Reversed-phase ultra-high-performance liquid chromatography coupled to electrospray ionization-quadrupole-time-of-flight mass spectrometry as a powerful tool for metabolic profiling of vegetables: Lactuca sativa as an example of its application

Polyphenolic profile of butterhead lettuce cultivar by ultrahigh performance liquid chromatography coupled online to UV-visible spectrophotometry and quadrupole time-of-flight mass spectrometry

In the present study, the butterhead lettuce cultivar was analyzed by ultrahigh performance liquid chromatography (UHPLC) coupled online to diode array detection (DAD), electrospray ionization (ESI) and quadrupole time-of-flight mass spectrometry (QToF/MS) in the positive and negative ion mode in order to characterize its polyphenolic profile for the first time. The instrument acquisition mode MSE was used to collect automatic and simultaneous information of exact mass at high and low collision energies of precursor ions as well as other ions produced as a result of their fragmentation. One hundred eleven phenolic compounds were identified in the acidified hydromethanolic extract of freeze-dried leaves of butterhead lettuce cultivar: 40 hydroxycinnamic acid derivatives, 21 hydroxybenzoic acid derivatives, 2 hydroxyphenylacetic acid derivatives, 18 flavonols, 9 flavones, one flavanone, 7 coumarins, one hydrolysable tannin and 12 lignans. Forty-seven of these compounds have been tentatively identified for the first time in lettuce.

Unravelling the phytonutrients and antioxidant properties of European Vicia faba L. seeds

For the first time, seven European varieties of Vicia faba L. seeds were investigated for (1) their phytonutrients profile by HPLC-DAD-MS/MS, (2) total phenolic content (TPC), and (3) antioxidant capacity (DPPH and FRAP assays). A wide range of compounds were identified, namely alkaloids, organic acids, terpenoids, jasmonates, and phenolics; these two latter being the most abundant. TPC ranged between 2.62 and 4.3 mg (gallic acid equivalent) g^-1 dry weight, for V. faba major variety Belshi and V. faba minor variety Bauska, respectively. The DPPH radical scavenging capacity showed poor correlation (r = 0.550, P = .041) with TPC, suggesting the presence of other antioxidant sources than phenolics. Still, FRAP was positively correlated with TPC (r = 0.709, P < .01) and DPPH (r = 0.819, P < .01). These results elucidated the phytonutrients and antioxidant properties of V. faba L. seeds as functional food sources.

Identification and quantification of phenolic compounds in edible wild leafy vegetables by UHPLC/Orbitrap-MS

BACKGROUND

A recent interest in edible wild leafy vegetables has been documented. Consumers often associate these species with health promotion. In this study, several wild species of the Asteraceae family and Knautia integrifolia (Dipsacaceae) were locally documented for their use in traditional cuisine and sampled from the wild.

RESULTS

Phenolic compounds were identified and quantified by ultra-high-performance liquid chromatography coupled to Orbitrap high-resolution mass spectrometry. Hydroxycinnamic acids ranging from 1388 to 53 076 mg kg^-1 dry weight (DW) were the most abundant compounds in all species (69-98% of the total phenolic content) except Tragopogon pratensis. Thirty compounds were identified as flavonoids, mostly as glycosidic forms of luteolin, apigenin, kaempferol and quercetin. The sum of flavonoids ranged between 212 and 12 598 mg kg^-1 DW; they represented 65% of the total phenolic content for T. pratensis. Three anthocyanins were detected, representing in most cases less than 1% of the total phenolic content (3-627 mg kg^-1 DW). Higher anthocyanin contents were observed for Cichorium types.

CONCLUSION

Different phenolic profiles were observed between species, especially considering the class of flavonoids. Individual species may be of some interest for their content of specific minor flavonoids. © 2017 Society of Chemical Industry.

Metabolomic Evaluation of the Quality of Leaf Lettuce Grown in Practical Plant Factory to Capture Metabolite Signature

Vegetables produce metabolites that affect their taste and nutritional value and compounds that contribute to human health. The quality of vegetables grown in plant factories under hydroponic cultivation, e.g., their sweetness and softness, can be improved by controlling growth factors including the temperature, humidity, light source, and fertilizer. However, soil is cheaper than hydroponic cultivation and the visual phenotype of vegetables grown under the two conditions is different. As it is not clear whether their metabolite composition is also different, we studied leaf lettuce raised under the hydroponic condition in practical plant factory and strictly controlled soil condition. We chose two representative cultivars, "black rose" (BR) and "red fire" (RF) because they are of high economic value. Metabolite profiling by comprehensive gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS) resulted in the annotation of 101 metabolites from 223 peaks detected by GC-MS; LC-MS yielded 95 peaks. The principal component analysis (PCA) scatter plot showed that the most distinct separation patterns on the first principal component (PC1) coincided with differences in the cultivation methods. There were no clear separations related to cultivar differences in the plot. PC1 loading revealed the discriminant metabolites for each cultivation method. The level of amino acids such as lysine, phenylalanine, tryptophan, and valine was significantly increased in hydroponically grown leaf lettuce, while soil-cultivation derived leaf lettuce samples contained significantly higher levels of fatty-acid derived alcohols (tetracosanol and hexacosanol) and lettuce-specific sesquiterpene lactones (lactucopicrin-15-oxalate and 15-deoxylactucin-8-sulfate). These findings suggest that the metabolite composition of leaf lettuce is primarily affected by its cultivation condition. As the discriminant metabolites reveal important factors that contribute to the nutritional value and taste characteristics of leaf lettuce, we performed comprehensive metabolite profiling to identify metabolite compositions, i.e., metabolite signature, that directly improve its quality and value.

A novel integrated non-targeted metabolomic analysis reveals significant metabolite variations between different lettuce (Lactuca sativa. L) varieties

Lettuce is an important leafy vegetable that represents a significant dietary source of antioxidants and bioactive compounds. However, the levels of metabolites in different lettuce cultivars are poorly characterized. In this study, we used combined GC × GC-TOF/MS and UPLC-IMS-QTOF/MS to detect and relatively quantify metabolites in 30 lettuce cultivars representing large genetic diversity. Comparison with online databases, the published literature, standards as well using collision cross-section values enabled putative identification of 171 metabolites. Sixteen of these 171 metabolites (including phenolic acid derivatives, glycosylated flavonoids, and one iridoid) were present at significantly different levels in leaf and head type lettuces, which suggested the significant metabolomic variations between the leaf and head types of lettuce are related to secondary metabolism. A combination of the results and metabolic network analysis techniques suggested that leaf and head type lettuces contain not only different levels of metabolites but also have significant variations in the corresponding associated metabolic networks. The novel lettuce metabolite library and novel non-targeted metabolomics strategy devised in this study could be used to further characterize metabolic variations between lettuce cultivars or other plants. Moreover, the findings of this study provide important insight into metabolic adaptations due to natural and human selection, which could stimulate further research to potentially improve lettuce quality, yield, and nutritional value.

Effect of glycine nitrogen on lettuce growth under soilless culture: a metabolomics approach to identify the main changes occurred in plant primary and secondary metabolism

BACKGROUND

Lettuce is a significant source of antioxidants and bioactive compounds. Nitrate is a cardinal fertilizer in horticulture and influences vegetable yield and quality; however, the negative effects of nitrate on the biosynthesis of flavonoids require further study. It is expected that using fertilizers containing organic nitrogen (N) could promote the synthesis of health-promoting compounds.

RESULTS

Lettuces were hydroponically cultured in media containing 9 mmol L-1 nitrate or 9 mmol L-1 glycine for 4 weeks. Primary and secondary metabolites were analyzed using gas chromatography/mass spectrometry (GC/MS) and ultra-performance liquid chromatography/ion mobility spectrometry/quadrupole time-of-flight mass spectrometry (UPLC/IMS/QTOF-MS). Data analysis revealed that 29 metabolites were significantly altered between nitrate and glycine treatments. Metabolites were tentatively identified by comparison with online databases, literature and standards and using collision cross-section values. Significant differences in flavonoid biosynthesis, phenolic biosynthesis and the tricarboxylic acid (TCA) cycle response were observed between N sources. Compared with nitrate, glycine promoted accumulation of glycosylated flavonoids (quercetin 3-glucoside, quercetin 3-(6″-malonyl-glucoside), luteolin 7-glucuronide, luteolin 7-glucoside), ascorbic acid and amino acids (l-valine, l-leucine, l-glutamine, asparagine, l-serine, l-ornithine, 4-aminobutanoic acid, l-phenylalanine) but reduced phenolic acids (dihydroxybenzoic acid hexose isomers 1 and 2, chicoric acid, chicoric acid isomer 1) and TCA intermediates (fumaric, malic, citric and succinic acids).

CONCLUSION

The novel methodology applied in this study can be used to characterize metabolites in lettuce. Accumulation of glycosylated flavonoids, amino acids and ascorbic acid in response to glycine supply provides strong evidence supporting the idea that using amino acids as an N source alters the nutritional value of vegetable crops. © 2017 Society of Chemical Industry.

Phytochemical profiling of anti-inflammatory Lavandula extracts via RP-HPLC-DAD-QTOF-MS and -MS/MS: Assessment of their qualitative and quantitative differences

As for other aromatic plants, there are many analytical methods for the determination of volatile compounds in lavender essential oils. Alternatively, in this study RP-HPLC-DAD-QTOF-MS was used for the profiling of the phytochemical constituents of hydromethanolic extracts of L. stoechas and L. dentata, which were obtained by pressurized liquid extraction. The spectrometric data revealed complex profiles constituted of a wide range of polar and semi-polar phytochemicals, mainly, phenolic compounds (68). Most phenolic compounds (55) have not been previously reported in Lavandula; such is the case of caffeic acid-based oligomers. Moreover, the analytical method was validated for the determination of phenolic compounds. Our findings showed both qualitative and quantitative differences between the extracts. In this sense, while hydroxycinnamic acids made up the largest class in both extracts, flavones were the most abundant class, accounting for 10.44 g (L. dentata) and 4.85 g (L. stoechas) per 100 g of dry extract. In conclusion, this analytical method provided essential information about the phytochemical composition of the studied medicinal plants, revealing novel constituents that were probably hidden for others. In addition, these results may help to understand the anti-inflammatory properties of these extracts.

Exogenous Glycine Nitrogen Enhances Accumulation of Glycosylated Flavonoids and Antioxidant Activity in Lettuce (Lactuca sativa L.)

Glycine, the simplest amino acid in nature and one of the most abundant free amino acids in soil, is regarded as a model nutrient in organic nitrogen studies. To date, many studies have focused on the uptake, metabolism and distribution of organic nitrogen in plants, but few have investigated the nutritional performance of plants supplied with organic nitrogen. Lettuce (Lactuca sativa L.), one of the most widely consumed leafy vegetables worldwide, is a significant source of antioxidants and bioactive compounds such as polyphenols, ascorbic acid and tocopherols. In this study, two lettuce cultivars, Shenxuan 1 and Lollo Rossa, were hydroponically cultured in media containing 4.5, 9, or 18 mM glycine or 9 mM nitrate (control) for 4 weeks, and the levels of health-promoting compounds and antioxidant activity of the lettuce leaf extracts were evaluated. Glycine significantly reduced fresh weight compared to control lettuce, while 9 mM glycine significantly increased fresh weight compared to 4.5 or 18 mM glycine. Compared to controls, glycine (18 mM for Shenxuan 1; 9 mM for Lollo Rossa) significantly increased the levels of most antioxidants (including total polyphenols, α-tocopherol) and antioxidant activity, suggesting appropriate glycine supply promotes antioxidant accumulation and activity. Glycine induced most glycosylated quercetin derivatives and luteolin derivatives detected and decreased some phenolic acids compared to nitrate treatment. This study indicates exogenous glycine supplementation could be used strategically to promote the accumulation of health-promoting compounds and antioxidant activity of hydroponically grown lettuce, which could potentially improve human nutrition.

Comprehensive characterization of phenolic and other polar compounds in the seed and seed coat of avocado by HPLC-DAD-ESI-QTOF-MS

Avocado seed and seed coat are important by-products from avocado industrialization, with important functional properties. The aim of the present study was to determine the phenolic profile and other polar compounds of avocado seed and seed coat using accelerated solvent extraction (ASE) and liquid chromatography coupled to Ultra-High-Definition Accurate-Mass Q-TOF. In this research 84 compounds were identified, within eight subclass group, among these 45 phenolic compounds were identified for first time in avocado seed. Condensed tannins, phenolic acids and flavonoids were the most representative groups in both samples. As far as we are concerned, this is the first time that avocado seed coat has been studied regarding its phenolic compounds using such a powerful instrumental technique. In addition, the radical-scavenging activities were analysed in order to estimate the antioxidant potential of extracts. These results point out that avocado seed and seed coat constitute a source of bioactive ingredients for its use in the food, cosmetic or pharmaceutical sector.

Characterization of phenolic compounds in green and red oak-leaf lettuce cultivars by UHPLC-DAD-ESI-QToF/MS using MSE scan mode

Lettuce (Lactuca sativa) is one of the most popular leafy vegetables in the world and constitutes a major dietary source of phenolic compounds with health-promoting properties. In particular, the demand for green and red oak-leaf lettuces has considerably increased in the last years but few data on their polyphenol composition are available. Moreover, the usage of analytical edge technology can provide new structural information and allow the identification of unknown polyphenols. In the present study, the phenolic profiles of green and red oak-leaf lettuce cultivars were exhaustively characterized by ultrahigh-performance liquid chromatography (UHPLC) coupled online to diode array detection (DAD), electrospray ionization (ESI), and quadrupole time-of-flight mass spectrometry (QToF/MS), using the MSE instrument acquisition mode for recording simultaneously exact masses of precursor and fragment ions. One hundred fifteen phenolic compounds were identified in the acidified hydromethanolic extract of freeze-dried lettuce leaves. Forty-eight of these compounds were tentatively identified for the first time in lettuce, and only 20 of them have been previously reported in oak-leaf lettuce cultivars in literature. Both oak-leaf lettuce cultivars presented similar phenolic composition, except for apigenin-glucuronide and dihydroxybenzoic acid, only detected in the green cultivar; and for luteolin-hydroxymalonylhexoside, an apigenin conjugate with molecular formula C40 H54 O19 (monoisotopic MW = 838.3259 u), cyanidin-3-O-glucoside, cyanidin-3-O-(3″-O-malonyl)glucoside, cyanidin-3-O-(6″-O-malonyl)glucoside, and cyanidin-3-O-(6″-O-acetyl)glucoside, only found in the red cultivar. The UHPLC-DAD-ESI-QToF/MSE approach demonstrated to be a useful tool for the characterization of phenolic compounds in complex plant matrices.

Alkaloids Profiling of Fumaria capreolata by Analytical Platforms Based on the Hyphenation of Gas Chromatography and Liquid Chromatography with Quadrupole-Time-of-Flight Mass Spectrometry

Two analytical platforms, gas chromatography (GC) coupled to quadrupole-time-of-flight (QTOF) mass spectrometry (MS) and reversed-phase ultrahigh performance liquid chromatography (UHPLC) coupled to diode array (DAD) and QTOF detection, were applied in order to study the alkaloid profile of Fumaria capreolata. The use of these mass analyzers enabled tentatively identifying the alkaloids by matching their accurate mass signals and suggested molecular formulae with those previously reported in libraries and databases. Moreover, the proposed structures were corroborated by studying their fragmentation pattern obtained by both platforms. In this way, 8 and 26 isoquinoline alkaloids were characterized using GC-QTOF-MS and RP-UHPLC-DAD-QTOF-MS, respectively, and they belonged to the following subclasses: protoberberine, protopine, aporphine, benzophenanthridine, spirobenzylisoquinoline, morphinandienone, and benzylisoquinoline. Moreover, the latter analytical method was selected to determine at 280 nm the concentration of protopine (9.6 ± 0.7 mg/g), a potential active compound of the extract. In conclusion, although GC-MS has been commonly used for the analysis of this type of phytochemicals, RP-UHPLC-DAD-QTOF-MS provided essential complementary information. This analytical method can be applied for the quality control of phytopharmaceuticals containing Fumaria extracts currently found in the market.

Liquid chromatography-high resolution mass spectrometry for the analysis of phytochemicals in vegetal-derived food and beverages

The recent years witnessed a change in the perception of nutrition. Diet does not only provide nutrients to meet the metabolic requirements of the body, but it also constitutes an active way for the consumption of compounds beneficial for human health. Fruit and vegetables are an excellent source of such compounds, thus the growing interest in characterizing phytochemical sources, structures and activities. Given the interest for phytochemicals in food, the development of advanced and suitable analytical techniques for their identification is fundamental for the advancement of food research. In this review, the state of the art of phytochemical research in food plants is described, starting from sample preparation, throughout extract clean-up and compound separation techniques, to the final analysis, considering both qualitative and quantitative investigations. In this regard, from an analytical point of view, fruit and vegetable extracts are complex matrices, which greatly benefit from the use of modern hyphenated techniques, in particular from the combination of high performance liquid chromatography separation and high resolution mass spectrometry, powerful tools which are being increasingly used in the recent years. Therefore, selected applications to real samples are presented and discussed, in particular for the analysis of phenols, polyphenols and phenolic acids. Finally, some hot points are discussed, such as waste characterization for high value-compounds recovery and the untargeted metabolomics approach.

Effect of Different Elicitors and Preharvest Day Application on the Content of Phytochemicals and Antioxidant Activity of Butterhead Lettuce (Lactuca sativa var. capitata) Produced under Hydroponic Conditions

The effect of four elicitors on phytochemical content in two varieties of lettuce was evaluated. The best preharvest day for application of each elicitor was chosen. Solutions of arachidonic acid (AA), salicylic acid (SA), methyl jasmonate (MJ), and Harpin protein (HP) were applied by foliar aspersion on lettuce leaves while cultivating under hydroponic conditions. Application of elicitors was done at 15, 7, 5, 3, or 1 day before harvest. Green lettuce showed the highest increase in phytochemical content when elicitors (AA, SA, and HP) were applied on day 7 before harvest. Similarly, antioxidant activity rose in all treatments on day 7. In red lettuce, the highest content of bioactive molecules occurred in samples treated on day 15. AA, SA, and HP were the elicitors with the highest effect on phytochemical content for both varieties, mainly on polyphenol content. Antioxidant activity also increased in response to elicitation. HPLC-MS showed an increase in the content of phenolic acids in green and red lettuce, especially after elicitation with SA, suggesting activation of the caffeic acid pathway due to elicitation.

LC-MS Untargeted Metabolomics To Explain the Signal Metabolites Inducing Browning in Fresh-Cut Lettuce

Enzymatic browning is one of the main causes of quality loss in lettuce as a prepared and ready-to-eat cut salad. An untargeted metabolomics approach using UPLC-ESI-QTOF-MS was performed to explain the wound response of lettuce after cutting and to identify the metabolites responsible of browning. Two cultivars of Romaine lettuce with different browning susceptibilities were studied at short time intervals after cutting. From the total 5975 entities obtained from the raw data after alignment, filtration reduced the number of features to 2959, and the statistical analysis found that only 1132 entities were significantly different. Principal component analysis (PCA) clearly showed that these samples grouped according to cultivar and time after cutting. From those, only 15 metabolites belonging to lysophospholipids, oxylipin/jasmonate metabolites, and phenolic compounds were able to explain the browning process. These selected metabolites showed different trends after cutting; some decreased rapidly, others increased but decreased thereafter, whereas others increased during the whole period of storage. In general, the fast-browning cultivar showed a faster wound response and a higher raw intensity of some key metabolites than the slow-browning one. Just after cutting, the fast-browning cultivar contained 11 of the 15 browning-associated metabolites, whereas the slow-browning cultivar only had 5 of them. These metabolites could be used as biomarkers in breeding programs for the selection of lettuce cultivars with lower browning potential for fresh-cut applications.

Constituent analysis of the ethanol extracts of Chimonanthus nitens Oliv. leaves and their inhibitory effect on α-glucosidase activity

The ethanol extracts of Chimonanthus nitens Oliv. leaves were prepared sequentially by ethanol gradient elution and tested for their α-glucosidase inhibitory. The fraction of 50% ethanol eluate (EE) exhibited the notable inhibition with IC50 of 0.376mg/mL. Also, 50% EE was chemically characterized by liquid chromatography-mass spectrometry (LC-MS) analysis. Eight compounds including rutin (1), hyperin (2), isoquercitrin (3), luteoloside (4), astragalin (6), quercetin (13), naringenin (14), kaempferol (15) were identified by compared with standard substances as well as proper luteolin-5-O-glucoside (5), kaempferol-7-O-rhamnoside (9), 5,7,8-trihydroxy-2-methoxyl-flavone-7-O-glucoside (10), kaempferol-7-O-acetyl-galactoside (11). The experiments of ultra-filtration combined with liquid chromatography-mass spectrometry (UF-LC-MS) guided quercetin and kaempferol as the key factors for 50% EE showing highly inhibitory activity on α-glucosidase. Quercetin and kaempferol inhibited yeast α-glucosidase in a mixed-type manner with IC50 of 66.8 and 109μg/mL, respectively. These results would provide theoretical underpinning for the C. nitens Oliv. leaves ethanol extracts used as nutraceutical health supplement in the management of type 2 diabetes.

RP-HPLC-DAD-ESI-QTOF-MS based metabolic profiling of the potential Olea europaea by-product "wood" and its comparison with leaf counterpart

INTRODUCTION

Olea europaea L. organs such as leaves, stems and roots have been associated with numerous in vivo and in vitro biological activities and used for traditional medicinal purposes. However, tree wood is an untapped resource with little information about their chemical composition.

OBJECTIVE

That is why, the objective of this study is to increase the knowledge about phytochemicals from 'Chemlali' olive wood by means of mass spectrometry-based analyses. Its comparison with by-products derived from leaves was also studied.

METHODOLOGY

Hydromethanol extracts from wood and leaves with stems of 'Chemlali' olive cultivar were analysed using reversed-phase (RP) high-performance liquid chromatography (HPLC) coupled to two detection systems: diode-array detection (DAD) and quadrupole time-of-flight (QTOF) mass spectrometry (MS) in negative ion mode. Tandem MS experiments were performed to establish the chemical structure of olive phytochemicals.

RESULTS

A total of 85 compounds were characterised in the studied olive parts and classified as: sugars (3), organic acids (5), one phenolic aldehyde, simple phenolic acids (6), simple phenylethanoids (5), flavonoids (14), coumarins (3), caffeoyl phenylethanoid derivatives (6), iridoids (5), secoiridoids (32), and lignans (5). To our knowledge, the major part of these metabolites was not previously reported in olive tree wood, and 10 olive chemical constituents were identified for the first time in the Oleaceae family.

CONCLUSION

The results presented here demonstrated the usefulness of the methodology proposed, based on RP-HPLC-DAD-ESI-QTOF-MS and MS/MS, to develop an exhaustive metabolic profiling and to recover new biologically active compounds in olive wood with pharmacologic and cosmetic potential. Copyright © 2017 John Wiley & Sons, Ltd.

Antihyperlipidemic and Antioxidant Activities of Edible Tunisian Ficus carica L. Fruits in High Fat Diet-Induced Hyperlipidemic Rats

The phenolic constituents of the aqueous-ethanolic extract of Tunisian Ficus carica (F. carica) fruit (FE) and its antihyperlipidemic and antioxidant activities in high-fat diet-induced hyperlipidemic rats (HFD) were evaluated. The obtained results demonstrated that the FE improved the lipid profile by decreasing the total cholesterol, triglyceride, low-density lipoprotein cholesterol and increasing high-density lipoprotein cholesterol levels. It also reduced the content of thiobarbituric acid-reactive substances and increased the antioxidant enzymes in liver, heart and kidney in HFD-fed rats. These antihyperlipidemic effects and in vivo antioxidative effects correlated with the in vitro phenolic content scavenging ability. Thus, the major phenolic compounds were identified using reversed-phase ultra-high-performance liquid chromatography (RP-UHPLC) coupled with two detection systems: diode-array detection (DAD) and quadrupole time-of-flight (QTOF) mass spectrometry (MS). Therefore, in the negative ionization mode, 28 phenolic compounds, including hydroxybenzoic acids, hydroxycinnamic acids, flavanoids and hydroxycoumarins were characterized. Dihydroxybenzoic acid di-pentoside, the flavonol quercetin 3-O-rutinoside and the flavone assigned as apigenin 8-C-glucoside were the main representative compounds in 'Tounsi' fruits. This work was complemented by the detection of seven other phenolic compounds in the positive ionization mode, including anthocyanins and furanocoumarins. Overall, these results have shown that the FE has a significant hypocholesterolemic effect and antioxidant activity in HFD-fed rats. This beneficial effect may be partly due to these phenolic constituents, especially vitexin, dihydroxybenzoic acid di-pentoside as well as rutin.

Structural and Sensory Characterization of Novel Sesquiterpene Lactones from Iceberg Lettuce

Lactuca sativa var. capitate (iceberg lettuce) is a delicious vegetable and popular for its mild taste. Nevertheless, iceberg lettuce is a source of bitter substances, such as the sesquiterpene lactones. Chemical investigations on the n-butanol extract led to the isolation of three novel sesquiterpene lactones. All compounds were isolated by multilayer countercurrent chromatography followed by preparative high-performance liquid chromatography. The structures were verified by means of spectroscopic methods, including NMR and mass spectrometry techniques. For the first time 11ß,13-dihydrolactucin-8-O-sulfate (jaquinelin-8-O-sulfate) was structurally elucidated and identified in plants. In addition, the sesquiterpene lactones cichorioside B and 8-deacetylmatricarin-8-O-sulfate were identified as novel ingredients of iceberg lettuce. Further flowering plants in the daisy family Asteraceae were examined for the above three compounds. At least one of the compounds was identified in nine plants. The comparison between the lettuce butt end and the leaves of five types of the Cichorieae tribe showed an accumulation of the compounds in the butt end. Further experiments addressed the impact of sesquiterpene lactones on color formation and bitter taste.

Advanced development in phytochemicals analysis of medicine and food dual purposes plants used in China (2011-2014)

In 2011, we wrote a review for summarizing the phytochemical analysis (2006-2010) of medicine and food dual purposes plants used in China (Zhao et al., J. Chromatogr. A 1218 (2011) 7453-7475). Since then, more than 750 articles related to their phytochemical analysis have been published. Therefore, an updated review for the advanced development (2011-2014) in this topic is necessary for well understanding the quality control and health beneficial phytochemicals in these materials, as well as their research trends.

LC-MS-based metabolite profiling of methanolic extracts from the medicinal and aromatic species Mentha pulegium and Origanum majorana

INTRODUCTION

There has been increasing interest dedicated to the phenolic compounds with a view to their antioxidant and healthy properties. Recent studies have focused on plants from the Lamiaceae family with special interest in phenolic compounds antioxidant potential.

OBJECTIVE

The metabolite profile of methanolic extracts from two Lamiacea medicinal plants was investigated.

MATERIALS AND METHODS

Mentha pulegium and Origanum majorana methanolic extracts were analysed using reversed-phase ultra-high-performance liquid chromatography (RP-UHPLC) coupled to electrospray ionisation quadrupole time-of-flight mass spectrometry (ESI-QTOF-MS) detection in the negative ion mode.

RESULTS

A total of 85 metabolites were characterised from different families, such as organic acids and derivatives, amino acids and derivatives, nucleosides, phenolic compounds as well as other polar metabolites, by using the MS and MS/MS information provided by the QTOF-MS. However, the total phenols and flavonoids were also quantified spectrophotometrically and they registered higher amounts in Mentha pulegium than in Origanum majorana extract. Gallocatechin was the major compound in M. pulegium extract whereas quercetin dimethyl ether, jaceidin and dihydrokaempferide were the major ones in O. majorana extract.

CONCLUSION

The distribution of phenolic compounds in the methanolic extract showed a variation among studied plants. Mentha pulegium can be considered as a source of gallocatechin.

Metabolic profiling of antioxidants constituents in Artemisia selengensis leaves

This study aimed to evaluate the antioxidant potential of Artemisia selengensis Turcz (AST) leaves, a byproduct when processing AST stalk, and identify the antioxidant constituents by using HPLC-QTOF-MS(2). The total phenolics content (TPC), total flavonoids content (TFC) and antioxidant abilities of fractions resulted from the successively partition of chloroform, ethyl acetate and n-butanol were compared. Ethyl acetate fraction (EAF) exhibited the highest TFC (65.44 mg QuE/g fraction), n-butanol fraction (nBuF) showed the highest TPC (384.78 mg GAE/g fraction) and the best DPPH scavenging ability, ABTS(+) scavenging ability and reducing power. Totally, 57 compounds were identified or tentatively identified in nBuF and EAF, 40 of them were reported in AST for the first time. The major constituents in EAF were flavonoids, and the major constituents in nBuF were phenolic acids and organic acids. Thus, AST leaves might be a potential low-cost resource of natural antioxidants.

Evaluation of anti-inflammatory activity and fast UHPLC-DAD-IT-TOF profiling of polyphenolic compounds extracted from green lettuce (Lactuca sativa L.; var. Maravilla de Verano)

Fresh cut vegetables represent a widely consumed food worldwide. Among these, lettuce (Lactuca sativa L.) is one of the most popular on the market. The growing interest for this "healthy" food is related to the content of bioactive compounds, especially polyphenols, that show many beneficial effects. In this study, we report the anti-inflammatory and antioxidant potential of polyphenols extracted from lettuce (var. Maravilla de Verano), in J774A.1 macrophages stimulated with Escherichia coli lipopolysaccharide (LPS). Lettuce extract significantly decreased reactive oxygen species, nitric oxide release, inducible nitric oxide synthase and cycloxygenase-2 expression. A detailed quali/quantitative profiling of the polyphenolic content was carried out, obtaining fast separation (10 min), good retention time and peak area repeatability, (RSD% 0.80 and 8.68, respectively) as well as linearity (R(2)⩾ 0.999) and mass accuracy (⩽ 5 ppm). Our results show the importance in the diet of this cheap and popular food for his healthy properties.

UHPLC-ESI-QTOF-MS-based metabolic profiling of Vicia faba L. (Fabaceae) seeds as a key strategy for characterization in foodomics

Vicia faba (Fabaceae) is a popular food in many countries and a good source of nutrients. However, little is known about its phytochemical composition, specially referring to phenolic compounds. In the present work, the dietary metabolites from a hydro-methanolic extract of V. faba seeds were thoroughly characterized by a nontargeted analytical approach based on reversed-phase ultra-HPLC (UHPLC) coupled to QTOF-MS. A total of 155 primary and secondary metabolites of various structural types were characterized: carbohydrates, amino acids, organic acids, alkaloids, terpenoids, jasmonates, and, mainly, polyphenols. Among the latter group, 73 compounds were characterized for the first time in this legume. In addition, 24 new structures, belonging to jasmonates and glycosylated N-containing compounds, were also proposed. Thus, this methodology could be implemented in foodomics as a characterization strategy to complement the knowledge of the phytochemical composition of vegetables.

New insights into the qualitative phenolic profile of Ficus carica L. fruits and leaves from Tunisia using ultra-high-performance liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry and their antioxidant activity

RP-UHPLC-DAD-QTOF-MS gives new insights into the fig phenolic constituents that correlate with their antioxidant potency.

Assessment of the distribution of phenolic compounds and contribution to the antioxidant activity in Tunisian fig leaves, fruits, skins and pulps using mass spectrometry-based analysis

The qualitative and quantitative phenolic composition explains the differences in the antioxidant activity of fig leaves, fruits, pulps, and skins.

Profiling of phenolic and other compounds from Egyptian cultivars of chickpea (Cicer arietinum L.) and antioxidant activity: a comparative study

The metabolic profiling of seven Egyptian cultivars of chickpeaviaRP-HPLC-DAD-ESI-QTOF-MS enabled the characterization of 96 phenolic compounds.

Changes in the metabolome of lettuce leaves due to exposure to mancozeb pesticide

This paper describes a proton high resolution magic angle spinning (HRMAS) nuclear magnetic resonance (NMR) metabolomic study of lettuce (Lactuca sativa L.) leaves to characterise metabolic adaptations during leaf growth and exposure to mancozeb. Metabolite variations were identified through multivariate analysis and checked through spectral integration. Lettuce growth was accompanied by activation of energetic metabolism, preferential glucose use and changes in amino acids, phospholipids, ascorbate, nucleotides and nicotinate/nicotinamide. Phenylalanine and polyphenolic variations suggested higher oxidative stress at later growth stages. Exposure to mancozeb induced changes in amino acids, fumarate and malate, suggesting Krebs cycle up-regulation. In tandem disturbances in sugar, phospholipid, nucleotide and nicotinate/nicotinamide metabolism were noted. Additional changes in phenylalanine, dehydroascorbate, tartrate and formate were consistent with a higher demand for anti-oxidant defence mechanisms. Overall, lettuce exposure to mancozeb was shown to have a significant impact on plant metabolism, with mature leaves tending to be more extensively affected than younger leaves.

A chemometric approach to determine the phenolic compounds in different barley samples by two different stationary phases: a comparison between C18 and pentafluorophenyl core shell columns

Barley (Hordeum vulgare L.) is a cereal crop that has been cultivated since ancient times. However, its interest as nutritional food and as food ingredient is relatively new. Thus, in this study, the phenolic compounds of eighteen different varieties of barley (4 waxy and 14 non-waxy) grown under the same agronomic conditions in the same experimental field have been determined by HPLC-DAD-MS. Two new methodologies were developed using new generation superficially porous HPLC columns with different stationary phases: C18 and pentafluorophenyl (PFP). Twelve free phenolic compounds and eight bound phenolic compounds could be identified in barley samples in less than 22min. The study of different method parameters showed that C18 column was more suitable for the analysis of phenolic compounds of barley. Hierarchical cluster analysis (HCA) was conducted in order to assess the different ability of the two different core shell HPLC columns in the discrimination between "waxy" and "non-waxy" varieties, and only HCA of C18 column could separate waxy and non-waxy genotypes. Significant differences in the content of phenolic compounds between waxy and non-waxy samples were found, being waxy barley samples the ones which presented higher content of free and bound phenolic compounds. Once the best discriminant HPLC column was established, principal component analysis (PCA) was applied and it was able to discriminate between "waxy" and "non-waxy" varieties; however it discriminated the barley samples based only in free phenolic compounds. Because of that, partial least squares discriminant analysis (PLS-DA) and Artificial Neural Networks (ANN) were carried out. PLS-DA and ANN permitted the classification of waxy and non-waxy genotypes from both free and bound phenolic compounds.

Chicoric acid: chemistry, distribution, and production

Though chicoric acid was first identified in 1958, it was largely ignored until recent popular media coverage cited potential health beneficial properties from consuming food and dietary supplements containing this compound. To date, plants from at least 63 genera and species have been found to contain chicoric acid, and while the compound is used as a processing quality indicator, it may also have useful health benefits. This review of chicoric acid summarizes research findings and highlights gaps in research knowledge for investigators, industry stakeholders, and consumers alike. Additionally, chicoric acid identification, and quantification methods, biosynthesis, processing improvements to increase chicoric acid retention, and potential areas for future research are discussed.