Extracellular DNA secreted in yeast cultures is metabolism-specific and inhibits cell proliferation

Extracellular DNA (exDNA) can be actively released by living cells and different putative functions have been attributed to it. Further, homologous exDNA has been reported to exert species-specific inhibitory effects on several organisms. Here, we demonstrate by different experimental evidence, including 1H-NMR metabolomic fingerprint, that the growth rate decline in Saccharomyces cerevisiae fed-batch cultures is determined by the accumulation of exDNA in the medium. Sequencing of such secreted exDNA represents a portion of the entire genome, showing a great similarity with extrachromosomal circular DNA (eccDNA) already reported inside yeast cells. The recovered DNA molecules were mostly single strands and specifically associated to the yeast metabolism displayed during cell growth. Flow cytometric analysis showed that the observed growth inhibition by exDNA corresponded to an arrest in the S phase of the cell cycle. These unprecedented findings open a new scenario on the functional role of exDNA produced by living cells.

Advantages of using biologically generated 13C-labelled multiple internal standards for stable isotope-assisted LC-MS-based lipidomics

In comprehensive lipidomics studies, accurate quantification is essential but biological and/or clinical relevance is often hindered due to unwanted variations such as lipid degradation during sample preparation, matrix effects and non-linear responses of analytical instruments. In addition, the wide chemical diversity of lipids can complicate the accurate identification of individual lipids. These analytical limitations can potentially be corrected efficiently by the use of lipid-specific isotopically labelled internal standards (IS) but currently such IS mixtures have limited coverage of the mammalian lipidome. In this study, an in vivo¹³C labelling strategy was employed to explore four species (Escherichia coli, Arthrospira platensis, Saccharomyces cerevisiae and Pichia pastoris) as a source of ¹³C-labelled internal standards (¹³C-ISs) for more accurate and quantitative liquid chromatography (LC)-mass spectrometry (MS)-based lipidomics. Results showed that extracts from ¹³C-labelled P. pastoris and S. cerevisiae contain the highest percentage of uniformly labelled lipids (both 83% compared to 67% and 69% in A. platensis and E. coli, respectively) and ¹³C-labelled P. pastoris extract was identified as the optimum source of ¹³C-ISs for comprehensive data normalisation to correct unwanted variations during sample preparation and LC-MS analysis. Overall, use of a biologically generated ¹³C-IS lipid mixture of 357 identified lipid ions resulted in significant reduction in the lipid CV% of normalisation compared with other normalisation methods using total ion counts or a commercially available deuterated internal standard mixture. This improved normalisation using ¹³C-IS was confirmed in a typical lipidomics analysis using a large number of samples (>100+) and long analysis time (>70 h). This study highlights the benefit of an in vivo labelling strategy for reducing technical and analytical variations introduced during sample preparation and analysis in lipidomics studies.

Leaf metabolomics and molecular networking of wild type and mutant genotypes of chia (Salvia hispanica L.)

Salvia hispanica L., commonly named Chia, is a food plant from Central America and Australia, producing seeds whose consumption has been increasing in the last decade. Several articles analysed the seeds metabolite content. However, few is known about Chia leaves. This work is the first report on the whole metabolite profile of chia leaves, determined by spectroscopic methods including NMR, GC-MS and LC-MS coupled with chemometrics analysis. Additionally, molecular networking has been applied to the LC-MS data to determine the flavonoid composition. Different chia sources were compared: one commercial (black) and three early flowering (G3, G8 and G17) mutant genotypes cultivated at two irrigation regimes (50 and 100%). Organic extracts were mainly composed by saturated and mono- and polyunsaturated fatty acids with palmitic being the most abundant followed by oleic and linolenic acids. Aqueous extracts contained glucose, galactose, and fructose as main sugars. Flavonoids were based on vitexin and orientin and their analogues. Chemical composition of early flowering genotypes was quite similar to commercial black chia with the exception of G8 showing significant differences in the polar phase. A generally highest content of omega-9 fatty acids has been found in the early flowering genotypes along with high content of nutraceuticals suggesting them as a potential source of raw materials for the food/feed industry.

Edible Flowers Used in Some Countries of the Mediterranean Basin: An Ethnobotanical Overview

Edible flowers are becoming an essential component of people's nutrition in the Mediterranean basin. In the last decades, many researchers also have focused their attention on the nutritional composition of the edible flowers, as well as their antioxidant and antimicrobial properties, including studies on their safety issues. Despite the growing interest in the use of flowers in human nutrition, the ethnobotanical literature is lacking coverage of some important issues, particularly those which concern the use of flowers in the folk tradition. Only recently, a review regarding the contribution of 32 edible flowers to the Mediterranean diet was published. The aim of the present review is to document the plant lore regarding the wild and cultivated edible flowers consumed in the Mediterranean basin. Based on the 112 studies reviewed, we documented 251 taxa as being used in the Mediterranean basin as edible flowers. The plant species belong to 45 families and 141 genera. Asteraceae (54 taxa) is the most frequently cited family. Sambucus nigra L. is the most cited species. This study can be the basis for future research on the supposed bioactivity and toxicity of wild and cultivated flowers.

Metabolic flux analysis: a comprehensive review on sample preparation, analytical techniques, data analysis, computational modelling, and main application areas

Metabolic flux analysis (MFA) quantitatively describes cellular fluxes to understand metabolic phenotypes and functional behaviour after environmental and/or genetic perturbations. In the last decade, the application of stable isotopes became extremely important to determine and integrate in vivo measurements of metabolic reactions in systems biology. 13C-MFA is one of the most informative methods used to study central metabolism of biological systems. This review aims to outline the current experimental procedure adopted in 13C-MFA, starting from the preparation of cell cultures and labelled tracers to the quenching and extraction of metabolites and their subsequent analysis performed with very powerful software. Here, the limitations and advantages of nuclear magnetic resonance spectroscopy and mass spectrometry techniques used in carbon labelled experiments are elucidated by reviewing the most recent published papers. Furthermore, we summarise the most successful approaches used for computational modelling in flux analysis and the main application areas with a particular focus in metabolic engineering.

Metabolomics and chemometrics of seven aromatic plants: Carob, eucalyptus, laurel, mint, myrtle, rosemary and strawberry tree

INTRODUCTION

Arbutus unedo L. (strawberry tree), Ceratonia siliqua L. (carob), Eucalyptus camaldulensis Dehnh. (eucalyptus), Laurus nobilis L. (laurel), Mentha aquatica L. (water mint), Myrtus communis L. (common myrtle), and Rosmarinus officinalis L. (rosemary) are aromatic plants from the Mediterranean region whose parts and preparations are used for their nutritional properties and health benefits.

OBJECTIVES

To evaluate and compare the metabolites profile, total phenol content (TPC), and antioxidant activity of plant leaves for their future use. Gas chromatography-mass spectrometry (GC-MS) was used for metabolomics. Data comparison was performed by chemometrics.

METHODOLOGY

Polar and apolar extracts were analysed using untargeted GC-MS metabolomics followed by chemometrics (principal component analysis, heatmap correlation and dendrogram) to identify, quantify and compare the major organic compounds in the plants. Additionally, nuclear magnetic resonance (NMR) spectroscopy was used for the laurel polar extract to identify d-gluco-l-glycero-3-octulose whose presence was unclear from the GC-MS data. TPC and antioxidant assays were performed using classical methods (Folin-Ciocalteu, 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH)) and correlated to the phytochemical profiles.

RESULTS

Forty-three metabolites were identified including amino acids, organic acids, carbohydrates, phenols, polyols, fatty acids, and alkanes. Eight metabolites (d-fructose, d-glucose, d-mannose, gallic acid, quinic acid, myo-inositol, palmitic and stearic acids) were in common between all species. d-Gluco-l-glycero-3-octulose (37.29 ± 1.19%), d-pinitol (31.33 ± 5.12%), and arbutin (1.30 ± 0.44%,) were characteristic compounds of laurel, carob, and strawberry tree, respectively. Carob showed the highest values of TPC and antioxidant activity.

CONCLUSION

GC-MS metabolomics and chemometrics analyses are fast and useful methods to determine and compare the metabolomics profiling of aromatic plants of food and industrial interest.

Metabolomic analysis and antioxidant activity of wild type and mutant chia (Salvia hispanica L.) stem and flower grown under different irrigation regimes

BACKGROUND

Chia (Salvia hispanica L.) is a functional food from Central America. Interest in it is growing rapidly due to the many health benefits from the seed. However, when chia is grown at high latitudes, seed yield may be low whereas a high stem biomass and immature inflorescences are produced. Little is known about the chemical composition and the properties of stems and flowers. In this work, the metabolite profile, the antioxidant activity, and the total polyphenol content of stems and inflorescences were evaluated in a factorial experiment with different chia populations (commercial black chia and long-day flowering mutants G3, G8, and G17) and irrigation (100% and 50% of evapotranspiration).

RESULTS

The results show the influence of irrigation and seed source on the antioxidant activity and total polyphenol content of chia flower and stem. Inflorescences exhibit higher antioxidant activity, suggesting their potential use as natural antioxidant. The mutants G3 and G8, at 50% irrigation, contained the highest amounts of compounds with nutraceutical value, especially within the flower. The mutant G17 showed lower antioxidant activity and polyphenol content compared to other seed sources but exhibited high omega 3 content in flowers but low in stems. This indicates that chia varieties should be chosen according to the objective of cultivation.

CONCLUSION

These findings, indicating a close relation of metabolite content with irrigation and seed source, may provide the basis for the use of chia flower and stem for their nutraceutical value in the food, feed, and supplement industries. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Diterpenes from Euphorbia myrsinites and Their Anti-inflammatory Property

Euphorbia myrsinites is one of the oldest spurges described and used in folk medicine. It is characterized by blue-grey stems similar to myrtle, and it is spread in the Mediterranean region, Asia, and the USA. Chemical analysis of E. myrsinites collected in Turkey afforded the isolation of 4 diterpenes based on the so-called myrsinane skeleton being tetraesters of the tetracyclic diterpene alcohol myrsinol. In this study, the phytochemical analysis of this species collected in Italy has been undertaken to afford the isolation of a new atisane diterpene, named myrsatisane, 3 ingenol derivatives, along with the 4 tetraester derivatives previously found. A triterpene compound based on the euphane skeleton has also been isolated. Structural elucidation of the new myrsatisane was based on spectroscopic techniques, including HR-MS and 1- and 2-dimensional NMR experiments. Its relative configuration was determined by NOE correlations, while absolute stereochemistry was obtained by quantum-mechanical DFT studies. While diterpenes with the atisane skeleton are relatively common in Euphorbia species, this is the first report of an atisane diterpene from E. myrsinites. All the isolated terpenes were tested for anti-inflammatory activity on J774A.1 macrophages stimulated with lipopolysaccharide by evaluation of nitrite and pro-inflammatory cytokine Il-1β levels. Among tested compounds, the 3 ingenol diterpenes exhibited a dose-dependent (0.001 - 3 µM) significant activity, thus showing their potential as anti-inflammatory drug candidates.

Reducing toxic reactive carbonyl species in e-cigarette emissions: testing a harm-reduction strategy based on dicarbonyl trapping

Reducing the concentration of reactive carbonyl species (RCS) in e-cigarette emissions represents a major goal to control their potentially harmful effects. Here, we adopted a novel strategy of trapping carbonyls present in e-cigarette emissions by adding polyphenols in e-liquid formulations. Our work showed that the addition of gallic acid, hydroxytyrosol and epigallocatechin gallate reduced the levels of carbonyls formed in the aerosols of vaped e-cigarettes, including formaldehyde, methylglyoxal and glyoxal. Liquid chromatography mass spectrometry analysis highlighted the formation of covalent adducts between aromatic rings and dicarbonyls in both e-liquids and vaped samples, suggesting that dicarbonyls were formed in the e-liquids as degradation products of propylene glycol and glycerol before vaping. Short-term cytotoxic analysis on two lung cellular models showed that dicarbonyl-polyphenol adducts are not cytotoxic, even though carbonyl trapping did not improve cell viability. Our work sheds lights on the ability of polyphenols to trap RCS in high carbonyl e-cigarette emissions, suggesting their potential value in commercial e-liquid formulations.

A Strategy for Efficiently Collecting Aerosol Condensate Using Silica Fibers: Application to Carbonyl Emissions from E-Cigarettes

Analyzing harmful constituents in e-cigarette aerosols typically involves adopting a methodology used for analyzing tobacco smoke. Cambridge filter pads (CFP) are the basis of numerous protocols for analyzing the various classes of compounds representing 93 harmful and potentially harmful constituents identified in tobacco smoke by the FDA. This paper describes a simplified method for trapping the low volatility components of e-cigarette aerosols using a single trapping procedure followed by physical extraction. The trap is a plug of amorphous silica fibers (0.75 g of 4 μm diameter) within a 10 mL syringe inserted between the e-cigarette mouthpiece and the pump of the vaping machine. The method is evaluated for emissions from three generations of e-cigarette device (Kangertech CE4, EVOD, and Subox Mini-C). On average, the silica wool traps about 94% of the vaporized liquid mass in the three devices and higher levels of condensate is retained before reaching saturation compared with CFP. The condensate is then physically extracted from the silica wool plug using a centrifuge. Condensate is then available for use directly in multiple analytical procedures or toxicological experiments. The method is tested by comparison with published analyses of carbonyls, among the most potent toxicants and carcinogens in e-cigarette emissions. Ranges for HPLC-DAD analyses of carbonyl-DNPH derivatives in a laboratory formulation of e-liquid are formaldehyde (0.182 ± 0.023 to 9.896 ± 0.709 μg puff-1), acetaldehyde (0.059 ± 0.005 to 0.791 ± 0.073 μg puff-1), and propionaldehyde (0.008 ± 0.0001 to 0.033 ± 0.023 μg puff-1); other carbonyls are identified and quantified. Carbonyl concentrations are also consistent with published experiments showing marked increases with variable power settings (10W to 50W). Compared with CFPs, e-cigarette aerosol collection by silica wool requires only one vaping session for multiple analyte groups, traps more condensate per puff, and collects more condensate before saturation.

Metabolomics approach based on NMR spectroscopy and multivariate data analysis to explore the interaction between the leafminer Tuta absoluta and tomato (Solanum lycopersicum)

INTRODUCTION

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most devastating and harmful pests of tomato (Solanum lycopersicum) crops causing up to 80-100% yield losses. A large arsenal of plant metabolites is induced by the leafminer feeding including defence compounds that could differ among varieties.

OBJECTIVE

To compare the metabolomic changes of different genotypes of tomato (tolerant "T", susceptible "S" and "F1" hybrid obtained between T and S) after exposition to T. absoluta.

METHODOLOGY

Nuclear magnetic resonance (NMR) spectroscopy followed by multivariate data analysis were performed to analyse the metabolic profiles of control and infested samples on three different tomato genotypes.

RESULTS

Signals related to GABA (γ-aminobutyric acid) were relatively much higher in all infested samples compared to the non-infested plants used as control. Infested T genotype samples were the most abundant in organic acids, including fatty acids and acyl sugars, chlorogenic acid, neo-chlorogenic acid and feruloyl quinic acid, indicating a clear link between the exposure to leafminer. Results also showed an increase of trigonelline in all tomato varieties after exposition to T. absoluta.

CONCLUSION

Metabolomics approach based on NMR spectroscopy followed by multivariate data analysis allowed for a detailed metabolite profile of plant defences, providing fundamental information for breeding programmes in plant crops.

Explorative investigation of the anti-glycative effect of a rapeseed by-product extract

The formation of advanced glycation end-products (AGEs) in biological systems is increased during hyperglycaemia due to higher levels of circulating glucose and carbonyl reactive species. AGEs are causative factors of common chronic diseases. Since synthetic AGE-inhibitors exert unwanted side effects and polyphenols act as potent antiglycative agents, vegetables (fruits, seeds and related by-products) are good candidates when searching for natural inhibitors. The aim of this research is to explore the suitability of a polyphenol-rich rapeseed cake extract (RCext) to decrease the formation of AGEs in an in vitro model. Different phenols, amino acids, carbohydrates, organic acids and fatty acids were identified in the RCext by GC-MS. The results confirm a high concentration of polyphenols (73.85 ± 0.64 and 86.85 ± 2.08 mg of gallic acid equivalents per g of RCext spray dried and freeze dried, respectively) which is correlated with the antioxidant capacity and anti-glycative activity in a dose dependent manner. Rapeseed cake extract (3.7 mg mL-1) significantly reduced the formation of free fluorescent AGEs and pentosidine up to 34.85%. The anti-glycative activity of the extract is likely to be due to the high concentration of sinapinic acid (0.108 ± 0.0043 mg g-1) in its metabolic profile, and the mechanism of action is mediated by methylglyoxal trapping. The results show promising potential for using rapeseed cake extract as a food supplement to ameliorate the formation of AGEs. Rapeseed cake extract should therefore be considered a potential candidate for the prevention of glycation-associated complications of age-related pathologies.

Dithiosulfinates and Sulfoxides with Antifungal Activity from Bulbs of Allium sativum L. var. Voghiera

A bioassay guided phytochemical analysis of the bulbs of Allium sativum L. var. Voghiera, typical of Voghiera, Ferrara (Italy), allowed the isolation of six new sulfur compounds with dithiosulfinates and sulfoxides functionalities. Structure elucidation of the isolated compounds was carried out by spectroscopic analyses, including NMR spectroscopy and MS spectrometry. Compounds showed significant antimicrobial activity towards two fungal species, the air-borne pathogen Botrytis cinerea and the beneficial fungus Trichoderma harzianum.

Metabolomic Fingerprinting of Romaneschi Globe Artichokes by NMR Spectroscopy and Multivariate Data Analysis

INTRODUCTION

Globe artichoke (Cynara cardunculus L. var. scolymus L. Fiori) and cardoon (Cynara cardunculus L. var. altilis DC) are sources of nutraceuticals and bioactive compounds.

OBJECTIVES

To apply a NMR metabolomic fingerprinting approach to Cynara cardunculus heads to obtain simultaneous identification and quantitation of the major classes of organic compounds.

METHODOLOGY

The edible part of 14 Globe artichoke populations, belonging to the Romaneschi varietal group, were extracted to obtain apolar and polar organic extracts. The analysis was also extended to one species of cultivated cardoon for comparison. The (1) H-NMR of the extracts allowed simultaneous identification of the bioactive metabolites whose quantitation have been obtained by spectral integration followed by principal component analysis (PCA).

RESULTS

Apolar organic extracts were mainly based on highly unsaturated long chain lipids. Polar organic extracts contained organic acids, amino acids, sugars (mainly inulin), caffeoyl derivatives (mainly cynarin), flavonoids, and terpenes. The level of nutraceuticals was found to be highest in the Italian landraces Bianco di Pertosa zia E and Natalina while cardoon showed the lowest content of all metabolites thus confirming the genetic distance between artichokes and cardoon.

CONCLUSION

Metabolomic approach coupling NMR spectroscopy with multivariate data analysis allowed for a detailed metabolite profile of artichoke and cardoon varieties to be obtained. Relevant differences in the relative content of the metabolites were observed for the species analysed. This work is the first application of (1) H-NMR with multivariate statistics to provide a metabolomic fingerprinting of Cynara scolymus. Copyright © 2016 John Wiley & Sons, Ltd.