Synthesis and antioxidant activity of hydroxylated phenanthrenes as cis-restricted resveratrol analogues

Study of phenanthrenes from their unique mass spectrometric behavior through quantum chemical calculations to liquid chromatographic quantitation

Phenanthrenes and their derivatives have biological relevance owing to their antimicrobial, antioxidant, and cytotoxic effects on cancer cells. They can be efficiently analyzed through ultrahigh-performance liquid chromatography coupled to tandem high-resolution mass spectrometry (UHPLC-MS/HRMS). Herein, we first studied the unique fragmentation behavior of phenanthrenes based on direct infusion MS/HRMS analysis. As a newly described phenomenon, "organ pipe distribution", we found a structural connection linking their unique fragmentation pattern to serial H radical losses. The bonds responsible for this behavior were identified through quantum chemical calculations using a stepwise approach. Furthermore, the chromatographic aspect of this study was enhanced by developing, validating, and applying a new unscheduled targeted UHPLC-MS/HRMS method for quantifying phenanthrenes in Juncus compressus herb. Targeted compounds were efficiently separated within 4 min upon utilizing the Accucore C30 column, and the unscheduled targeted analytical approach afforded five new isomers. Compounds 1 (effususol), 3 (dehydroeffusol), and 6 (7-hydroxy-1-methyl-2-methoxy-5-vinyl-9,10-dihydrophenanthrene) had their linearity limits determined within 10-5000 nM, and Compounds 2 (effusol), 4 (juncusol), 5 (effususin A), and 7 (compressin A) within 25-5000 nM. The coefficients of variation for precision ranged from 1.4 % to 15.2 %. The obtained matrix effects and accuracy values were also within acceptable ranges. Compounds 2 (effusol) and 3 (dehydroeffusol) were present in both methanolic and dichloromethanolic extracts of Plants 1 and 3 at the highest concentrations. Furthermore, the relationship between phenanthrene fingerprints, obtained through ANOVA statistical analysis of quantitative data, and the geographical location of herbs was also established.

UV-exposure decreases antimicrobial activities of a grapevine cane extract against Plasmopara viticola and Botrytis cinerea as a consequence of stilbene modifications-a kinetic study

BACKGROUND

Stilbenoid extracts, such as those originating from grapevine by-products (e.g. canes), are of interest for use as biopesticides in vineyard owing to their antimicrobial activities. However, stilbenoids are unstable in the environment, especially under light. This study aimed to chemically characterize the effect of UV light on stilbenoids present in a grapevine cane extract (CE), and to evaluate the antimicrobial activities against two major grapevine pathogens (Plasmopara viticola and Botrytis cinerea) of grapevine extracts exposed to UV.

RESULTS

Treatment with UV (365 nm) on a grapevine CE led to degradation of stilbenoids (up to 71% after 1 h). The stilbenoid stability depended on their chemical structure: only those possessing CC, as trans-resveratrol and trans-ε-viniferin, were affected with first their isomerization and secondly their oxidation/cyclization. As a consequence, UV-exposed extracts (UV-CEs) showed reduced antimicrobial activities against the two pathogens (mycelium and spores). For instance, regarding P. viticola, an UV-CE exposed during 4 h showed an almost total loss of its activity on oomycete development and a 2.4-fold inhibition of zoospore mobility in comparison to CE. For B. cinerea, the inhibition capacity of the same UV-CE was reduced by only 1.1-fold on mycelial development and by 3.2-fold on conidial germination compared to CE.

CONCLUSION

UV light triggered modifications on the structure of bioactive stilbenoids, resulting in losses of their antimicrobial activities. Photoprotection of stilbenoids has to be considered in the perspective of using them in vineyards as biopesticides. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Cardiovascular risk of dietary trimethylamine oxide precursors and the therapeutic potential of resveratrol and its derivatives

Overall diet, lifestyle choices, genetic predisposition, and other underlying health conditions may contribute to higher trimethylamine N-oxide (TMAO) levels and increased cardiovascular risk. This review explores the potential therapeutic ability of RSV to protect against cardiovascular diseases (CVD) and affect TMAO levels. This review considers recent studies on the association of TMAO with CVD. It also examines the sources, mechanisms, and metabolism of TMAO along with TMAO-induced cardiovascular events. Plant polyphenolic compounds, including resveratrol (RSV), and their cardioprotective mechanism of regulating TMAO levels and modifying gut microbiota are also discussed here. RSV's salient features and bioactive properties in reducing CVD have been evaluated. The close relationship between TMAO and CVD is clearly understood from currently available data, making it a potent biomarker for CVD. Precise investigation, including clinical trials, must be performed to understand RSV's mechanism, dose, effects, and derivatives as a cardioprotectant agent.

Crystal structure of (E)-1-(4-(3,5-dimethoxystyryl)phenyl)-7-ethylheptanedioate, C25H30O6

C25H30O6, orthorhombic, Pna21 (no. 33), a = 7.556(2) Å, b = 37.198(12) Å, c = 8.113(2) Å, V = 2280.2(11) Å3, Z = 4, R gt (F) = 0.0610, wR ref (F 2) = 0.1634, T = 170 K.

Separation and Identification of Resveratrol Butyrate Ester Complexes and Their Bioactivity in HepG2 Cell Models

Resveratrol butyrate ester (RBE) complexes have demonstrated higher antioxidant capacity and anti-fat accumulation activity in previous studies. In this study, silica gel, high-performance liquid chromatography, and 1H nuclear magnetic resonance were used for separation and identification of RBE complex components. With the exception of resveratrol, five different structures of ester derivatives were separated from silica gel: 3,4′-di-O-butanoylresveratrol (ED2, 18.8%), 3-O-butanoylresveratrol (ED4, 35.7%), 4′-O-butanoylresveratrol (ED5, 4.4%), 3,5,4′-tri-O-butanoylresveratrol (ED6, 1.5%), and 3,5-di-O-butanoylresveratrol (ED7, 0.7%). Among the ester derivatives obtained, ED2 and ED4 were the main ester derivatives in the RBE complex. Thus, the cellular antioxidant activities of the RBE mixture, ED2, and ED4 were evaluated. Results showed that the antioxidant capacity of ED2 and ED4 was higher than that of the RBE mixture, demonstrating that the number and position of butyrate esterification sites are related to cell survival rate and antioxidant capacity. This study is the first to report the successful isolation, structural identification, and cellular biological antioxidant activity of RBE complex derivatives, which are key characteristics for the potential practical application of RBE complexes.

Resveratrol: a review of plant sources, synthesis, stability, modification and food application

Resveratrol, a stilbene molecule belonging to the polyphenol family, is usually extracted from a great many natural plants. The technologies of preparation and extraction methods are developing rapidly. As resveratrol has many beneficial properties, it has been widely utilized in food and medicine industry. In terms of its structure, it is susceptible to degradation and can undergo chemical changes during food processing. Different studies have therefore given more attention to various aspects of resveratrol, including anti-aging, anti-oxidant, and anti-cancer activity. This review classifies the study of resveratrol, considers plant sources, synthesis, stability, common reactions, and food applications, and provides references to boost its food and medical utilization. © 2019 Society of Chemical Industry.

Gas Chromatographic-Mass Spectrometric Method for the Simultaneous Determination of Resveratrol Isomers and 2,4,6-Trihydroxyphenanthrene in Red Wines Exposed to UV-Light

Resveratrol (3,5,4'-trihydroxystilbene) is one of the most abundant polyphenols in red grapes, and red wine represents one of the most important dietary sources of this compound. Although its beneficial properties on human health have been widely investigated over the last 30 years, very little is known about its derivatives. Resveratrol can indeed undergo glycosylation, oligomerization and, upon UV-light exposure, it can isomerize from the trans-to the cis-isomer, which can further cyclize to 2,4,6-trihydroxyphenanthrene (THP). Although the effects of THP on human health are not yet known, being a polycyclic aromatic hydrocarbon, it can be potentially harmful. Because no data about THP occurrence in plant food and beverages are available, a simple procedure based on liquid-liquid extraction and gas chromatography-mass spectrometry has been developed and validated for the simultaneous qualitative and quantitative analysis of trans-resveratrol, cis-resveratrol, and THP in red wine, before and after UV-light exposure.

Novel vanillin derivatives: Synthesis, anti-oxidant, DNA and cellular protection properties

Antioxidants have been the subject of intense research interest mainly due to their beneficial properties associated with human health and wellbeing. Phenolic molecules, such as naturally occurring Resveratrol and Vanillin, are well known for their anti-oxidant properties, providing a starting point for the development of new antioxidants. Here we report, for the first time, the synthesis of a number of new vanillin through the reductive amination reaction between vanillin and a selection of amines. All the compounds synthesised, exhibited strong antioxidant properties in DPPH, FRAP and ORAC assays, with compounds 1b and 2c being the most active. The latter also demonstrated the ability to protect plasmid DNA from oxidative damage in the presence of the radical initiator AAPH. At cellular level, neuroblastoma SH-SY5Y cells were protected from oxidative damage (H₂O₂, 400 μM) with both 1b and 2c. The presence of a tertiary amino group, along with the number of vanillin moieties in the molecule contribute for the antioxidant activity. Furthermore, the delocalization of the electron pair of the nitrogen and the presence of an electron donating substituent to enhance the antioxidant properties of this new class of compounds. In our opinion, vanillin derivatives 1b and 2c described in this work can provide a viable platform for the development of antioxidant based therapeutics.

Synthesis and antioxidant properties of Lycium barbarum polysaccharides capped selenium nanoparticles using tea extract

Selenium nanoparticles (SeNPs) have attracted increasing interest over the last decades because of their activities on redox balance in human body. However, the SeNPs tend to aggregate into large clusters, resulting in lower bioactivity, bioavailability and biocompatibility. Surface-capping agents on SeNPs play crucial roles in its stabilization and biological activity. Here, a green synthesis method for the preparation of Lycium barbarum polysaccharides capped SeNPs using green tea extracts as reductants under mild conditions, at room temperature, is reported. The structure, size, morphology and thermal behaviour were analyzed by various characterization techniques. The functionalized nanoparticles demonstrated high antioxidant activity, including DPPH and ABTS free radical scavenging. Moreover, the SeNPs significantly protected the H₂O₂-induced PC-12 cell death. Taken together, these results evidence the possible application of these SeNPs as antioxidants food supplement or ingredient and neuroprotective agent.

Tetrahydropyrrolization of Resveratrol and Other Stilbenes Improves Inhibitory Effects on DNA Oxidation

The inhibitory effect of resveratrol on DNA oxidation caused by 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH) was found to be enhanced if the C=C bond in resveratrol was converted into tetrahydropyrrole by reaction with azomethine ylide (CH2 =N(+) (CH3 )CH2 (-) ). This encouraged us to explore whether the inhibitory activities of other stilbenes could also be increased by the same method. We found that the inhibitory effects of the tetrahydropyrrole derivatives on AAPH-induced oxidation of DNA were higher than those of the corresponding stilbenes, because the tetrahydropyrrole motif can provide hydrogen atoms to be abstracted by radicals. Therefore, the tetrahydropyrrolization offered an advantage for enhancing the antioxidant effects of stilbenes. Notably, (CH3 )3 SiCH2 N(CH3 )CH2 OCH3 (in the presence of CF3 COOH) and (CH3 )3 NO (in the presence of LiN(iPr)2 ) can be used to generate azomethine ylide for the tetrahydropyrrolization of stilbenes containing electron-withdrawing and -donating groups, respectively.

Directed Metalation-Suzuki-Miyaura Cross-Coupling Strategies: Regioselective Synthesis of Hydroxylated 1-Methyl-phenanthrenes

A general, efficient, and regioselective synthesis of a series of hydroxylated 1-methylphenanthrenes 9 by a combined directed ortho metalation (DoM)-Suzuki-Miyaura cross-coupling-directed remote metalation (DreM) sequence is reported. Diversity to this methodology was achieved by a regioselective DoM rather than DreM reaction, affording more highly substituted phenanthrols ( Table 2 ). Application of the turbo-Grignard reagent (i-PrMgCl·LiCl) in the Ni-catalyzed Corriu-Kumada reaction gave efficient decarbamoylation ( Tables 3 and 4 ). Additional features are the TMS protecting group and halo-induced ipso-desilylation tactics applied to the regioselective synthesis of phenanthrenes ( Scheme 2 ).

Anticancer activities of self-assembled molecular bowls containing a phenanthrene-based donor and Ru(II) acceptors

Nano-sized multinuclear ruthenium complexes have rapidly emerged as promising therapeutic candidates with unique anticancer activities. Here, we describe the coordination-driven self-assembly and anticancer activities of a set of three organometallic tetranuclear Ru(II) molecular bowls. [2+2] Coordination-driven self-assembly of 3, 6-bis(pyridin-3- ylethynyl) phenanthrene (bpep) (1) and one of the three dinuclear arene ruthenium clips, [(η6-p-iPrC6H4Me)2Ru2-(OO\OO)][OTf]2 (OO\OO =2, 5-dioxido-1, 4-benzoquinonato, OTf = triflate) (2), 5, 8-dioxido-1, 4-naphthoquinonato (3), or 6, 11-dioxido-5, 12-naphthacenediona (4), resulted in three molecular bowls 5-7 of general formula [{(η6-p-iPrC6H4Me)2Ru2-(OO\OO)}2(bpep)2][OTf]4. All molecular bowls were obtained as triflate salts in very good yields (>90%) and were fully characterized using multinuclear nuclear magnetic resonance (NMR), electrospray ionization-mass spectrometry (ESI-MS), and elemental analysis. The structure of the representative molecular bowl 5 was confirmed by single-crystal X-ray diffraction analysis. The anticancer activities of molecular bowls 5-7 were determined by 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide, autophagy, and Western blot analysis. Bowl 6 showed the strongest cytotoxicity in AGS human gastric carcinoma cells and was more cytotoxic than doxorubicin. In addition, autophagic activity and the ratio of apoptotic cell death increased in AGS cells by treatment with bowl 6. Bowl 6 also induced autophagosome formation via upregulation of p62 and promotion of the conversion of LC3-I to LC3-II. Moreover, bowl 6 promoted apoptotic cell death through downregulation of Akt/mTOR activation, followed by increased caspase-3 activity. These results suggest that bowl 6 induces gastric cancer cell death via modulation of autophagy and apoptosis. Bowl 6 is a potent anticancer agent and a potential treatment for human gastric cancer that merits further study.

Theoretical study of complexation of resveratrol with cyclodextrins and cucurbiturils: structure and antioxidative activity

The inclusion complexation of resveratrol with cyclodextrins and cucurbiturils and the influence of complexation on the antioxidative activity of resveratrol have been theoretically studied.

Tritium-labeled (E,E)-2,5-bis(4'-hydroxy-3'-carboxystyryl)benzene as a probe for β-amyloid fibrils

Accumulation of Aβ in the brains of Alzheimer disease (AD) patients reflects an imbalance between Aβ production and clearance from their brains. Alternative cleavage of amyloid precursor protein (APP) by processing proteases generates soluble APP fragments including the neurotoxic amyloid Aβ40 and Aβ42 peptides that assemble into fibrils and form plaques. Plaque-buildup occurs over an extended time-frame, and the early detection and modulation of plaque formation are areas of active research. Radiolabeled probes for the detection of amyloid plaques and fibrils in living subjects are important for noninvasive evaluation of AD diagnosis, progression, and differentiation of AD from other neurodegenerative diseases and age-related cognitive decline. Tritium-labeled (E,E)-1-[(3)H]-2,5-bis(4'-hydroxy-3'-carbomethoxystyryl)benzene possesses an improved level of chemical stability relative to a previously reported radioiodinated analog for radiometric quantification of Aβ plaque and tau pathology in brain tissue and in vitro studies with synthetic Aβ and tau fibrils.

Density functional study of the antioxidant activity of some recently synthesized resveratrol analogues

In this paper we have investigated the two main working mechanisms (H atom and single-electron transfer) of five new potential antioxidant analogues of cis-resveratrol. The O-H bond dissociation energy (BDE) and ionization potential (IP) key parameters were computed in methanol. Results obtained indicate that all the examined compounds are more efficient antioxidants than the molecule from which they derive, mainly due to their higher degree of conjugation and the capability to delocalize the π-electrons which contribute to the stabilization of the radical species. The enhancement of these stabilizing effects is in part a result of the introduction of a single bond between the C2' and C6 carbon atoms of cis-resveratrol that generates a new central aromatic ring. However, the number of hydroxyl groups and in particular the presence of the catechol moiety remains the most significant features in determining the order of radical scavenging potentiality. Spectroscopic UV-Vis characterization is also reported and discussed.

Influence of glucuronidation and reduction modifications of resveratrol on its biological activities

Resveratrol (3,5,4'-trihydroxystilbene, RES), a star among dietary polyphenols, shows a wide range of biological activities, but it is rapidly and extensively metabolized into its glucuronide and sulfate conjugates as well as to the corresponding reduced products. This begs the question of whether the metabolites of RES contribute to its in vivo biological activity. To explore this possibility, we synthesized its glucuronidation (3-GR and 4'-GR) and reduction (DHR) metabolites, and evaluated the effect of these structure modifications on biological activities, including binding ability with human serum albumin (HSA), antioxidant activity in homogeneous solutions and heterogeneous media, anti-inflammatory activity, and cytotoxicity against various cancer cell lines. We found that 1) 4'-GR, DHR and RES show nearly equal binding to HSA, mainly through hydrogen bonding, whereas 3-GR adopts a quite different orientation mode upon binding, thereby resulting in reduced ability; 2) 3-GR shows comparable (even equal) ability to RES in FRAP- and AAPH-induced DNA strand breakage assays; DHR, 3-GR, and 4'-GR exhibit anti-hemolysis activity comparable to that of RES; additionally, 3-GR and DHR retain some degree activity of the parent molecule in DPPH.-scavenging and cupric ion-initiated oxidation of LDL assays, respectively; 3) compared to RES, 4'-GR displays equipotent ability in the inhibition of COX-2, and DHR presents comparable activity in inhibiting NO production and growth of SMMC-7721 cells. Relative to RES, its glucuronidation and reduction metabolites showed equal, comparable, or some degree of activity in the above assays, depending on the specific compound and test model, which probably supports their roles in contributing to the in vivo biological activities of the parent molecule.