Stilbenes from Vitis vinifera L. Waste: A Sustainable Tool for Controlling Plasmopara Viticola

Progress of Antimicrobial Mechanisms of Stilbenoids

Antimicrobial drugs have made outstanding contributions to the treatment of pathogenic infections. However, the emergence of drug resistance continues to be a major threat to human health in recent years, and therefore, the search for novel antimicrobial drugs is particularly urgent. With a deeper understanding of microbial habits and drug resistance mechanisms, various creative strategies for the development of novel antibiotics have been proposed. Stilbenoids, characterized by a C6-C2-C6 carbon skeleton, have recently been widely recognized for their flexible antimicrobial roles. Here, we comprehensively summarize the mode of action of stilbenoids from the viewpoint of their direct antimicrobial properties, antibiofilm and antivirulence activities and their role in reversing drug resistance. This review will provide an important reference for the future development and research into the mechanisms of stilbenoids as antimicrobial agents.

Targeting of Antifungal Metabolites from Grapevine Byproducts by UPLC-HRMS/MS Approaches Using Bioactivity-Based Molecular Networking

This study focuses on countering Fusarium graminearum, a harmful fungal pathogen impacting cereal crops and human health through mycotoxin production. These mycotoxins, categorized as type B trichothecenes, pose significant health risks. Research explores natural alternatives to synthetic fungicides, particularly investigating phenolics in grapevine byproducts. Thirteen eco-extracts from five French grape varieties (Merlot, Cabernet Sauvignon, Sauvignon blanc, Tannat, and Artaban) exhibited substantial antifungal properties, with ten extracts displaying remarkable effects. Extracts from grapevine stems and roots notably reduced fungal growth by over 91% after five days. Through UHPLC-HRMS/MS analysis and metabolomics, the study identified potent antifungal compounds such as ampelopsin A and cyphostemmin B, among other oligomeric stilbenes. Interestingly, this approach showed that flavan-3-ols have been identified as markers for extracts that induce fungal growth. Root extracts from rootstocks, rich in oligostilbenes, demonstrated the highest antifungal activity. This research underscores grapevine byproducts' potential both as a sustainable approach to control F. graminearum and mycotoxin contamination in cereal crops and the presence of different metabolites from the cultivars of grapevine, suggesting different activities.

Trends in the Potential of Stilbenes to Improve Plant Stress Tolerance: Insights of Plant Defense Mechanisms in Response to Biotic and Abiotic Stressors

Stilbenes belong to the naturally synthesized plant phytoalexins, produced de novo in response to various biotic and abiotic stressors. The importance of stilbenes in plant resistance to stress and disease is of increasing interest. However, the defense mechanisms and potential of stilbenes to improve plant stress tolerance have not been thoroughly reviewed. This work overviewed the pentose phosphate pathway, glycolysis pathway, shikimate pathway, and phenylalanine pathway occurred in the synthesis of stilbenes when plants are subjected to biotic and abiotic stresses. The positive implications and underlying mechanisms regarding defensive properties of stilbenes were demonstrated. Ten biomimetic chemosynthesis methods can underpin the potential of stilbenes to improve plant stress tolerance. The prospects for the application of stilbenes in agriculture, food, cosmetics, and pharmaceuticals industries are anticipated. It is hoped that some of the detailed ideas and practices may contribute to the development of stilbene-related products and improvement of plant resistance breeding.

Are Basic Substances a Key to Sustainable Pest and Disease Management in Agriculture? An Open Field Perspective

Pathogens and pests constantly challenge food security and safety worldwide. The use of plant protection products to manage them raises concerns related to human health, the environment, and economic costs. Basic substances are active, non-toxic compounds that are not predominantly used as plant protection products but hold potential in crop protection. Basic substances' attention is rising due to their safety and cost-effectiveness. However, data on their protection levels in crop protection strategies are lacking. In this review, we critically analyzed the literature concerning the field application of known and potential basic substances for managing diseases and pests, investigating their efficacy and potential integration into plant protection programs. Case studies related to grapevine, potato, and fruit protection from pre- and post-harvest diseases and pests were considered. In specific cases, basic substances and chitosan in particular, could complement or even substitute plant protection products, either chemicals or biologicals, but their efficacy varied greatly according to various factors, including the origin of the substance, the crop, the pathogen or pest, and the timing and method of application. Therefore, a careful evaluation of the field application is needed to promote the successful use of basic substances in sustainable pest management strategies in specific contexts.

Additive and synergistic antifungal effects of copper and phenolic extracts from grape cane and apples

BACKGROUND

Organic viticulture seeks sustainable alternatives for eco-toxic copper fungicides to control downy mildew caused by Plasmopara viticola. (Poly)phenol-rich extracts of agricultural byproducts are known to possess antifungal activity, but high production costs often limit their actual implementation.

RESULTS

We developed and produced novel ligninsulfonate-based grape cane extract (GCE) formulations and an apple extract on a pilot plant scale, including a detailed (poly)phenol characterization by high-performance liquid chromatography photodiode array mass spectrometry (HPLC-PDA-MS). Our GCE formulations alone reduced downy mildew disease severity in greenhouse trials by 29%-69% in a dose-dependent manner, whereas a standard application of the copper-based agent alone reached ~56%. When applied together, disease severity was diminished by 78%-92%, revealing a synergistic effect that depended on the mixture ratio. Combining GCE formulations with the apple extract, additive effects were found (80% disease severity reduction).

CONCLUSION

The studied plant extracts are proposed to both substitute for and synergistically reinforce copper fungicides in grapevine downy mildew control. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Antifungal activity of chili pepper extract with potential for the control of some major pathogens in grapevine

BACKGROUND

In recent years, biofungicides have drawn increasing interest in vineyards for a more sustainable integrated and copper-limited pest management. Among alternatives, botanicals could represent valuable tools, being rich sources of biologically active compounds. Conversely to the well-known antioxidant and biological properties in relation to health benefits, investigation on bioactivity of hot pungent Capsicum sp. products against fungal phytopathogens in vineyards is still scarce. Therefore, the present study aimed at exploring the biologically active compounds profile of a chili pepper (Capsicum chinense Jacq.) pod extract and its antimicrobial properties against some of the major fungal and Oomycetes pathogens of grapevine, including Botrytis cinerea Pers., Guignardia bidwellii (Ellis) Viala & Ravaz and Plasmopara viticola (Berk. & M.A. Curtis) Berl. & De Toni.

RESULTS

The ethyl acetate-extracted oleoresin from the most pungent varieties was rich in capsaicinoids and polyphenols (371.09 and 268.5 μg mg-1 dry weight, respectively). Capsaicin and dihydrocapsaicin, hydroxycinnamic and hydroxybenzoic acids and quercetin derivatives were the most abundant, while carotenoids represented only a minor fraction. The oleoresin was efficient to inhibit all three pathogenic fungi and ED50 values were determined, evidencing that G. bidwellii was the more sensitive (0.233 ± 0.034 mg mL-1 ).

CONCLUSION

The results suggested a potentiality of chili pepper extract for the control of some important grapevine pathogens, their possible application being helpful for the recommended limitation in extensive use of copper in vineyard. The complex mixture of high amounts of capsaicinoids, associated to specific phenolic acids and other minor bioactive components might contribute to the observed antimicrobial action of chili pepper extract. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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.

Stilbenoids as Promising Natural Product-Based Solutions in a Race against Mycotoxigenic Fungi: A Comprehensive Review

Exposure to mycotoxins can pose a variety of adverse health effects to mammals. Despite dozens of mycotoxin decontamination strategies applied from pre- to postharvest stages, it is always challenging to guarantee a safe level of these natural toxic compounds in food and feedstuffs. In the context of the increased occurrence of drug-resistance strains of mycotoxin-producing fungi driven by the overuse of fungicides, the search for new natural-product-based solutions is a top priority. This review aims to shed a light on the promising potential of stilbenoids extracted from renewable agricultural wastes (e.g., grape canes and forestry byproducts) as antimycotoxin agents. Deeper insights into the mode of actions underlying the bioactivity of stilbenoid molecules against fungal pathogens, together with their roles in plant defense responses, are provided. Safety aspects of these natural compounds on humans and ecology are discussed. Perspectives on the development of stilbenoid-based formulations using encapsulation technology, which allows the bypassing of the limitations related to stilbenoids, particularly low aqueous solubility, are addressed. Optimistically, the knowledge gathered in the present review supports the use of currently underrated agricultural byproducts to produce stilbenoid-abundant extracts with a high efficiency in the mitigation of mycotoxins in food and feedstuffs.

Antifungal Activities of a Grapevine Byproduct Extract Enriched in Complex Stilbenes and Stilbenes Metabolization by Botrytis cinerea

Grapevine co-products, as canes, represent a source of compounds of interest to control vineyard diseases with a sustainable approach. We chose to study an extract that we produced from grapevine trunk and roots. This extract, enriched in complex stilbenes, strongly reduced mycelial growth and spore germination of Botrytis cinerea, the fungal agent causing gray mold. The most active stilbenes were resveratrol, r-viniferin, and ε-viniferin. This grapevine extract also inhibited the production of Botrytis laccases. Conversely, Botrytis secretome metabolized resveratrol into δ-viniferin and pallidol (2 dimers); and ε-viniferin, a dimer, into hopeaphenol, r-viniferin, and r2-viniferin (3 tetramers). r-Viniferin and hopeaphenol (2 tetramers) were not metabolized. The biotransformed extract maintained an effective antimycelial activity. This study provides evidence that a grapevine extract enriched in oligomerized stilbenes exerts different anti-Botrytis activities, notwithstanding the ability of the fungus to metabolize some stilbenes.

Holistic understanding of the response of grapevines to foliar application of seaweed extracts

Viticulture is highly dependent on phytochemicals to maintain good vineyard health. However, to reduce their accumulation in the environment, green regulations are driving the development of eco-friendly strategies. In this respect, seaweeds have proven to be one of the marine resources with the highest potential as plant protective agents, representing an environmentally-friendly alternative approach for sustainable wine production. The current work follows an interdisciplinary framework to evaluate the capacity of Ulva ohnoi and Rugulopteryx okamurae seaweeds to induce defense mechanisms in grapevine plants. To our knowledge, this is the first study to evaluate Rugulopteryx okamurae as a biostimulator . This macroalgae is relevant since it is an invasive species on the Atlantic and Mediterranean coast causing incalculable economic and environmental burdens. Four extracts (UL1, UL2, RU1 and RU2 developed from Ulva and Rugulopteryx, respectively) were foliar applied to Tempranillo plants cultivated under greenhouse conditions. UL1 and RU2 stood out for their capacity to induce defense genes, such as a PR10, PAL, STS48 and GST1, mainly 24 hours after the first application. The increased expression level of these genes agreed with i) an increase in trans-piceid and trans-resveratrol content, mainly in the RU2 treated leaves, and, ii) an increase in jasmonic acid and decrease in salicylic acid. Moreover, an induction of the activity of the antioxidant enzymes was observed at the end of the experiment, with an increase in superoxide dismutase and catalase in the RU2-treated leaves in particular. Interestingly, while foliar fungal diversity was not influenced by the treatments, alga extract amendment modified fungal composition, RU2 application enriching the content of various groups known for their biocontrol activity. Overall, the results evidenced the capacity of Rugulopteryx okamurae for grapevine biostimulation, inducing the activation of several secondary metabolite pathways and promoting the abundance of beneficial microbiota involved in grapevine protection. While further studies are needed to unravel the bioactive compound(s) involved, including conducting field experiments etc., the current findings are the first steps towards the inclusion of Rugulopteryx okamurae in a circular scheme that would reduce its accumulation on the coast and benefit the viticulture sector at the same time.

Grape Waste Materials-An Attractive Source for Developing Nanomaterials with Versatile Applications

In the last decade, researchers have focused on the recycling of agro-food wastes for the production of value-added products. This eco-friendly trend is also observed in nanotechnology, where recycled raw materials may be processed into valuable nanomaterials with practical applications. Regarding environmental safety, replacing hazardous chemical substances with natural products obtained from plant wastes is an excellent opportunity for the "green synthesis" of nanomaterials. This paper aims to critically discuss plant waste, with particular emphasis on grape waste, methods of recovery of active compounds, and nanomaterials obtained from by-products, along with their versatile applications, including healthcare uses. Moreover, the challenges that may appear in this field, as well as future perspectives, are also included.

Chemistry, Biosynthesis and Pharmacology of Viniferin: Potential Resveratrol-Derived Molecules for New Drug Discovery, Development and Therapy

Viniferin is a resveratrol derivative. Resveratrol is the most prominent stilbenoid synthesized by plants as a defense mechanism in response to microbial attack, toxins, infections or UV radiation. Different forms of viniferin exist, including alpha-viniferin (α-viniferin), beta-viniferin (β-viniferin), delta-viniferin (δ-viniferin), epsilon-viniferin (ε-viniferin), gamma-viniferin (γ-viniferin), R-viniferin (vitisin A), and R2-viniferin (vitisin B). All of these forms exhibit a range of important biological activities and, therefore, have several possible applications in clinical research and future drug development. In this review, we present a comprehensive literature search on the chemistry and biosynthesis of and the diverse studies conducted on viniferin, especially with regards to its anti-inflammatory, antipsoriasis, antidiabetic, antiplasmodic, anticancer, anti-angiogenic, antioxidant, anti-melanogenic, neurodegenerative effects, antiviral, antimicrobial, antifungal, antidiarrhea, anti-obesity and anthelminthic activities. In addition to highlighting its important chemical and biological activities, coherent and environmentally acceptable methods for establishing vinferin on a large scale are highlighted to allow the development of further research that can help to exploit its properties and develop new phyto-pharmaceuticals. Overall, viniferin and its derivatives have the potential to be the most effective nutritional supplement and supplementary medication, especially as a therapeutic approach. More researchers will be aware of viniferin as a pharmaceutical drug as a consequence of this review, and they will be encouraged to investigate viniferin and its derivatives as pharmaceutical drugs to prevent future health catastrophes caused by a variety of serious illnesses.

Identification and structural elucidation of bioactive compounds from Scirpoides holoschoenus

Phytochemical investigations of dichloromethane and methanol extracts of roots and rhizomes of Scirpoides holoschoenus afforded 21 stilbenes, six flavonoids, six ferulic acid derivatives and four diterpenes. Among these constituents, six stilbenes, one flavonoid, one diterpene and two ferulic acid derivatives, represent previously unreported natural products. Structure elucidation was performed by HRESI-MS, NMR, GC-MS, and ECD data evaluation. The monoprenylated flavonoid (sophoraflavanone B) and all isolated stilbene oligomers (trans-scirpusin B, scirpusin A, cassigarol E, cyperusphenol B, cyperusphenol D, passiflorinol A, cyperusphenol A and mesocyperusphenol A) showed strong inhibitory activities on spore germination of two Botrytis cinerea strains isolated from field-infected grape berries and apple fruits compared to the reference controls resveratrol, piceid, and fenhexamid at a test concentration of 2.0 mM. For sophoraflavanone B and cyperusphenol A, the EC₅₀ values were determined by concentration response curves and resulted in values of 0.35 mM and 0.53 mM, respectively. The data suggest that stilbene oligomers but also prenylated flavonoids should be examined further to gain more information on their antimicrobial activity and might be a suitable addition to chemical fungicides on the market to combat gray mold.

Comparative Transcriptomics Suggests Early Modifications by Vintec® in Grapevine Trunk of Hormonal Signaling and Secondary Metabolism Biosynthesis in Response to Phaeomoniella chlamydospora and Phaeoacremonium minimum

Given their well-known antifungal abilities, species of the genus Trichoderma are of significant interest in modern agriculture. Recent studies have shown that Trichoderma species can induce plant resistance against different phytopathogens. To further extend this line of investigation, we investigate herein the transcriptomic response of grapevine trunk to Vintec^®, which is a Trichoderma atroviride SC1-based commercial formulation for biological control of grapevine trunk diseases and which reduces wood colonization. The aim of the study is to understand whether the biocontrol agent Vintec^® modifies the trunk response to Phaeoacremonium minimum and Phaeomoniella chlamydospora, which are two esca-associated fungal pathogens. An analysis of transcriptional regulation identifies clusters of co-regulated genes whose transcriptomic reprogramming in response to infection depends on the absence or presence of Vintec^®. On one hand, the results show that Vintec^® differentially modulates the expression of putative genes involved in hormonal signaling, especially those involved in auxin signaling. On the other hand, most significant gene expression modifications occur among secondary-metabolism-related genes, especially regarding phenylpropanoid metabolism and stilbene biosynthesis. Taken together, these results suggest that the biocontrol agent Vintec^® induces wood responses that counteract disease development.

Stilbenes: Source plants, chemistry, biosynthesis, pharmacology, application and problems related to their clinical Application-A comprehensive review

Stilbenes are some of the important phenolic compounds originating from plant families like Vitaceae, Leguminaceae, Gnetaceae, and Dipterocarpaceae. Structurally, they have a C6-C2-C6 skeleton, usually with two isomeric forms. Stilbenes are biosynthesized due to biotic and abiotic stresses such as microbial infections, high temperatures, and oxidation. This review aims to provide a comprehensive overview of stilbenes' botanical sources, chemistry, biosynthetic pathways, pharmacology, and clinical applications and challenges based on up-to-date data. All included studies were collected from PubMed, ScienceDirect, Google Scholar, and CNKI, and the presented data from these indexed studies were analyzed and summarized. A total of 459 natural stilbene compounds from 45 plant families and 196 plant species were identified. Pharmacological studies also show that stilbenes have various activities such as anticancer, antimicrobial, antioxidant, anti-inflammatory, anti-degenerative diseases, anti-diabetic, neuroprotective, anti-aging, and cardioprotective effects. Stilbene synthase (STS) is the key enzyme involved in stilbene biosynthetic pathways. Studies on the therapeutic application of stilbenes pinpoint that challenges such as low bioavailability and isomerization are the major bottlenecks for their development as therapeutic drugs. Although the medicinal uses of several stilbenes have been demonstrated in vivo and in vitro, studies on the development of stilbenes deserve more attention in the future.

Wood Waste from Fruit Trees: Biomolecules and Their Applications in Agri-Food Industry

In the European Union (EU), a total of 11,301,345 hectares are dedicated to the cultivation of fruit trees, mainly olive orchards, grapevines, nut trees (almond, walnut, chestnut, hazelnut, and pistachio), apple and pear trees, stone fruit trees (peach, nectarine, apricot, cherry, and plum), and citrus fruit trees (orange, clementine, satsuma, mandarin, lemon, grapefruit, and pomelo). Pruning these trees, together with plantation removal to a lesser extent, produces a huge amount of wood waste. A theoretical calculation of the wood waste in the European Union estimates approximately 2 and 25 million tons from wood plantation removal and pruning, respectively, per year. This wood waste is usually destroyed by in-field burning or crushing into the soil, which result in no direct economic benefits. However, wood from tree pruning, which is enriched in high added-value molecules, offers a wide spectrum of possibilities for its valorization. This review focuses on the contribution of wood waste to both sustainability and the circular economy, considering its use not only as biomass but also as a potential source of bioactive compounds. The main bioactive compounds found in wood are polyphenols, terpenes, polysaccharides, organic compounds, fatty acids, and alkaloids. Polyphenols are the most ubiquitous compounds in wood. Large amounts of hydroxytyrosol (up to 25 g/kg dw), resveratrol (up to 66 g/kg dw), protocatechuic acid (up to 16.4 g/kg), and proanthocyanins (8.5 g/kg dw) have been found in the wood from olive trees, grapevines, almond trees and plum trees, respectively. The bioactivity of these compounds has been demonstrated at lower concentrations, mainly in vitro studies. Bioactive compounds present antioxidant, antimicrobial, antifungal, biostimulant, anti-inflammatory, cardioprotective, and anticarcinogenic properties, among others. Therefore, wood extracts might have several applications in agriculture, medicine, and the food, pharmaceutical, nutraceutical, and cosmetics industries. For example, olive tree wood extract reduced thrombin-induced platelet aggregation in vitro; grapevine tree wood extract acts a preservative in wine, replacing SO₂; chestnut tree wood extract has antifungal properties on postharvest pathogens in vitro; and stone tree wood extracts are used for aging both wines and brandies. Moreover, the use of wood waste contributes to the move towards both a more sustainable development and a circular economy.

Resveratrol and cyclodextrins, an easy alliance: Applications in nanomedicine, green chemistry and biotechnology

Most drugs or the natural substances reputed to display some biological activity are hydrophobic molecules that demonstrate low bioavailability regardless of their mode of absorption. Resveratrol and its derivatives belong to the chemical group of stilbenes; while stilbenes are known to possess very interesting properties, these are limited by their poor aqueous solubility as well as low bioavailability in animals and humans. Among the substances capable of forming nanomolecular inclusion complexes which can be used for drug delivery, cyclodextrins show spectacular physicochemical and biomedical implications in stilbene chemistry for their possible application in nanomedicine. By virtue of their properties, cyclodextrins have also demonstrated their possible use in green chemistry for the synthesis of stilbene glucosylated derivatives with potential applications in dermatology and cosmetics. Compared to chemical synthesis and genetically modified microorganisms, plant cell or tissue systems provide excellent models for obtaining stilbenes in few g/L quantities, making feasible the production of these compounds at a large scale. However, the biosynthesis of stilbenes is only possible in the presence of the so-called elicitor compounds, the most commonly used of which are cyclodextrins. We also report here on the induction of resveratrol production by cyclodextrins or combinatory elicitation with methyljasmonate in plant cell systems as well as the mechanisms by which they are able to trigger a stilbene response. The present article therefore discusses the role of cyclodextrins in stilbene chemistry both at the physico-chemical level as well as the biomedical and biotechnological levels, emphasizing the notion of "easy alliance" between these compounds and stilbenes.

Synthesis, fungicidal activity, and 3D-QSAR of tetrazole derivatives containing phenyloxadiazole moieties

In an effort to discover new agents with good fungicidal activities against CDM (cucumber downy mildew), a series of tetrazole derivatives containing phenyloxadiazole moieties were designed and synthesized. The EC₅₀ values for fungicidal activities against CDM were determined. Bioassay results indicated that most synthesized compounds exhibited potential in vivo fungicidal activity against CDM. A CoMFA (comparative molecular field analysis) model based on the bioactivity was developed to identify some primary structural quality for the efficiency. The values of q² and r² for the established model were 0.791 and 0.982 respectively, which reliability and predict abilities were verified. Three analogues (q3, q4, q5) were designed and synthesized based on the model. All these compounds exhibited significant fungicidal activity on CDM with the EC₅₀ of 1.43, 1.52, 1.77 mg·L^-1. This work could provide a useful instruction for the further structure optimization.

The Role of Polyphenols in Abiotic Stress Response: The Influence of Molecular Structure

Abiotic stressors such as extreme temperatures, drought, flood, light, salt, and heavy metals alter biological diversity and crop production worldwide. Therefore, it is important to know the mechanisms by which plants cope with stress conditions. Polyphenols, which are the largest group of plant-specialized metabolites, are generally recognized as molecules involved in stress protection in plants. This diverse group of metabolites contains various structures, from simple forms consisting of one aromatic ring to more complex ones consisting of large number of polymerized molecules. Consequently, all these molecules, depending on their structure, may show different roles in plant growth, development, and stress protection. In the present review, we aimed to summarize data on how different polyphenol structures influence their biological activity and their roles in abiotic stress responses. We focused our review on phenolic acids, flavonoids, stilbenoids, and lignans.

Phytostilbenes as agrochemicals: biosynthesis, bioactivity, metabolic engineering and biotechnology

Covering: 1976 to 2020. Although constituting a limited chemical family, phytostilbenes represent an emblematic group of molecules among natural compounds. Ever since their discovery as antifungal compounds in plants and their ascribed role in human health and disease, phytostilbenes have never ceased to arouse interest for researchers, leading to a huge development of the literature in this field. Owing to this, the number of references to this class of compounds has reached the tens of thousands. The objective of this article is thus to offer an overview of the different aspects of these compounds through a large bibliography analysis of more than 500 articles. All the aspects regarding phytostilbenes will be covered including their chemistry and biochemistry, regulation of their biosynthesis, biological activities in plants, molecular engineering of stilbene pathways in plants and microbes as well as their biotechnological production by plant cell systems.

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.

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.

Semi-Targeted Metabolomics to Validate Biomarkers of Grape Downy Mildew Infection Under Field Conditions

Grape downy mildew is a devastating disease worldwide and new molecular phenotyping tools are required to detect metabolic changes associated to plant disease symptoms. In this purpose, we used UPLC-DAD-MS-based semi-targeted metabolomics to screen downy mildew symptomatic leaves that expressed oil spots (6 dpi, days post-infection) and necrotic lesions (15 dpi) under natural infections in the field. Leaf extract analyses enabled the identification of 47 metabolites belonging to the primary metabolism including 6 amino acids and 1 organic acid, as well as an important diversity of specialized metabolites including 9 flavonols, 11 flavan-3-ols, 3 phenolic acids, and stilbenoids with various degree of polymerization (DP) including 4 stilbenoids DP1, 8 stilbenoids DP2, and 4 stilbenoids DP3. Principal component analysis (PCA) was applied as unsupervised multivariate statistical analysis method to reveal metabolic variables that were affected by the infection status. Univariate and multivariate statistics revealed 33 and 27 metabolites as relevant infection biomarkers at 6 and 15 dpi, respectively. Correlation-based networks highlighted a general decrease of flavonoid-related metabolites, whereas stilbenoid DP1 and DP2 concentrations increased upon downy mildew infection. Stilbenoids DP3 were identified only in necrotic lesions representing late biomarkers of downy mildew infection.

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.

Metabolite profiling during graft union formation reveals the reprogramming of primary metabolism and the induction of stilbene synthesis at the graft interface in grapevine

BACKGROUND

Grafting with rootstocks is essential for the culture of many perennial fruit crops and is increasing being used in the production of annual fruits and vegetables. Our previous work based on microarrays showed that transcripts encoding enzymes of both primary and secondary metabolism were differentially expressed during graft union formation in both homo-grafts (a genotype grafted with itself) and hetero-grafts (two different genotypes grafted together). The aim of this study was to profile primary and secondary metabolites, and quantify the activity of phenylalanine ammonia lyase (PAL) and neutral invertase (NI) in the scion and rootstock tissues and the graft interface of homo and hetero-grafts of grapevine 1 month after grafting. Table-top grafting was done on over-wintering stems (canes) of grapevine and the graft interface tissues (containing some woody stem tissues and callus) were compared to the surrounding rootstock and scion tissues. The objective was to identify compounds involved in graft union formation and hetero-grafting responses.

RESULTS

A total of 54 compounds from primary and secondary metabolism (19 amino acids, five primary and 30 secondary compounds metabolites) and the activity of two enzymes were measured. The graft interface was associated with an increase in the accumulation of the branched-chain amino acids, basic amino acids, certain stilbene compounds and higher PAL and NI activity in comparison to the surrounding woody stem tissues. Some amino acids and stilbenes were identified as being accumulated differently between the graft interfaces of the scion/rootstock combinations in a manner which was unrelated to their concentrations in the surrounding woody stem tissues.

CONCLUSIONS

This study revealed the modification of primary metabolism to support callus cell formation and the stimulation of stilbene synthesis at the graft interface, and how these processes are modified by hetero-grafting. Knowledge of the metabolites and/or enzymes required for successful graft union formation offer us the potential to identify markers that could be used by nurseries and researchers for selection and breeding purposes.

Exhibition of Local but Not Systemic Induced Phenolic Defenses in Vitis vinifera L. Affected by Brown Wood Streaking, Grapevine Leaf Stripe, and Apoplexy (Esca Complex)

Balance between constitutive and induced responses provides plants flexibility to cope with biotic stresses. This study tested the hypothesis that invasion of grapevine wood by esca-associated fungi induces the production of defensive compounds as part of locally- and systemically-induced responses. In a vineyard, different symptomatic expressions of "Esca complex" in Vitis vinifera L. 'Malvasia' were evaluated in annual inspections. Then, levels of phenolics and fatty acids were determined in asymptomatic leaves of brown wood streaking (BWS) and grapevine leaf stripe (GLSD) vines, and in symptomatic leaves of GLSD and apoplectic vines; the results were compared with levels in healthy vines. In asymptomatic leaves of BWS and some GLSD vines, levels of phenolics decreased, independent of the total phenolic group. Such responses were usually associated with an increase in levels of linoleic, γ-linolenic and arachidonic acids, well-known signal transduction mediators. In symptomatic leaves, levels of phenolics increased, which is consistent with a locally-induced response; the onset of symptoms coincided with the highest increases e.g., 35% for quercetin-3-O-glucuronide. Thus, the long latency period between trunk invasion by fungi and visible foliar damage and the year-to-year fluctuation in symptomatic expressions observed with "Esca complex" might be partially attributed to a better utilization of constitutive defenses.

Strategies to Improve Resveratrol Systemic and Topical Bioavailability: An Update

In recent years, a great deal of attention has been paid to natural compounds due to their many biological effects. Polyphenols are a class of plant derivatives that have been widely investigated for preventing and treating many oxidative stress-related pathological conditions, such as neurodegenerative and cardiovascular diseases, cancer, diabetes mellitus and inflammation. Among these polyphenols, resveratrol (RSV) has attracted considerable interest owing to its high antioxidant and free radical scavenging activities. However, the poor water solubility and rapid metabolism of RSV lead to low bioavailability, thus limiting its clinical efficacy. After discussing the main biochemical mechanisms involved in RSV biological activities, this review will focus on the strategies attempted to improve RSV effectiveness, both for systemic and for topical administration. In particular, technological approaches involving RSV incorporation into different delivery systems such as liposomes, polymeric and lipid nanoparticles, microemulsions and cyclodextrins will be illustrated, highlighting their potential clinical applications. In addition, chemical modifications of this antioxidant aimed at improving its physicochemical properties will be described along with the results of in vitro and in vivo studies.

Dual Mode of Action of Grape Cane Extracts against Botrytis cinerea

Crude extracts of Vitis vinifera canes represent a natural source of stilbene compounds with well characterized antifungals properties. In our trials, exogenous application of a stilbene extract (SE) obtained from grape canes on grapevine leaves reduces the necrotic lesions caused by Botrytis cinerea. The SE showed to possess a direct antifungal activity by inhibiting the mycelium growth. The activation of some grapevine defense mechanism was also investigated. H₂O₂ production and activation of mitogen-activated protein kinase (MAPK) phosphorylation cascades as well as accumulation of stilbenoid phytoalexins were explored on grapevine cell suspension. Moreover, the transcription of genes encoding for proteins affecting defense responses was analyzed on grapevine plants. The SE induced some grapevine defense mechanisms including MAPK activation, and the expression of pathogenesis-related (PR) genes and of a gene encoding the glutathione-S-transferase 1 ( GST1) . By contrast, treatment of grapevine leaves with SE negatively regulates de novo stilbene production.

Vineyard evaluation of stilbenoid-rich grape cane extracts against downy mildew: a large-scale study

BACKGROUND

Plasmopara viticola control in organic viticulture requires copper-based fungicides with harmful effects on health and the environment. Plant extracts represent a biorational eco-friendly alternative to copper. The aim of this study was to evaluate the potential of stilbenoid-rich grape cane extract (GCE) against downy mildew on three cultivars over 3 years following natural downy mildew infection.

RESULTS

Over all field trials, GCE treatments showed an average reduction in disease incidence of -35% and -38% on leaves and clusters, respectively. The average reduction in disease severity was -35% and -43% on leaves and clusters, respectively. Under artificial downy mildew infection, GCE efficacy corresponded to 1 g L^-1 of copper. Neither phytotoxicity nor adverse effects on auxiliary fauna were observed after treatment with GCE.

CONCLUSION

Because few or no biocontrol agents are active alone against P. viticola, GCE is a promising alternative to copper-based fungicides. Grape canes, an abundant by-product of viticulture, have great potential for valorization as a biocontrol agent for sustainable viticulture. © 2018 Society of Chemical Industry.

Wood and roots of major grapevine cultivars and rootstocks: A comparative analysis of stilbenes by UHPLC-DAD-MS/MS and NMR

INTRODUCTION

Grapevine wood and roots are by-products obtained during vineyard management. This plentiful biomass is known to be rich in stilbenes and can be used as a source of high-value compounds as well as active natural extracts. However, the stilbenes in grapevine wood and roots from different cultivars and rootstocks remain to be characterized.

OBJECTIVE

The present study investigated the stilbene content of eight major Vitis vinifera cultivars and six different rootstocks. In addition, the distribution of stilbenes was established for each of seven parts into which the plants were sub-divided.

METHODOLOGY

For stilbene characterization and quantification purposes, an ultra-high performance liquid chromatography-diode array detector-mass spectrometry (UHPLC-DAD-MS/MS) analysis of different samples was carried out. Moreover, structural data of stilbenes was unambiguously studied by nuclear magnetic resonance (NMR) spectra.

RESULTS

Whatever the cultivar/rootstock combination, stilbenes were found to be oligomerized from the aerial part to the root system. Furthermore, stilbene content varied widely depending on the cultivars and rootstocks. For instance, the cultivars Merlot, Tannat and Gamay noir were the richest in stilbenes while the rootstocks Gravesac, Fercal and 3390C contained the highest amounts.

CONCLUSION

These findings provide insight into the knowledge that major grapevine cultivars and rootstocks can be used as a potential source of complex stilbenes.

The Rpv3-3 Haplotype and Stilbenoid Induction Mediate Downy Mildew Resistance in a Grapevine Interspecific Population

The development of new resistant varieties to the oomycete Plasmopara viticola (Berk.& Curt) is a promising way to combat downy mildew (DM), one of the major diseases threatening the cultivated grapevine (Vitis vinifera L.). Taking advantage of a segregating population derived from "Merzling" (a mid-resistant hybrid) and "Teroldego" (a susceptible landrace), 136 F1 individuals were characterized by combining genetic, phenotypic, and gene expression data to elucidate the genetic basis of DM resistance and polyphenol biosynthesis upon P. viticola infection. An improved consensus linkage map was obtained by scoring 192 microsatellite markers. The progeny were screened for DM resistance and production of 42 polyphenols. QTL mapping showed that DM resistance is associated with the herein named Rpv3-3 specific haplotype and it identified 46 novel metabolic QTLs linked to 30 phenolics-related parameters. A list of the 95 most relevant candidate genes was generated by specifically exploring the stilbenoid-associated QTLs. Expression analysis of 11 genes in Rpv3-3 +/- genotypes displaying disparity in DM resistance level and stilbenoid accumulation revealed significant new candidates for the genetic control of stilbenoid biosynthesis and oligomerization. These overall findings emphasized that DM resistance is likely mediated by the major Rpv3-3 haplotype and stilbenoid induction.

Neuroprotective Mechanisms of Resveratrol in Alzheimer's Disease: Role of SIRT1

Alzheimer's disease (AD) is a progressive and neurodegenerative disorder of the cortex and hippocampus, which eventually leads to cognitive impairment. Although the etiology of AD remains unclear, the presence of β-amyloid (Aβ) peptides in these learning and memory regions is a hallmark of AD. Therefore, the inhibition of Aβ peptide aggregation has been considered the primary therapeutic strategy for AD treatment. Many studies have shown that resveratrol has antioxidant, anti-inflammatory, and neuroprotective properties and can decrease the toxicity and aggregation of Aβ peptides in the hippocampus of AD patients, promote neurogenesis, and prevent hippocampal damage. In addition, the antioxidant activity of resveratrol plays an important role in neuronal differentiation through the activation of silent information regulator-1 (SIRT1). SIRT1 plays a vital role in the growth and differentiation of neurons and prevents the apoptotic death of these neurons by deacetylating and repressing p53 activity; however, the exact mechanisms remain unclear. Resveratrol also has anti-inflammatory effects as it suppresses M1 microglia activation, which is involved in the initiation of neurodegeneration, and promotes Th2 responses by increasing anti-inflammatory cytokines and SIRT1 expression. This review will focus on the antioxidant and anti-inflammatory neuroprotective effects of resveratrol, specifically on its role in SIRT1 and the association with AD pathophysiology.

Phenolic Compounds Characteristic of the Mediterranean Diet in Mitigating Microglia-Mediated Neuroinflammation

Neuroinflammation is a pathological feature of quite a number of Central Nervous System diseases such as Alzheimer and Parkinson's disease among others. The hallmark of brain neuroinflammation is the activation of microglia, which are the immune resident cells in the brain and represents the first line of defense when injury or disease occur. Microglial activated cells can adopt different phenotypes to carry out its diverse functions. Thus, the shift into pro-inflammatory/neurotoxic or anti-inflammatory/neuroprotective phenotypes, depending of the brain environment, has totally changed the understanding of microglia in neurodegenerative disease. For this reason, novel therapeutic strategies which aim to modify the microglia polarization are being developed. Additionally, the understanding of how nutrition may influence the prevention and/or treatment of neurodegenerative diseases has grown greatly in recent years. The protective role of Mediterranean diet (MD) in preventing neurodegenerative diseases has been reported in a number of studies. The Mediterranean dietary pattern includes as distinctive features the moderate intake of red wine and extra virgin olive oil, both of them rich in polyphenolic compounds, such as resveratrol, oleuropein and hydroxytyrosol and their derivatives, which have demonstrated anti-inflammatory effects on microglia on in vitro studies. This review summarizes our understanding of the role of dietary phenolic compounds characteristic of the MD in mitigating microglia-mediated neuroinflammation, including explanation regarding their bioavailability, metabolism and blood-brain barrier.

Oligostilbenoids in Vitis vinifera L. Pinot Noir grape cane extract: Isolation, characterization, in vitro antioxidant capacity and anti-proliferative effect on cancer cells

The following oligostilbenoids were isolated from extracts of Vitis vinifera L. Pinot Noir grape canes produced at a pilot-plant scale: (E)-ε-viniferin, (E)-resveratrol, (E)-piceatannol, ampelopsin A, vitisin B, pallidol, (E)-δ-viniferin, (E)-ω-viniferin, (E)-trans-cis-miyabenol C, isorhapontigenin, scirpusin A, and a new isomer named isoscirpusin A. The antioxidant capacity of the isolated stilbenoids was studied by three different assays, and their 50% inhibition concentration (IC₅₀) against cancer cells was determined by MTT reduction assay. Besides (E)-resveratrol, stilbenoids have outstanding antioxidant capacity in the ORAC-FL assay. The strongest antiproliferative effect was observed for (E)-piceatannol and ampelopsin A against the bladder cancer cell line J82. (E)-Piceatannol has inhibitory effect on human lung cancer SK-MES-1 cells. Moreover, the whole extract has antiproliferative effect on all tested cell lines. In conclusion, beside (E)-resveratrol, grape cane extract contains oligostilbenoids with potential health benefits. This underexploited viticultural residue has the potential to produce valuable phytochemicals or ingredients in functional foods.

Pinus pinaster Knot: A Source of Polyphenols against Plasmopara viticola

Pine knot extract from Pinus pinaster byproducts was characterized by UHPLC-DAD-MS and NMR. Fourteen polyphenols divided into four classes were identified as follows: lignans (nortrachelogenin, pinoresinol, matairesinol, isolariciresinol, secoisolariciresinol), flavonoids (pinocembrin, pinobanksin, dihydrokaempferol, taxifolin), stilbenes (pinosylvin, pinosylvin monomethyl ether, pterostilbene), and phenolic acids (caffeic acid, ferulic acid). The antifungal potential of pine knot extract, as well as the main compounds, was tested in vitro against Plasmopara viticola. The ethanolic extract showed a strong antimildew activity. In addition, pinosylvins and pinocembrin demonstrated significant inhibition of zoospore mobility and mildew development. These findings strongly suggest that pine knot is a potential biomass that could be used as a natural antifungal product.

Identification of Biomarkers for Defense Response to Plasmopara viticola in a Resistant Grape Variety

Downy mildew (Plasmopara viticola) is one of the most destructive diseases of the cultivated species Vitis vinifera. The use of resistant varieties, originally derived from backcrosses of North American Vitis spp., is a promising solution to reduce disease damage in the vineyards. To shed light on the type and the timing of pathogen-triggered resistance, this work aimed at discovering biomarkers for the defense response in the resistant variety Bianca, using leaf discs after inoculation with a suspension of P. viticola. We investigated primary and secondary metabolism at 12, 24, 48, and 96 h post-inoculation (hpi). We used methods of identification and quantification for lipids (LC-MS/MS), phenols (LC-MS/MS), primary compounds (GC-MS), and semi-quantification for volatile compounds (GC-MS). We were able to identify and quantify or semi-quantify 176 metabolites, among which 53 were modulated in response to pathogen infection. The earliest changes occurred in primary metabolism at 24-48 hpi and involved lipid compounds, specifically unsaturated fatty acid and ceramide; amino acids, in particular proline; and some acids and sugars. At 48 hpi, we also found changes in volatile compounds and accumulation of benzaldehyde, a promoter of salicylic acid-mediated defense. Secondary metabolism was strongly induced only at later stages. The classes of compounds that increased at 96 hpi included phenylpropanoids, flavonols, stilbenes, and stilbenoids. Among stilbenoids we found an accumulation of ampelopsin H + vaticanol C, pallidol, ampelopsin D + quadrangularin A, Z-miyabenol C, and α-viniferin in inoculated samples. Some of these compounds are known as phytoalexins, while others are novel biomarkers for the defense response in Bianca. This work highlighted some important aspects of the host response to P. viticola in a commercial variety under controlled conditions, providing biomarkers for a better understanding of the mechanism of plant defense and a potential application in field studies of resistant varieties.

Variability in the Content of Trans-Resveratrol, Trans-ε-Viniferin and R2-Viniferin in Grape Cane of Seven Vitis vinifera L. Varieties during a Three-Year Study

Grape canes are a waste product from viticulture that show potential as an industrially extractable source of stilbenes, which are valuable for medical and other purposes. In this work, grape canes collected in three consecutive years (2014–2016) at six different places in South Moravia, Czech Republic were extracted, and the contents of trans-resveratrol, trans-ε-viniferin, and r2-viniferin were determined by high-performance liquid chromatography. The study included three blue grape varieties of Vitis vinifera L. (Cabernet Moravia, Blaufränkisch, and Piwi variety Laurot) and four white grape varieties (Chardonnay, Green Veltliner, Piwi variety Hibernal, and Piwi variety Malverina). From the viewpoint of producing extracts with high stilbenes content, the Hibernal variety is clearly the best. The mean amounts of the stilbenes for this variety at all localities and for all three years were 4.99 g/kg for trans-resveratrol, 3.24 g/kg for trans-ε-viniferin, and 1.73 g/kg for r2-viniferin. The influence of vintage, locality, and variety on the amounts of stilbenes was studied using PCA analysis. In contrast to expectations, there was no strong impact of locality on stilbenes content. The differences were varietal for most varieties, regardless of the area of cultivation. Laurot and Hibernal varieties did differ significantly in that respect, however, as they exhibited clear dependence on location.