Rapid ultra-high-performance liquid chromatography/quadrupole time-of-flight tandem mass spectrometry and selected reaction monitoring strategy for the identification and quantification of minor spinacetin derivatives in spinach

Impacts of Colored Light-Emitting Diode Illumination on the Reproductive Performance and Bioactive Constituents and the Molecular Mechanism of Hypothalamus Gland in Zi-geese

Goose is a seasonal breeding animal. Its reproduction is regulated by hypothalamus-pituitary-gonad axis and also affected by environmental factors such as light and location. Zi-goose is characterized with long egg-laying period and high egg-laying potential and belongs to the long-day type of seasonal breeding. In this study, the regulation mechanism of different lighting on reproductive performance of Zi-goose by using metabonomics analysis technology. In addition, 1,481 differential metabolites were screened out totally. 583 differential metabolites were identification in hypothalamus of Zi-goose. 196 differential metabolites were identification in pituitary of Zi-goose. 692 differential metabolites were identification in ovary of Zi-goose. Under red light condition for 12 h, expression of 433 differential metabolites were down-regulated and expression of 150 differential metabolites were up regulated in hypothalamus of Zi-goose, expression of 125 differential metabolites were down-regulated and expression of 71 differential metabolites were up-regulated in pituitary of Zi-goose, expression of 355 differential metabolites were down-regulated and expression of 337 differential metabolites were up-regulated in ovary of Zi-goose. 33 differential metabolites were closely associated with 1,264 transcripts and 400 homologous genes of related enzymes in hypothalamus of Zi-goose. 15 differential metabolites were closely associated with 163 transcripts and 47 homologous genes of related enzymes in pituitary of Zi-goose. 55 differential metabolites were closely associated with 1,255 transcripts and 360 homologous genes of related enzymes in ovary of Zi-goose. It was confirmed that four metabolic pathways were closely related to light regulation of reproductive performance of Zi-goose, namely GnRH signaling pathway, prolactin signaling pathway, thyroid hormone synthesis and ovarian steroidogenesis. Typical differential metabolites of arachidonic acid, glucose-6-phosphate, progesterone, glutathione, oxidized glutathione, testosterone, deoxyepiandrosterone and their related protein genes would play an important role in light regulation of reproductive performance of Zi-goose.

Optimization of Extraction Solvent and Fast Blue BB Assay for Comparative Analysis of Antioxidant Phenolics from Cucumis melo L

Melon (Cucumis melo L.) fruits contain multiple health-promoting compounds, including phenolic compounds, which are antioxidants. Accurate measurement of antioxidant activities and total phenolic contents (TPCs) require an efficient solvent extraction. In this study, we evaluated free radical scavenging activity and TPC of melon extracts extracted with 22 different solvent combinations. The DPPH scavenging activities were high in 100% methanolic (39.48 ± 0.36 µg g⁻¹) and 80% methanolic extracts (38.99 ± 0.44 µg g⁻¹). Similarly, the ABTS scavenging activities were high in 100% methanolic (315.11 ± 10.38 µg g⁻¹) and 80% methanol extracts (297.39 ± 14.98 µg g⁻¹). The Folin–Ciocalteu (F–C) assay is typically used to measure TPC but may be affected by interference from sugars and other compounds. Therefore, we optimized an assay for TPC using Fast Blue (FB) salt and developed a standard operating procedure for microplate analysis using FB. Our analysis of standard samples and comparisons with the F–C assay suggested that the optimized FB assay could be used to measure TPC in fruit and juice samples. Moreover, we successfully detected six phenolic compounds in methanol extracts of melon by LC-HR-QTOF/MS.

Improved Sample Preparation and Optimized Solvent Extraction for Quantitation of Carotenoids

Accurate, rapid quantitation of key antioxidants such as carotenoids is important for assessment of food quality. Carotenoids are lipid-soluble pigments that are susceptible to oxidation due to their highly conjugated carbon-carbon double bonds. Therefore, the present work focuses on improving sample preparation to facilitate rapid analysis of carotenoids. The method involves optimized carotenoid extraction followed by direct HPLC analysis without further concentration and redissolution. For extraction, we tested the effect of blending time (1, 3 and 5 min) and 12 different solvent combinations for carotenoid extraction from cantaloupe (Cucumis melo var. cantalupensis) and oranges (Citrus sinensis), two popular fruits that are high in carotenoids. The identification of carotenoids was performed by LC-APCI-QTOF-HR-MS in positive-ionization mode. In melon, 1 min blending time gave significantly higher β-carotene content with CHCl₃: Ace (1:1) solvent. The optimized method was validated with tomato, watermelon, oranges, grapefruit, melon varieties and commercial products such as fruit juices. Among the different melon varieties, Western Shipper had significantly higher β-carotene (25.1 ± 0.4 µg/g) contents. In oranges, β-carotene and (all-E)-lycopene contents were 4.4 ± 0.1and 3.8 ± 0.1 µg/g, respectively. The optimized method has fewer unit operations and is reproducible for the quantitation of carotenoids and their isomers. This is the first report on the identification of ζ-carotene isomers, and lycopene isomers from cantaloupe varieties and lycopene from oranges. Graphical Abstract.

Comparative Metabolomics Profiling of Polyphenols, Nutrients and Antioxidant Activities of Two Red Onion (Allium cepa L.) Cultivars

Onion is among the most widely cultivated and consumed economic crops. Onions are an excellent dietary source of polyphenols and nutrients. However, onions phytonutrient compositions vary with cultivars and growing locations. Therefore, the present study involved the evaluation of polyphenol, nutritional composition (proteins, nitrogen, and minerals), sugars, pyruvate, antioxidant, and α-amylase inhibition activities of red onion cultivars, sweet Italian, and honeysuckle grown in California and Texas, respectively. The total flavonoid for honeysuckle and sweet Italian was 449 and 345 μg/g FW, respectively. The total anthocyanin for honeysuckle onion was 103 μg/g FW, while for sweet Italian onion was 86 μg/g FW. Cyanidin-3-(6”-malonoylglucoside) and cyanidin-3-(6”-malonoyl-laminaribioside) were the major components in both the cultivars. The pungency of red onions in honeysuckle ranged between 4.9 and 7.9 μmoL/mL, whereas in sweet Italian onion ranged from 8.3 to 10 μmoL/mL. The principal component analysis was applied to determine the most important variables that separate the cultivars of red onion. Overall results indicated that total flavonoids, total phenolic content, total anthocyanins, protein, and calories for honeysuckle onions were higher than the sweet Italian onions. These results could provide information about high quality and adding value to functional food due to the phytochemicals and nutritional composition of red onions.

The Effects of Biostimulants, Biofertilizers and Water-Stress on Nutritional Value and Chemical Composition of Two Spinach Genotypes (Spinacia oleracea L.)

In the present study, the effect of biostimulants application on the nutritional quality and bioactive properties of spinach cultivated in protected environment under water stress conditions was evaluated. For this purpose, four commercially available biostimulant products (Megafol (MEG), Aminovert (AM), Veramin Ca (V), Twin Antistress (TA), and two spinach genotypes (Fuji F1 and Viroflay) were tested under two irrigation regimes (normal irrigation (W+), and water-holding (W–). Fat and carbohydrates content was favored by water stress when Megafol (MEGW+) and Veramin (VW+) were applied on Fuji plants, while calorific value was also increased by MEGW+ treatment. In contrast, protein and ash content increased when AMW– and TAW+ were applied on Viroflay plants. Raffinose and glucose were the most abundant sugars, followed by sucrose and fructose, with the highest contents recorded for Fuji plants when AMW+ (fructose, glucose and total carbohydrates), CW– (sucrose), and TAW– (raffinose) treatments were applied. Regarding organic acids, oxalic and malic acid which had the highest contents for the TAW– (Viroflay plants) and AMW– (Fuji plants) treatments, respectively. α- and γ-tocopherol were the only isoforms detected with MEGW– and VW– inducing the biosynthesis of α-tocopherol, while AMW+ increased γ-tocopherol content in Fuji plants. The main fatty acids were α-linolenic and linoleic acids which were detected in the highest amounts in AMW–, AMW+, and TAW+ the former and in AMW–, VW–, and CW+ the latter. Regarding phenolic compounds content, peak 12 (5,3′,4′-Trihydroxy-3-methoxy-6:7-methylenedioxyflavone-4′-glucuronide) was the most abundant compound, especially in Viroflay plants under normal irrigation and no biostimulants added (CW–). The antioxidant and cytotoxic activity of the tested samples did not show promising results when compared with the positive controls, while a variable antibacterial activity was recorded depending on the tested biostimulant, irrigation regime and genotype. In conclusion, a variable effect of the tested biostimulants and irrigation regimes was observed on bioactive properties and chemical composition of both spinach genotypes which highlights the need for further research in order to make profound conclusions regarding the positive effects of biostimulants under water stress conditions.

Puccinellia maritima, Spartina maritime, and Spartina patens Halophytic Grasses: Characterization of Polyphenolic and Chlorophyll Profiles and Evaluation of Their Biological Activities

Halophytic grasses have been recently targeted as possible sources of nutraceutical and medicinal compounds. Nonetheless, few studies have been conducted on the phytochemistry and biological activities of metabolites produced by these plants. Among these, Spartina maritima (Curtis) Fernald, Spartina patens (Aiton.) Muhl., and Puccinellia maritima (Hudson) Parl. are three halophytic grasses whose chemical composition and bioactivities are unknown. The present work broadens the knowledge on the polyphenolic and chlorophyll composition of these species identifying for the first time hydroxycinnamic acids and their derivatives, flavones, flavonols, lignans, as well as chlorophylls and xantophylls. The extracts were particularly rich in caffeic and ferulic acids as well as in trihydroxymethoxyflavone, apigenin and tricin derivatives. Interestingly, several of the identified compounds are relevant from a medicinal and nutraceutical point of view putting in evidence the potential of these species. Thus, the antioxidant, anti-acetylcholinesterase, antibacterial, and antifungal activities of the polyphenolic extracts were assessed as well as the photophysical properties of the chlorophyll-rich extracts. The results, herein presented for the first time, reinforce the nutritional and the medicinal potential of these halophytic grasses.

Metabolite profiling and in vitro biological activities of two commercial bitter melon (Momordica charantia Linn.) cultivars

The current study was designed to characterize the metabolite profile and bioactivity of two commercial bitter melon (Momordica charantia Linn.) genotypes. UPLC-high resolution mass spectrometry (HRMS) was used to identify 15 phenolic and 46 triterpenoids in various bitter melon extracts. Total phenolic levels were the highest (57.28 ± 1.02) in methanolic extract of the inner tissue of Indian Green cultivar, which also correlated to the highest DPPH radical scavenging activity (30.48 ± 2.49 ascorbic acid equivalents (mg of AAE)/g of FD). In addition, highest levels of total saponins were observed in chloroform extract of the Chinese bitter melon pericarp (75.73 mg ± 4.67 diosgenin equivalents (DE)/g of FD). Differential inhibition of α-amylase and α-glucosidase activity was observed in response to polarity of extract, cultivar and tissue type. These results suggest that consumption of whole bitter melon may have potential health benefits to manage diabetes.

Effect of harvest time on the levels of phytochemicals, free radical-scavenging activity, α-amylase inhibition and bile acid-binding capacity of spinach (Spinacia oleracea)

BACKGROUND

Spinach is a green leafy vegetable that is rich in health-promoting compounds. The present study analyzed the levels of phytochemicals and health-promoting properties of spinach harvested at 20, 30, 40, 50 and 60 days after planting.

RESULTS

The time of harvest had a significant effect on nitrate levels, which increased from 1909 ± 70.6 µg g^-1 (20 days) to 3668 ± 101.3 µg g^-1 (40 days) and then decreased to 974 ± 164 µg g^-1 (60 days). Lutein and chlorophylls a and b were found to be maximum at 60 days, whereas β-carotene was higher at 50 days. Liquid chromatography/high-resolution quadrupole time-of-flight tandem mass spectrometry (LC/HR-QTOF-MS) was used to identify 12 flavonoids, and their tentative fragmentation pathways have been proposed. Spinach harvested at 30 and 60 days exhibited significantly higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radical-scavenging activities and inhibition of amylase. The levels of total phenolics ranged from 885 ± 35.1 to 1162 ± 112.4 µg g^-1 in the samples. In vitro bile acid-binding capacity showed that glycochenodeoxycholate and glycodeoxycholate were bound to maximum levels in all spinach samples.

CONCLUSION

The harvest time has a major effect on the levels of phytochemicals and health-beneficial properties, which indicates that consumption of both baby and mature spinach will provide maximum health benefits. © 2017 Society of Chemical Industry.

An optimized solvent extraction and characterization of unidentified flavonoid glucuronide derivatives from spinach by UHPLC-HR-QTOF-MS

A rapid, sensitive analytical method using ultra-high-pressure liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-HR-QTOF-MS) was developed for the identification and quantification of flavonoids from spinach. The extraction efficiency of flavonoids was evaluated by different solvents such as acetone, ethanol, methanol, acetone: water (70:30), ethanol: water (70:30) and methanol: water (70:30). Flavonoid identification was achieved by UV spectra, high resolution accurate mass and their fragmentation pattern. The precursor and product ions were recorded by both broadband collision ion dissociation (bbCID) and multiple reaction monitoring (MRM) techniques. Different collision energies (5, 10, 15, 20, 40, and 70 eV) were optimized to obtain the mass spectra of flavonoids in positive and negative ionization modes. For the first time, five minor flavonoid glucuronide derivatives were identified in spinach. MRM and bbCID provided glucuronide fingerprint ions at m/z 175.0278 and m/z 113.0257 respectively in negative ionization mode. The quantification of identified flavonoids was achieved by 5,3',4'-trihydroxy-3-methoxy-6:7-methylen-dioxyflavone-4'-β-D-glucuronide which was purified by semi-preparatory HPLC. The purity of the isolated compound was confirmed by NMR analysis. The identified 5,3',4'-trihydroxy-3-methoxy-6:7-methylen-dioxyflavone-4'-β-D-(2'-O-feurloyl-glucuronide) was the prominent flavonoid and the level was significantly higher in the acetone fraction (2.95 ± 0.16 µg/g FW). This study demonstrates the systematic identification of potential bioactive compounds especially glucuronide derivatives from spinach.

Storage Stability of Dietary Nitrate and Phenolic Compounds in Beetroot (Beta vulgaris) and Arugula (Eruca sativa) Juices

Nitrate and polyphenols from the diet may enhance the production and bioavailability of nitric oxide, a radical signaling molecule critical for cardiovascular health. Understanding the stability of these bioactives in beetroot and arugula juices is important for their functions. In this study, the stability of nitrate and phenolics in beetroot and arugula juices was measured for 32 days at different temperatures (25, 4, -20, and -80 °C). The levels of nitrate were measured by reversed-phase HPLC and initial levels were found to be 4965.34 ± 72.69 μg/mL for beetroot and 6310.20 ± 24.79 μg/mL for arugula. Interestingly, nitrate degradation started within 24 hr at 25 °C and after 4 days at 4 °C. At -20 °C and -80 °C, nitrate levels remained stable for one month. Total phenolics and free radical scavenging activity varied significantly during storage conditions. Beetroot juice at 25 °C, significant decrease in total phenolics and antioxidant activity was observed, whereas at 4, -20 and -80 °C, the levels remained relatively stable. By contrast, arugula juice at 25 and 4 °C, an increase in total phenolics and antioxidant activity were observed after one month. Furthermore, UPLC-HR-QTOF-MS analysis demonstrated that flavonoid glucosides were converted to their aglycones and lower phenolics, resulting in higher total phenolics and antioxidant activity during storage. In conclusion, beetroot and arugula juices required frozen conditions for long-term storage to prevent degradation of nitrate and to maintain their nutritional value.

PRACTICAL APPLICATION

Beetroot and arugula juices have health-beneficial compounds such as nitrate and phenolics. Understanding the proper storage conditions can allow consumers to make informed choices that can help fresh juices to maintain their health promoting properties.

Rapid and Efficient Desulfonation Method for the Analysis of Glucosinolates by High-Resolution Liquid Chromatography Coupled with Quadrupole Time-of-Flight Mass Spectrometry

The goal of our present research was to develop a simple and rapid method for the quantitation of desulfoglucosinolates (desulfoGLS) without using column chromatography. The proposed method involves extraction, concentration, incubation of glucosinolates with a sulfatase enzyme, and HPLC analysis. Identification of desulfoGLS in green kohlrabi was performed by LC-HR-ESI-QTOF-MS in positive-ionization mode. A total of 11 desulfoGLS were identified with neoglucobrassicin (3.32 ± 0.05 μmol/g DW) as the predominant indolyl, whereas progoitrin and sinigrin were the major aliphatic desulfoGLS. The levels of the aliphatic desulfoGLS glucoiberin, progoitrin, and glucoerucin at 7 h were found to be 3.6-, 1.9-, and 1.6-fold higher, respectively, than those produced through the conventional method. This technique was successfully applied in the identification of desulfoGLS from cabbage. The developed method has fewer unit operations, has maximum recovery, and is reproducible in the determination of desulfoGLS in a large number of Brassicaceae samples in a short time.