C18 core-shell column with in-series absorbance and fluorescence detection for simultaneous monitoring of changes in stilbenoid and proanthocyanidin concentrations during grape cane storage

Separation of polyphenols by HILIC methods with diode array detection, charged aerosol detection and mass spectrometry: Application to grapevine extracts rich in stilbenoids

The characterization of plant extracts is usually accomplished by reverse-phase liquid chromatography, but the development of new complementary approaches, such as HILIC, offers an orthogonal method. In this study, five HILIC stationary phases were evaluated to assess their ability to retain polyphenols. They were selected to cover the main different HILIC mechanisms: bare silica; silica with ethylene bridge; neutral amide; amino; zwitterionic. A total of 31 polyphenol standards were used for the screening, including 9 stilbenes, 8 flavonoids, 6 anthocyanins, and 8 phenolic acids. Three different detections were tested: diode array detector, charged aerosol detector and mass spectrometry. Results indicated that silica supports were not suitable for retaining polyphenols, with no or low retention observed except for anthocyanins. The effectiveness of stationary phases in retention of phenolics following the order related to increased retention: zwitterionic, amide, and amino. The choice of mobile phase also influenced retention. Mobile phases containing TFA as pH modifier limited retention, while formic acid was found to be more effective for polyphenol retention. Ammonium buffers also improved retention but often compromised peak shape. pH changes mainly impacted ionizable compounds, such as phenolic acids, by increasing their retention when they were ionized. DAD was wellsuited for detecting polyphenols that possess aromatic rings, though peak wavelengths depend on the structures of the polyphenols. CAD, while less sensitive than DAD and MS, provided an almost similar response for structurally related compounds, even with gradient elution. MS was the preferred detector for quantification when resolution between compounds was challenging, as it is often the case with natural extracts. The study successfully demonstrated that best HILIC conditions were obtained using an amino stationary phase composed of a polyethylenimine and formic acid-based mobile phase. These conditions were successfully applied to the analysis of stilbenoid-rich extracts from different parts of the vine. The elution order of stilbenoids followed the degree of polymerization. With CAD, the chromatographic profile was more representative of sample composition. It was demonstrated for the first time the interest of a combination of HILIC and CAD for analyzing stilbenes, offering a complementary approach to the classic RP analysis.

Background and Perspectives on the Utilization of Canes' and Bunch Stems' Residues from Wine Industry as Sources of Bioactive Phenolic Compounds

Viticulture activity produces a significant amount of grapevine woody byproducts, such as bunch stems and canes, which constitute potential sources of a wide range of phenolic compounds (PCs) with purported applications. Recently, the study of these byproducts has been increased as a source of health-promoting phytochemicals. Antioxidant, antimicrobial, antifungal, and antiaging properties have been reported, with most of these effects being linked to the high content of PCs with antioxidant properties. This Review summarizes the data related to the qualitative and quantitative composition of PCs recovered from canes and bunch stems side streams of the wine industry, the influence that the different environmental and storage conditions have on the final concentration of PCs, and the current reported applications in specific technological fields. The objective is to give a complete valuation of the key factors to consider, starting from the field to the final extracts, to attain the most suitable and stable characterized product.

A ratiometric fluorescent sensing of proanthocyanidins by MnO2 nanosheets simultaneously tuning the photoluminescence of Au/AgNCs and thiamine

By simultaneously regulating the photoluminescence of alloy Au/Ag nanoclusters (NCs) and thiamine (VB1) through MnO₂ nanosheets (MnO₂ NS), a novel ratiometric fluorescent probe (RF-probe) was established for sensitively and selectively monitoring proanthocyanidins (PAs). The introduction of Ag (I) ions could enhance significantly the quantum yields (QYs, 11.1%) of AuNCs based on the synthetic method of UVI (UV irradiation) combined with MWH (microwave heating). MnO₂ NS could quench the fluorescence (FL) of Au/AgNCs mainly coming from Förster resonance energy transfer (FRET), while it could act as a nanozyme catalyst for directly catalyzing the oxidation of VB1 to produce highly fluorescent oxVB1. In the presence of PAs, MnO₂ was reduced to Mn²⁺, which caused that its quenching capacity and oxidase-like activity were vanished, thus the FL of oxVB1 and Au/AgNCs was reduced and recovered. The concentration of PAs could be monitored by the RF-probe with a linear range of 0.27-22.4 μmol L^-1 and corresponding limit of detection (LOD) and limit of quantification (LOQ) were calculated to be 75.9 and 250.5 nmol L^-1. Furthermore, the RF-probe was successfully used for the determination of PAs in mineral water, PAs additive and PAs capsule with satisfactory results compared to the standard HPLC method.

Pilot-plant scale extraction of phenolic compounds from grape canes: Comprehensive characterization by LC-ESI-LTQ-Orbitrap-MS

Grape canes, also named vine shoots, are well-known viticultural byproducts containing high levels of phenolic compounds, which are associated with a broad range of health benefits. In this work, grape canes (Vitis vinifera cv. Pinot noir) were extracted in a 750 L pilot-plant reactor under the following conditions: temperature 80 °C, time 100 min, solid/liquid ratio 1:10. The comprehensive characterization of grape cane phenolic compounds was performed by liquid chromatography coupled to high-resolution/accurate mass measurement LTQ-Orbitrap mass spectrometry. A total of 44 compounds were identified and, 26 of them also quantified, consisting of phenolic acids and aldehydes (17), flavonoids (12), and stilbenoids (15). The most abundant class of phenolics were stilbenoids, among which (E)-ε-viniferin predominated. The phenolic profile of grape canes obtained using pilot plant extraction differed significantly from the results of laboratory-scale studies obtained previously. Additionally, we observed a high antioxidant capacity of grape cane pilot-plant extract measured by the radical antioxidant scavenging potential (ABTS⁺) (2209 ± 125 µmol TE/g DW) and oxygen radical absorbance capacity using fluorescein (ORAC-FL) (4612 ± 155 µmol TE/g DW). Grape cane pilot-plant extract for their phenolic profile may be used as a by-product for the development of novel nutraceutical and pharmaceutical products, improving the value and the sustainability of these residues.

Polyphenol Profiles of Just Pruned Grapevine Canes from Wild Vitis Accessions and Vitis vinifera Cultivars

Grapevine canes are an abundant byproduct of the wine industry. The stilbene contents of Vitis vinifera cultivars have been largely studied, but little is known about the stilbene contents of wild Vitis accessions. Moreover, there have only been few studies on the quantification of other phenolic compounds in just pruned grapevine canes. In our study, we investigated the polyphenol profile of 51 genotypes belonging to 15 Vitis spp. A total of 36 polyphenols (20 stilbenes, 6 flavanols, 7 flavonols, and 3 phenolic acids) were analyzed by high-performance liquid chromatography coupled with a triple quadrupole mass spectrometer. Our results suggest that some wild Vitis accessions could be of interest in terms of the concentration of bioactive polyphenols and that flavanols contribute significantly to the antioxidant activity of grapevine cane extracts. To the best of our knowledge, this is the most exhaustive study of the polyphenolic composition of grapevine canes of wild Vitis spp.

Tandem absorbance and fluorescence detection following liquid chromatography for the profiling of multiclass phenolic compounds in different winemaking products

A liquid chromatography method coupling diode-array and fluorescence detectors (DAD and FLD, respectively) has been developed for the simultaneous quantification of 32 phenolic compounds (PCs) in winemaking products. With the combination of both detectors it was possible to determine phenolic acids, flavanols, flavonols, stilbenes and other PCs in the matrices under study. An excitation wavelength of 290 nm was selected and three different emission wavelengths (315, 360 and 400 nm) were recorded. The method provided detection and quantification limits (LODs and LOQs) within the ranges of 0.01-1.46 mg/L and 0.03-4.9 mg/L, respectively. The LODs and LOQs using FLD for flavanols, stilbenes and phenyl ethanol analogues were improved between 65 and 1000% as compared with DAD. The combination of DAD with FLD increased both, sensitivity and the ability to reduce interfering signals. The developed method was applied for the characterization of PCs of wines, bunch stems and grape canes.

Grapevine Cane Extracts: Raw Plant Material, Extraction Methods, Quantification, and Applications

Grapevine canes are viticulture waste that is usually discarded without any further use. However, recent studies have shown that they contain significant concentrations of health-promoting compounds, such as stilbenes, secondary metabolites of plants produced as a response to biotic and abiotic stress from fungal disease or dryness. Stilbenes have been associated with antioxidant, anti-inflammatory, and anti-microbial properties and they have been tested as potential treatments of cardiovascular and neurological diseases, and even cancer, with promising results. Stilbenes have been described in the different genus of the Vitaceae family, the Vitis genera being one of the most widely studied due to its important applications and economic impact around the world. This review presents an in-depth study of the composition and concentration of stilbenes in grapevine canes. The results show that the concentration of stilbenes in grapevine canes is highly influenced by the Vitis genus and cultivar aspects (growing conditions, ultraviolet radiation, fungal attack, etc.). Different methods for extracting stilbenes from grapevine canes have been reviewed, and the extraction conditions have also been studied, underlining the advantages and disadvantages of each technique. After the stilbenes were extracted, they were analyzed to determine the stilbene composition and concentration. Analytical techniques have been employed with this aim, in most cases using liquid chromatography, coupled with others such as mass spectrometry and/or nuclear magnetic resonance to achieve the individual quantification. Finally, stilbene extracts may be applied in multiple fields based on their properties. The five most relevant are preservative, antifungal, insecticide, and biostimulant applications. The current state-of-the-art of the above applications and their prospects are discussed.

Simple and Fast Determination of Terbinafine in Human Urine by Dilute and Shoot HPLC-DAD Using a Core-Shell Column

BACKGROUND

Terbinafine is an allylamine antifungal that is effective against many fungi, dermatophytes and moulds. Analytical methods are required for the determination of terbinafine in biological fluids to perform therapeutic drug monitoring and pharmacokinetic studies.

OBJECTIVE

The aim of this study was to develop and validate a novel and fast method combining dilute and shoot approach and high-performance liquid chromatography coupled with photodiode array detection for the determination of terbinafine in human urine.

METHODS

Chromatographic parameters including mobile phase composition, pH, flow rate and injection volume were assessed and optimized. The separation of terbinafine and naproxen (internal standard) was achieved within 3 min using a C18 core-shell column (Raptor ARC-18, 100 x 4.6 mm, 2.7 μm) under isocratic conditions. Samples were eluted from the column at the flow rate of 1.4 mL/min using a mobile phase containing 0.2% triethylamine in water (pH 3.4 with formic acid): acetonitrile (45:55, v/v).

RESULTS

The presented technique was linear in the range of 25-2000 ng/mL. Intra- and inter-day reproducibility at four quality control levels (25, 200, 750 and 1500 ng/mL) were less than 7%, with relative errors ranging from -5.40% to 5.91%. The limit of detection was 12.60 ng/mL. The developed method has three main advantages compared to existing methods: simplicity and greenness of sample preparation, use of core-shell column and short analysis time.

CONCLUSION

The results of this study indicate that the combination of dilute and shoot approach and core-shell column can be regarded as an advantageous application for the fast determination of terbinafine in the urine.

A Reference List of Phenolic Compounds (Including Stilbenes) in Grapevine (Vitis vinifera L.) Roots, Woods, Canes, Stems, and Leaves

Due to their biological activities, both in plants and in humans, there is a great interest in finding natural sources of phenolic compounds or ways to artificially manipulate their levels. During the last decade, a significant amount of these compounds has been reported in the vegetative organs of the vine plant. In the roots, woods, canes, stems, and leaves, at least 183 phenolic compounds have been identified, including 78 stilbenes (23 monomers, 30 dimers, 8 trimers, 16 tetramers, and 1 hexamer), 15 hydroxycinnamic acids, 9 hydroxybenzoic acids, 17 flavan-3-ols (of which 9 are proanthocyanidins), 14 anthocyanins, 8 flavanones, 35 flavonols, 2 flavones, and 5 coumarins. There is great variability in the distribution of these chemicals along the vine plant, with leaves and stems/canes having flavonols (83.43% of total phenolic levels) and flavan-3-ols (61.63%) as their main compounds, respectively. In light of the pattern described from the same organs, quercetin-3-O-glucuronide, quercetin-3-O-galactoside, quercetin-3-O-glucoside, and caftaric acid are the main flavonols and hydroxycinnamic acids in the leaves; the most commonly represented flavan-3-ols and flavonols in the stems and canes are catechin, epicatechin, procyanidin B1, and quercetin-3-O-galactoside. The main stilbenes (trans-ε-viniferin, trans-resveratrol, isohopeaphenol/hopeaphenol, vitisin B, and ampelopsins) accumulate primarily in the woods, followed by the roots, the canes, and the stems, whereas the leaves, which are more exposed to environmental stresses, have a low concentration of these compounds. Data provided in this review could be used as (i) a metabolomic tool for screening in targeted and untargeted analyses and (ii) a reference list in studies aimed at finding ways to induce naturally occurring polyphenols on an industrial scale for pant and human disease control.

Influence of pruning time and viral infection on stilbenoid levels in Pinot noir grape canes

BACKGROUND

Grapevine canes represent a large source of waste derived from grape cultivation. In the present study, the effect of different processes of storage and different pruning times on the stilbene accumulation on Pinot noir canes was analyzed. Whether the alteration of the secondary metabolism accompanying leafroll symptom expressions could affect the stilbenoid accumulation in canes harvested at pruning time was also investigated.

RESULTS

The maximum accumulation of trans-resveratrol and trans-piceatannol was obtained in canes harvested in October and dried at 40 °C. Even in grape canes harvested in October, November, and December and stored for different times at room temperature (20 ± 2 °C) a marked increase in trans-resveratrol and trans-piceatannol was evident, which reached a maximum at around 8 weeks of storage. A significant higher accumulation of trans-resveratrol and trans-piceatannol was also found in canes harvested from symptomatic plants compared to those harvested from asymptomatic plants for all the pruning times.

CONCLUSION

This study confirms that the biosynthetic enzyme activities and, particularly, those involved in the stilbene pathway, persist during Pinot noir cane storage at different harvest times, with different storage times and conditions, and different sanitary status. © 2019 Society of Chemical Industry.

Compact optical detector utilizing light emitting diodes, 50 nL L-shaped silica capillary cell and CCD spectrometer for simultaneous multi-wavelength monitoring of absorbance and fluorescence in microcolumn liquid chromatography

Optical detection setup utilizing light emitting diodes (LEDs), 50 nL L-shaped silica capillary detection cell (L-cell), and low-cost CCD spectrometer is described in this work. Experimental configuration can be equipped with two different LEDs for absorbance measurement and other two LEDs for fluorescence excitation. This setup is capable of simultaneous multi-wavelength monitoring of absorbance and fluorescence when light produced by the individual LEDs and light emitted by the fluorescent analytes is resolved in the spectrum outputted by the CCD spectrometer. Effective optical path of the 0.25 μm I. D. L-cell is 1 mm. Absorbance baseline noise is 1 mAU due to use of low-cost and relatively noisy CCD spectrometer and LED drivers. Nevertheless, the setup can detect adenosine 5'-monophosphate down to micromolar concentration. Performance of fluorescence monitoring allows detection of 5·10^-10 M fluorescein when 23 mW 470 nm LED is used for excitation. The dynamic range of absorbance and fluorescence measurement is 867:1 and 1622:1, respectively. Separation of test mixture (alkylbenzenes and polyaromatic hydrocarbons) demonstrate the effective use of the detector for simultaneous absorbance and fluorescence detection with 0.2 × 150 mm packed capillary column. The benefits of the setup are relative simplicity, compact design and the fact that it can be operated without any optical filters, slits, and extremely precise positioning of the optical elements.

Viticultural wood waste as a source of polyphenols of interest: Opportunities and perspectives through conventional and emerging extraction methods

Viticultural waste has been widely demonstrated to contain high-added value compounds named the stilbenes. Among them, trans-resveratrol (Rsv) and trans-ε-viniferin (Vf) are the most abundant in particular in grape canes. Various emerging methods such as ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE) or pressurized solvent extraction (PSE) have been studied to recover Rsv and Vf from grape canes in order to enhance their extraction. This paper gives a critical overview of the techniques used to this end, integrating conventional and non-conventional methods investigated in the literature as well as those used in industrial processes. It finally highlights that the unconventional technics are usually less time-consuming than conventional extraction ones but further investigations for the discussed compounds and biomass are needed to optimize and understand the influence of the individual parameters of each extraction process.

Bioactive compounds and total antioxidant capacity of cane residues from different grape varieties

BACKGROUND

Every year, the viticulture activity generates considerable amounts of underused lignocellulosic residues as grape cane, which are generally composted or burned despite their potential value as a source of bioactive compounds. Determination of their phytochemical composition and total antioxidant capacity (TAC) may be a useful way of exploiting different high-added value applications.

RESULTS

Twenty-one phenolic compounds (PC) and two carotenoids (Car) were quantified by high performance-liquid chromatography-diode array detection in eight grape varieties from different locations in Mendoza, Argentina. The maximum concentrations corresponded to the stilbene ϵ-viniferin [10 552 μg g^-1 dry weight (DW)], followed by the flavanols (+)-catechin (3718 μg g^-1 DW) and (-)-epicatechin (2486 μg g^-1 DW). In addition, lutein and β-carotene were quantified at levels ranging between 350 and 2400 ng g^-1 DW. The TAC of the extracts was assessed by oxygen radical absorbance capacity, 2,20-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid and 1,1-diphenyl-2-picrylhydrazyl assays, with a good correlation between TAC and total PC for each sample (r ≥ 0.82).

CONCLUSION

Samples of cv. Malbec, the most representative variety of Argentina's winemaking industry, presented high contents of PC, particularly ϵ-viniferin, (+)-catechin and (-)-epicatechin. Quercetin-3-galactoside, OH-tyrosol and Car were reported for the first time in grape canes of the eight varieties. The results add to the existing knowledge related to this inexpensive source of high-value bioactive compounds, which could be used as functional ingredients. © 2019 Society of Chemical Industry.

Separation, Identification, and Antioxidant Activity of Polyphenols from Lotus Seed Epicarp

Lotus seed epicarp, the main by-product of lotus seed processing, is abundant in polyphenols. In this study, polyphenols in lotus seed epicarp were separated by Sephadex LH-20 gel filtration chromatography to yield Fraction-I (F-I), Fraction-II (F-II), and Fraction-III (F-III). The polyphenol compounds in the three fractions were identified by UPLC-MI-TOF-MS. Six kinds of polyphenol compounds including cyanidin-3-O-glucoside, procyanidin trimer, and phlorizin were identified in F-I, and prodelphinidin dimer B, procyanidin dimer, and quercetin hexoside isomer were found in F-II. However, there was only procyanidin dimer identified in F-III. The in vitro antioxidant activities of the three fractions were also investigated. We found F-I, F-II, and F-III had strong potential antioxidant activities in the order of F-III > F-II > F-I. Our results suggested that polyphenols from lotus seed epicarp might be suitable for use as a potential food additive.

Phenolic Profile of Grape Canes: Novel Compounds Identified by LC-ESI-LTQ-Orbitrap-MS

Grape canes (Vitis vinifera L.) are a viticulture industry by-product with an important content of secondary metabolites, mainly polyphenols with a broad spectrum of demonstrated health benefits. Grape canes, therefore, have considerable economic potential as a source of high-value phytochemicals. In this work, liquid chromatography coupled with electrospray ionization hybrid linear trap quadrupole-Orbitrap mass spectrometry (LC-LTQ-Orbitrap) was used for the comprehensive identification of polyphenolic compounds in grape canes. Identification of polyphenols was performed by comparing their retention times, accurate mass measured, and mass fragmentation patterns with those of reference substances or available data in the literature. A total of 75 compounds were identified, including phenolic acids, flavanols, flavonols, flavanonols, flavanones, and stilbenoids. The most abundant polyphenols were proanthocyanidins and stilbenoids and their oligomers. Moreover, the high-resolution mass spectrometry analysis revealed the occurrence of 17 polyphenols never described before in grape canes, thereby providing a more complete polyphenolic profile of this potentially valuable by-product.

Characteristics, Biological Properties and Analytical Methods of Trans-Resveratrol: A Review

Trans-resveratrol (TR) is the biological active isomer of resveratrol and the one responsible for therapeutic effects; both molecules are non-flavonoid phenolics of the stilbenes class found mainly in berries and red grapes. TR biological properties lie in modulation of various enzymatic classes. It is a promising candidate to novel drugs due its applications in pharmaceutical and cosmetic industries, such as anticarcinogenic, antidiabetic, antiacne, antioxidant, anti-inflammatory, neuroprotective, and photoprotector agent. It has effects on bone metabolism, gastrointestinal tract, eyes, kidneys, and in obesity treatment as well. Nevertheless, its low solubility in water and other polar solvents may be a hindrance to its therapeutic effects. Various strategies been developed to overcome these issues, such as the drug delivery systems. The present study performed a research about methods to identify TR and RESV in several samples (raw materials, wines, food supplements, drug delivery systems, and blood plasma). Most of the studies tend to analyze TR and RESV by high performance liquid chromatography (HPLC) coupled with different detectors, even so, there are reports of the use of capillary electrophoresis, electron spin resonance, gas chromatography, near-infrared luminescence, UV-Vis spectrophotometer, and vibrational spectrophotometry, for this purpose. Thus, the review evaluates the biological activity of TR and demonstrates the currently used analytical methods for its quantification in different matrices.

Vine-Shoot Tannins: Effect of Post-pruning Storage and Toasting Treatment

For the first time vine-shoot tannin composition was carried out by means of HPLC-DAD-ESI-MS/MS. Two vine-shoot cultivars (Airén and Cencibel) with different post-pruning storage times were submitted to a toasting process and assayed. There were no traces of gallotannins nor ellagitannins, but a high proanthocyanidin content and a mean degree of polymerization (mDP) close to 3 were characterized. The higher concentration of proanthocyanidins corresponded to Airén after 6 months post-pruning storage and at 3 months for Cencibel. Procyanidins were the most abundant fraction (70-95%), which decreased with storage, and especially significant was the contribution of B1, B2, and B4 dimers. Prodelphinidins were also found (8-24%), increasing their % with storage time. Toasting produced a considerable reduction of proanthocyanidin content and a loss of a monomer mDP unit, suggesting that if used as oenological tannins, then they may be more bitter and less astringent when compared with the nontoasted vine-shoot samples.