Molecular Characteristics of Organosulfur Compounds in Guangzhou, South China: Heterogeneous Secondary Reactions Drivers the Molecular Distribution

Organosulfur compounds (OrgSs), especially organosulfates, have been widely reported at large quantities in particulate organic matter found in various atmospheric environments. Despite various kinds of organosulfates and their formation mechanisms being previously identified, a large fraction of OrgSs remain unexplained at the molecular level, impeding further knowledge on additional formation pathways and critical environmental parameters that help to explain their concentrations. In this work, the abundance and molecular composition of OrgSs in fine particulate samples collected in Guangzhou was reported. Our results revealed that organic sulfur can averagely contribute to 30 % of total particulate sulfur, and showed positively correlations with the SO2 (r = 0.37, p < 0.05) and oxidants (NOx+O3, r = 0.40, p < 0.01). Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) results presented that more than 80 % by number of the detected OrgSs in our samples have the elemental composition of O/(4S+3N) ≥ 1, indicating that they were largely in the form of oxidized organosulfates and/or nitrooxy organosulfates. Many OrgSs, which are tentatively attributed to previously identified biogenic and anthropogenic origins, were also present in aerosols derived from freshly-emitted combustion sources. Results show that the formation of OrgSs through an epoxide intermediate pathway could be as much as 46 %, and the oxidants levels could explain 20 % variation of organic sulfur mass. The analysis from our large FT-ICR MS dataset suggests that relative humidity, oxidation of biogenic volatile organic compounds via ozonolysis, and NOx-related nitrooxy organosulfate formations were the major reasons for the molecular variation of OrgSs, possibly highlighting the importance of heterogeneous reactions involving either the uptake of SO2 or the heterogeneous oxidations of particulate organosulfates into additional unrecognized OrgSs.

S-Methylcysteine Ameliorates the Intestinal Damage Induced by Eimeria tenella Infection via Targeting Oxidative Stress and Inflammatory Modulators

Avian coccidiosis is one of the major parasitic diseases in the poultry industry. The infection is caused by Eimeria species, and its treatment relies mainly on the administration of anticoccidial drugs, which can result in drug resistance and side effects. The recent trends in avian coccidiosis treatment is directed to the development of a new therapy using herbal compounds. S-Methylcysteine (SMC) is considered one of the organosulfur compounds in garlic that showed promising activity in the treatment of different pathological conditions via a wide range of anti-inflammatory and antioxidant mechanisms. In this study, the anticoccidial activity of SMC was investigated in Eimeria tenella-infected chickens compared to diclazuril as a widely used anticoccidial drug. In this regard, 14-day-old broilers were divided into six groups (n = 18). The first group (G1) was the healthy control group, while the second group (G2) was the non-infected SMC group treated at a dose of 50 mg/kg b.w. (high dose). Moreover, the third group (G3) was the positive control group (infected and non-treated). The fourth group (G4) was the infected group treated with SMC of 25 mg/kg b.w. (low dose), while the fifth group (G5) was the infected group treated with SMC of 50 mg/kg b.w. (high dose). Conversely, the sixth group (G6) was the diclazuril-treated group. The anticoccidial effects of SMC and diclazuril were evaluated by counting oocysts and recording the body weight gain, feed conversion ratio, clinical signs, lesions, and mortality rate. Interestingly, SMC showed potent anticoccidial activity, which was exemplified by reduction of oocyst count. Furthermore, the biochemical, antioxidant, and anti-inflammatory parameters in the cecal tissues were restored toward their control levels in G4, G5, and G6. Histopathological observation of cecal tissues was consistent with the aforementioned results revealing the ameliorative effect of SMC against E. tenella infection. This study concluded novel findings in relation to the anticoccidial role of SMC as a plant-based compound against the E. tenella-induced coccidiosis in broiler chickens combined with its antioxidative and anti-inflammatory properties. Further studies for exploring the mechanistic pathways involved in this activity and the potential benefits from its use in association with conventional anticoccidial drugs are warranted.

Chemical Transformation of α-Pinene derived Organosulfate via Heterogeneous OH Oxidation: Implications for Sources and Environmental Fates of Atmospheric Organosulfates

Organosulfur compounds are found to be ubiquitous in atmospheric aerosols — a majority of which are expected to be organosulfates (OSs). Given the atmospheric abundance of OSs, and their potential to form a variety of reaction products upon ageing, it is imperative to study the transformation kinetics and chemistry of OSs to better elucidate their atmospheric fates and impacts. In this work, we investigated the chemical transformation of an α-pinene derived organosulfate (C10H17O5SNa, αpOS-249) through heterogeneous OH oxidation at a relative humidity of 50 % in an oxidation flow reactor (OFR). The aerosol-phase reaction products were characterized using the high-performance liquid chromatography-electrospray ionization-high resolution mass spectrometry and the ion chromatography. By monitoring the decay rates of αpOS-249, the effective heterogeneous OH reaction rate was measured to be (6.72 ± 0.55) × 10−13 cm3 molecule−1 s−1. This infers an atmospheric lifetime of about two weeks at an average OH concentration of 1.5 × 106 molecules cm–3. Product analysis shows that OH oxidation of αpOS-249 can yield more oxygenated OSs having a nominal mass-to-charge ratio (m/z) at 247 (C10H15O5S−), 263 (C10H15O6S−), 265 (C10H17O6S−), 277 (C10H13O7S−), 279 (C10H15O7S−), and 281 (C10H17O7S−). The formation of fragmentation products, including both small OSs (C < 10) and inorganic sulfates, is found to be insignificant. These observations suggest that functionalization reactions are likely the dominant processes and that multigenerational oxidation possibly leads to formation of products with one or two hydroxyl and carbonyl functional groups adding to αpOS-249. Furthermore, all product ions except m/z = 277 have been detected in laboratory generated α-pinene derived secondary organic aerosols as well as in atmospheric aerosols. Our results reveal that OSs freshly formed from the photochemical oxidation of α-pinene could react further to form OSs commonly detected in atmospheric aerosols through heterogeneous OH oxidation. Overall, this study provides more insights into the sources, transformation, and fate of atmospheric OSs.

Deodorant Activity of Black Cumin Seed Essential Oil against Garlic Organosulfur Compound

The deodorant activity of black cumin (Nigella sativa L.) seed, a spice used to flavor curry and vegetable foods in Southwest Asia, against garlic (Allium sativum L.) organosulfur compounds related to human malodor was evaluated. Black cumin seed essential oil showed remarkable deodorant activity against garlic essential oil. The mode of action of this deodorant activity was presumed to be that black cumin seed essential oil covalently reacted with the organosulfur compounds in garlic. Therefore, thymoquinone, which is a major constituent in black cumin seed essential oil, and allyl mercaptan, which is one of the organosulfur compounds produced by cutting garlic, were reacted in vitro, and the products were purified and elucidated using spectroscopic data. As a result, these substances were identified as different allyl mercaptan adducts to dihydrothymoquinone. This chemical reaction was presumed to play a key role in the deodorant activity of black cumin seed essential oil.

Microbial cysteine degradation is a source of hydrogen sulfide in oxic freshwater lakes

The sulfur-containing amino acid cysteine is abundant in the environment including in freshwater lakes. Biological degradation of cysteine can result in hydrogen sulfide (H2S), a toxic and ecologically relevant compound that is a central player in biogeochemical cycling in aquatic environments, including freshwater lakes. Here, we investigated the ecological significance of cysteine in oxic freshwater lake environments, using model systems of isolated cultures, controlled growth experiments, and multi-omics. We screened bacterial isolates enriched from natural lake water for their ability to produce H2S when provided cysteine. In total, we identified 29 isolates that produced H2S and belonged to the phylum Proteobacteria Bacteroidetes, and Actinobacteria. To understand the genomic and genetic basis for cysteine degradation and H2S production, we further characterized 3 freshwater isolates using whole-genome sequencing, and quantitatively tracked cysteine and H2S levels over their growth ranges: Stenotrophomonas maltophila, Stenotrophomonas bentonitica (Gammaproteobacteria) and Chryseobacterium piscium (Bacteroidetes). We observed a decrease in cysteine and increase in H2S, and identified genes involved in cysteine degradation in all 3 genomes. Finally, to assess the presence of these organisms and genes in the environment, we surveyed a five-year time series of metagenomic data from the same isolation source at Lake Mendota and identified their presence throughout the time series. Overall, our study shows that sulfur-containing amino acids can drive microbial H2S production in oxic environments. Future considerations of sulfur cycling and biogeochemistry in oxic environments should account for H2S production from degradation of organosulfur compounds.

Switchable Synthesis of Sulfoxides, Sulfones and Thiosulfonates through Selectfluor-Promoted Oxidation with H2O as O-Source

A practical and efficient protocol for the switchable synthesis of sulfoxides, sulfones, and thiosulfonates via Selectfluor-mediated oxidation of sulfides has been developed at ambient temperature. These organosulfur compounds can be prepared with nearly all quantitative yields by applying eco-friendly H2O as O- source. The formation of sulfoxides and thiosulfonates takes only a few minutes (3-20 min). As suggested by the control experiments, the oxidation procedure might proceed through the fluorination of sulfide, nucleophilic addition with H2O and the elimination of hydrogen fluoride.

Effect of Adding Chelating Ligands on the Catalytic Performance of Rh-Promoted MoS2 in the Hydrodesulfurization of Dibenzothiophene

Hydrodesulfurization (HDS) is a widely used process currently employed in petroleum refineries to eliminate organosulfur compounds in fuels. The current hydrotreating process struggles to remove organosulfur compounds with a steric hindrance due to the electronic nature of the current catalysts employed. In this work, the effects of adding chelating ligands such as ethylenediaminetetraacetic acid (EDTA), citric acid (CA) and acetic acid (AA) to rhodium (Rh) and active molybdenum (Mo) species for dibenzothiophene (DBT) HDS catalytic activity was evaluated. HDS activities followed the order of RhMo/ɣ-Al2O3 (88%) > RhMo-AA/ɣ-Al2O3 (73%) > RhMo-CA/ɣ-Al2O3 (72%) > RhMo-EDTA/ɣ-Al2O3 (68%). The observed trend was attributed to the different chelating ligands with varying electronic properties, thus influencing the metal–support interaction and the favorable reduction of the Mo species. RhMo/ɣ-Al2O3 offered the highest HDS activity due to its (i) lower metal–support interaction energy, as observed from the RhMo/ɣ-Al2O3 band gap of 3.779 eV and the slight shift toward the lower BE of Mo 3d, (ii) increased Mo-O-Mo species (NMo-O-Mo ~1.975) and (iii) better sulfidation of Rh and MoO in RhMo/ɣ-Al2O3 compared to the chelated catalysts. The obtained data provides that HDS catalytic activity was mainly driven by the structural nature of the RhMo-based catalyst, which influences the formation of more active sites that can enhance the HDS activity.

Biodesulfurization of Dibenzothiophene and Its Alkylated Derivatives in a Two-Phase Bubble Column Bioreactor by Resting Cells of Rhodococcus erythropolis IGTS8

Biodesulfurization (BDS) is considered a complementary technology to the traditional hydrodesulfurization treatment for the removal of recalcitrant sulfur compounds from petroleum products. BDS was investigated in a bubble column bioreactor using two-phase media. The effects of various process parameters, such as biocatalyst age and concentration, organic fraction percentage (OFP), and type of sulfur compound—namely, dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT), and 4,6-diethyldibenzothiophene (4,6-DEDBT)—were evaluated, using resting cells of Rhodococcus erythropolis IGTS8. Cells derived from the beginning of the exponential growth phase of the bacterium exhibited the highest biodesulfurization efficiency and rate. The biocatalyst performed better in an OFP of 50% v/v. The extent of DBT desulfurization was dependent on cell concentration, with the desulfurization rate reaching its maximum at intermediate cell concentrations. A new semi-empirical model for the biphasic BDS was developed, based on the overall Michaelis-Menten kinetics and taking into consideration the deactivation of the biocatalyst over time, as well as the underlying mass transfer phenomena. The model fitted experimental data on DBT consumption and 2-hydroxibyphenyl (2-HBP) accumulation in the organic phase for various initial DBT concentrations and different organosulfur compounds. For constant OFP and biocatalyst concentration, the most important parameter that affects BDS efficiency seems to be biocatalyst deactivation, while the phenomenon is controlled by the affinities of biodesulfurizing enzymes for the different organosulfur compounds. Thus, desulfurization efficiency decreased with increasing initial DBT concentration, and in inverse proportion to increases in the carbon number of alkyl substituent groups.

Evaluation of the Anti-Shigellosis Activity of Dietary Isothiocyanates in Galleria mellonella Larvae

Cruciferous vegetables, widely present in daily diets, are a rich source of organosulfur compounds with proven health benefits, especially chemopreventive or antioxidative effects. Isothiocyanate derivatives (ITCs) exhibit a broad spectrum of biological and pharmacological activity and recently, their antibacterial properties have been of particular importance. Here, we have focused on the anti-shigellosis activity of sulforaphane (SFN) and phenethyl ITC (PEITC). The genus Shigella causes gastroenteritis in humans, which constitutes a threat to public health. Production of a potent Stx toxin by S. dysenteriae type 1 results not only in more severe symptoms but also in serious sequela, including the hemolytic uremic syndrome. Here, we present evidence that two aliphatic and aromatic ITCs derivatives, SFN and PEITC, have an effective antibacterial potency against S. dysenteriae, also negatively regulating the stx gene expression. The molecular mechanism of this effect involves induction of the global stress-induced stringent response. ITCs also inhibit bacterial virulence against the Vero and HeLa cells. We present evidence for the therapeutic effect of sulforaphane and phenethyl ITC against a S. dysenteriae infection in the Galleria mellonella larvae model. Thus, our results indicate that isothiocyanates can be effectively used to combat dangerous bacterial infections.