Phenolic Inhibitors Research Articles

Nanodisc-associated acetylcholinesterase as a novel model system of physiological relevant membrane-bound cholinesterases. Inhibition by phenolic compounds

Acetylcholinesterase (AChE) plays a pivotal role in the cholinergic system, and its inhibition is sought after in a wide range of applications, from insect control to Alzheimer's disease treatment. While the primary physiological isoforms of AChE are membrane-bound proteins, most assays for discovering new, safer, and potent inhibitors are conducted using commercially available soluble isoforms, such as the electric eel AChE (eeAChE). In this study, we conducted a comparative analysis of the activity and selectivity to phenolic inhibitors of recombinant human AChE, eeAChE and a mutant variant of human AChE known as dAChE4. Despite numerous mutations, dAChE4 closely resembles its parental protein and serves as a suitable model for monomeric human AChE. We also established an in vitro system of membrane-bound AChE to create a model that closely mimics the physiological isoforms. This system ensures the proper work of the enzyme and allowed us to control the exact concentration of enzyme and lipids per assay.

Removal of phenolic inhibitor compounds from hydrolysates and post-fermentation broths by using a hydrophobic magnetic deep eutectic solvent

Hydroxymethylfurfural (HMF), furfural (FF), hydroquinone (HQ), and vanillin (VAN) are among the main inhibitors generated during most of biomass pre-treatments prior to fermentation processes. They are recognized as toxic to several fermentative microorganisms and therefore cause a decrease in biohydrogen or biofuel production (after hydrolysis). Moreover, if they are released into aqueous solutions (after fermentation), they can be detrimental to the ecosystem. In this research, a new method for removing these inhibitor compounds from the broth after hydrolysis and fermentation is proposed. A hydrophobic magnetic deep eutectic solvent (HMDES), based on menthol: nonanoic acid in a mole ratio of 2:1 was prepared and magnetized with Fe3O4 nanoparticles and applied for effective sorption and removal of these inhibitors from the broth after fermentation and for biomass hydrolysates. Parameters affecting sorption, such as pH, volume of the inhibitors, initial concentration of inhibitors, volume of HMDES, temperature, stirring speed, and contact time, were studied and optimized. Under optimum conditions, the removal efficiency for HQ, HMF, FF, and VAN was obtained as 92.97, 86.72, 82.86 and 95.12% for the model samples. In addition, the removal efficiency of real samples after hydrolysis and fermentation for HQ, HMF, FF and VAN were higher than 83.3, 71.42, 69.99 and 76.80%, respectively. The studies on HMDES regeneration revealed that the removal efficiency remained constant even after undergoing 13 cycles of regeneration. The mechanism of inhibitor removal suggests that hydrogen bonding or van der Waals interactions may serve as the predominant factor influencing the extraction process.

Efficient production of butyric acid from lignocellulosic biomass by revealing the mechanisms of Clostridium tyrobutyricum tolerance to phenolic inhibitors

Phenolic compounds (PCs) generated during pretreatment of lignocellulosic biomass severely hinder the biorefinery by Clostridia. As a hyperbutyrate-producing strain, Clostridium tyrobutyricum has excellent tolerance to PCs, but its tolerance mechanism is poorly understood. In this study, a comprehensive transcriptome analysis was applied to elucidate the response of C. tyrobutyricum to four typical PCs. The findings revealed that the expression levels of genes associated with PC reduction, HSPs, and membrane transport were significantly altered under PC stress. Due to PCs being reduced to low-toxicity alcohols/acids by C. tyrobutyricum, enhancing the reduction of PCs by overexpressing reductase genes could enhance the strain’s tolerance to PCs. Under 1.0 g/L p-coumaric acid stress, compared with the wild-type strain, ATCC 25755/sdr1 exhibited a 31.2 % increase in butyrate production and a 38.5 % increase in productivity. These insights contribute to the construction of PC-tolerant Clostridia, which holds promise for improving biofuel and chemical production from lignocellulosic biomass.

Promoting microbial fermentation in lignocellulosic hydrolysates by removal of inhibitors using MTES and PEI-modified chitosan-chitin nanofiber hybrid aerogel

To further enhance the removal efficiency for furanic and phenolic compounds in lignocellulosic hydrolysates, a new detoxification strategy was proposed, which retained fermentable sugars and promoted the growth and metabolism of subsequent bacteria. The best adsorbent (P/M-CCA) was prepared by hybrid chitosan-chitin nanofiber, graft modification with polyethylenimine, and silanization with methyl triethoxylsilane in order. Taken corn cob hydrolysate as object, the removal rates of HMF and furfural were 85.1 % and 99.0 %, respectively. The removal rates of six out of nine phenolic inhibitors were 100 %, and the other three were more than 65 %. Even better, the retention rates of glucose and xylose were both 100 %. In contrast to no growth in undetoxified hydrolysates, Bacillus coagulans grew normally in detoxified hydrolysates, and lactic acid reached 19.1 g/L after 12 h fermentation. P/M-CCA achieves both removal of multiple inhibitors and retain sugars, which would promote the valorization of highly toxic lignocellulosic hydrolysates.

Efficient polymalic acid production from corn straw hydrolysate by detoxification of phenolic inhibitors.

Inhibitory compounds generated from lignocellulose pretreatment would inhibit Poly (malic acid) (PMA) production by Aureobasidium pullulans, but the tolerance mechanism of A. pullulans to lignocellulosic inhibitor is poorly understood. In this study, the cellular response of A. pullulans to lignocellulosic inhibitor stress was studied. Among the three groups of inhibitors (furans, weak acids and phenolic aldehydes), phenolic aldehyde was the dominant inhibitor for PMA production. Phenolic aldehyde was mainly converted into phenolic alcohol by A. pullulans, and phenolic alcohol also exhibited severe inhibition on PMA production. Furthermore, the effect of detoxification methods on inhibitor-removal and PMA fermentation was investigated, both CaCO3 and overliming presented poor detoxification effect, whereas resin H103 could remove both furan derivatives and phenolic compounds efficiently, thereby producing 26.27g/L of PMA with a yield of 0.30g/g in batch fermentation. This study will be beneficial for the development of PMA production from lignocellulosic biomass.

Simultaneous enhancement of lignin-derived inhibitor tolerance and lipid accumulation of oleaginous yeast Trichosporon cutaneum by adaptive evolution

Inhibitory compounds should be removed from the pretreated lignocellulose feedstock before fermentative production of microbial lipid by oleaginous yeast. Biodetoxification effectively degrades furan aldehydes and weak organic acids, but is less efficient against complex and various lignin-derived phenolic aldehydes. Residual phenolics in lignocellulose hydrolysates require a tolerant fermentation strain. This study adopted the long-term adaptive evolution combined with centrifugal enrichment in corn stover hydrolysate to simultaneously improve the phenolic inhibitors tolerance and lipid synthesis of Trichosporon cutaneum. The obtained mutant T. cutaneum MS28 showed significant improved performances of phenolic aldehydes tolerance and lipid accumulation. The final cellulosic lipid production of T. cutaneum MS28 utilizing corn stover reached 33.8 ± 0.1 g/L, approximately 6-fold higher than that of the starting strain. Transcriptional analysis suggested that T. cutaneum MS28 had more active lignocellulose-derived sugars metabolism and lipid synthesis shunts. The intracellular contents of lipid synthesis precursors including NADPH and acetyl-CoA increased 1.7–3.0 folds. This adaptive evolution in lignocellulose hydrolysate combined with centrifugal enrichment is an efficient tool to targeted enhancement of inhibitors tolerance and cellulosic lipid production of oleaginous yeast.

Exogenous control of dormancy and chemical regulation of germination in Texas wintergrass (Nassella leucotricha (Trin. & Rupr.) Pohl) seeds

AbstractTexas wintergrass (Nassella leucotricha (Trin. & Rupr.) Pohl) has potential as a cool‐season forage but has not been used for such purpose due to its poor seed germination. This study focused on understanding the determinants of dormancy and identifying means of inducing maximum germination in Texas wintergrass toward making it more readily available for grazing systems. Scarification using sulfuric acid resulted in a significant improvement (≥50%) in the overall germination performance of the seeds. Chemical profiling of the seed coat identified diverse phenolic compounds, primarily in the form of flavonoids, which have been previously reported to induce seed dormancy in other plant species. Together, these results indicate the presence of exogenous dormancy in Texas wintergrass that prevents it from germinating even under optimum conditions. Treatment with low hydrogen peroxide (H2O2) titers in combination with scarification further increased seed germination up to 85%. This positive germination response is attributed to H2O2‐induced weakening of the seed coat that makes it semipermeable, oxidation and leaching of phenolic inhibitors of germination, and hydrolysis of H2O2 that provides seeds with access to more water and O2. Additionally, treatment with low H2O2 concentrations within the first 24 h of water uptake downregulated abscisic aldehyde oxidase (AAO3) and upregulated abscisic 8′ hydroxylase (A8H1) expression. AAO3 converts abscisic aldehyde into abscisic acid (ABA), whereas A8H1 breaks down ABA to produce phaseic acid. Treatment with the phytohormones gibberellic acid (GA) and 6‐benzylaminopurine (BAP) in combination with scarification also improved the germination performance of Texas wintergrass, with BAP producing better results than GA.

Removal of phenolic inhibitors from lignocellulose hydrolysates using laccases for the production of fuels and chemicals.

Lignocellulose is the most abundant biopolymer in the biosphere. It is inexpensive and therefore considered an attractive feedstock to produce biofuels and other biochemicals. Thermochemical and/or enzymatic pretreatment is used to release fermentable monomeric sugars. However, a variety of inhibitory by-products such as weak acids, furans, and phenolics that inhibit cell growth and fermentation are also released. Phenolic compounds are among the most toxic components in lignocellulosic hydrolysates and slurries derived from lignin decomposition, affecting overall fermentation processes and production yields and productivity. Ligninolytic enzymes have been shown to lower inhibitor concentrations in these hydrolysates, thereby enhancing their fermentability into valuable products. Among them, laccases, which are capable of oxidizing lignin and a variety of phenolic compounds in an environmentally benign manner, have been used for biomass delignification and detoxification of lignocellulose hydrolysates with promising results. This review discusses the state of the art of different enzymatic approaches to hydrolysate detoxification. In particular, laccases are used in separate or in situ detoxification steps, namely in free enzyme processes or immobilized by cell surface display technology to improve the efficiency of the fermentative process and consequently the production of second-generation biofuels and bio-based chemicals.

Green solvents extraction-based detoxification to enhance the enzymatic hydrolysis of steam-exploded lignocellulosic biomass and recover bioactive compounds

A novel strategy for pre-treated biomass detoxification combining emerging green solvents and low environmental impact extraction technologies was evaluated. Steam-exploded biomass was subjected to microwave-assisted or orbital shaking extraction using bio-based or eutectic solvents. The extracted biomass was enzymatically hydrolysed. The potential of this detoxification methodology was studied in terms of phenolic inhibitors extraction and sugar production improvement. The effect of adding a post-extraction water washing step before hydrolysis was also evaluated. Excellent results were achieved when steam-exploded biomass was subjected to the microwave-assisted extraction combined with the washing step. The highest sugar production was achieved when ethyl lactate was used as extraction agent (49.80 ± 3.10 g total sugar/L) over the control (30.43 ± 0.34 g total sugar/L). Results suggested that a detoxification step based on green solvents would be a promising option to extract phenolic inhibitors, which can be revalorized as antioxidants, and improve the sugar production from the extracted pre-treated biomass.

Liquid–liquid phase separation in binary mixtures of quaternary alkylammonium chlorides with carboxylic acids

We reported the phase separation measurements of mixtures obtained from choline, tetramethylammonium and tetraethylammonium chlorides with methacrylic (MAA), butyric (BA) and isobutyric (IBA) acids as solvents. Liquid-liquid equilibrium (LLE) experiments were performed under atmospheric pressure in a temperature range of 287–403 K using cloud-point method and the data were correlated with the Non-Random Two Liquid (NRTL) solution model. The density, the viscosity, the Kamlet-Taft and the solvent polarity (ET(30)) parameters were measured for coexisting liquid phases. The applicability of the obtained binary biphasic system in extraction process, particularly purification of MAA from a phenolic inhibitor, was demonstrated.

Photoinduced Ion-Pair Inner-Sphere Electron Transfer-Reversible Addition-Fragmentation Chain Transfer Polymerization.

Photoredox-mediated reversible deactivation radical polymerization (RDRP) is a promising method of precise synthesis of polymers with diverse structures and properties. However, its mechanism mainly based on the outer-sphere electron transfer (OSET) leads to stringent requirements for an efficient photocatalyst. In this paper, the zwitterionic organoboranes [L2B]+X- are prepared and applied in reversible addition-fragmentation chain transfer (RAFT) polymerization with the photoinduced ion-pair inner-sphere electron transfer (IP-ISET) mechanism. The ion-pair electron transfer mechanism and the formation of the radical [L2B]• are supported by electron paramagnetic resonance (EPR) radical capture experiments, 1H/11B NMR spectroscopy, spectroelectrochemical spectroscopy, transient absorption spectroscopy, theoretical calculation, and photoluminescence quenching experiments. Photoluminescence quenching experiments show that when [CTA]/[[L2B]+] ≥ 0.6, it is static quenching because of the in situ formation of [L2B]+[ZCS2]-, the real catalytic species. [L2B]+[C3H7SCS2]- is synthesized, and its photoluminescence lifetime is the same as the lifetime in the static quenching experiment, indicating the formation of [L2B]+[ZCS2]- in polymerization and the IP-ISET mechanism. The matrix-assisted laser desorption ionization time-of-flight mass (MALDI-TOF MS) spectra show that the structure of [C3H7SCS2] was incorporated into the polymer, indicating that ion-pair electron transfer occurs in catalytic species. The polymerization shows high catalytic activity at ppb catalyst loading, a wide range of monomers, excellent tolerance in the presence of 5 mol % phenolic inhibitors, and the synthesis of ultrahigh-molecular-weight polymers. This protocol with the IP-ISET mechanism exhibits a value in the development of new organic transformations and polymerization methods.

The conversion of biomass to fuels via cutting-edge technologies: Explorations from natural utilization systems

Biomass can be used to manufacture both hydrocarbon fuels and chemical compounds such as rubber, alcohols, lipid-based products, sugars, etc. Due to their abundant supply and lower greenhouse gas emissions, fuels derived from biomass have received much attention in recent years. Biofuels can be made from grasses, agricultural waste, animal waste and trash, old oils, and other organic things. The characteristics of various feedstocks and fuels, as well as the techniques for converting biomass to biofuels, physical and chemical parameters, and limitations that affect biomass to fuel conversion, are all discussed. pH, temperature, and residence time are all process parameters. Other chemical factors include the availability of carbon, nutrients, acid and alkaline hydrolysis agents, phenolic inhibitors, and sugars produced throughout the process. The list of obstacles to biomass bioconversion includes reduced particle size, crystallinity, fermentation inhibitory byproducts, cellulase deactivation, yeast ethanol tolerance, and sugar co-fermentation. The research and development of biomass-to-energy conversion technology have been accelerating significantly, according to this review. The choice of the conversion method depends on the type and quality of the biomass, the final energy form, environmental requirements, economic conditions, and project-specific considerations. Biowaste is initially improved (depending on the conditions). This process includes size reduction, densification, drying, and torrefaction. The two most popular conversion methods for biomass to energy are thermochemical and biochemical. Utilizing the power of microorganisms, biochemical conversion transforms biomass into liquid or gaseous fuels. The processes of anaerobic digestion, fermentation, and photobiological hydrogen generation are currently the most widely used biochemical technologies. Recent advancements in recombinant DNA technology and protein engineering, as well as future technology like extraction, and application towards green, are targeted at addressing bioconversion restrictions.

Degradation of phenolic inhibitors by laccase immobilized on tannic acid/polyethylenimine modified magnetic nanoparticles

Magnetic Fe3O4 nanoparticles were successfully functionalized with the low-cost mussel-inspired tannic acid (TA)/polyethylenimine (PEI) under mild conditions and then activated with glutaraldehyde (GA) to covalently immobilize laccase for degradation of four model phenolic inhibitors commonly found in lignocellulosic hydrolysate. The immobilized laccase showed the highest relative enzyme activity with the laccase loading of 39.9 mg/g and the enzyme activity recovery of 53.1%. Compared with free laccase, immobilized laccase possessed better relative enzyme activity at acidic pH and wide temperature range, as well as exhibited excellent storage stability and satisfactory reusability. Moreover, it was found that the phenolic degradation products by immobilized laccase did not exhibit obvious inhibition on subsequent enzymatic cellulose hydrolysis. Thus, the low-cost TA/PEI coating for modification of magnetic nanoparticles will provide a promising support for laccase immobilization and the immobilized laccase has great potential in removal of phenolic inhibitors present in lignocellulosic hydrolysate.

Bioprospecting Phenols as Inhibitors of Trichothecene-Producing Fusarium: Sustainable Approaches to the Management of Wheat Pathogens.

Fusarium spp. are ubiquitous fungi able to cause Fusarium head blight and Fusarium foot and root rot on wheat. Among relevant pathogenic species, Fusarium graminearum and Fusarium culmorum cause significant yield and quality loss and result in contamination of the grain with mycotoxins, mainly type B trichothecenes, which are a major health concern for humans and animals. Phenolic compounds of natural origin are being increasingly explored as fungicides on those pathogens. This review summarizes recent research activities related to the antifungal and anti-mycotoxigenic activity of natural phenolic compounds against Fusarium, including studies into the mechanisms of action of major exogenous phenolic inhibitors, their structure-activity interaction, and the combined effect of these compounds with other natural products or with conventional fungicides in mycotoxin modulation. The role of high-throughput analysis tools to decipher key signaling molecules able to modulate the production of mycotoxins and the development of sustainable formulations enhancing potential inhibitors’ efficacy are also discussed.

Engineering the Oleaginous Yeast Rhodosporidium toruloides for Improved Resistance Against Inhibitors in Biomass Hydrolysates.

Conversion of lignocellulosic biomass into lipids and related chemicals has attracted much attention in the past two decades, and the oleaginous yeast Rhodosporidium toruloides has been widely used in this area. While R. toruloides species naturally have physiological advantages in terms of substrate utilization, lipid accumulation, and inhibitor resistance, reduced lipid production and cell growth are noticed when biomass hydrolysates are used as feedstocks. To improve the robustness of R. toruloides, here, we devised engineered strains by overexpressing genes responsible for phenolic compound degradation. Specifically, gene expression cassettes of the manganese peroxidase gene (MNP) and versatile peroxidase gene (VP) were constructed and integrated into the genome of R. toruloides NP11. A series of engineered strains were evaluated for lipid production in the presence of typical phenolic inhibitors. The results showed that R. toruloides strains with proper expression of MNP or VP indeed grew faster in the presence of vanillin and 5-hydroxymethylfurfural than the parental strain. When cultivated in concentrated mode biomass hydrolysates, the strain VP18 had improved performance as the cell mass and lipid content increased by 30% and 25%, respectively. This study provides more robust oleaginous yeast strains for microbial lipid production from lignocellulosic biomass, and similar efforts may be used to devise more advanced lipid producers.

Ultrafast selective adsorption of pretreatment inhibitors from lignocellulosic hydrolysate with metal-organic frameworks: Performance and adsorption mechanisms

• Four MOFs were evaluated for adsorption of furfural and four phenolic inhibitors. • MIL-140C exhibited excellent adsorption capacity and ultrafast adsorption kinetics. • MIL-140C demonstrated good reusability and high stability. • Possible adsorption mechanisms were proposed. In this work, four metal-organic frameworks materials (MOFs, MIL-140A, MIL-140C, MIL-101(Fe) and NH 2 -MIL-101(Fe) were prepared, characterized and compared for the adsorptive removal of furfural and four phenolic inhibitors. MIL-140C demonstrated the best adsorption capability among the tested MOFs. Effects of pH, ionic strength, contact time, adsorbent dosage, temperature and sugars on adsorption of inhibitors on MIL-140C were systematically investigated. Inhibitors adsorption was ultrafast within minutes and kinetic data fitted pseudo-second-order model well. The Langmuir isotherm described the adsorption process satisfactorily with maximum adsorption capacities of 222.72, 240.38, 231.48, 207.04 and 60.79 mg/g for vanillin, syringaldehyde, ferulic acid, p-coumaric acid and furfural, respectively. Thermodynamic parameters disclosed that nature of the adsorption was exothermic and spontaneous under the experimental conditions. MIL-140C demonstrated exceptional adsorption selectivity towards inhibitors even with excessive amount of xylose and glucose, as well as excellent regeneration performance after five adsorption/desorption cycles. MIL-140C also exhibited satisfactory detoxification performance after treatment of real corn stover dilute acid hydrolysate. Furthermore, analysis of underlying adsorption mechanism showed that π-π interaction, hydrophobic interaction and hydrogen bonding/metal-coordination (depending on solution pH) were involved in the adsorption of tested phenolic inhibitors, while the π-π and hydrophobic interactions contributed to the furfural adsorption. The overall results revealed that MIL-140C could hold great promise in removing phenolic and furan inhibitors from lignocellulosic hydrolysate.

Substituent positions and types for the inhibitory effects of phenolic inhibitors in coal spontaneous combustion

This study is aimed at investigating the effects of substituent positions and types on the activities of phenolic inhibitors for inhibiting coal spontaneous combustion (CSC). To achieve this aim, six phenolic inhibitors with different substituent positions (ortho-, meta- and para-) and types (methyl, ethyl, isopropyl and tert butyl) were selected for testing their inhibitory effects on Xilinhe coal. First, the temperature-programmed oxidation experiment was performed on the raw coal sample and the inhibited coal samples to explore their CO generation volumes and crossing-point temperatures under low-temperature oxidation conditions. Meanwhile, the corresponding inhibition rates, oxygen consumption rates and apparent activation energy values were calculated. Furthermore, the weight loss processes, surface morphologies and active functional group variations of the raw coal sample and the inhibited coal samples were analyzed with the aid of a thermogravimetric analyzer, a scanning electron microscope and a Fourier transform infrared spectrometer. The test results showed that the phenolic inhibitors can not only infilter into coal but also accumulate on coal surface to form an inhibitor layer. Besides, they can inhibit CSC in both physical and chemical ways during low-temperature oxidation of coal, and their inhibitory effects exhibit varying characteristics in different stages. When the temperature is below 120 °C, the physical inhibitory effects of oxygen isolation and water retention dominate. When it exceeds 120 °C, the chemical inhibitory effect of capturing active free radicals in coal plays a dominant role. The types of substituents have a more notable effect on the activities of phenolic inhibitors than the positions of substituents. The inhibitor with smaller substituent steric hindrance and stronger infiltration ability is more capable of inhibiting CSC physically and chemically. Among the inhibitors with different substituent types, m-cresol boasts the optimal inhibitory effect. Its inhibition rate is 84.4% at 170 °C; the oxygen consumption rate is only 1/4 of that of raw coal; the crossing-point temperature is raised by 30.3 °C to 181.7 °C; and the apparent activation energy values are increased by 7.74 kJ/mol, 16.18 kJ/mol and 20.61 kJ/mol in the slow oxidation stage, the accelerated oxidation stage and the intense oxidation stage, respectively.

QM and QM/MM study on inhibition mechanism of polyphenolic compounds as non-classical inhibitors of α-human carbonic anhydrase (II)

Phenolic and polyphenolic compounds are distributed in plant tissues as a secondary metabolite which are compromised in multiple and imperative physiological phenomena. Herein, inhibition mechanism of human carbonic anhydrase isoform II, hCAII, with seven phenolic compounds including phenol, catechol, resorcinol, 4-methyl catechol, vanillic acid, trans-cinnamic acid and ortho-coumaric acid has been investigated using quantum mechanical and ONIOM calculations. B3LYP-D3/6–311++G** method has been employed to calculate the electronic structure and electronic energy of different species through the reaction mechanism path. The model system of hCAVII has been used that includes the core of the catalytic center, Zn2+, binds to three histidine residues and a hydroxide ion or water molecule forming a first coordination shell. Thr199 and Glu106 were considered as neighboring residues to the ones binding zinc. All thermodynamic functions through the reaction path are evaluated in different phases. The calculated results indicate that all phenolic inhibitors do not directly interact with the zinc ion in the CA active center, and the presence of aromatic moieties was associated with more effective inhibition. In addition, the implicit and explicit solvent effect has been considered for water solvent using QM and ONIOM (QM/MM) calculations.

Acaricidal Activity of Phenolic Crude Extract from Artocapus lakoocha Leaves against Cattle Tick Rhipicephalus (Boophilus) microplus

Cattle ticks and tick-borne diseases (TBDs) are well known for their harmful effects to cattle health. The problem of TBDs has been ranked high in terms of their adverse impact on the livelihood of poor farming communities in developing countries including Thailand. The aim of this research was to evaluate the efficacy of phenolic compounds of crude acetone extract and crude ethanol extract from Artocapus lakoocha leaves in the elimination of the cattle ticks which were tested in the form of crude extract at the concentration of 400, 800 and 1600μg/ml. From the record of mortality rate within 48 hours and propagation index within 15 days, it was found that the extract at the concentration of 1600μg/ml had the best efficacy to eliminate cattle ticks when compared to control group and other concentrations (P<0.05). It was also discovered that the mortality rate of ticks was 72%. Moreover, index of egg laying, and inhibition percentage were equal to 0.14 and 49, respectively. The negative control group adding with polyethylene glycol (PEG, Phenolic inhibitors) had mortality rate of cattle ticks at 0% and median of toxic concentration (Lethal Concentration 50: LC50) of phenolic crude extract was 1050μg/ml. Thus, the phenolic crude extract from Atrocapus lakoocha leaves was effective in getting rid of cattle ticks, this approach could be further developed as the effective method for controlling and eliminating ticks in the form of products such as shampoo and tick spray for cattle or other animals.

Role of F124 in the inhibition of Bacillus firmus K-1 Xyn11A by monomeric aromatic phenolic compounds

This study aimed to investigate the inhibitory effect of monomeric aromatic phenolic compounds on Xyn11A and its F124A mutant. The inhibitory assay showed gallic acid as the most potent inhibitor for the WT. Conversely, gallic acid completely lost its inhibitory effect and resistance to the other compounds increased significantly in the F124A mutant. Molecular docking revealed that phenolic compounds inhibited WT by simultaneously binding to E78, R112, and F124. The pi-pi stacking of F124 and aromatic rings of phenolic compounds mediated the hydrogen bonds formed between phenolic inhibitors and E78. Gallic acid's strongest inhibitory effects in WT may be due to the high number of hydroxyl groups. However, in F124A, the phenolic compounds bound tyrosine residues sitting far from the catalytic site. Gallic acid's binding to Y69, which is furthest away from the catalytic site and highest specific binding energy, may have contributed to gallic acid's loss of inhibitory effects in F124A.