Two Resveratrol Oligomers Inhibit Cathepsin L Activity to Suppress SARS-CoV-2 Entry

Cell entry of severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) depends on specific host cell proteases, which are the key targets for preventing and treating viral infections. Herein, we describe miyabenol C and trans-ε-viniferin, two resveratrol oligomers that specifically inhibit SARS-CoV-2 entry by targeting host protease cathepsin L. Several cell-based assays were used to demonstrate the effect of resveratrol oligomers, and their target was identified via screening of antiviral targets. Molecular docking analysis suggested that the oligomers could occupy the active cavity of cathepsin L. The surface plasmon resonance assay showed that the equilibrium dissociation constant (KD) values of miyabenol C-cathepsin L and trans-ε-viniferin-cathepsin L were 5.54 and 8.54 μM, respectively, indicating their excellent binding ability for cathepsin L. Our study demonstrated the potential application of resveratrol oligomers as lead compounds in controlling SARS-CoV-2 infection by targeting cathepsin L.

Resveratrol Oligomers, Plant-Produced Natural Products With Anti-virulence and Plant Immune-Priming Roles

Antibiotic resistance has become increasingly prevalent in the environment. Many alternative strategies have been proposed for the treatment and prevention of diverse diseases in agriculture. Among them, the modulation of bacterial virulence to bypass antibiotic resistance or boost plant innate immunity can be considered a promising drug target. Plant-produced natural products offer a broad spectrum of stereochemistry and a wide range of pharmacophores, providing a great diversity of biological activities. Here, we present a perspective on the putative role of plant-produced resveratrol oligomers as anti-virulence and plant-immune priming agents for efficient disease management. Resveratrol oligomers can decrease (1) bacterial motility directly and (2) indirectly by attenuating the bacterial type III secretion system (TT3S). They induce enhanced local immune responses mediated by two-layered plant innate immunity, demonstrating (3) a putative plant immune priming role.

Screening of Natural Stilbene Oligomers from Vitis vinifera for Anticancer Activity on Human Hepatocellular Carcinoma Cells

The characterization of bioactive resveratrol oligomers extracted from Vitis vinifera canes has been recently reported. Here, we screened six of these compounds (ampelopsin A, trans-ε-viniferin, hopeaphenol, isohopeaphenol, R2-viniferin, and R-viniferin) for their cytotoxic activity to human hepatocellular carcinoma (HCC) cell lines p53 wild-type HepG2 and p53-null Hep3B. The cytotoxic efficacy depended on the cell line. R2-viniferin was the most toxic stilbene in HepG2, with inhibitory concentration 50 (IC₅₀) of 9.7 ± 0.4 µM at 72 h, 3-fold lower than for resveratrol, while Hep3B was less sensitive (IC₅₀ of 47.8 ± 2.8 µM). By contrast, hopeaphenol (IC₅₀ of 13.1 ± 4.1 µM) and isohopeaphenol (IC₅₀ of 26.0 ± 3.0 µM) were more toxic to Hep3B. Due to these results, and because it did not exert a large cytotoxicity in HH4 non-transformed hepatocytes, R2-viniferin was selected to investigate its mechanism of action in HepG2. The stilbene tended to arrest cell cycle at G2/M, and it also increased intracellular reactive oxygen species (ROS), caspase 3 activity, and the ratio of Bax/Bcl-2 proteins, indicative of apoptosis. The distinctive toxicity of R2-viniferin on HepG2 encourages research into the underlying mechanism to develop the oligostilbene as a therapeutic agent against HCC with a particular genetic background.

Effects of a Grapevine Shoot Extract Containing Resveratrol and Resveratrol Oligomers on Intestinal Adenoma Development in Mice: In Vitro and In Vivo Studies

SCOPE

Evidence suggests that the dietary consumption of plant extracts containing polyphenols might help prevent the onset of cancers of the gastrointestinal tract. In the present study, the chemopreventive and antiproliferative efficacy of a grapevine shoot extract (Vineatrol®30) containing resveratrol and resveratrol oligomers is investigated in vivo and in vitro.

METHODS AND RESULTS

The in vivo study is performed using Apc^Min mice on a high-fat diet, which represents a model of human adenomatous polyposis, while the potential of the extract as well as some of its isolated constituents to inhibit intestinal adenoma cell proliferation in vitro is investigated using APC10.1 cells derived from an Apc^Min mouse. Vineatrol®30 at a low (2.3 mg kg^-1  diet) or high dose (476 mg kg^-1  diet) reduces the adenoma number in male and adenoma volume in female animals. Furthermore, Vineatrol®30 as well as resveratrol and two resveratrol tetramers compromise the expansion of APC10.1 cells by reducing cell number, inducing cell cycle arrest, cellular senescence, and apoptosis. However, except for the extract, none of the isolated resveratrol oligomers is more efficacious than resveratrol in these cells.

CONCLUSION

Vineatrol®30 may merit further investigation as a potential dietary gastrointestinal cancer chemopreventive agent in humans.

Update on Phytochemistry and Pharmacology of Naturally Occurring Resveratrol Oligomers

Resveratrol oligomers (REVs), a major class of stilbenoids, are biosynthesized by regioselective oxidative coupling of two to eight units of resveratrol monomer. Due to their unique structures and pleiotropic biological activities, natural product chemists are increasingly focusing on REVs in the last few decades. This study presents a detailed and thorough examination of REVs, including chemical structures, natural resources, and biological activities, during the period of 2010–2017. Ninety-two new REVs compounds, including 39 dimers, 23 trimers, 13 tetramers, six resveratrol monomers, six hexamers, four pentamers, and one octamer, have been reported from the families of Dipterocarpaceae, Paeoniaceae, Vitaceae, Leguminosae, Gnetaceae, Cyperaceae, Polygonaceae Gramineae, and Poaceae. Amongst these families, Dipterocarpaceae, with 50 REVs, accounts for the majority, and seven genera of Dipterocarpaceae are involved, including Vatica, Vateria, Shorea, Hopea, Neobalanocarpus, Dipterocarpus, and Dryobalanops. These REVs have shown a wide range of bioactivities. Pharmacological studies have mainly focused on potential efficacy on tumors, bacteria, Alzheimer’s disease, cardiovascular diseases, and others. The information updated in this review might assist further research and development of novel REVs as potential therapeutic agents.

Gnetin-C and other resveratrol oligomers with cancer chemopreventive potential

Resveratrol has been extensively studied to investigate its biological effects, including its chemopreventive potential against cancer. Over the past decade, various resveratrol oligomers, both naturally occurring and synthetic, have been described. These resveratrol oligomers result from the polymerization of two or more resveratrol units to form dimers, trimers, tetramers, or even more complex derivatives. Some oligomers appear to have antitumor activities that are similar or superior to monomeric resveratrol. In this review, we discuss resveratrol oligomers with anticancer potential, with emphasis on well-characterized compounds, such as the dimer gnetin-C and other oligomers from Gnetum gnemon, whose safety, pharmacokinetic, and biological activities have been studied in humans.

Total Synthesis of Viniferifuran, Resveratrol-Piceatannol Hybrid, Anigopreissin A and Analogues - Investigation of Demethylation Strategies

Resveratrol-based natural products constitute a valuable source of unique compounds with diverse biological activities. In this report we investigate demethylation strategies to minimize formation of cyclized and dimerized products during the synthesis of viniferifuran and analogues. We found that boron trichloride/tetra-n-butylammonium iodide (BCl3/TBAI) is typically more effective than boron tribromide (BBr3). Based on these findings we carried out the first syntheses of dehydro-δ-viniferin, resveratrol-piceatannol hybrid and anigopreissin A. In addition, we have developed a short and efficient route to viniferifuran that was obtained in 13% yield over six steps.

Topoisomerase II-targeting properties of a grapevine-shoot extract and resveratrol oligomers

Grapevine-shoot extracts (GSE), containing trans-resveratrol and resveratrol oligomers, are commercially available as food supplements. Considering the topoisomerase-targeting properties of trans-resveratrol, the question of whether GSE affect these enzymes, thereby potentially causing DNA damage, was addressed. In a decatenation assay, GSE potently suppressed the catalytic activity of topoisomerase IIα (≥5 μg/mL). The resveratrol oligomers ε-viniferin, r2-viniferin, and hopeaphenol, isolated from GSE, were also identified as topoisomerase IIα inhibitors. In the in vivo complexes of enzyme to DNA (ICE) bioassay, neither GSE, r2-viniferin, nor hopeaphenol affected the level of enzyme-DNA intermediates in A431 cells, thus representing catalytic inhibitors rather than topoisomerase poisons. GSE caused moderate DNA strand breaks (≥25 μg/mL) in the comet assay. Taken together, GSE presumably acts as a catalytic inhibitor of topoisomerase II with r2-viniferin and hopeaphenol as potentially contributing constituents. However, the increase of FPG-sensitive sites points to an additional mechanism that may contribute to the DNA-damaging properties of GSE constituents.