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.

Lunularin Producers versus Non-producers: Novel Human Metabotypes Associated with the Metabolism of Resveratrol by the Gut Microbiota

We describe here for the first time the consistent observation of two metabotypes associated with resveratrol metabolism by the human gut microbiota, that is, lunularin (LUNU)-producers and LUNU non-producers. In healthy volunteers (n = 195), resveratrol was reduced to dihydroresveratrol, which only in the LUNU-producer metabotype was sequentially dehydroxylated at the 5-position to yield LUNU and the 3-position to produce 4-hydroxydibenzyl. These metabolites (also 3,4'-dihydroxy-trans-stilbene in some LUNU-producers) were detected in the urine and (or) feces of 74% of volunteers after consuming resveratrol, while 26% lacked these dehydroxylase activities. The LUNU non-producer metabotype was more prevalent in females (P < 0.05) but independent of individuals' BMI and age. A 4-styrylphenol reductase in both metabotypes converted stilbenes to their corresponding dibenzyls, while no 4-dehydroxylation in stilbenes or dibenzyls was observed. 4-Hydroxy-trans-stilbene, pinosylvin, dihydropinosylvin, 3-hydroxydibenzyl, and 3-hydroxy-trans-stilbene were not detected in vivo or in vitro. Further research on LUNU metabotypes, their associated gut microbiota, and their impact on health is worthwhile.

4-Hydroxydibenzyl: a novel metabolite from the human gut microbiota after consuming resveratrol

Resveratrol (RSV) was known to be metabolised by the gut microbiota to dihydroresveratrol, lunularin (LUNU), and (or) 3,4'-dihydroxy-trans-stilbene (DHST). We describe here for the first time that LUNU can be further dehydroxylated, but only at the 3-position, to yield 4-hydroxydibenzyl, a novel metabolite found in human urine after RSV intake in 41 out of 59 healthy participants. In contrast, DHST was not further dehydroxylated, and thus, 4-hydroxy-trans-stilbene was not detected as a gut microbial metabolite of RSV. Faecal in vitro incubations confirmed the in vivo results.

Aerobic Copper-Catalyzed Intramolecular Cascade Oxidative Isomerization/[4+4] Cyclization of 2,2'-Disubstituted Stilbenes

An aerobic copper-catalyzed cascade oxidative isomerization/[4+4] cyclization of 2,2'-disubstituted stilbenes is described. Under the mild CuCl/DBED/air catalytic system, various 5,10-heteroatom-containing tetrahydroindeno[2,1-a]indenes were efficiently prepared through the difunctionalizations of alkenes in a highly atom economic manner. Mechanistic investigations suggested the bicyclic product was likely formed through a sequence of rapid single-electron oxidation/[4+4] cyclization from 2,2'-disubstituted stilbene. The antarafacial manner of the thermally allowed [4+4] cyclization was further proven by series of control experiments and density functional theory calculations. Our findings provide an important addition to the aerobic copper-catalyzed oxidative cyclization.

Dihydroxystilbenes prevent azoxymethane/dextran sulfate sodium-induced colon cancer by inhibiting colon cytokines, a chemokine, and programmed cell death-1 in C57BL/6J mice

The incidence of colon cancer increased worldwide in 2019 and its treatment is urgent from a quality of life perspective. A relationship has been reported between elevated numbers of tumor-associated macrophages (TAMs) in the tumor microenvironment and a poor prognosis in cancer patients, and M2 TAMs have been shown to promote tumor growth by immunosuppression through the stimulation of programmed death-1 (PD-1, an immune check point receptor), interleukin (IL)-1β, and monocyte chemoattractant protein (MCP)-1. We herein examined the effects of three synthetic dihydroxystilbenes (2,3-, 3,4-, and 4,4'-dihydroxystilbenes) on colon carcinogenesis, colon tumor growth, and colon cytokines (IL-1β, IL-6, and tumor necrosis factor (TNF)-α), a chemokine (MCP-1), vascular endothelial growth factor (VEGF), and PD-1 levels in azoxymethane (AOM) plus dextran sulfate sodium (DSS)-treated C57BL/6J mice. The three dihydroxystilbenes inhibited colon carcinogenesis and tumor growth as well as increases in colon IL-1β, IL-6, MCP-1, and PD-1 levels in AOM/DDS-treated mice (in vivo). The three dihydroxystilbenes also suppressed COX-2 expression in colon tumors (in vivo). The results obtained also revealed that the three dihydroxystilbenes inhibited PD-1 elevations in M2-THP-1 macrophages (in vitro). Therefore, the inhibition of AOM/DSS-induced colon carcinogenesis and colon tumor growth by 2,3-, 3,4-, and 4,4'-dihydroxystilbenes appears to be due to the suppression of M2 TAM differentiation and activation and PD-1 expression (immunosuppression) via reductions in COX-2 expression levels in the colon tumor microenvironment.

Antiproliferative activity of stilbene derivatives and other constituents from the stem bark of Morus nigra L

The antiproliferative activities of 2',3,4',5,5'-pentahydroxy-cis-stilbene 1, resveratrol 2, oxyresveratrol 3, norartocarpetin 4, kuwanon C 5, morusin 6, cudraflavone A7, kuwanon G 8, albafuran C 9, mulberrofuran G 10, 3-acetyl-O-α-amyrin 11, 3-acetyl-O-β-amyrin 12, ursolic acid-3-O-acetate 13 and uvaol 14, previously identified from the barks of Morus nigra L., were investigated against HepG2 and MCF-7 cell lines. In addition, a series of methylated stilbenes 15-19 were prepared using compounds 1-3 and their antiproliferative effects were similarly investigated. The structure of a new 2',3,4'-trimethoxy-5-hydroxy-trans-stilbene 19 was elucidated using spectroscopic techniques. It showed remarkable activity against MCF-7 cells with IC₅₀ 12.5 μM. However, kuwanon C (5) showed the highest antiproliferative activity with IC₅₀ 3.92 and 9.54 μM against MCF-7 and HepG2, respectively.

Steric Factors in the Preparation of Nitrostilbenes

The influence of an adjacent methyl group on the conformation of an aromatic nitro group and the consequent effect on the ease of synthesis of nitrostilbenes, has been examined using X-ray crystallographic studies to reveal the extent of the rotation of the nitro group.

Natural Stilbenoids Have Anti-Inflammatory Properties in Vivo and Down-Regulate the Production of Inflammatory Mediators NO, IL6, and MCP1 Possibly in a PI3K/Akt-Dependent Manner

Stilbenoids are a group of polyphenolic compounds found in plants, trees, berries, and nuts. Stilbenoids have been shown to serve an antimicrobial and antifungal function in plants. There is also evidence that as a part of the human diet, stilbenoids play an important role as antioxidants and may have anti-inflammatory effects. The PI3K/Akt pathway is a well-characterized signaling pathway controlling cellular functions involved in growth and cell cycle and in metabolism. There is also increasing evidence to show the involvement of this pathway in the regulation of inflammatory responses. In the present study, an attempt was made to investigate the anti-inflammatory properties of the naturally occurring stilbenoids pinosylvin (1), monomethylpinosylvin (2), resveratrol (3), pterostilbene (4), piceatannol (5), and rhapontigenin (6). Glycosylated derivatives of piceatannol and rhapontigenin, namely, astringin (7) and rhaponticin (8), respectively, were also investigated. In addition to the natural stilbenoids, pinosylvin derivatives (9-13) were synthesized and subjected to the testing of their effects on the PI3K/Akt pathway in inflammatory conditions. The investigated natural stilbenoids (except the glycosylated derivatives) were found to down-regulate Akt phosphorylation, which is a well-acknowledged marker for PI3K activity. It was also found that all of the studied natural stilbenoids had anti-inflammatory effects in vitro. The three most potent stilbenoids, piceatannol, pinosylvin, and pterostilbene, were selected for in vivo testing and were found to suppress inflammatory edema and to down-regulate the production of inflammatory mediators IL6 and MCP1 in carrageenan-induced paw inflammation in mice. When compared to the commercial PI3K inhibitor LY294002, the anti-inflammatory effects appeared to be quite similar. The results reveal hitherto unknown anti-inflammatory effects of natural stilbenoids and suggest that those effects may be mediated via inhibition of the PI3K/Akt pathway.

Synthetic approaches toward stilbenes and their related structures

Compounds belonging to the stilbene family have gained remarkable significance in pharmaceutical as well as material chemistry. The current review covers the various synthetic approaches for the syntheses of stilbene scaffold and related structures over last 30 years. In addition, this review also highlights the role of stilbene intermediates used in the synthesis of important molecules with diverse applications in the field of pharmaceutics and material science.

Synthesis and anticancer activity of a hydroxytolan series

This paper describes the development of novel anticancer poly-hydroxylated tolans. Based on structural similarity to resveratrol, a series of hydroxytolans were synthesized and evaluated for their antitumor capability against three tumor cell lines and one fibroblast cell line for selectivity comparisons. The 4,4'-dihydroxytolan (KST-201) exhibited the most significant anticancer activity with increased selectivity when compared to resveratrol and other hydroxytolans. Unlike resveratrol, KST-201 can boost hydrogen peroxide in tumor cells, which are often at high basal level of reactive oxygen species, to cause cell death by overwhelming the cellular tolerance of oxidative stress.

TRPA1 channels as targets for resveratrol and related stilbenoids

A series of twenty resveratrol analogues was synthesized and tested on TRPA1 and TRPV1 channels. None was able to significantly modulate TRPV1 channels. Conversely, most of them exhibited remarkably higher TRPA1 modulating activity than resveratrol. Optimal potency was observed with ortho monoxygenated stilbenes 6 and 17.

Biomimetic oxidative dimerization of anodically generated stilbene radical cations: effect of aromatic substitution on product distribution and reaction pathways

A systematic study of the electrochemical oxidation of 1,2-diarylalkenes was carried out with the focus on detailed product studies and variation of product type as a function of aromatic substitution. A reinvestigation of the electrochemical oxidation of 4,4'-dimethoxystilbene under various conditions was first carried out, and all products formed were fully characterized and quantitated. This was followed by a systematic investigation of the effect of aromatic substitution on the nature and distribution of the products. The aromatic substituents were found to fall into three main categories, viz., substrates in which the nature and position of the aromatic substituents gave rise to essentially the same products as 4,4'-dimethoxystilbene, for example, tetraaryltetrahydrofurans, dehydrotetralins, and aldehydes (p-MeO or p-NMe2 on one ring and X on the other ring, where X = o-MeO or p-alkyl, or m- or p-EWG; e.g., 4-methoxy-4'-trifluoromethylstilbene); those that gave rise to a mixture of indanyl (or tetralinyl) acetamides and dehydrotetralins (or pallidols) (both or one ring substituted by alkyl groups, e.g., 4,4'-dimethylstilbene); and those where strategic placement of donor groups, such as OMe and OH, led to the formation of ampelopsin F and pallidol-type carbon skeletons (e.g., 4,3',4'-trimethoxystilbene). Reaction pathways to rationalize the formation of the different products are presented.

Total synthesis of chiricanine A, arahypin-1, trans-arachidin-2, trans-arachidin-3, and arahypin-5 from peanut seeds

The first and efficient syntheses of the naturally occurring prenylated stilbenes chiricanine A (2), arahypin-1 (3), trans-arachidin-2 (4), trans-arachidin-3 (5), and arahypin-5 (6) are described. Syntheses of 2 and 3 were accomplished by either a convergent sequence or a one-step reaction starting from pinosylvin. Syntheses of 4, 5, and 6 were achieved from (E)-3,5-bis-methoxymethyl-4'-triisopropylsilyloxystilbene obtained by a Horner-Wadsworth-Emmons reaction between a benzaldehyde possessing bis-methoxymethyl ether groups and a benzyl phosphonate with a triisopropylsilyloxy group.

Ring strain and total syntheses of modified macrocycles of the isoplagiochin type

Macrocycles of the bisbibenzyl-type are natural products that are found exclusively in bryophytes (liverworts). The molecular framework of the subtype "isoplagiochin" is of substantial structural interest because of the chirality of the entire molecule, which arises from two biaryl axes in combination with two helical two-carbon units in a cyclic arrangement. From a structural as well as a synthetic point of view we report on the total synthesis of compounds which possess more rigid two-carbon biaryl bridges like stilbene (E or Z) or even tolane moieties which were introduced starting with a Sonogashira protocol. The McMurry method proved to be a powerful tool for the cyclization to these considerably ring-strained macrocycles.

Antibacterial and antifungal activity of cicerfuran and related 2-arylbenzofurans and stilbenes

Cicerfuran, 2-(2-methoxy-4,5-methylenedioxyphenyl)-6-hydroxybenzofuran, is an antifungal phytoalexin previously isolated from the roots of chickpea, Cicer spp. The synthesis of cicerfuran, five 2-arylbenzofuran analogues and nine stilbene intermediates was reported recently. The antimicrobial activities of these compounds were evaluated against two species of bacteria, Bacillus subtilis and Pseudomonas syringae, and four species of filamentous fungi, Aspergillus niger, Botrytis cinerea, Cladosporium herbarum and Monilinia aucupariae. Stilbenes with a free hydroxyl group were active against both bacteria and fungi with MICs in the range 25-100microg/ml. Cicerfuran was the only 2-arylbenzofuran that showed antimicrobial activity with MICs as low as 25microg/ml. Some aspects of the structure-activity relationship are discussed.

Effect of base on alkyltriphenylphosphonium salts in polar aprotic solvents

When arylmethyl phosphonium salts are treated with a base (e.g., t-BuOK or NaH) they homocouple to form symmetric 1,2-diarylethenes. In some cases, dilution and (or) use of excess base lead to very high yields of the product. This reaction is solvent sensitive: the reaction occurs only when polar aprotic solvents such as acetonitrile or DMSO are used. Other alkyl phosphonium salts (e.g., ethoxycarbonylmethyltriphenylphosphonium bromide and n-butyltriphenylphosphonium bromide) form a ylid (when an α-carbonyl group is present) or lose a phenyl group to form alkyldiphenylphosphine oxides when treated with the base. Mechanistic investigation of the homocoupling reaction indicates that the reaction proceeds through a ylid that acts as a nucleophile on an unreacted phosphonium salt. The resulting adduct undergoes elimination to form the observed product. The E/Z ratio seems to depend on the amount of the base used and the phosphonium salt involved.Key words: phosphonium salts, homocoupling, 1,2-diarylalkene, Ylids.

The nematocidal activity and the structure–activity relationships of stilbenes

The pinewood nematode, Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle, is the causative agent of the pine wilt disease which has been devastating forests of Pinus densiflora Sieb.et Zucc. and P. thunbergii Parl. in Japan. To prevent the pine wilt disease, the development of nematocidal compound is required. Twenty-one synthesized stilbenes (1)-(20), (23), salicylic acid (21), and phenylsalicilate (22) were examined for their nematocidal activity against an isolate of B. xylophilus (T-4). Among the tested compounds, two fluorinated stilbenes (15) and (13), were found to be most potent compounds against T-4, demonstrating 99% and 98% lethality at 10 ppm concentration. The LD50 values of compounds 15 and 13 were 3 ppm, respectively.

Efficient and selective reduction protocols of the 2,2-dimethyl-1,3-benzodioxan-4-one functional group to readily provide both substituted salicylaldehydes and 2-hydroxybenzyl alcohols

Two complementary procedures have been developed that selectively allow for the synthesis of either substituted salicylaldehydes or the corresponding 2-hydroxylbenzyl alcohols upon treatment of the 2,2-dimethyl-1,3-benzodioxan-4-one functional group with DIBAL-H or LAH, respectively.

Stereoselective synthesis of olefins by a reductive coupling reaction

Ketones and aldehydes are converted to symmetrical and (E)-olefins (1-15) by reaction with 2,4-bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide (PhPSe(2))(2), Woollins' reagent, in refluxing toluene; use of diketones was demonstrated by the reaction of PhC(O)CH(2)C(O)Ph which gives 1,2,4,5-tetraphenylbenzene (16) in 83% yield.

Synthesis of stilbene derivatives with inhibition of SARS coronavirus replication

Stilbene derivatives have wide range of activities. In an effort to find other potential activities of this kind of compounds, 17 derivatives, including resveratrol, were synthesized. Twelve of them were evaluated for their antiviral potential against severe acute respiratory syndrome (SARS)-CoV-induced cytopathicity in Vero E6 cell culture. The result showed that SARS virus was totally inhibited by compounds 17 and 19 ( Collapse

Key Words

• severe acute respiratory syndrome
• coronavirus
• stilbene derivatives
• cpe, cytopathic effect
• sars, severe acute respiratory syndrome

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MESH Headings

• Animals
• Chlorocebus aethiops
• Molecular Structure
• Severe acute respiratory syndrome-related coronavirus/drug effects
• Severe acute respiratory syndrome-related coronavirus/physiology
• Stilbenes/chemical synthesis
• Stilbenes/chemistry
• Stilbenes/pharmacology
• Structure-Activity Relationship
• Vero Cells
• Virus Replication/drug effects

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Affiliation(s)

Yue-Qing Li State Key Laboratory of Fine Chemicals, Dalian University of Technology, 158 Zhongshan Road, BOX 90, Dalian, Liaoning Province 116012, China
Ze-Lin Li College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100022, China
Wei-Jie Zhao State Key Laboratory of Fine Chemicals, Dalian University of Technology, 158 Zhongshan Road, BOX 90, Dalian, Liaoning Province 116012, China
Rui-Xing Wen College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100022, China
Qing-Wei Meng State Key Laboratory of Fine Chemicals, Dalian University of Technology, 158 Zhongshan Road, BOX 90, Dalian, Liaoning Province 116012, China
Yi Zeng College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100022, China

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Reductive olefination of aldehydes via chromium Brook rearrangement

[reaction: see text] The combination of CrCl(2) and silyl chlorides converts aryl and conjugated aldehydes into olefinic adducts in good to excellent yields. When constrained by structural features, the intermediate vic-diol can be isolated. Available data are consistent with a novel chromium Brook rearrangement.

Structure–activity relationship studies of resveratrol and its analogues by the reaction kinetics of low density lipoprotein peroxidation

Resveratrol (3,5,4'-trans-trihydroxystibene) is a natural phytoalexin present in grapes and red wine, which possesses a variety of biological activities including antioxidative activity. To find more active antioxidants, with resveratrol as the lead compound, we synthesized resveratrol analogues, i.e., 3,4,3',4'-tetrahydroxy-trans-stilbene (3,4,3',4'-THS), 3,4,4'-trihydroxy-trans-stilbene (3,4,4'-THS), 2,4,4'-trihydroxy-trans-stilbene (2,4,4'-THS), 3,3'-dimethoxy-4,4'-dihydroxy-trans-stilbene (3,3'-DM-4,4'-DHS), 3,4-dihydroxy-trans-stilbene (3,4-DHS), 4,4'-dihydroxy-trans-stilbene (4,4'-DHS), 3,5-dihydroxy-trans-stilbene (3,5-DHS) and 2,4-dihydroxy-trans-stilbene (2,4-DHS). Antioxidative effects of resveratrol and its analogues against free-radical-induced peroxidation of human low density lipoprotein (LDL) were studied. The peroxidation was initiated either by a water-soluble initiator 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH), or by cupric ion (Cu(2+)). The reaction kinetics were monitored either by the uptake of oxygen and the depletion of alpha-tocopherol (TOH) presented in the native LDL, or by the formation of thiobarbituric acid reactive substances (TBARS). Kinetic analysis of the antioxidation process demonstrates that these trans-stilbene derivatives are effective antioxidants against both AAPH- and Cu(2+)-induced LDL peroxidation with the activity sequence of 3,4,3',4'-THS approximately 3,3'-DM-4,4'-DHS>3,4-DHS approximately 3,4,4'-THS>2,4,4'-THS>resveratrol approximately 3,5-DHS>4,4'-DHS approximately 2,4-HS, and 3,4,3',4'-THS approximately 3,4-DHS approximately 3,4,4'-THS>3,3'-DM-4,4'-DHS>4,4'-DHS>resveratrol approximately 2,4-HS>2,4,4'-THS approximately 3,5-DHS, respectively. Molecules bearing ortho-dihydroxyl or 4-hydroxy-3-methoxyl groups possess significantly higher antioxidant activity than those bearing no such functionalities.

Synthesis and antimicrobial activity of new (E)-4-[piperidino (4'-methylpiperidino-, morpholino-) N-alkoxy]stilbenes

The synthesis of twenty-one new (E)-4-[piperidino-(4;-methylpiperidino-, morpholino-)N-alkoxy] stilbenes is reported. The compounds were tested for antimicrobial activities against Gram-negative, Gram-positive bacteria, and fungi. In particular, compounds 3b, 3c, 3f, 3g, 3h, 3k, 3l showed good antibacterial activity against Staphylococcus aureus and 3h, 3k, 3m, 3n also against Bacillus subtilis, as well as 3h, 3n also against Streptococcus faecalis.

A new diterpenoid and active stilbenes from Pinus armandii heartwood

8(17),13-Labdadien-16,14-olid-18-oic acid (1), a new diterpenoid, has been isolated from the heartwood of Pinus armandii Francher, along with seven known diterpenoids (2-8) and four known stilbenes (9-12). Their structures have been elucidated by spectral evidence. (E)-3-Hydroxy-5-methoxystilbene (9) showed significant inhibition against white-rot fungi.

Synthesis and Anti-inflammatory Activity of Resveratrol Analogs

Seventeen novel resveratrol derivatives were synthesized. Their anti-inflammatory activities were tested on xylene-induced mouse ear edema. The pharmacological results showed that some compounds have potent anti-inflammatory activities.

G2/M cell cycle arrest and induction of apoptosis by a stilbenoid, 3,4,5-trimethoxy-4′-bromo-cis-stilbene, in human lung cancer cells

Stilbenoids, including resveratrol (3,5,4'-trihydroxy-trans-stilbene) which is a naturally occurring phytoalexin abundant in grapes and several plants, have been shown to be active in inhibiting proliferation and inducing apoptosis in human cancer cell lines. Using resveratrol as the prototype, we have synthesized various analogs and evaluated their growth inhibitory effects in cultured human cancer cells. In the present study, we show that one of the stilbenoids, 3,4,5-trimethoxy-4'-bromo-cis-stilbene (BCS), was more effective than its corresponding trans-isomer and resveratrol on the inhibition of cancer cell growth. Prompted by the strong growth inhibitory activity of BCS (IC50; 0.03 microM) compared to its trans-isomer (IC50; 6.36 microM) and resveratrol (IC50; 33.0 microM) in cultured human lung cancer cells (A549), we investigated its mechanism of action. BCS induced arrest at the G2/M phase cell cycle in the early time and subsequently increased in the sub-G1 phase DNA contents in a time-dependent manner, indicating induction of apoptosis. Morphological observation with round-up shape and DNA fragmentation was also revealed the apoptotic phenomena. BCS treatment elevated the expression levels of the pro-apoptotic protein p53, the cyclin-dependent kinase inhibitor p21, and the release of cytochrome c in the cytosol. The down-regulation of checkpoint protein cyclin B1 by BCS was well correlated with the cell cycle arrest at G2/M. These data suggest the potential of BCS to serve as a cancer chemotherapeutic or chemopreventive agent by virtue of arresting the cell cycle and induction of apoptosis of human lung cancer cells.