High-resolution Mass Spectrometry Research Articles

Rapid detection of ricin at trace levels in complex matrices by asialofetuin-coated beads and bottom-up proteomics using high-resolution mass spectrometry.

Ricin is a toxic protein regarded as a potential chemical weapon for bioterrorism or criminal use. In the event of a ricin incident, rapid analytical methods are essential for ricin confirmation in a diversity of matrices, from environmental to human or food samples. Mass spectrometry-based methods provide specific toxin identification but require prior enrichment by antibodies to reach trace-level detection in matrices. Here, we describe a novel assay using the glycoprotein asialofetuin as an alternative to antibodies for ricin enrichment, combined with the specific detection of signature peptides by high-resolution mass spectrometry. Additionally, optimizations made to the assay reduced the sample preparation time from 5h to 80min only. Method evaluation confirmed the detection of ricin at trace levels over a wide range of pH and in protein-rich samples, illustrating challenging matrices. This new method constitutes a relevant antibody-free solution for the fast and specific mass spectrometry detection of ricin in the situation of a suspected toxin incident, complementary to active ricin determination by adenine release assays.

Upconversion Luminescence in a Photostable Ion-Paired Yb-Eu Heteronuclear Complex.

Lanthanide-based upconversion molecular complexes have potential application in diverse fields and attracted considerable research interest in recent years. However, the similar coordination reactivity of lanthanide ions has constrained the designability of target molecule with well-defined structure, and many attempts obtained statistical mixtures. Herein, an ion-paired Yb-Eu heteronuclear complex [Eu(TpPy)2][Yb(ND)4] (TpPy = tris[3-(2-pyridyl)pyrazolyl]hydroborate, ND = 3-cyano-2-methyl-1,5-naphthyridin-4-olate) was designed and synthesized. Thanks to the radius difference between Eu3+ (1.07 Å) and Yb3+ (0.98 Å) ions, the hexadentate TpPy ligand was selected to coordinate with Eu3+ and the Yb3+ with a smaller radius was chelated by bidentate ND ligand. As a result, the sites of Eu3+ and Yb3+ in the complex can be clarified by high-resolution mass spectrometry and single-crystal structure analysis. Upon the excitation of Yb3+ at 980 nm, the upconversion emission of Eu3+ was realized through a cooperative sensitization process. Furthermore, [Eu(TpPy)2][Yb(ND)4] demonstrated excellent photostability during continuous high-power density 980 nm laser irradiation, with a LT95 (the time to 95% of the initial emission intensity) of 420 minutes. This work provides the first example of a pure ion-paired Yb-Eu heteronuclear complex upconversion system and may bring insights into rational design of lanthanide-based upconversion molecular complexes.

Reaction Discovery Using Spectroscopic Insights from an Enzymatic C-H Amination Intermediate.

Engineered hemoproteins can selectively incorporate nitrogen from nitrene precursors like hydroxylamine, O-substituted hydroxylamines, and organic azides into organic molecules. Although iron-nitrenoids are often invoked as the reactive intermediates in these reactions, their innate reactivity and transient nature have made their characterization challenging. Here we characterize an iron-nitrosyl intermediate generated from NH2OH within a protoglobin active site that can undergo nitrogen-group transfer catalysis, using UV-vis, electron paramagnetic resonance (EPR) spectroscopy, and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) techniques. The mechanistic insights gained led to the discovery of aminating reagents─nitrite (NO2-), nitric oxide (NO), and nitroxyl (HNO)─that are new to both nature and synthetic chemistry. Based on the findings, we propose a catalytic cycle for C-H amination inspired by the nitrite reductase pathway. This study highlights the potential of engineered hemoproteins to access natural nitrogen sources for sustainable chemical synthesis and offers a new perspective on the use of biological nitrogen cycle intermediates in biocatalysis.

Phosphorescent PdII-PdII Emitter-Based Red OLEDs with an EQEmax of 20.52.

Three dinuclear Pd(II) complexes (1, 2, and 3) with intense red phosphorescence at room temperature are here synthesized using strong ligand field strength compounds. All three complexes are characterized by nuclear magnetic resonance, high-resolution mass spectrometry, and elemental analyses. Complexes 2 and 3 are characterized by single-crystal X-ray diffraction. The crystalline data of 2 and 3 reveal complex double-layer structures, with Pd-Pd distances of 2.8690(9) Å and 2.8584(17) Å, respectively. Furthermore, complexes 1, 2, and 3 show phosphorescence at room temperature in their solid states at the wavelengths of 678, 601, and 672nm, respectively. In addition, they show phosphorescence at 634, 635, and 582nm, respectively, in the 2wt.% (PMMA) films, and phosphorescence at 670, 675, and 589nm, respectively, in the deoxygenated CH2Cl2 solutions. Among three complexes, complex 1 shows red emission at 634nm with phosphorescent quantum yield Ф = 67% in the 2wt.% PMMA film. Furthermore, complex 1-based organic light-emitting diode is fabricated using a vapor-phase deposition process, and their maximum external quantum efficiency reaches 20.52%, which is the highest percentage obtained by using the dinuclear Pd(II) complex triplet emitters with the CIE coordinates of (0.62, 0.38).

Degradation of Isotianil in Water and Soil: Kinetics, Degradation Pathways, Mechanisms, and Ecotoxicity Assessments.

Pesticides are transported and transformed in soil and can enter surface water through various pathways. They undergo hydrolysis, oxidation, and photoconversion in surface water. Isotianil is a new fungicide that effectively controls rice blast. However, there are limited reports on its degradation. Herein, the hydrolysis and photolysis of isotianil in water and its degradation in soil samples from five provinces of China were investigated. The degradation products of isotianil were identified using ultrahigh-performance liquid chromatography-Q exactive hybrid quadrupole-orbitrap high-resolution accurate mass spectrometry, and four compounds were discovered for the first time. The degradation pathways of isotianil were inferred, and the reaction active site and degradation mechanism of isotianil were clarified based on density functional theory calculations. The ecotoxicity of the degradation product M118 (aminobenzonitrile) was found to be moderate toward Daphnia magna, which was predicted and confirmed by Ecological Structure Activity Relationships and the experiment, respectively. The results of this study will contribute to a better understanding of the fate of isotianil in the environment.

Structural characterization and bioactivity profiling of the fungal peptaibiotic tolypin reveal protective effects against influenza viruses.

In a bioprospection for new antivirals, we tested nonribosomally biosynthesized polypeptide antibiotics in MDCK II cells for their actions on influenza A and B viruses (IAV/IBV). Only tolypin, a mixture of closely related 16-residue peptaibiotics from the fungus Tolypocladium inflatum IE 1897, showed promising activity. It was selected for further investigation and structural characterization byultrahigh performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HR-MS/MS) and ultrahigh performance liquid chromatography coupled to in-source collision-induced dissociation tandem mass spectrometry (UHPLC-isCID-HR-MS/MS), revealing 12 partially co-eluting individual peptides that were fully sequenced. Since tolypin-related efrapeptins are potent inhibitors of F1/Fo-ATPase, we screened tolypin for its toxicity against MDCK II cells and larvae of the greater wax moth Galleria mellonella. We found that a nontoxic concentration of tolypin (1 µg/mL) reduced the titer of two IBV strains by 4-5 log values, and that of an H3N2 strain by 1-2 log values, but the H1N1pdm strain was not affected. The higher concentrations of tolypin were cytostatic to MDCK II cells, shifted their metabolism from oxidative phosphorylation to glycolysis, and induced paralysis in G. mellonella, supporting the inhibition of F1/Fo-ATPase as the mode of action. Our results lay the foundations for future work to investigate the interplay between viral replication and cellular energy metabolism, as well as the development of drugs that target host factors.

Exploring the therapeutic potential of Thai medicinal plants: in vitro screening and in silico docking of phytoconstituents for novel anti-SARS-CoV-2 agents

BackgroundThe high virulence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), responsible for coronavirus disease 2019 (COVID-19), has triggered global health and economic concerns. The absence of specific antiviral treatments and the side effects of repurposed drugs present persistent challenges. This study explored a promising antiviral herbal extract against SARS-CoV-2 from selected Thai medicinal plants based on in vitro efficacy and evaluated its antiviral lead compounds by molecular docking.MethodsTwenty-two different ethanolic-aqueous crude extracts (CEs) were rapidly screened for their potential activity against porcine epidemic diarrhea virus (PEDV) as a surrogate using a plaque reduction assay. Extracts achieving ≥ 70% anti-PEDV efficacy proceeded to the anti-SARS-CoV-2 activity test using a 50% tissue culture infectious dose method in Vero E6 cells. Molnupiravir and extract-free media served as positive and negative controls, respectively. Potent CEs underwent water/ethyl acetate fractionation to enhance antiviral efficacy, and the fractions were tested for anti-SARS-CoV-2 performance. The fraction with the highest antiviral potency was identified using liquid chromatography–high-resolution mass spectrometry (LC–HRMS). Molecular docking analyses of these compounds against the main protease (Mpro) of SARS-CoV-2 (6LU7) were performed to identify antiviral lead molecules. The top three hits were further evaluated for their conformational stability in the docked complex using molecular dynamics (MD) simulation.ResultsThe water fraction of mulberry (Morus alba Linn.) leaf CE (WF-MLCE) exhibited the most potent anti-SARS-CoV-2 efficacy with low cytotoxicity profile (CC50 of ~ 0.7 mg/mL), achieving 99.92% in pre-entry mode and 99.88% in postinfection treatment mode at 0.25 mg/mL. Flavonoids and conjugates were the predominant compounds identified in WF-MLCE. Molecular docking scores of several flavonoids against SARS-CoV-2 Mpro demonstrated their superior antiviral potency compared to molnupiravir. Remarkably, myricetin-3-O-β-D-galactopyranoside, maragrol B, and quercetin 3-O-robinobioside exhibited binding energies of ~ − 9 kcal/mol. The stability of each ligand–protein complex of these compounds with the Mpro system showed stability during MD simulation. These three molecules were pronounced as antiviral leads of WF-MLCE. Given the low cytotoxicity and high antiviral potency of WF-MLCE, it holds promise as a candidate for future therapeutic development for COVID-19 treatment, especially considering its economic and pharmacological advantages.

Suspect screening of per- and polyfluoroalkyl substances in paper by selective and non-selective extraction with UHPLC-Q Orbitrap MS

Non-targeted analysis and suspect screening of per- and polyfluoroalkyl substances (PFAS) in various matrices have gained traction with advancements in accurate mass analytical instruments. This study employed ultra-high performance liquid chromatography coupled to quadrupole orbitrap high-resolution mass spectrometry for PFAS suspect screening of paper grades used in the paper recycling chain. The samples were prepared using two extraction techniques; selective accelerated solvent extraction with weak anionic exchange solid-phase extraction and non-selective ultrasonic-assisted extraction. A suspect screening protocol was established to tentatively identify suspected PFAS against spectral databases using a systematic approach of peak filtering and study-specific thresholds for reporting, linked to a confidence level. The possible prevalence of previously unreported PFAS in several paper materials across the various collection sites in the paper recycling chain was inferred by the common detection of short-chain polyfluoroalkyl ketones and diketones in the paper recycling chain. The suspect screening tentatively identified 41 unique PFAS, with 3 common to both pre-treatment techniques. The detection of unique PFAS by the two sample pre-treatment techniques highlighted the significance of both selective and non-selective extraction in PFAS screening endeavours. Further, it showed the importance of understanding the acquisition mechanisms employed in mass spectrometry where data-dependent acquisition triggered fragmentation in certain identified compounds, and not in others. The tentatively identified PFAS indicated that there were several previously unreported PFAS in the paper recycling chain and that additional studies were required to investigate their abundance, possible persistence, bioaccumulation and toxicity, in relation to their functional groups and carbon chains.

Unraveling Interspecies Differences in the Phase I Hepatic Metabolism of Alternariol and Alternariol Monomethyl Ether: Closing Data Gaps for a Comprehensive Risk Assessment.

The Alternaria mycotoxins alternariol (AOH) and alternariol 9-O-monomethyl ether (AME) are pervasive food contaminants known to exert adverse effects in vitro, yet their toxicokinetics remain inadequately understood. Thus, this study endeavors to elucidate the qualitative and quantitative aspects of the phase I metabolism of AOH and AME. To pursue this goal, reduced nicotinamide adenine dinucleotide phosphate (NADPH)-fortified porcine, rat, and human liver microsomes were incubated for 0-10 min with AOH or AME within a concentration range of 1-100 and 1-50 μM, respectively. The decline in the parent toxin concentration was monitored via liquid chromatography coupled to tandem mass spectrometry, whereas coupling to high-resolution mass spectrometry provided insights into the composition of the arising metabolic mixture. The collected quantitative data allowed us to calculate the hepatic intrinsic clearance rates of AOH and AME, marking a notable contribution to the field. Moreover, we unveiled interspecies differences in the pattern and rate of the phase I metabolism of the investigated mycotoxins. The presented findings lay the groundwork for physiologically based toxicokinetic modeling aimed at estimating local concentrations of these mycotoxins in specific organs, enhancing our understanding of their mode of action and adverse health effects.

Chemical Diversity of Aspergillus alliaceus Phenotypes: Discovery of brominated bianthrones with activity against triple-negative breast cancer cell lines.

Marine-derived fungi have emerged as a source for novel metabolites with a broad range of bioactivities. However, accessing the full potential of fungi under standard laboratory conditions remains challenging. LC-MS-based metabolomics in combination with varied culture conditions is a fast and powerful tool to detect new metabolites. Here, three developmental forms of the marine-derived fungusAspergillus alliaceuswere analyzed and 14 fungal metabolites, including new brominated polyketides (11-14) were isolated.Structure elucidation relied mainly on 1D and 2D NMR techniques and was supported by low- and high-resolution mass spectrometry and DFT-based computations. We sequenced theA. alliaceusgenome, identified the bianthrone-producing biosynthetic gene cluster, and conducted expression analysis on genes involved in sexual development and biosynthesis. TheNCI-60 cell line panel revealed selectivein vitroactivity against triple-negative breast cancer (TNBC) for the halogenated allianthrones and their full anti-proliferative and cytotoxic effects were evaluated in fiveTNBCcell lines.

Isolation and biological activity of six new polyketide and terpenoid derivatives from Neopestalotiopsis Clavispora AL01

A fungus strain, Neopestalotiopsis clavispora AL01, was isolated from the leaf spot of the plant Phoenix dactylifera. Further chemical investigation of the fermentation extract of this strain afforded six new secondary metabolites (1–6), along with 11 known compounds (7–17) which included a new natural compound (7). Their structures were determined by extensive spectroscopic analysis including one-and two-dimensional (1D and 2D) NMR spectroscopy, high-resolution electrospray ionization mass spectrometry (HRESIMS), and ECD and NMR calculations. All compounds were evaluated for their phytotoxic activities. Among them, compounds 10, 12 and 13 exhibited phytotoxic activities against Nicotiana tabacum. Compound 3 exhibited weak antibacterial activity against methicillin-resistant Staphylococcus aureus, Micrococcus luteus and Vibrio harveyi. Taken collectively, these findings establish a solid research foundation for future investigations on bioactive natural products derived from phytopathogenic fungi.

Grafting of -Electroactive Probe onto the glassy carbon electrode for the Detection of Tetracycline in Milk sample

ABSTRACT This paper presents a new Schiff base molecule of (Z)-N’-(2-hydroxy-5-nitrobenzylidene) nicotinohydrazide (BNH) that has been synthesised and characterised using Fourier transform infrared spectroscopy, Proton and Carbon-13 Nuclear Magnetic Resonance and High-resolution Ionisation Mass Spectroscopy. The study herein describes the novel chemical modification of glassy carbon electrode (GCE) by drop casting method using the synthesised Schiff base molecule to detect tetracycline (TC) antibiotic. Improved sensitivity of the electrode to the analyte results from the electrode modification using functional group present in the Schiff bases. The electrochemical behaviour of a modified electrode on tetracycline using voltammetric techniques were studied and optimised. The modified electrode showed a good selectivity in the presence of some interferences. The calibration curve for TC was achieved in a linear range of 10–60 μmol L−1 under optimised conditions. The detection limit and quantification for TC was found to be 2.1 μmol L−1 and 9 μmol L−1. The obtained results suggested that tetracycline may be measured in milk samples using the BNH modified glassy carbon electrode.

Application of untargeted liquid chromatography-mass spectrometry to routine analysis of food using three-dimensional bucketing and machine learning

For the detection of food adulteration, sensitive and reproducible analytical methods are required. Liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) is a highly sensitive method that can be used to obtain analytical fingerprints consisting of a variety of different components. Since the comparability of measurements carried out with different devices and at different times is not given, specific adulterants are usually detected in targeted analyses instead of analyzing the entire fingerprint. However, this comprehensive analysis is desirable in order to stay ahead in the race against food fraudsters, who are constantly adapting their adulterations to the latest state of the art in analytics. We have developed and optimized an approach that enables the separate processing of untargeted LC‑HRMS data obtained from different devices and at different times. We demonstrate this by the successful determination of the geographical origin of honey samples using a random forest model. We then show that this approach can be applied to develop a continuously learning classification model and our final model, based on data from 835 samples, achieves a classification accuracy of 94% for 126 test samples from 6 different countries.

Unraveling iron oxides as abiotic catalysts of organic phosphorus recycling in soil and sediment matrices

In biogeochemical phosphorus cycling, iron oxide minerals are acknowledged as strong adsorbents of inorganic and organic phosphorus. Dephosphorylation of organic phosphorus is attributed only to biological processes, but iron oxides could also catalyze this reaction. Evidence of this abiotic catalysis has relied on monitoring products in solution, thereby ignoring iron oxides as both catalysts and adsorbents. Here we apply high-resolution mass spectrometry and X-ray absorption spectroscopy to characterize dissolved and particulate phosphorus species, respectively. In soil and sediment samples reacted with ribonucleotides, we uncover the abiotic production of particulate inorganic phosphate associated specifically with iron oxides. Reactions of various organic phosphorus compounds with the different minerals identified in the environmental samples reveal up to ten-fold greater catalytic reactivities with iron oxides than with silicate and aluminosilicate minerals. Importantly, accounting for inorganic phosphate both in solution and mineral-bound, the dephosphorylarion rates of iron oxides were within reported enzymatic rates in soils. Our findings thus imply a missing abiotic axiom for organic phosphorus mineralization in phosphorus cycling.

The spatial distribution of components in Moringa oleifera (Lam) seed by matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI)

In this paper, 70 % methanol was used as solvent to extract the principal components from Moringa oleifera (Lam) seed with the ratio (w/v, 1:10) by ultrasonic-assisted extraction. The extract in Lam seed was detected by high resolution mass spectrometry and MS/MS spectra. The result suggests that there are three principal components including malic acid, d-trehalose and 4-(α-L-rhamnopyranosyloxy) benzyl glucosinolate in this extract. Based on this result, the spatial distribution of these components in Lam seed was visually obtained by matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI). There is much malic acid in the center of endosperm in Lam kernel and little in the shell of Lam seed. d-trehalose is mainly distributed in the seed coat of Lam seed, and almost no d-trehalose is distributed in the kernel of Lam seed. 4-(α-L-rhamnopyranosyloxy) benzyl glucosinolate is distributed in the seed coat and endosperm of Lam seed. The relative content of this compound in the seed coat of Lam seed is much higher than that in the endosperm. The result further suggests that the different component in Lam seed is distributed in different part. This study can provide some valuable reference for efficient extracting active components from Lam.

Ultrasound-assisted synthesis of 4-thiazolidinone Schiff bases and their antioxidant, α-glucosidase, α-amylase inhibition, mode of inhibition and computational studies

AbstractDiabetes mellitus (DM) has become a growing concern to global public health, being at the forefront of acute disorders and causes of mortality across the globe. Clinically approved drugs that are currently being used are faced with severe side effects, consequently necessitating the development of new drugs with no/fewer side effects and improved pharmacological potency. Herein, we report a rapid and efficient synthesis of thiazolidinone Schiff bases (2a-2t) from benzylidenehydrazines and thioglycolic acid under neat conditions through ultra-sonication. All the synthesized compounds were obtained in exceptional yields (89–95%) and confirmed by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, as well as High-resolution mass spectrometry (HRMS). The synthesized compounds were then evaluated for their antidiabetic activity through α-glucosidase and α-amylase inhibitory potentials and their antioxidant activity through Nitric Oxide (NO), 2,2′-diphenyl-1-picrylhydrazyl (DPPH), and Ferric reducing antioxidant power (FRAP) assays. Among them, 2q (IC50 = 96.63 μM) and 2h (IC50 = 125.27 μM) emerged as the most potent derivatives against α-amylase relative to reference drug acarbose (IC50 = 131.63 µM), respectively. Antioxidant evaluation further revealed that the synthesized derivatives were excellent NO scavengers disclosing 2n (IC50 = 44.95 µM) as the most potent derivative. Moreover, in silico ADME calculations predicted these compounds to have excellent drug-like properties. Kinetic studies disclosed the mode of α-amylase inhibition as competitive while molecular docking studies of the most active derivatives performed into the binding active site of human pancreatic α-amylase enzyme deciphered their ligand-protein interactions that explicated their observed experimental potencies.

Unraveling Grewia bilamellata Gagnep. Role in cerebral ischemia: Comprehensive in vivo and in silico studies.

The present study investigated the neuroprotective properties of whole plants of Grewia bilamellata Gagnep. extract (GBEE) against cerebral ischemia by harnessing both In vivo studies in a rat model and In silico studies focusing on nitric oxide synthase (NOS) inhibition. High-resolution liquid chromatography‒mass spectrometry (HR LC‒MS) analysis identified 32 phytochemicals in the GBEE, 15 of which adhered to Lipinski's rule of five. These compounds exhibited diverse physicochemical properties and high binding affinity to NOS, with cleomiscosin D showing the greatest potential. In vivo, GBEE had significant neuroprotective effects on bilateral common carotid artery occlusion/reperfusion (BCCAO/R) in rats, especially at doses of 200mg/kg and 400mg/kg body weight. GBEE treatment improved brain function, as evidenced by EEG normalization, substantial reductions in cerebral infarction size, mitigated neuronal loss, and the restoration of regular histological arrangement in the CA1 hippocampal area of the brain. Furthermore, GBEE enhanced antioxidant defenses by augmenting the activity of catalase (CAT) and superoxide dismutase (SOD), reducing malondialdehyde (MDA) levels, and restoring reduced glutathione (GSH) levels. These effects were accompanied by a decrease in nitric oxide (NO) levels, indicative of attenuated oxidative and nitrosative stress. Collectively, our findings suggest that GBEE is a promising natural therapeutic agent that may prevent or alleviate ischemic brain injury through a multifaceted mechanism involving NOS inhibition and attenuation of the oxidative stress response. This study highlights the therapeutic potential of GBEE and warrants further research into its mechanism of action and possible clinical applications.

The marriage between stable isotope ecology and plant metabolomics - new perspectives for metabolic flux analysis and the interpretation of ecological archives.

Even though they share many thematical overlaps, plant metabolomics and stable isotope ecology have been rather separate fields mainly due to different mass spectrometry demands. New high-resolution bioanalytical mass spectrometers are now not only offering high-throughput metabolite identification but are also suitable for compound- and intramolecular position-specific isotope analysis in the natural isotope abundance range. In plant metabolomics, label-free metabolic pathway and metabolic flux analysis might become possible when applying this new technology. This is because changes in the commitment of substrates to particular metabolic pathways and the activation or deactivation of others alter enzyme-specific isotope effects. This leads to differences in intramolecular and compound-specific isotope compositions. In plant isotope ecology, position-specific isotope analysis in plant archives informed by metabolic pathway analysis could be used to reconstruct and separate environmental impacts on complex metabolic processes. A technology-driven linkage between the two disciplines could allow to extract information on environment-metabolism interaction from plant archives such as tree rings but also within ecosystems. This would contribute to a holistic understanding of how plants react to environmental drivers, thus also providing helpful information on the trajectories of the vegetation under the conditions to come.

Secondary Organic Aerosol from OH-Initiated Oxidation of Mixtures of d-Limonene and β-Myrcene.

The chemical composition and physical properties of secondary organic aerosol (SOA) generated through OH-initiated oxidation of mixtures containing β-myrcene, an acyclic monoterpene, and d-limonene, a cyclic monoterpene, were investigated to assess the extent of the chemical interactions between their oxidation products. The SOA samples were prepared in an environmental smog chamber, and their composition was analyzed offline using ultraperformance liquid chromatography coupled with electrospray ionization high-resolution mass spectrometry (UPLC-ESI-HRMS). Our results suggested that SOA containing β-myrcene showed a higher proportion of oligomeric compounds with low volatility compared to that of SOA from d-limonene. The formula distribution and signal intensities of the mixed SOA could be accurately predicted by a linear combination of the mass spectra of the SOA from individual precursors. Effects of cross-reactions were observed in the distribution of isomeric oxidation products within the mixed SOA, as made evident by chromatographic analysis. On the whole, β-myrcene and d-limonene appear to undergo oxidation by OH largely independently from each other, with only subtle effects from cross-reactions influencing the yields of specific oxidation products.

Discovery of Novel Antioomycete Metabolites from the Marine-Derived Fungus Paraconiothyrium sporulosum.

In our screening program for natural products that are effective in controlling plant diseases, we found that the culture filtrate of Paraconiothyrium sporulosum SFC20160907-M11 effectively suppressed the development of tomato late blight disease caused by Phytophthora infestans. Using a bioassay-guided fractionation of antioomycete activity, 12 active compounds (1-12) were obtained from an ethyl acetate extract of the culture filtrate. Chemical structures of five new compounds 1-5 were determined by the extensive analyses of nuclear magnetic resonance (NMR), high resolution mass spectrometry (HRMS), and circular dichroism (CD) data. Interestingly, mycosporulonol (1) and botrallin (8) completely inhibited the growth of P. infestans at concentrations of 8 and 16 μg/mL, respectively. Furthermore, the spray treatment of 1 and 8 (500 μg/mL) successfully protected tomato seedlings against P. infestans with disease control values of 92%. Taken together, these results suggest that the culture filtrates of P. sporulosum SFC20160907-M11 and their bioactive metabolites can be used as new antioomycete agents for Phytophthora late blight control.