Isorhapontin

Targeted UPLC-QqQ-MS/MS profiling of phenolic compounds for differentiation of monovarietal wines and corroboration of particular varietal typicity concepts.[Pubmed:31357018]

Food Chem. 2019 Dec 1;300:125251.

Targeted ultra-performance liquid chromatography with triple quadrupole mass spectrometric (UPLC-QqQ-MS/MS) profiling of phenolic compounds was utilised for varietal differentiation of 173 wines made from four red and six white grape varieties. Among 58 identified phenols many were found relevant as exclusive or partial discriminators between wines. Successful differentiation models were built by linear discriminant analysis with the percentage of correct classification higher than 95% in all cases, with peonidin 3-(6''-acetyl)-glucoside and taxifolin as the most potent differentiators between red, and cis-piceid between white monovarietal wines. Diverse typical colour attributes among the monovarietal wines were tentatively ascribed to the variations in the composition of monomeric anthocyanins. Plavac mali red wine exhibited the most specific composition, and its most typical samples were distinguished by the abundance in trans-fertaric acid, Isorhapontin, phlorizin, quercetin 3-rhamnoside, and myricitrin. Despite positive correlations with particular astringent flavonols, the typical astringency of Plavac mali wine remained unresolved.

Hydroxystilbene Glucosides Are Incorporated into Norway Spruce Bark Lignin.[Pubmed:31023874]

Plant Physiol. 2019 Jul;180(3):1310-1321.

Recent investigations have revealed that, in addition to monolignols, some phenolic compounds derived from the flavonoid and hydroxystilbene biosynthetic pathways can also function as true lignin monomers in some plants. In this study, we found that the hydroxystilbene glucosides Isorhapontin (isorhapontigenin-O-glucoside) and, at lower levels, astringin (piceatannol-O-glucoside) and piceid (resveratrol-O-glucoside) are incorporated into the lignin polymer in Norway spruce (Picea abies) bark. The corresponding aglycones isorhapontigenin, piceatannol, and resveratrol, along with glucose, were released by derivatization followed by reductive cleavage, a chemical degradative method that cleaves beta-ether bonds in lignin, indicating that the hydroxystilbene glucosides are (partially) incorporated into the lignin structure through beta-ether bonds. Two-dimensional NMR analysis confirmed the occurrence of hydroxystilbene glucosides in this lignin, and provided additional information regarding their modes of incorporation into the polymer. The hydroxystilbene glucosides, particularly Isorhapontin and astringin, can therefore be considered genuine lignin monomers that participate in coupling and cross-coupling reactions during lignification in Norway spruce bark.

Optimization of Bioactive Polyphenols Extraction from Picea Mariana Bark.[Pubmed:29194377]

Molecules. 2017 Dec 1;22(12). pii: molecules22122118.

Reported for its antioxidant, anti-inflammatory and non-toxicity properties, the hot water extract of Picea mariana bark was demonstrated to contain highly valuable bioactive polyphenols. In order to improve the recovery of these molecules, an optimization of the extraction was performed using water. Several extraction parameters were tested and extracts obtained analyzed both in terms of relative amounts of different phytochemical families and of individual molecules concentrations. As a result, low temperature (80 degrees C) and low ratio of bark/water (50 mg/mL) were determined to be the best parameters for an efficient polyphenol extraction and that especially for low molecular mass polyphenols. These were identified as stilbene monomers and derivatives, mainly stilbene glucoside Isorhapontin (up to 12.0% of the dry extract), astringin (up to 4.6%), resveratrol (up to 0.3%), isorhapontigenin (up to 3.7%) and resveratrol glucoside piceid (up to 3.1%) which is here reported for the first time for Picea mariana. New stilbene derivatives, piceasides O and P were also characterized herein as new Isorhapontin dimers. This study provides novel information about the optimal extraction of polyphenols from black spruce bark, especially for highly bioactive stilbenes including the trans-resveratrol.

Association genetics of phenolic needle compounds in Norway spruce with variable susceptibility to needle bladder rust.[Pubmed:28190131]

Plant Mol Biol. 2017 Jun;94(3):229-251.

KEY MESSAGE: Accumulation of phenolic needle metabolites in Norway spruce is regulated by many genes with small and additive effects and is correlated with the susceptibility against fungal attack. Norway spruce accumulates high foliar concentrations of secondary phenolic metabolites, with important functions for pathogen defence responses. However, the molecular genetic basis underlying the quantitative variation of phenolic compounds and their role in enhanced resistance of spruce to infection by needle bladder rust are unknown. To address these questions, a set of 1035 genome-wide single nucleotide polymorphisms (SNPs) was associated to the quantitative variation of four simple phenylpropanoids, eight stilbenes, nine flavonoids, six related arithmetic parameters and the susceptibility to infection by Chrysomyxa rhododendri in an unstructured natural population of Norway spruce. Thirty-one significant genetic associations for the flavonoids gallocatechin, kaempferol 3-glucoside and quercetin 3-glucoside and the stilbenes resveratrol, piceatannol, astringin and Isorhapontin were discovered, explaining 22-59% of phenotypic variation, and indicating a regulation of phenolic accumulation by many genes with small and additive effects. The phenolics profile differed between trees with high and low susceptibility to the fungus, underlining the importance of phenolic compounds in the defence mechanisms of Norway spruce to C. rhododendri. Results highlight the utility of association studies in non-model tree species and may enable marker-assisted selection of Norway spruce adapted to severe pathogen attack.

Stilbene biosynthesis in the needles of spruce Picea jezoensis.[Pubmed:27576046]

Phytochemistry. 2016 Nov;131:57-67.

Stilbenes are valuable phenolic compounds that are synthesized in plants via the phenylpropanoid pathway where stilbene synthase (STS) directly catalyzes resveratrol or pinosylvin formation. Currently, there is a lack of information about the stilbene biosynthetic pathway in spruce (Picea). Resveratrol and piceatannol derivatives have been detected in the spruce bark, needles, and roots. We analyzed seasonal variation in stilbene spectrum and content in the needles of different ages of one tree of spruce Picea jezoensis. HPLC analysis revealed the presence of nine stilbenes: t- and cis-astringin, t- and cis-piceid, t- and cis-Isorhapontin, and t-piceatannol were present in amounts of 0.01-6.07 mg/g of dry weight (DW), while t-isorhapontigenin and t-resveratrol were present in traces (0.001-0.312 mug/g DW). T-astringin prevailed over other stilbenoid compounds (66-86% of all stilbenes). The highest total stilbene content was detected in one-year-old needles collected in the autumn and spring (5.4-7.77 mg/g DW). We previously cloned and sequenced full-length cDNAs of the four STS transcripts (PjSTS1a, PjSTS1b, PjSTS2, and PjSTS3) of P. jezoensis. This study presents a detailed analysis of seasonal variations in PjSTS1a, 1b, 2, and 3 transcript levels in the needles of P. jezoensis of different ages using qRT-PCR. PjSTS1a and PjSTS1b transcription was higher in the needles collected in the autumn, spring, or summer than in the winter. PjSTS2 was actively transcribed in the needles of all ages collected in the winter, spring, and summer. PjSTS3 expression did not significantly change during the year and did not depend on the age of the needles. Therefore, the data show that high levels of the stilbene glucosides and PjSTS expression are present in the needles of P. jezoensis.

Insight into the Presence of Stilbenes in Medicinal Plants Traditionally Used in Croatian Folk Medicine.[Pubmed:27534129]

Nat Prod Commun. 2016 Jun;11(6):833-5.

Over the last years, great interest has arisen concerning plant stilbenes, especially resveratrol, which has a whole spectrum of positive biological activities. In this study, we investigated the presence of resveratrol monomers (trans- and cis- form) and naturally occurring derivatives of trans-resveratrol (piceid, astringin and Isorhapontin) in phenolic extracts of twenty medicinal plants traditionally used in Croatian folk medicine. The investigated compounds were present in the samples, in free form or as glucosides, and the highest share was found in immortelle, common yarrow and Lamiaceae plants. The obtained results indicate that biological activity of selected medicinal plants can be related to the presence of this valuable group of phytochemicals.

In Planta Localization of Stilbenes within Picea abies Phloem.[Pubmed:27531441]

Plant Physiol. 2016 Oct;172(2):913-928.

Phenolic stilbene glucosides (astringin, Isorhapontin, and piceid) and their aglycons commonly accumulate in the phloem of Norway spruce (Picea abies). However, current knowledge about the localization and accumulation of stilbenes within plant tissues and cells remains limited. Here, we used an innovative combination of novel microanalytical techniques to evaluate stilbenes in a frozen-hydrated condition (i.e. in planta) and a freeze-dried condition across phloem tissues. Semiquantitative time-of-flight secondary ion-mass spectrometry imaging in planta revealed that stilbenes were localized in axial parenchyma cells. Quantitative gas chromatography analysis showed the highest stilbene content in the middle of collapsed phloem with decreases toward the outer phloem. The same trend was detected for soluble sugar and water contents. The specimen water content may affect stilbene composition; the glucoside-to-aglycon ratio decreased slightly with decreases in water content. Phloem chemistry was correlated with three-dimensional structures of phloem as analyzed by microtomography. The outer phloem was characterized by a high volume of empty parenchyma, reduced ray volume, and a large number of axial parenchyma with porous vacuolar contents. Increasing porosity from the inner to the outer phloem was related to decreasing compactness of stilbenes and possible secondary oxidation or polymerization. Our results indicate that aging-dependent changes in phloem may reduce cell functioning, which affects the capacity of the phloem to store water and sugar, and may reduce the defense potential of stilbenes in the axial parenchyma. Our results highlight the power of using a combination of techniques to evaluate tissue- and cell-level mechanisms involved in plant secondary metabolite formation and metabolism.

Rapid chemical characterisation of stilbenes in the root bark of Norway spruce by off-line HPLC/DAD-NMR.[Pubmed:24777944]

Phytochem Anal. 2014 Nov-Dec;25(6):529-36.

INTRODUCTION: Stilbenes are plant secondary metabolites that have shown promising and varied biological activities. Stilbenes are presently actively studied for the exploitation of this primary raw material resource, involving the concept of biorefining. Methods for the rapid discovery of new and known stilbene structures from various plant sources are thus keenly sought. OBJECTIVE: To establish a simple and rapid technique of off-line HPLC with a diode-array detector (DAD) and NMR for the unambiguous structural elucidation of stilbene structures in the root bark of Norway spruce [Picea abies (L.) Karst.]. MATERIAL AND METHODS: The stilbene containing fraction was extracted from the plant bark with an ethanol:water mixture (95:5, v/v) preceded by defatting of hydrophobic compounds with n-hexane using the accelerated solvent extraction technique. A portion of the ethanol-water soluble extract was hydrolysed with beta-glucosidase to prepare stilbene aglycones. The extracts were further purified and enriched using a polymeric adsorbent. Stilbene-enriched extracts were directly characterised by off-line HPLC/DAD-NMR in conjunction with HPLC/DAD and HPLC/DAD with electrospray ionisation MS(n). RESULTS: Trans-Isorhapontin and trans-astringin were identified as the major, and trans-piceid as a minor, stilbene glucosides of the bark of roots of Picea abies. Not only stilbene glucosides but also the corresponding stilbene aglycones, such as trans-resveratrol, trans-piceatannol and trans-isorhapontigenin, were rapidly identified from the hydrolysed extract. The acquired heteronuclear single-quantum coherence and heteronuclear multiple bond correlation spectra were used to assign the complete carbon NMR chemical shifts of trans-Isorhapontin and trans-astringin without the need of acquiring a (13)C-NMR spectrum. CONCLUSION: The off-line HPLC/DAD-NMR method is expedient for the unambiguous identication of structurally similar stilbenes in plant extracts.

The antimicrobial effects of wood-associated polyphenols on food pathogens and spoilage organisms.[Pubmed:23624538]

Int J Food Microbiol. 2013 Jun 3;164(1):99-107.

The antimicrobial effects of the wood-associated polyphenolic compounds pinosylvin, pinosylvin monomethyl ether, astringin, piceatannol, Isorhapontin, isorhapontigenin, cycloXMe, dHIMP, ArX, and ArXOH were assessed against both Gram-negative (Salmonella) and Gram-positive bacteria (Listeria monocytogenes, Staphylococcus epidermidis, Staphylococcus aureus) and yeasts (Candida tropicalis, Saccharomyces cerevisiae). Particularly the stilbenes pinosylvin, its monomethyl ether and piceatannol demonstrated a clear antimicrobial activity, which in the case of pinosylvin was present also in food matrices like sauerkraut, gravlax and berry jam, but not in milk. The destabilization of the outer membrane of Gram-negative microorganisms, as well as interactions with the cell membrane, as indicated by the NPN uptake and LIVE/DEAD viability staining experiments, can be one of the specific mechanisms behind the antibacterial action. L. monocytogenes was particularly sensitive to pinosylvin, and this effect was also seen in L. monocytogenes internalized in intestinal Caco2 cells at non-cytotoxic pinosylvin concentrations. In general, the antimicrobial effects of pinosylvin were even more prominent than those of a related stilbene, resveratrol, well known for its various bioactivities. According to our results, pinosylvin could have potential as a natural disinfectant or biocide in some targeted applications.

Localization of phenolics in phloem parenchyma cells of Norway spruce (Picea abies).[Pubmed:23150460]

Chembiochem. 2012 Dec 21;13(18):2707-13.

Norway spruce (Picea abies) bark contains specialized phloem parenchyma cells that swell and change their contents upon attack by the bark beetle Ips typographus and its microbial associate, the blue stain fungus Ceratocystis polonica. These cells exhibit bright autofluorescence after treatment with standard aldehyde fixatives, and so have been postulated to contain phenolic compounds. Laser microdissection of spruce bark sections combined with cryogenic NMR spectroscopy demonstrated significantly higher concentrations of the stilbene glucoside astringin in phloem parenchyma cells than in adjacent sieve cells. After infection by C. polonica, the flavonoid (+)-catechin also appeared in phloem parenchyma cells and there was a decrease in astringin content compared to cells from uninfected trees. Analysis of whole-bark extracts confirmed the results obtained from the cell extracts and revealed a significant increase in dimeric stilbene glucosides, both astringin and Isorhapontin derivatives (piceasides A to H), in fungus-infected versus uninfected bark that might explain the reduction in stilbene monomers. Phloem parenchyma cells thus appear to be a principal site of phenolic accumulation in spruce bark.

Inhibition of LFA-1/ICAM-1-mediated cell adhesion by stilbene derivatives from Rheum undulatum.[Pubmed:23139127]

Arch Pharm Res. 2012 Oct;35(10):1763-70.

Six stilbenes were isolated from the methanol extract of Rheum undulatum rhizomes by bioactivity-guided fractionation. The structures of the compounds were determined by spectroscopic analysis ((1)H-, (13)C-NMR and MS), to be desoxyrhapontigenin (1), rhapontigenin (2), trans-resveratrol (3), piceatannol (4), piceatannol-3'-O-beta-D-glucopyranoside (5) and Isorhapontin (6). Compounds 1-4 inhibited the direct binding between sICAM-1 and LFA-1 of the THP-1 cells in a dose-dependent manner with IC(50) values of 50.1, 25.4, 33.4 and 45.9 muM, respectively. On the other hand, the other compounds 5 and 6 with a glucose moiety in each molecule did not show any inhibitory activity in the cell adhesion assay (IC(50) values of >100.0 muM). Compounds 2, 3 and 4 also had an inhibitory effect on direct binding between sVCAM-1 and VLA-4 of THP-1 cells. This suggests that the stilbenes from Rheum undulatum rhizomes are good candidates for therapeutic strategies towards inflammation.

Extraction of antioxidants from spruce (Picea abies) bark using eco-friendly solvents.[Pubmed:22144103]

Phytochem Anal. 2012 Jan-Feb;23(1):1-11.

INTRODUCTION: Antioxidants are known to avert oxidation processes and they are found in trees and other plant materials. Tree bark is a major waste product from paper pulp industries; hence it is worthwhile to develop an extraction technique to extract the antioxidants. OBJECTIVE: To develop a fast and environmentally sustainable extraction technique for the extraction of antioxidants from bark of spruce (Picea abies) and also to identify the extracted antioxidants that are abundant in spruce bark. METHODOLOGY: A screening experiment that involved three different techniques was conducted to determine the best technique to extract antioxidants. The antioxidant capacity of the extracts was determined with DPPH (2,2-diphenyl-1-picrylhydrazyl) assay. Pressurised fluid extraction (PFE) turned out to be the best technique and a response surface design was therefore utilised to optimise PFE. Furthermore, NMR and HPLC-DAD-MS/MS were applied to identify the extracted antioxidants. RESULTS: PFE using water and ethanol as solvent at 160 and 180 degrees C, respectively, gave extracts of the highest antioxidant capacity. Stilbene glucosides such as Isorhapontin, piceid and astringin were identified in the extracts. CONCLUSION: The study has shown that PFE is a fast and environmentally sustainable technique, using water and ethanol as solvent for the extraction of antioxidants from spruce bark.

Biosynthesis of the major tetrahydroxystilbenes in spruce, astringin and isorhapontin, proceeds via resveratrol and is enhanced by fungal infection.[Pubmed:21865488]

Plant Physiol. 2011 Oct;157(2):876-90.

Stilbenes are dibenzyl polyphenolic compounds produced in several unrelated plant families that appear to protect against various biotic and abiotic stresses. Stilbene biosynthesis has been well described in economically important plants, such as grape (Vitis vinifera), peanut (Arachis hypogaea), and pine (Pinus species). However, very little is known about the biosynthesis and ecological role of stilbenes in spruce (Picea), an important gymnosperm tree genus in temperate and boreal forests. To investigate the biosynthesis of stilbenes in spruce, we identified two similar stilbene synthase (STS) genes in Norway spruce (Picea abies), PaSTS1 and PaSTS2, which had orthologs with high sequence identity in sitka (Picea sitchensis) and white (Picea glauca) spruce. Despite the conservation of STS sequences in these three spruce species, they differed substantially from angiosperm STSs. Several types of in vitro and in vivo assays revealed that the P. abies STSs catalyze the condensation of p-coumaroyl-coenzyme A and three molecules of malonyl-coenzyme A to yield the trihydroxystilbene resveratrol but do not directly form the dominant spruce stilbenes, which are tetrahydroxylated. However, in transgenic Norway spruce overexpressing PaSTS1, significantly higher amounts of the tetrahydroxystilbene glycosides, astringin and Isorhapontin, were produced. This result suggests that the first step of stilbene biosynthesis in spruce is the formation of resveratrol, which is further modified by hydroxylation, O-methylation, and O-glucosylation to yield astringin and Isorhapontin. Inoculating spruce with fungal mycelium increased STS transcript abundance and tetrahydroxystilbene glycoside production. Extracts from STS-overexpressing lines significantly inhibited fungal growth in vitro compared with extracts from control lines, suggesting that spruce stilbenes have a role in antifungal defense.