Stilbene Dimers Research Articles

Study of phenoxy radical couplings using the enzymatic secretome of Botrytis cinerea.

Phenoxy radical coupling reactions are widely used in nature for the synthesis of complex molecules such as lignin. Their use in the laboratory has great potential for the production of high value compounds from the polyphenol family. While the enzymes responsible for the generation of the radicals are well known, the behavior of the latter is still enigmatic and difficult to control in a reaction flask. Previous work in our laboratory using the enzymatic secretome of B. cinerea containing laccases has shown that incubation of stilbenes leads to dimers, while incubation of phenylpropanoids leads to dimers as well as larger coupling products. Building on these previous studies, this paper investigates the role of different structural features in phenoxy radical couplings. We first demonstrate that the presence of an exocyclic conjugated double bond plays a role in the generation of efficient reactions. In addition, we show that the formation of phenylpropanoid trimers and tetramers can proceed via a decarboxylation reaction that regenerates this reactive moiety. Lastly, this study investigates the reactivity of other phenolic compounds: stilbene dimers, a dihydro-stilbene, a 4-O-methyl-stilbene and a simple phenol with the enzymatic secretome of B. cinerea. The observed efficient dimerization reactions consistently correlate with the presence of a para-phenol conjugated to an exocyclic double bond. The absence of this structural feature leads to variable results, with some compounds showing low conversion or no reaction at all. This research has allowed the development of a controlled method for the synthesis of specific dimers and tetramers of phenylpropanoid derivatives and novel stilbene derivatives, as well as an understanding of features that can promote efficient radical coupling reactions.

A new flavonostilbene glycoside and four new stilbene derivatives from the roots of Polygonum multiflorum

One new flavonostilbene glycoside, polygonflavanol C (1), two new dimeric stilbene glycosides, multiflorumiside M and multiflorumiside N (2−3), one new diphenyl ethanol glycoside, (R)-2,3,5,4′-tetrahydroxy-diphenylethanol 2-O-β-D-glucopyranoside (4), and one new deoxybenzoin glycoside, 2,4,3′,5′-tetrahydroxy-6-methyl-deoxybenzoin 2-O-β-D-glucopyranoside (5), together with six known ones (6−11), were isolated from the roots of Polygonum multiflorum. Their structures were elucidated by the comprehensive spectroscopic analyses. In addition, compounds 1 and 7 showed significantly in vitro anti-inflammatory activity.

Polyphenols from Maackia amurensis Heartwood Protect Neuronal Cells from Oxidative Stress and Prevent Herpetic Infection.

Here, we continued the investigation of anti-HSV-1 activity and neuroprotective potential of 14 polyphenolic compounds isolated from Maackia amurensis heartwood. We determined the absolute configurations of asymmetric centers in scirpusin A (13) and maackiazin (10) as 7R,8R and 1″S,2″S, respectively. We showed that dimeric stilbens maackin (9) and scirpusin A (13) possessed the highest anti-HSV-1 activity among polyphenols 1-14. We also studied the effect of polyphenols 9 and 13 on the early stages of HSV-1 infection. Direct interaction with the virus (virucidal activity) was the main mechanism of the antiviral activity of these compounds. The neuroprotective potential of polyphenolic compounds from M. amurensis was studied using models of 6-hydroxydopamine (6-OHDA)-and paraquat (PQ)-induced neurotoxicity. A dimeric stilbene scirpusin A (13) and a flavonoid liquiritigenin (6) were shown to be the most active compounds among the tested polyphenols. These compounds significantly increased the viability of 6-OHDA-and PQ-treated Neuro-2a cells, elevated mitochondrial membrane potential and reduced the intracellular ROS level. We also found that scirpusin A (13), liquiritigenin (6) and retusin (3) considerably increased the percentage of live Neuro-2a cells and decreased the number of early apoptotic cells. Scirpusin A (13) was the most promising compound possessing both anti-HSV-1 activity and neuroprotective potential.

Structurally diverse stilbenes from Gnetum parvifolium and their anti-neuroinflammatory activities

Phytochemical investigation on the aerial parts of Gnetum parvifolium led to the isolation of 15 new and eight known structurally diverse stilbenes. The isolated compounds comprised (E)- or (Z)-stilbene (1–6, 15–20), dihydrostilbene (21), phenylbenzofuran (7, 8, 22), benzylated stilbene (9–11), benzylated stilbene dimer (12), and nitrogen-containing stilbene (13a, 13b, 14) types. The structures of the new compounds (1–12, 13a, 13b, 14) were established through spectroscopic analyses and experimental and calculated ECD data. Compound 12 is the first stilbene dimer connected through a benzyl group. In the anti-neuroinflammatory activity assay, compounds 4, 5, 9–11, 13b, and 16–21 displayed significant inhibitory effects against LPS-induced NO release in BV-2 microglial cells, with IC50 values of 0.35–16.1 μM. Compound 10 had the most potent activity (IC50 = 0.35 μM), and the further research indicated that it could decrease the mRNA levels of iNOS, IL-1β, IL-6, and TNF-α in a dose-dependent manner.

Generation of potent antibacterial compounds through enzymatic and chemical modifications of the trans-δ-viniferin scaffold

Stilbene dimers are well-known for their diverse biological activities. In particular, previous studies have demonstrated the high antibacterial potential of a series of trans-δ-viniferin-related compounds against gram-positive bacteria such as Staphylococcus aureus. The trans-δ-viniferin scaffold has multiple chemical functions and can therefore be modified in various ways to generate derivatives. Here we report the synthesis of 40 derivatives obtained by light isomerization, O-methylation, halogenation and dimerization of other stilbene monomers. The antibacterial activities of all generated trans-δ-viniferin derivatives were evaluated against S. aureus and information on their structure–activity relationships (SAR) was obtained using a linear regression model. Our results show how several parameters, such as the O-methylation pattern and the presence of halogen atoms at specific positions, can determine the antibacterial activity. Taken together, these results can serve as a starting point for further SAR investigations.

Antiviral properties of trans-δ-viniferin derivatives against enveloped viruses

Over the last century, the number of epidemics caused by RNA viruses has increased and the current SARS-CoV-2 pandemic has taught us about the compelling need for ready-to-use broad-spectrum antivirals. In this scenario, natural products stand out as a major historical source of drugs. We analyzed the antiviral effect of 4 stilbene dimers [1 (trans-δ-viniferin); 2 (11’,13’-di-O-methyl-trans-δ-viniferin), 3 (11,13-di-O-methyl-trans-δ-viniferin); and 4 (11,13,11’,13’-tetra-O-methyl-trans-δ-viniferin)] obtained from plant substrates using chemoenzymatic synthesis against a panel of enveloped viruses. We report that compounds 2 and 3 display a broad-spectrum antiviral activity, being able to effectively inhibit several strains of Influenza Viruses (IV), SARS-CoV-2 Delta and, to some extent, Herpes Simplex Virus 2 (HSV-2). Interestingly, the mechanism of action differs for each virus. We observed both a direct virucidal and a cell-mediated effect against IV, with a high barrier to antiviral resistance; a restricted cell-mediated mechanism of action against SARS-CoV-2 Delta and a direct virustatic activity against HSV-2. Of note, while the effect was lost against IV in tissue culture models of human airway epithelia, the antiviral activity was confirmed in this relevant model for SARS-CoV-2 Delta. Our results suggest that stilbene dimer derivatives are good candidate models for the treatment of enveloped virus infections.

Anti-Alzheimer's Activity of Polyphenolic Stilbene-Rich Acetone Fraction of the Oil-Removed Seeds of Passiflora edulis: in Vivo and in Silico Studies.

The stilbene-rich acetone fraction in high yield (6.6 %, PEAS) of Passiflora edulis Sims was prepared and evaluated for neuroprotective activity in murine Alzheimer's disease model induced by aluminum chloride and D-galactose. The phytochemical and HPLC-DAD-MS analysis of the polyphenolic stilbene-rich acetone fraction showed that it contained different stilbenes including trans-piceatannol, scirpusins A-B and cassigarol E. The total phenolic content (TPC) of PEAS was 413.87±1.71 mg GAE eqv/g. The neuroprotective activity of PEAS is typically presented in the Morris water maze-reference Spatial Memory test, where the Alzheimer's mice treated at 100 mg/kg (Alz-ED1) and 200 mg/kg (Alz-ED2) spent less than 47 % and 66 % of the time, respectively, than the Alzheimer's model mice (Alz). Two simple stilbenes, trans-piceatannol and trans-resveratrol, showed selectively inhibitory activity in silico against acetylcholinesterase (AChE). Two stilbene dimers, cassigarol E and scirpusin A, exhibited low nanomolar inhibitory potential against AChE and butyrylcholinesterase (BChE), significantly lower than those of the positive control, donepezil and tacrine. These findings suggest that the stilbenes from P. edulis seeds, particularly the stilbene dimers, warrant further investigation as potential neuroprotective candidates in the prevention of cognitive deficits associated with Alzheimer's disease.

An Arylbenzofuran, Stilbene Dimers, and Prenylated Diels-Alder Adducts as Potent Diabetic Inhibitors from Morus bombycis Leaves.

Morus bombycis has a long history of usage as a treatment for metabolic diseases, especially, diabetes mellitus (DM). Thus, we aimed to isolate and evaluate bioactive constituents derived from M. bombycis leaves for the treatment of DM. According to bioassay-guided isolation by column chromatography, eight compounds were obtained from M. bombycis leaves: two phenolic compounds, p-coumaric acid (1) and chlorogenic acid methyl ester (2), one stilbene, oxyresveratrol (3), two stilbene dimers, macrourin B (4) and austrafuran C (6), one 2-arylbenzofuran, moracin M (5), and two Diels-Alder type adducts, mulberrofuran F (7) and chalcomoracin (8). Among the eight isolated compounds, the anti-DM activity of 3-8 (which possess chemotaxonomic significance in Morus species) was evaluated by inhibition of α-glucosidase, protein tyrosine phosphatase 1B (PTP1B), human recombinant aldose reductase (HRAR), and advanced glycation end-product (AGE) formation as well as by scavenging peroxynitrite (ONOO-), which are crucial therapeutic targets of DM and its complications. Compounds 4 and 6-8 significantly inhibited α-glucosidase, PTP1B, and HRAR enzymes with mixed-type and non-competitive-type inhibition modes. Furthermore, the four compounds had low negative binding energies in both enzymes according to molecular docking simulation, and compounds 3-8 exhibited strong antioxidant capacity by inhibiting AGE formation and ONOO- scavenging. Overall results suggested that the most active stilbene-dimer-type compounds (4 and 6) along with Diels-Alder type adducts (7 and 8) could be promising therapeutic and preventive resources against DM and have the potential to be used as antioxidants, anti-diabetic agents, and anti-diabetic complication agents.

Chiral analysis of E-ε-viniferin enantiomers, towards a new chemotaxonomic marker of the vine.

The accurate characterization of grapevine cultivars (Vitis vinifera) is crucial for grape growers, winemakers, wine sellers, consumers and authorities, considering that mistakes could involve significant damage to the wine economic system. To avoid any misunderstanding, morphological, molecular and chemical tools are developed to positively identify grape varieties. E-ε-viniferin is a stilbene dimer mainly present in the woody part of grapevine and present as a mixture of two enantiomers: (7aR, 8aR)-(-)-E-ε-viniferin (1) and (7aS, 8aS)-(+)-E-ε-viniferin (2). In addition to phenotypic and genotypic approaches, a chemotaxonomic method using E-ε-viniferin enantiomers as chemical markers of grapevine cultivars was investigated. The isolation and purification of E-ε-viniferin enantiomers by preparative high-performance liquid chromatography (HPLC) and chiral HPLC from 14 red and eight white grapevine cane cultivars enabled us to determine the proportion of each enantiomer and therefore to calculate the enantiomeric excess for each variety. The relative abundance of each E-ε-viniferin enantiomer permitted us to distinguish grape varieties, as well as to establish cultivar relationships and patterns through statistical analysis. This pioneering work highlighting the enantiomeric excess of E-ε-viniferin as a chemical marker of grapevine paves the way for further studies to understand what mechanisms are involved in the production of these enantiomers in grapevine. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Bioassay-Guided Isolation of Anti-Inflammatory Constituents of the Subaerial Parts of Cyperus articulatus (Cyperaceae).

Based on data from a previous ethnobotanical study in northern Angola, phytochemical investigations into the methanolic rhizomes and roots extract of Cyperus articulatus, monitored by in vitro assays, resulted in the recovery of 12 sesquiterpenes, 3 stilbenes, 2 phenolic acids, 1 monoterpene, and 1 flavonoid. Among them, 14 compounds were isolated for the first time from this species. Their inhibitory potential against nitric oxide (NO) production, as well as inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression, was evaluated in LPS-treated J774A.1 murine macrophages. Especially, both stilbene dimer trans-scirpusin B and trimer cyperusphenol B showed promising inhibitory activity against the production of the inflammatory mediator, NO, in a concentration-dependent manner (10–1 µM). The obtained data are the first results confirming the anti-inflammatory potential of C. articulatus and support its indigenous use as a traditional remedy against inflammation-related disorders.

Three new cytotoxic stilbene dimers from paphiopedilum dianthum

Three new stilbene dimers, paphiodianthins A-C (1–3), and nine known stilbenes, lignan and flavonoids (4–12) were isolated from the roots and leaves of Paphiopedilum dianthum (Orchidaceae). The structures of new compounds were elucidated from their NMR, HRESIMS and IR spectroscopic data. Cytotoxic activity of all isolated compounds was evaluated by in vitro MTT assay against two human cancer cell lines (MCF-7, Caco-2), doxorubicin-resistant and mitoxantrone-resistant MCF-7 sublines, as well as a normal cell line (NIH/3T3). Stilbenes 1, 3, 10 and 11 were strongly cytotoxic to both cancer cell lines with IC50 values ranging from 0.50 to 4.51 µM. Compounds 1, 10 and 11 were also active against chemotherapy-resistant MCF-7 sublines.

Chiroptical and potential in vitro anti-inflammatory properties of viniferin stereoisomers from grapevine (Vitis vinifera L.)

Determination of stereochemistry and enantiomeric excess in chiral natural molecules is a research of great interest because enantiomers can exhibit different biological activities. Viniferin stilbene dimers are natural molecules present in grape berries and wine but also, in larger amount, in stalks of grapevine. Four stereoisomers of viniferin stilbene dimers (7aS,8aS)-E-ε-viniferin (1a), (7aR,8aR)-E-ε-viniferin (1b), (7aS,8aR)-E-ω-viniferin (2a), and (7aR,8aS)-E-ω-viniferin (2b) were isolated from grapevine stalks of Cabernet Sauvignon, Merlot and Sauvignon Blanc, using a combination of centrifugal partition chromatography (CPC), preparative and chiral HPLC. The structure elucidation of these molecules was achieved by NMR whereas the absolute configurations of the four stereoisomers were investigated by vibrational circular dichroism spectroscopy in combination with density functional theory (DFT) calculations. This study unambiguously established the (+)-(7aS,8aS) and (+)-(7aR,8aS) configurations for E-ε-viniferin and E-ω-viniferin, respectively. Finally, we show that Cabernet Sauvignon provided the quasi enantiopure (+)-(7aS,8aS)-E-ε-viniferin compound which presents the best anti-inflammatory and anti-oxidant activities.

Chiral Separation of Stilbene Dimers Generated by Biotransformation for Absolute Configuration Determination and Antibacterial Evaluation.

A series of complex stilbene dimers have been generated through biotransformation of resveratrol, pterostilbene, and the mixture of both using the enzymatic secretome of Botrytis cinerea Pers. The process starts with achiral molecules and results in the generation of complex molecules with multiple chiral carbons. So far, we have been studying these compounds in the form of enantiomeric mixtures. In the present study, we isolated the enantiomers to determine their absolute configuration and assess if the stereochemistry could impact their biological properties. Eight compounds were selected for this study, corresponding to the main scaffolds generated (pallidol, leachianol, restrytisol and acyclic dimers) and the most active compounds (trans-δ-viniferin derivatives) against a methicillin-resistant strain of Staphylococcus aureus (MRSA). To isolate these enantiomers and determine their absolute configuration, a chiral HPLC-PDA analysis was performed. The analysis was achieved on a high-performance liquid chromatography system equipped with a chiral column. For each compound, the corresponding enantiomeric pair was obtained with high purity. The absolute configuration of each enantiomer was determined by comparison of experimental and calculated electronic circular dichroism (ECD). The antibacterial activities of the four trans-δ-viniferin derivatives against two S. aureus strains were evaluated.

Chemoenzymatic Synthesis of Original Stilbene Dimers Possessing Wnt Inhibition Activity in Triple-Negative Breast Cancer Cells Using the Enzymatic Secretome of Botrytis cinerea Pers.

The Wnt signaling pathway controls multiple events during embryonic development of multicellular animals and is carcinogenic when aberrantly activated in adults. Breast cancer and triple-negative breast cancer (TNBC) in particular depend upon Wnt pathway overactivation. Despite this importance, no Wnt pathway-targeting drugs are currently available, which necessitates novel approaches to search for therapeutically relevant compounds targeting this oncogenic pathway. Stilbene analogs represent an under-explored field of therapeutic natural products research. In the present work, a library of complex stilbene derivatives was obtained through biotransformation of a mixture of resveratrol and pterostilbene using the enzymatic secretome of Botrytis cinerea. To improve the chemodiversity, the reactions were performed using i-PrOH, n-BuOH, i-BuOH, EtOH, or MeOH as cosolvents. Using this strategy, a series of 73 unusual derivatives was generated distributed among 6 scaffolds; 55 derivatives represent novel compounds. The structure of each compound isolated was determined by nuclear magnetic resonance and high-resolution mass spectrometry. The inhibitory activity of the isolated compounds against the oncogenic Wnt pathway was comprehensively quantified and correlated with their capacity to inhibit the growth of the cancer cells, leading to insights into structure-activity relationships of the derivatives. Finally, we have dissected mechanistic details of the stilbene derivatives activity within the pathway.

A concise and efficient total synthetic route of active stilbene dimer (±)-ε-viniferin.

A concise and efficient procedure for the total synthesis of natural stilbene dimer (±)-ε-viniferin was accomplished with high overall yield. Demethylation of the key intermediate methyl 3-arylbenzofuran-4-carboxylate was achieved successfully through bromination followed by BBr3-or BCl3/TBAI-mediated ether cleavage reaction. Pd/C and bromobenzene-catalyzed MOM ether cleavage was successfully carried out to aquire (±)-ε-viniferin.

Stilbene dimer xylosides and flavanols from the roots of Lysidice rhodostegia and their antioxidant activities

Eight new stilbene dimer xylosides (1–8) and one new flavanol (9), along with seven known ones (10–16) were isolated from the roots of Lysidice rhodostegia. Their structures were elucidated by extensive analysis of spectroscopic data (IR, UV, HR-ESI-MS, 1D and 2D NMR), ECD calculations and acid hydrolysis. Compounds 1–16 were evaluated for their antioxidant activities using DPPH radical-scavenging assay. Especially, compounds 9 and 10 exhibited stronger antioxidant effects than the positive control (vitamin E), with IC50 values of 9.57 ± 1.30 and 13.60 ± 1.47 μM, respectively.

Chemical constituents from coconut waste and their in silico evaluation as potential antiviral agents against SARS-CoV-2

Eleven compounds were isolated from the ethyl acetate extract of Cocos nucifera L endocarp, jezonofol 1, scirpusin A 2, cassigarol G 3, maackin A 4, threoguiacyl glycerol-8’-vanillic acid ether 5, erythroguiacyl glycerol-8’-vanillic acid ether 6, apigenin-7-O-β-D-glucoside 7, piceatannol 8, p-hydroxy-benzoic acid 9, protocatechuic acid 10 and vanillic acid 11. Compounds 1-7 were isolated for the first time from the plant. The isolated compounds were virtually screened against four critical components of severe acute respiratory syndrome corona virus 2 (SARS-CoV-2), the main protease (Mpro), papain-like protease (PLpro), nonstructural protein 13 (nsp13) and RNA dependent RNA polymerase (RdRp). Stilbene dimers 1-4 showed remarkable binding affinities towards the investigated targets (binding energy <−7.6 kcal/mol). Compounds 1, 3 and 4 interacted with the catalytic dyad (Cys145-His41) at the active pocket of Mpro which is essential for achieving good inhibitory activity. Compounds 1-3 showed molecular interaction with the conserved ubiquitin-specific protease residues of PLpro, responsible for binding ability at different active sites of nsp13, which are crucial for decreasing the resistance caused by viral immune evasion. Compounds 2 and 3 showed the ability to bind at different active sites of nsp13, which is a key binding site for reducing antiviral resistance. Finally, compounds 1-3 showed the ability to bind with RdRp before and after RNA binding. Our findings suggested that the dimeric stilbene skeleton is a promising candidate for developing anti-COVID-19 drugs. Particularly, 1, 2 and 3, showed a promiscuity pattern binding to multiple targets of SARS-CoV-2 replication. Herein, 20 ns molecular dynamics (MD) simulations combined with molecular mechanics-generalized Born surface area (MM-GBSA) binding energy calculations were performed to estimate the binding affinity of the most potent three compounds against the viral SARS-CoV-2 targets. MM-GBSA calculations unveiled the outshine potency of compound 1 towards PLpro with a binding energy of −60.7 kcal/mol. Structural and energetic analyses over 20 ns MD simulation displayed the high stability of compound 1 in complex with PLpro. The list of the compounds was considered herein forms a primer for clinical investigation in COVID-19 patients and directing for further antiviral examinations. Drug likeness properties of compounds 1-4 were evaluated.

Cajanusoids A-D, Unusual Atropisomeric Stilbene Dimers with PTP1B Inhibitory Activities from the Leaves of Cajanus cajan.

Four novel stilbene dimers (1-4), together with their biosynthetically related stilbene monomers (5 and 6), were isolated from the leaves of Cajanus cajan. Their structures with absolute configurations were determined by comprehensive analysis of spectroscopic data and electronic circular dichroism calculations. Compounds 1 and 2 are two novel dimeric stilbenes with an unusual coupling pattern that resulted in a rare configurationally stable Csp2-Csp3 chiral axis with both point and axial chirality in their molecules. Due to their unique inherent structural features, both of them naturally occur as equilibrating mixtures of unequally populated atropo-diastereomers and their respective enantiomers. Compounds 3 and 4 are two pairs of novel dimeric stilbene atropisomers featuring a rotationally hindered central biaryl axis. Notably, 3 contains a rare arylbenzoquinone core and 4 is a symmetric dimer with a C2 symmetry axis. The hypothetical biosynthetic pathway of 1-4 was also proposed herein. All the new compounds exhibited significant protein tyrosine phosphatase-1B (PTP1B) inhibition effects. In addition, the preliminary mode of action for the most potent compound 3 was investigated by molecular docking and binding free energy calculation.

A New Stilbene Dimer and Other Chemical Constituents from Monanthotaxis littoralis with Their Antimicrobial Activities

A New Stilbene Dimer and Other Chemical Constituents from Monanthotaxis littoralis with Their Antimicrobial Activities

Combined MS/MS-NMR Annotation Guided Discovery of Iris lactea var. chinensis Seed as a Source of Viral Neuraminidase Inhibitory Polyphenols.

In this study, the chemical diversity of polyphenols in Iris lactea var. chinensis seeds was identified by combined MS/MS-NMR analysis. Based on the annotated chemical profile, the isolation of stilbene oligomers was conducted, and consequently, stilbene oligomers (1-10) were characterized. Of these, compounds 1 and 2 are previously undescribed stilbene dimer glycoside (1) and tetramer glycoside (2), respectively. Besides, to evaluate this plant seed as a rich source of stilbene oligomers, we quantified three stilbene oligomers of I. lactea var. chinensis seeds. The contents of three major stilbene oligomers—trans-ε-viniferin (3), vitisin A (6), and vitisin B (9)—in I. lactea var. chinensis seeds were quantified as 2.32 (3), 4.95 (6), and 1.64 (9) mg/g dry weight (DW). All the isolated compounds were tested for their inhibitory activities against influenza neuraminidase. Compound 10 was found to be active with the half maximal inhibitory concentration (IC50) values at 4.76 μM. Taken together, it is concluded that I. lactea var. chinensis seed is a valuable source of stilbene oligomers with a human health benefit.