antimicrobial agents (PDAs) that are generally considered as safe, i.e., trans-cinnamaldehyde, eugenol, carvacrol, thymol, and β-resorcylic acid, on EHEC motility, adhesion to human intestinal epithelial cells, verotoxin production, and virulence gene expression. All tested PDAs reduced EHEC motility and attachment to human intestinal epithelial cells (P < 0.05) and decreased verotoxin synthesis by EHEC. The reverse transcription real-time PCR data revealed that PDAs decreased the expression of critical virulence genes in EHEC (P < 0.05). The results collectively suggest that these PDAs could be used to reduce EHEC virulence, but follow-up studies in animal models are necessary to validate these findings.

Inactivation of Salmonella enteritidis on shell eggs by coating with phytochemicals

Salmonella enteritidis (SE) is a major foodborne pathogen that causes human infections largely by consumption of contaminated eggs. The external surface of eggs becomes contaminated with SE from multiple sources, highlighting the need for effective egg surface disinfection methods. This study investigated the efficacy of three GRAS-status, phytochemicals, namely carvacrol (CR), eugenol (EG), and β-resorcylic acid (BR) applied as pectin or gum arabic based coating for reducing SE on shell eggs. White-shelled eggs, spot inoculated with a 5-strain mixture of nalidixic acid (NA) resistant SE (8.0 log CFU/mL) were coated with pectin or gum arabic solution containing each phytochemical (0.0, 0.25, 0.5, or 0.75%), and stored at 4°C for 7 days. SE on eggs was enumerated on days 0, 1, 3, and 7 of storage. Approximately 4.0 log CFU/egg of SE was recovered from inoculated and pectin or gum arabic coated eggs on day 0. All coating treatments containing CR and EG, and BR at 0.75% reduced SE to undetectable levels on day 3 (P <0.05). Results suggest that the aforementioned phytochemicals could effectively be used as a coating to reduce SE on shell eggs, but detailed studies on the sensory and quality attributes of coated eggs need to be conducted before recommending their use.

Synthesis and cytotoxic activities of semisynthetic zearalenone analogues

Zearalenone is a β-resorcylic acid macrolide with various biological activities. Herein we report the synthesis and cytotoxic activities of 34 zearalenone analogues against human oral epidermoid carcinoma (KB) and human breast adenocarcinoma (MCF-7) cells as well as noncancerous Vero cells. Some zearalenone analogues showed moderately enhanced cytotoxic activities against the two cancer cell lines. We have discovered the potential lead compounds with diminished or no cytotoxicity to Vero cells. Preliminary structure–activity relationship studies revealed that the double bond at the 1′ and 2′ positions of zearalenone core was crucial for cytotoxic activities on both cell lines. In addition, for zearalenol analogues, the unprotected hydroxyl group at C-2 and an alkoxy substituent at C-4 played key roles on cytotoxic effects of both cell lines.

Efficacy of beta-resorcylic acid spray in reducing Escherichia coli O157:H7 on flat cut beef steaks

Efficacy of beta-resorcylic acid spray in reducing Escherichia coli O157:H7 on flat cut beef steaks

Synthon preference in a hydrated β-resorcylic acid structure and its cocrystal with thymine.

Multicomponent crystals or cocrystals play a significant role in crystal engineering, the main objective of which is to understand the role of intermolecular interactions and to utilize such understanding in the design of novel crystal structures. Molecules possessing carboxylic acid and amide functional groups are good candidates for forming cocrystals. β-Resorcylic acid monohydrate, C7H6O4·H2O, (I), crystallizes in the triclinic space group P-1 with one β-resorcylic acid molecule and one water molecule in the asymmetric unit. The cocrystal thymine-β-resorcylic acid-water (1/1/1), C5H6N2O2·C7H6O4·H2O, (II), crystallizes in the orthorhombic space group Pca21, with one molecule each of thymine, β-resorcylic acid and water in the asymmetric unit. All available donor and acceptor atoms in (I) and (II) are utilized for hydrogen bonding. The acid and amide functional groups are well known for the formation of self-complementary acid-acid and amide-amide homosynthons. In (I), an acid-acid homosynthon is observed, while in (II), an amide-acid heterosynthon is present. In (I), the β-resorcylic acid molecule exhibits the expected intramolecular S(6) motif between the hydroxy and carbonyl O atoms, and an intermolecular R2(2)(8) dimer motif between the carboxylic acid groups; only the former motif is observed in (II). The water solvent molecule in (I) propagates the discrete dimers into two-dimensional hydrogen-bonded sheets. In (II), thymine and β-resorcylic acid molecules do not form self-complementary amide-amide and acid-acid homosynthons; instead, a thymine-β-resorcylic acid heterosynthon is observed. With the help of the water molecule, this heterosynthon is aggregated into a three-dimensional hydrogen-bonded network. The absence of thymine base pairing in (II) might be linked to the availability of additional functional groups and the preference of the donor and acceptor hydrogen-bond combinations.

Synergism between carvacrol or thymol increases the antimicrobial efficacy of soy sauce with no sensory impact

Here, we examined the antimicrobial effects of soy sauce containing essential oils (EOs) against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes at 22°C and 4°C. To screen a variety of combined effects, soy sauce was mixed with six different EOs (carvacrol, thymol, eugenol, trans-cinnamaldehyde, β-resorcylic acid, and vanillin), each at a concentration of 1mM for 10min. None of the oils showed bactericidal activity when used alone. Soy sauce combined with carvacrol and thymol induced the greatest antibacterial activity against all tested bacteria; therefore, these oils were further tested at 0.25, 0.5, and 1mM (0.0039%, 0.0078%, and 0.0157%) for 1, 5, and 10min at 4°C and 22°C. In addition, sensory evaluation of soy sauce containing each EO at 0.25, 0.5, 1, and 2mM was performed using the nine point hedonic test. Carvacrol or thymol (1mM) eliminated all the test bacteria (initial population, 7.0–7.5logCFU/ml) in 1–5min at 22°C and within 10min at 4°C. L. monocytogenes was slightly more tolerant at 4°C, which may be attributable to the ability of the cell membrane to adapt to low temperatures. The sensory scores for soy sauce containing EOs were not significantly different from that of soy sauce without EOs (P>0.05). The stability of EO efficacy in soy sauce was also verified. These results suggest that carvacrol and thymol act synergistically with other factors present in soy sauce to increase antimicrobial activity against major foodborne pathogens at both 4°C and 22°C. The synergism may be attributable to the combination of factors (mainly high salt concentration and low pH imparted by organic acids) present in soy sauce and the membrane attacking properties of carvacrol and thymol. This method will facilitate the production of microbiologically safe soy sauce, soy sauce-based marinades, and various marinated foods.

Highly enhanced bactericidal effects of medium chain fatty acids (caprylic, capric, and lauric acid) combined with edible plant essential oils (carvacrol, eugenol, β-resorcylic acid, trans-cinnamaldehyde, thymol, and vanillin) against Escherichia coli O157:H7

Medium chain fatty acids (MCFAs) and essential oils (EOs) are known to be natural antimicrobials, but their combined effects have not been fully investigated. The objective of the present study was to examine the bactericidal effects of various combined treatments of MCFAs [caprylic (CA), capric (CPA), and lauric acid (LRA)] and EOs [carvacrol (CAR), eugenol (EUG), β-resorcylic acid (RA), trans-cinnamaldehyde (TC), thymol (TM), and vanillin (VNL)]. Escherichia coli O157:H7, was treated with 1) control (2% ethanol), 2) MCFA alone, 3) EO alone, and 4) different combinations of MCFAs and EOs at 37 °C for 5 and 10 min. Synergistic bactericidal effects were observed with combined treatments; the log reduction in viable bacteria in response to the combined treatments was much greater than the sum of the effects of the two compounds applied individually. For example, individual treatment with 0.2 mM CPA (0.004%) and 0.4 mM RA (0.006%) for 5 min resulted in a negligible reduction in bacterial load (0.25 and 0.21 log reduction, respectively), whereas combined treatment at the same concentrations and for the same time reduced the bacterial population in the test sample to an undetectable level (initial population: 7.51 log CFU/ml; detection limit: 1 CFU/ml). The ranking of EOs showing the highest bacterial killing activities when combined with MCFAs was generally RA, CAR, TM > EUG > TC > VNL. All the antimicrobials used in this study are natural compounds that have been widely used in industry, so they are both consumer- and user-friendly. Combined treatment can overcome the disadvantages of MCFAs and EOs such as unpleasant odor and high cost because the required concentrations can be reduced. Our results indicate that the combined treatments used here could be successfully used to eliminate foodborne pathogens, significantly improving the microbiological safety of foods.

β-Resorcylic acid derivatives with α-glucosidase inhibitory activity from Lasiodiplodia sp. ZJ-HQ1, an endophytic fungus in the medicinal plant Acanthus ilicifolius

Three new β-resorcylic acid derivatives, compounds 1–3, along with six known analogues (4–9) were isolated from an endophytic fungus Lasiodiplodia sp. ZJ-HQ1 derived from medicinal plant Acanthus ilicifolius. Their structures were elucidated by 1D and 2D NMR spectroscopic analysis, high resolution mass spectrometric (HREIMS) data, and X-ray crystallography. The absolute configurations of compounds 1 and 2 were determined by the modified Mosher’s method. Compounds 1–7 showed more potent inhibitory effects against α-glucosidase activity than the clinical α-glucosidase inhibitor acarbose.

Conversion of carbon dioxide to resorcylic acid under ultrasonication by Kolbe–Schmitt reaction

The present work focuses on a new approach for the synthesis of β-resorcylic acid based on Kolbe–Schmitt reaction using carbon dioxide under ultrasonic and mild condition. The Kolbe–Schmitt reaction is a process for the synthesis of β-resorcylic acid (2,4-dihydroxybenzoic acid) from resorcinol in aqueous potassium hydroxide solution with gaseous CO2. The influences of carbonation time, flow rate of CO2 and the molar ratio of resorcinol/potassium hydroxide on the yield percentage of resorcylic acid were investigated. The study was assessed with the conventional thermal method (non ultrasonic method) for Kolbe–Schmitt reaction and it was observed that applying ultrasound to save more than 95% and 38.6% energy as shown by energy consumption calculations in bath type and horn type sonicator respectively. β-Resorcylic acid formed was characterized by 1H NMR, 13C NMR, DEPT NMR and FTIR spectroscopy. The amount of CO2 utilized in the reaction was evaluated from the yield percentage of β-resorcylic acid yield. The maximum yield of resorcylic acid of 30% and 65% was obtained at the resorcinol/potassium hydroxide ratio of 1:3, carbonation time of 150min and the CO2 flow rate of 2L/min in bath type and horn type ultrasonicator, respectively. The applicability of the research work was examined in two different positional isomers of resorcinol under optimum conditions.

The chemistry of resorcinol carboxylation and its possible application to the CO2 removal from exhaust gases

The carbon dioxide uptake by resorcinol solutions has been investigated under different operational procedures and experimental conditions. Batch experiments have been carried out in aqueous and glycerol–water solutions of KOH, KHCO3 or K2CO3, and the yield of resorcinol carbonatation has been investigated as a function of the CO2 partial pressure as well as reaction temperature and time. The β-resorcylic acid (2,4-dihydroxy benzoic acid) has been isolated in the solid state and identified on the basis of its IR spectrum. The 13C NMR analysis has been applied to identify and quantify the carbonated species in solution upon CO2 uptake and after thermal resorcinol regeneration. The maximum yield of resorcinol conversion into β-resorcylic acid was 60% with 1.0bar of CO2 and 120min reaction time at 110°C. A 34% yield of resorcinol conversion was also obtained with the resorcinol/K2CO3 solution in the absence of CO2. A relationship between the CO2 absorption capacity and the possible mechanism of CO2 capture has been proposed. The CO2 absorption efficiency from a simulated flue gases (15% CO2 in air) has been measured in continuous cycles of CO2 absorption–desorption carried out in packed columns and with a glycerol–water solution of resorcinol/KOH/KHCO3. The maximum absorption efficiency was 82% at absorption-desorption temperatures of 70°C and, respectively, 170°C. Oxidative conditions and the presence of H2S did not affect the yield of β-resorcylic acid and the resorcinol capacity of CO2 capture. Finally, a simple method for the selective separation of H2S from CO2 has been reported.

Design, synthesis and biological evaluation of FLT3 covalent inhibitors with a resorcylic acid core

A series of simplified ring-opened resorcylic acid lactone (RAL) derivatives were conveniently synthesized to target FLT3 and its mutants either irreversibly or reversibly. Our design of covalent FLT3 inhibitors is based on cis-enone RALs (e.g., L-783,277) that have a β-resorcylic acid as the core structure. The designed compounds contain three types of Michael acceptors (acrylamide, vinylsulfonamide and maleimide) as potential covalent traps of a cysteine residue at the binding site of kinases. A variety of functional substitutions were also introduced to maximize the binding interactions. Biological evaluations revealed that compound 17, despite the presence of a highly reactive maleimide Michael acceptor, is a potent covalent FLT3 inhibitor which shows some specificity in cellular assays. On the other hand, compounds 2 and 6 containing acrylamide or vinylsulfonamide groups are reversible towards FLT3 binding, and are potent and selective inhibitors of mutant FLT3-ITD versus wt-FLT3. They also inhibit cell proliferation in FLT3-ITD expressing cell line MV-4-11 as compared to wt-FLT3 expressing cell line THP-1 and non-FLT3 cell lines (K562, HL60 and Hek-293T).

Efficacy of plant-derived compounds combined with hydrogen peroxide as antimicrobial wash and coating treatment for reducing Listeria monocytogenes on cantaloupes

The efficacy of four plant-derived antimicrobials (PDAs), namely carvacrol, thymol, β-resorcylic acid, and caprylic acid, with or without hydrogen peroxide (HP), as antimicrobial wash and chitosan based coating for reducing Listeria monocytogenes (LM) on cantaloupes was investigated. Cantaloupe rind plugs inoculated with LM (107 CFU/cm2) were washed for 3, 6, 10 min at 25 °C or 1, 3, 5 min at 55 or 65 °C in water, or water containing 2% PDAs with or without 2% HP. Additionally, inoculated cantaloupes (108 CFU/fruit) washed with 2% PDA-HP combinations at 55 or 65 °C (5 min) were cut into rindless cubical pieces, stored at 4 °C for 7 days and sampled for LM. Furthermore, inoculated plugs coated with 2% PDAs were stored for 7 days and sampled for surviving LM. Individual PDA washes reduced LM on rinds by ≥2.5 log CFU/cm2 by 3 min (P < 0.05). PDA-HP combinations decreased LM to undetectable levels by 5 min at 55, 65 °C, and 10 min at 25 °C (P < 0.05) and reduced LM transfer from cantaloupe surface to interior (P < 0.0001). All PDA coating treatments reduced LM on cantaloupe to undetectable levels by 5 days (P < 0.05). Results indicate that PDAs alone, or with HP could be used to reduce LM on cantaloupes.

In vitro antioxidant, anti-mutagenic, anti-cancer and anti-angiogenic effects of Chinese Bowl tea

The in vitro bioactivities of Chinese Bowl tea for its antioxidant, anti-mutagenic, anti-cancer and anti-angiogenic effects were investigated. The tea extract showed high antioxidant activity both in the DPPH and hydroxyl radical scavenging activities. At concentrations of 1.25 and 2.5mg/plate, the tea extract exhibited an anti-mutagenicity induced by MNNG (N-methyl-N′-nitro-N-nitrosoguanidine) against the Salmonella typhimurium TA100 strain. High concentration (200μg/mL) of the tea extract significantly induced apoptosis in human tongue carcinoma TCA8113 cells by upregulating Bax, caspase-3, and caspase-9, and downregulating Bcl-2. The expression of genes associated with inflammation, e.g., NF-κB, iNOS, and COX-2, was significantly downregulated by the tea extract, demonstrating its anti-inflammatory properties. In addition, the tea showed strong anti-angiogenic effect at high concentrations. Moreover, LC–MS/MS analysis showed that gallic acid, beta-resorcylic acid, quercetin and kaempferol and their derivatives may contribute to the above mentioned effects. Especially beta-resorcylic acid showed strong anticancer effect in vitro. Beta-resorcylic acid was tested by MTT and RT-PCR assays. 100μg/mL beta-resorcylic acid showed the effect as 200μg/mL Bowl tea did, which indicated that it is an important compound in Bowl tea.