Thiol Compounds Research Articles

Disentangling the Puzzling Regiochemistry of Thiol Addition to o-Quinones.

The addition of thiol compounds to o-quinones, as exemplified by the biologically relevant conjugation of cysteine to dopaquinone, displays an anomalous 1,6-type regiochemistry compared to the usual 1,4-nucleophilic addition, for example, by amines, which has so far eluded intensive investigations. By means of an integrated experimental and computational approach, herein, we provide evidence that the addition of glutathione, cysteine, or benzenethiol to 4-methyl-o-benzoquinone, modeling dopaquinone, proceeds by a free radical chain mechanism triggered by the addition of thiyl radicals to the o-quinone. In support of this conclusion, DFT calculations consistently predicted the correct regiochemistry only for the proposed thiyl radical-quinone addition pathway. These results would prompt a revision of the commonly accepted mechanisms for thiol-o-quinone conjugation and stimulate further work aimed at assessing the impact of the free radical processes in biologically relevant thiol–quinone interactions.

Metabolic Basis and Clinical Evidence for Skin Lightening Effects of Thiol Compounds.

Melanin pigment is a major factor in determining the color of the skin, and its abnormal increase or decrease can cause serious pigmentation disorders. The melanin pigment of the skin is divided into light pheomelanin and dark eumelanin, and a big difference between them is whether they contain sulfur. Melanin synthesis starts from a common reaction in which tyrosine or dihydroxyphenylalanine (DOPA) is oxidized by tyrosinase (TYR) to produce dopaquinone (DQ). DQ is spontaneously converted to leukodopachrome and then oxidized to dopachrome, which enters the eumelanin synthesis pathway. When DQ reacts with cysteine, cysteinyl dopa is generated, which is oxidized to cysteinyl DQ and enters the pheomelanin synthesis pathway. Therefore, thiol compounds can influence the relative synthesis of eumelanin and pheomelanin. In addition, thiol compounds can inhibit enzymatic activity by binding to copper ions at the active site of TYR, and act as an antioxidant scavenging reactive oxygen species and free radicals or as a modulator of redox balance, thereby inhibiting overall melanin synthesis. This review will cover the metabolic aspects of thiol compounds, the role of thiol compounds in melanin synthesis, comparison of the antimelanogenic effects of various thiol compounds, and clinical trials on the skin lightening efficacy of thiol compounds. We hope that this review will help identify the advantages and disadvantages of various thiol compounds as modulators of skin pigmentation and contribute to the development of safer and more effective strategies for the treatment of pigmentation disorders.

Fast coupling and detoxification of aqueous halobenzoquinones by extracellular nucleophiles: The relationship among structures, pathways and toxicity

Halobenzoquinones (HBQs), a metabolism of pentachlorophenol, arouse increasing concern for their high toxicity. This paper systematically studied the influences of 31 extracellular nucleophiles on the removal of dichlorobenzoquinones (DCBQs). The results showed that at pH 6.0–8.0, the transformation of DCBQs followed a pattern of pseudo first-order reaction. With the presence of different thiol compound (ratio 1:1), the apparent rate constant of 25DCBQ and 26DCBQ was between 0.028 and 0.204 min−1 and 0.061–0.156 min−1, respectively, which was 6.6–48.3 times faster than direct hydrolysis and 1.9–23.4 times of that with histidine, a typical amino acid. This was attributed to the different transformation pathways of DCBQs with thiol or amino groups. According to the MS spectrum and transition state theory, thiol compounds was stably incorporated into DCBQs via Michael addition or substitution, which also decreased the oxidative stress of DCBQs by 35.5–86.4% and cytotoxicity of hydrolyzed DCBQ by 44.9–100%, respectively. Conversely, amino acids promoted the hydrolysis of DCBQs by forming unstable AA-DCBQ intermediates that can be further hydrolyzed to OH-DCBQs, leading to an increased selectivity of OH-DCBQs, and increased the oxidative stress of 25DCBQs by 0.2–31.2% and cytotoxicity of hydrolyzed 25DCBQ by 42.0–52.7%. Such difference was inherently related to the nucleophilicity of different atoms. Moreover, it was revealed that the maximum condensed local nucleophilicity index of nucleophiles (Nk,max) can joint describe the relationship among nucleophilic structures, transformation pathways and toxicity of DCBQs. This paper provided a comprehensive perspective on the fast removal and detoxification of HBQs in extracellular environment.

Imidazole-stabilized gold nanoclusters with thiol depletion capacity for antibacterial application

Surface ligand plays a crucial role in regulating the physicochemical properties and functionalities of gold nanoclusters (AuNCs). Compared to the widely studied thiolate-stabilized AuNCs, the reports on imidazole-based ligands to protect AuNCs are still rare. Herein, we report the facile preparation of imidazole-stabilized AuNCs using 1-vinylimidazole as both a reducing and capping agent. The coordination pattern of imidazole ring to Au core was proved by formation of Au-N bond, which can protect the AuNCs with moderate stability against different pH and temperature. Owing to the weaker binding strength of Au-N bond than Au-S bond, the obtained AuNCs possessed thiol depletion capacity due to ligand exchange in the presence of thiol compounds. By consuming the cellular bio-thiols that act as the reducing species in redox balance, the imidazole-protected AuNCs can cause the accumulation of oxidizing species and the elevation of the oxidative stress. Accordingly, the obtained AuNCs exhibited intrinsic antibacterial activity toward Staphylococcus aureus, which could be a promising bactericidal nanomaterial for sterilization.

Methyl jasmonate increases aluminum tolerance in rice by augmenting the antioxidant defense system, maintaining ion homeostasis, and increasing nonprotein thiol compounds.

Aluminum (Al) stress is known as a serious threat to the growth and production of crops in acidic soils. Here, the effects of different concentrations of methyl jasmonate (MJ, 0.5 and 1µM) on rice plants were investigated hydroponically under different concentrations of Al (0.5 and 1mM). Aluminum treatments injured membrane lipids and photosynthetic apparatus by reducing the leaf contents of mineral nutrients and increasing the accumulation of free radicals (hydrogen peroxide, methylglyoxal, and superoxide anion), resulting in reduced growth and biomass of rice. In comparison to control plants, 0.5 and 1μM Al treatments lowered height by 21 and 37% and total dry weight by 24 and 41%, respectively. Exogenously added methyl diminished the inhibitory effects of Al stress on growth and photosynthetic apparatus by restoring ion homeostasis and improving chlorophyll metabolism. The application of MJ, by inducing the activity of antioxidant enzymes and the glyoxalase cycle, lessened the levels of the toxic compounds hydrogen peroxide, methylglyoxal, and superoxide anion and, as a result, dwindled the toxic Al-induced oxidative stress. Methyl jasmonate enhanced the leaf accumulation of nonprotein thiol compounds and improved plant tolerance under Al stress by increasing the activity of enzymes involved in the synthesis of thiol compounds. Methyl jasmonate increased the leaf accumulation of glutathione and phytochelatins in Al-stressed plants by increasing the expression of GSH1, PCS, and ABCC1, which reduced the toxicity of toxic Al accumulated in leaves by sequestering toxic Al in vacuoles. Together, the results revealed that MJ increased the tolerance of rice under Al toxicity by maintaining ion homeostasis, improving the activity of antioxidant enzymes and the glyoxalase system, and increasing the level of non-protein thiol compounds. This research adds to our understanding of how MJ may be used in the future to improve Al stress tolerance in sustainable agriculture.

Inhibitory effects of thiol compounds on theaflavin browning and structural analysis of the causative substances

Theaflavin, a polyphenol responsible for the bright orange color and various bioactivities of black tea exudates, is susceptible to autoxidation at neutral and mild alkaline pH, changing its color to brown. In the presence of cysteine (Cys), glutathione (GSH), or N-acetyl cysteine (NAC), the browning of theaflavin solution was inhibited concomitantly with time-dependent decreases in the concentrations of both theaflavin and thiol group. The rank order of the decrease was Cys ≅ GSH > NAC, suggesting the relevance of the nucleophilic property of the thiol group to its reaction with theaflavin. LC-MS analysis of the reaction products indicated formation of novel derivatives that were mono- or di-molecular adducts of thiol compounds. We determined the chemical structures of theaflavin-Cys and theaflavin-GSH adducts by NMR and proposed the reaction mechanisms. It was found that the theaflavin-Cys adduct was not a simple adduct, to which a new cyclic structure was added.

Two-Dimensional Cobalt-Doped Ti3C2 MXene Nanozyme-Mediated Homogeneous Electrochemical Strategy for Pesticides Assay Based on In Situ Generation of Electroactive Substances.

Common homogeneous electrochemical (HEC) sensors usually suffer from the drawbacks of high background signal, low signal-to-noise ratio, and even false positive results due to the preaddition of electroactive substances. Thus, it is necessary to develop novel HEC sensors based on in situ generation of electroactive substances to overcome these shortcomings, which, however, is underexplored. In this work, two-dimensional (2D) nanozymes, i.e., cobalt-doped 2D Ti3C2 MXene nanosheets (CMNSs), with excellent peroxidase-like properties were utilized to develop HEC sensors based on the in situ generation of electroactive substances for organophosphate pesticides (OPs) detection. The 2D CMNSs were synthesized via a template-directed wet chemical approach and displayed outstanding features of hydrophilia and water dispersibility, which could catalyze the oxidation of o-phenylenediamine (OPD) to generate significantly increased reduction current. Interestingly, the 2D CMNSs with peroxidase-like properties exhibited a unique response to thiol compounds and were thus employed as highly efficient catalysts to develop HEC sensors for OPs based on the hydrolysis of acetylthiocholine (ATCh) to form thiocholine catalyzed by acetylcholinesterase (AChE) and the inhibition of AChE activity by OPs. The recovery for OPs analysis of pakchoi extract solutions ranged from 97.4% to 103.3%. The as-proposed HEC sensor based on in situ generation of electroactive substances will provide a new way for the development of high-performance electrochemical sensors and demonstrate potential applicability for the determination of pesticide residues in real samples.

Probing Cell Redox State and Glutathione-Modulating Factors Using a Monochlorobimane-Based Microplate Assay.

Thiol compounds including predominantly glutathione (GSH) are key components of redox homeostasis, which are involved in the protection and regulation of mammalian cells. The assessment of cell redox status by means of in situ analysis of GSH in living cells is often preferable over established assays in cell lysates due to fluctuations of the GSH pool. For this purpose, we propose a microplate assay with monochlorobimane (MCB) as an available fluorescent probe for GSH, although poorly detected in the microplate format. In addition to the new procedure for improved MCB-assisted GSH detection in plate-grown cells and its verification with GSH modulators, this study provides a useful methodology for the evaluation of cell redox status probed through relative GSH content and responsiveness to both supplemented thiols and variation in oxygen pressure. The roles of extracellular interactions of thiols and natural variability of cellular glutathione on the assay performance were emphasized and discussed. The results are of broad interest in cell biology research and should be particularly useful for the characterization of pathological cells with decreased GSH status and increased oxidative status as well as redox-modulating factors.

AMF modulated rhizospheric microbial enzyme activities and their impact on sulphur assimilation along with thiol metabolism in pigeonpea under Cd stress

Presence of cadmium (Cd) in the soil has a negative impact on soil enzymatic activities, which, thus, reduce growth of the inhabiting plant species. Symbiotic association between plants and arbuscular mycorrhizal fungi-AMF have potential to overcome Cd stress. Therefore, the present study investigated the role of different AMF species [Claroideoglomus claroideum-Cc, C. etunicatum-Ce, Funneliformis mosseae-Fm and Rhizoglomus intraradices-Ri] in imparting Cd tolerance to pigeonpea-Cajanus cajan (L.) Millsp. Plants. The experiment was a complete factorial combination of two factors comprising of Cd concentrations (0, 25, 50 mg kg−1) and AMF treatments (Control/Non-AM, Cc, Ce, Fm, Ri) with twelve replicates for each treatment. A negative correlation between Cd concentration and plant growth, along with reactive oxygen species (ROS) build up were recorded. All mycorrhizal species reduced Cd uptake and lowered oxidative burden with maximum benefits provided by + Ri inoculation, followed by + Fm and + Ce, with + Cc the least. These effects could be associated with their relative root colonizing (RC) abilities and glomalin production in the soil. Greater efficiency of Ri than other three species could be related to maximum soil enzymatic activities [urease (URE), phosphatases (PHAs), dehydrogenase (DHase), arylsulfatase (AS)], which, enhanced the bioavailability of nutrients (P, S, N, K) to the plants. Moreover, higher activities of S assimilating enzymes [ATP sulfurylase (ATPS), γ-Glutamylcysteine synthetase (γ-ECS)] led to greater synthesis of thiol compounds [glutathiones (GSH), phytochelatins (PCs), non-protein thiol (NP-SH)] which, further reduced Cd translocation from roots to shoots. The study indicated that pigeonpea was highly responsive to different AMF species, with host-Ri combination displaying the strongest potential to alleviate Cd stress.

Changes in Thiols Indicators in the Lens of the Eye of White Rats under the Exposure of Radiation during Operation of a Cellular Mobile Phone

The results of previous work carried out at the Laboratory of Biophysics of Cellular Metabolism of the Institute of Physiology named after A.I. Karaev, which concerned the study of the effect of EMR on LPO processes and the antioxidant system in visual structures, pointed to the oxidative nature of the implementation of EMR exposure. Since thiol compounds in living tissues primarily interact with peroxide products, it was assumed that the effect of EMR should be reflected in the thiol content of the lens. For this purpose, a group of white outbred rats (40 species, half of which were identified as the control group) were studied, which were daily irradiated with EMR from a working cell phone. On the 7th, 14th, 21st and 28th day of the experiment, 5 animals from the experimental group and 5 animals from the control group were slaughtered. The lens of the eye was removed from the animals, in which the level of thiols was determined according to the modified Lindsey-Sedlak method based on the Ellman method. The results of the study showed that common and readily available (cytoplasmic) thiols in the nucleus of the lens of the eyes of rats irradiated with mobile phone EMR, in general, have similar dynamics of quantitative changes depending on the duration of exposure. Hidden thiols behave similarly. In the lens cortex, the nature of changes in thiols is not so pronounced, but generally similar to the results in the nucleus. The authors believe that these results may indicate the antioxidant properties of thiols in LPO reactions.

ESTUDO TEÓRICO E EXPERIMENTAL DE ESTRUTURA E REATIVIDADE RELACIONADO AO METABOLISMO E TOXICIDADE DO PARACETAMOL

THEORETICAL AND EXPERIMENTAL STUDY OF STRUCTURE AND REACTIVITY RELATED TO METABOLISM AND TOXICITY OF PARACETAMOL. An experimental and theoretical approach on oxidative metabolism of paracetamol was applied for the pharmaceutical chemistry learning. Classical reactions, functional group identification, structural parameter, and chemical reactivity using frontier orbitals and Fukui index were used explaining the main products between N-acetyl-p-benzosemiquinone (NAPQI) and thiolic compounds. The chemoprotection mechanisms by N-acetyl-cysteine on high dosage of paracetamol are consistent with theoretical and experimental results. The methods also described the relationship between the chemical reactivity of quinone-imine system and the induced-toxicity of paracetamol by Michael reaction. These results can be applied in experimental pharmaceutical chemistry teaching

Synthesis of a novel polysulfide via the reaction of a thiol compound and oxidant towards polymer self-healing application

Introduction: This legion is an indiscernible virtue of polysulfide that it has been employed in a range of fields. In addition, the oxidation of thiol to reversible disulfide is a dramatically preponderant process in biology and chemistry, especially the production of healable polymers. Interestingly, thiol is widely utilized to synthesize numerous polymers through the thiol-click reaction. From the sound of it, our underlying intent in this research is the synthesis of thiol-ended polysulfide potential for the self-healing polymer. Method: In this study, the synthesis of polysulfide carrying the thiol terminal group was undertaken out of the oxidizing reaction in the presence of iodine. Its reaction time was monitored by means of TLC. Furthermore, state-of-the-art measurements of FT-IR, 1H-NMR and GPC were used to represent a great deal of valuable information pertaining to its structure and molecular weight. Result: After a period of 24 hours at room temperature, the reaction producing pure polysulfide was completed. The FT-IR and 1H-NMR results show that the polymer was successfully synthesized; moreover, its Mn is approximately 12000 g/mol. Conclusion: This study will play a vital role in facilitating the use of thiol-terminated polysulfide in the synthesis of self-healing materials in the not-too-distant future.

Electrochemical sensing of limonene using thiol capped gold nanoparticles and its detection in the real breath sample of a cirrhotic patient

• Molar ratio of gold salt to thiol compound (2:1) synthesised best performing AuNPs. • Hexanethiolated capped AuNPs electrochemically detected limonene (LOD= 0.2 mmol L −1 ). • Limonene was detecteded in a cirrhotic patient breath sample using Hexanethiolated capped AuNPs. • Quantitative electrochemical detection of limonene was confirmed vusing GCMSto be 800 ppm. Volatile organic compounds (VOCs) are a major constituent of human breath which is being investigated as potential targets to be sensed in e-nose biosensors. Limonene is found in the breath of cirrhotic liver patients and can be used for early diagnosis using electrochemical biosensors. In the current study, electrochemical detection of limonene was performed using monolayer thiolated gold nanoparticles. Three different types of monolayer thiol capped AuNPs were synthesized by the modified biphasic method with the different molar ratios (2:1 and 1:1) of hydrogen tetrachloroaurate (III) (HAuCl 4 ·2H 2 O) and thiol groups: dodecanethiol, decanethiol, and hexanethiol. Thiol capped AuNPs were characterized physiochemically and for electrochemical sensing at different factors such as pHs, scan rate, current stability. Based on the best presented electrochemical results, hexanethiol AuNPs were selected as a sensor for analyzing the electrochemical detection of limonene as an analyte. Hexanethiol capped AuNPs based biosensing platform showed high sensitivity with a LOD of 0.2 mmol L −1 as observed via its DPV, and high specificity when was used against another VOC standard. The sensor was also used to detect limonene in the real breath sample of the clinical patient, besides testing the lab standard of limonene. The breath sample of cirrhotic patients was collected and tested for the presence of limonene by using GC–MS. The quantity of limonene measured via GC–MS was 800 ppm in cirrhotic patients and electrochemical sensor measurements of limonene were almost the same providing confidence over quantitative detection of the synthesized hexanethiol capped AuNPs based biosensing platform in this study.

Human Serum Albumin Cys34 Adducts in Newborn Dried Blood Spots: Associations With Air Pollution Exposure During Pregnancy.

Background: Increasing evidence suggests that exposure to air pollution during pregnancy is associated with adverse pregnancy outcomes. However, biomarkers associated with air pollution exposure are widely lacking and often transient. In addition, ascertaining biospecimens during pregnacy to assess the prenatal environment remains largely infeasible.Objectives: To address these challenges, we investigated relationships between air pollution exposure during pregnancy and human serum albumin Cys34 (HSA-Cys34) adducts in newborn dried blood spots (DBS) samples, which captures an integration of perinatal exposures to small reactive molecules in circulating blood.Methods: Newborn DBS were obtained from a state archive for a cohort of 120 children born at one Kaiser Permanente Southern California (KPSC) hospitals in 2007. These children were selected to maximize the range of residential air pollution exposure during the entire pregnancy to PM2.5, PM10, NO2, O3, based on monthly estimates interpolated from regulatory monitoring sites. HSA-Cys34 adducts were selected based on previously reported relationships with air pollution exposure and oxidative stress.Results: Six adducts measured in newborn DBS samples were associated with air pollution exposures during pregnancy; these included direct oxidation products, adducts formed with small thiol compounds, and adducts formed with reactive aldehydes. Two general trends were identified: Exposure to air pollution late in pregnancy (i.e., in the last 30 days) was associated with increased oxidative stress, and exposure to air pollution earlier in pregnancy (i.e., not in the last 30 days) was associated with decreased oxidative stress around the time of birth.Discussion: Air pollution exposure occurring during pregnancy can alter biology and leave measurable impacts on the developing infant captured in the newborn DBS adductome, which represents a promising tool for investigating adverse birth outcomes in population-based studies.

Selenium alleviates toxicity in Amaranthus hypochondriacus by modulating the synthesis of thiol compounds and the subcellular distribution of cadmium

As a beneficial element, Selenium (Se) reduces toxic cadmium (Cd) absorption in many crops, but the effects of Se on Cd hyperaccumulator plants are unclear. This study examined the effects of Se on Amaranthus hypochondriacus (K472). The results showed that Se increased antioxidant enzyme activities, reduced Cd concentrations and toxicity, restored cell viability, and enhanced photosynthesis; these effects increased the biomass of roots, stems, and leaves by 59.87%, 53.85%, 44.19%, respectively, and these values exceeded the biomass of roots and stems in untreated control plants by 56.69% and 15.37%, respectively. Moreover, Se promoted PC synthesis, stably chelated Cd in the form of PC3 and PC4 and transported PC-Cd to vacuoles. Furthermore, Se protected organelles and reduced Cd migration by increasing Cd levels in cell walls and vacuoles. Interestingly, although the Cd content in K472 was decreased, Se maintained the total extracted Cd concentrations and its remediation efficiency by improving biomass and increased tolerance to Cd by approximately 5 times. The experimental results provide novel insights and methods for mitigating toxicity, promoting growth, and broadening the engineering application scope of K472; these results also provide a theoretical basis for further application of Se in soil with high Cd concentrations.

Reduction of an asymmetric Pt(IV) prodrug fac-[Pt(dach)Cl3(OC(=O)CH3)] by biological thiol compounds: kinetic and mechanistic characterizations

Reduction of an asymmetric Pt(IV) prodrug fac-[Pt(dach)Cl3(OC(=O)CH3)] by biological thiol compounds: kinetic and mechanistic characterizations

A stable naked-eye colorimetric sensor for monitoring release of extracellular gamma-aminobutyric acid (GABA) neurotransmitter from SH-SY5Y cells

A novel optical γ-aminobutyric acid (GABA)-based sensor was developed on interacting thiol compounds and o-phthalaldehyde (OPA) to form thiacetal compounds. Then, the thiacetal interacts with the GABA molecule to form an isoindole compound. The effects of four thiol compounds on the stability of the resulting isoindole compound were assessed. The 2-mercaptoethanol, “one of the most used derivatizing agents,” is unexpectedly the least stable; while, 16-mercaptohexadecanoic acid resulted in the most durable isoindole compound. The developed sensor showed the capability for detecting GABA within a wide concentration range spanning from 500 nmol L–1 to 100 µmol L–1. The detection limit was about 330 nmol L–1, which indicated the high sensitivity of the developed sensor compared with those previously reported. The findings illustrated the ability to detect GABA at the physiological pH (pH = 7.4) without adjusting the pH value, opening the door for real applications. Furthermore, the sensor could detect various GABA concentrations in human serum with good recovery percentages (98% to 101.4%). In addition, this assay was applied to monitor GABA release from the SH-SY5Y cell line to convert glutamate into GABA. This result indicates the capability of the proposed assay for visually monitoring the release of GABA neurotransmitters.

Influence of Redox Imbalances on the Transposition of Insertion Sequences in Deinococcus geothermalis.

The transposition of insertion sequence elements was evaluated among different Deinococcus geothermalis lineages, including the wild-type, a cystine importer-disrupted mutant, a complemented strain, and a cystine importer-overexpressed strain. Cellular growth reached early exponential growth at OD600 2.0 and late exponential growth at OD600 4.0. Exposing the cells to hydrogen peroxide (80–100 mM) resulted in the transposition of insertion sequences (ISs) in genes associated with the carotenoid biosynthesis pathway. Particularly, ISDge7 (an IS5 family member) and ISDge5 (an IS701 family member) from the cystine importer-disrupted mutant were transposed into phytoene desaturase (dgeo_0524) via replicative transposition. Further, the cystine importer-overexpressed strain Δdgeo_1985R showed transposition of both ISDge2 and ISDge5 elements. In contrast, IS transposition was not detected in the complementary strain. Interestingly, a cystine importer-overexpressing strain exhibited streptomycin resistance, indicating that point mutation occurred in the rpsL (dgeo_1873) gene encoding ribosomal protein S12. qRT-PCR analyses were then conducted to evaluate the expression of oxidative stress response genes, IS elements, and low-molecular-weight thiol compounds such as mycothiol and bacillithiol. Nevertheless, the mechanisms that trigger IS transposition in redox imbalance conditions remain unclear. Here, we report that the active transposition of different IS elements was affected by intracellular redox imbalances caused by cystine importer deficiencies or overexpression.

Successive bacterial desulfurization and regeneration of liquid fuel over Ni-doped carbon beads using a single Enterococcus faecium strain isolated from an industrial wastewater

Adsorptive desulfurization of liquid fuels over a wide sulfur (S) concentration range remains as challenging as the regeneration of spent materials. This study describes the efficient desulfurization of the dibenzothiophene (DBT) and thiophene (TH) containing liquid fuels over 300 – 1200 mg L−1 S-concentration range, using a hybrid approach combining adsorptive desulfurization (ADS) and bacterial desulfurization (BDS) sequentially at 30 °C and 1 atm-pressure, with the Ni-doped activated carbon beads and Enterococcus faecium bacterium serving as the ADS and BDS agent, respectively. The novelty is in the successful regeneration of spent adsorbents using the identical bacterium that was used in the BDS step. Notably, the bacterium was isolated from the waste effluent of a petroleum industry, and was characterized via the colony morphology, Gram staining, and identification by 16S rRNA sequencing. ADS step was used over 300 – 1200 mg L−1, before switching over to BDS over the 50 – 300 mg L−1 S- concentration range, the sequential steps indicating an approximately 99% removal of the thiol compounds from the liquid. The spent adsorbents, post sequential test, were regenerated using the bacterial dose of 1% (v/v) of the liquid, and successfully reused up to five cycles of the hybrid method, with ∼97% DBT and 95% TH removal measured in the last cycle. The spent and regenerated materials were physicochemically characterized by FE-SEM, FT-IR and BET analysis. As the regulations decrease the limits of sulfur content in on-road fuels globally, the proposed hybrid approach combining ADS with BDS, in conjunction with bacterial regeneration can be a potentially energy and cost effective solution to the desulfurization of liquid fuels.

Natural Thiols, but Not Thioethers, Attenuate Patulin-Induced Endoplasmic Reticulum Stress in HepG2 Cells.

Patulin, a mycotoxin, is known to have cytotoxic effects, but few studies have focused on the involvement of the endoplasmic reticulum (ER) stress response in patulin toxicity and the natural compounds that attenuate it in HepG2 cells. This study tested the ability of patulin to induce ER stress, and that of four thiols and three thioethers to attenuate patulin-induced ER stress in HepG2 cells. Patulin dose-dependently inhibited cell proliferation (IC50, 8.43 μM). Additionally, patulin was found to increase the expression levels of ER stress-related genes and/or protein markers, including BiP, CHOP, and spliced XBP1, in HepG2 cells compared to the vehicle control, indicating its potential in ER stress induction. Patulin-induced cytotoxicity in HepG2 cells was reduced by naturally occurring thiol compounds (glutathione, L-acetyl-L-cysteine, cysteine, and captopril), but not by thioether compounds (sulforaphane, sulforaphene, and S-allyl-L-cysteine). Patulin-thiol co-treatment decreased CHOP expression and BiP and CHOP levels in HepG2 cells but did not alter BiP expression. Spliced XBP1 expression was decreased by patulin-thiol co-treatment. Thus, patulin induced ER stress in HepG2 cells and thiols, but not in thioethers, attenuated patulin-induced ER stress.