Cytotoxicity studies of a stilbene extract and its main components intended to be used as preservative in the wine industry.

The use of stilbenes has been proposed as an alternative to sulfur dioxide in wine. Provided the feasibility from a technological approach, the cytotoxicity of an extract from grapevine shoots containing a stilbene richness of 99% (ST-99 extract) was assessed in the human cell lines HepG2 and Caco-2. In addition, the effects of the main stilbenes found in ST-99, trans-resveratrol and trans-ε-viniferin were studied, as well as its mixture. Similar cytotoxic effects were obtained in the exposures to trans-ε-viniferin, ST-99 and the mixture; however, trans-resveratrol alone exerted less toxicity. When HepG2 cells were exposed to trans-ε-viniferin, ST-99 and the mixture, the mean effective concentration (EC50) were 28.28 ± 2.15, 31.91 ± 1.55 and 29.47 ± 3.54 µg/mL, respectively. However, in the exposure to trans-resveratrol, the EC50 was higher 50 µg/mL. The morphological study evidenced damage at ultrastructural level in HepG2 cells, highlighting the inhibition of cell proliferation and the induction of apoptosis. The type of interaction produced by trans-ε-viniferin and trans-resveratrol mixtures was assessed by an isobologram analysis using the CalcuSyn software, evidencing an antagonist effect. These data comprise a starting point in the toxicological assessment; further studies are needed in this field to assure the safety of the extract ST-99.

The estrogenic activity of resveratrol: a comprehensive review of in vitro and in vivo evidence and the potential for endocrine disruption.

trans-Resveratrol, a polyphenolic stilbene of plant origin is structurally similar to natural and synthetic estrogens and has been classified a phytoestrogen. Direct binding of resveratrol to the nuclear estrogen receptor (ER) and modulation of its genomic activity was among the first of its reported pharmacological actions. Additionally, resveratrol in some investigations interacted with membrane bound ER and modulated non-genomic estrogenic activities. The compound was also reported to interfere in steroidogenesis and estrogen biosynthesis at multiple steps along the pathway. Resveratrol also inhibited hepatic and intestinal metabolism of estrogens and increased circulating levels of sex hormone binding globulin (SHBG). Recent investigations report estrogenic activities for resveratrol metabolites, especially for the predominant sulfate conjugate. The majority of these estrogenic effects have been observed in vitro using micro-molar concentrations. However, the daily consumption of 0.5-1 g of resveratrol supplements is sufficient to furnish plasma levels sufficient to initiate most of these actions. The diverse modes of estrogenic and hormonal activities of resveratrol can produce a progressive shift in the homeostatic balance of estrogens and other steroidal hormones to a new operational set point. While this could represent an opportunity for therapeutic benefit in a variety of endocrine related diseases, it may also pose risk of endocrine disruption following chronic exposure that warrants caution. Herein, a review of the current knowledge of resveratrol's estrogenic activity at the molecular, cellular and whole organism since it was reported two decades ago is provided followed by an assessment of endocrine disruption via an estrogenic mode of action.KEY MESSAGEResveratrol interacts with ER and modulates its genomic and non-genomic activities. It also inhibits several enzymes in steroidogenesis and competes in estrogen metabolism. Commercial supplements reach dosages of 1000 mg per serving and the consumption of 0.5-1 g per day furnishes low micro-molar plasma levels sufficient to start these activities. The pleiotropic hormonal actions of resveratrol open an opportunity for clinical benefit, but also risk endocrine disruption if exposure is chronic or during critical windows of development.

Resveratrol cytotoxicity is energy-dependent.

Resveratrol is a phytochemical that may promote health. However, it has also been reported to be a toxic compound. The molecular mechanism by which resveratrol acts remains unclear. The inhibition of the oxidative phosphorylation (OXPHOS) pathway appears to be the molecular mechanism of resveratrol. Taking this into account, we propose that the cytotoxic properties of resveratrol depend on the energy (e.g., carbohydrates, lipids, and proteins) availability in the cells. In this regard, in a condition with low energy accessibility, resveratrol could enhance ATP starvation to lethal levels. In contrast, when cells are supplemented with high quantities of energy and resveratrol, the inhibition of OXPHOS might produce a low-energy environment, mimicking the beneficial effects of caloric restriction. This review suggests that investigating a possible complex relationship between caloric intake and the differential effects of resveratrol on OXPHOS may be justified. PRACTICAL APPLICATIONS: A low-calorie diet accompanied by significant levels of resveratrol might modify cellular bioenergetics, which could impact cellular viability and enhance the anti-cancer properties of resveratrol.

Embryoid body test with morphological and molecular endpoints implicates potential developmental toxicity of trans-resveratrol.

Developmental toxicity of compounds, which women of reproductive age are exposed to, should be assessed to minimize the incidence of miscarriage and birth defects. The present study examined the potential developmental toxicity of resveratrol, a dietary supplement widely marketed with various health claims, using the P19C5 embryoid body (EB) morphogenesis assay, which evaluates adverse effects of chemical exposures on tissue growth and axial elongation. Resveratrol (trans isoform) impaired morphogenesis at 4 µM and higher, creating smaller and rounder EBs, whereas cis isoform, and glucuronated and sulfonated metabolites did not. Trans-resveratrol also altered expression levels of developmental regulator genes involved in embryonic patterning, such as Wnt3a, Tbx6, and Cyp26a1. To investigate the mechanisms of trans-resveratrol action, the roles of estrogen receptor, sirtuin 1 (SIRT1), and DNA replication in EB morphogenesis were examined. Neither activators of estrogen receptors (diethylstilbestrol [18 µM] and raloxifene [8 µM]) nor activator of SIRT1 (SRT1720 [2.4-3.2 µM]) caused morphological and molecular alterations that are comparable to trans-resveratrol (10 µM). By contrast, a reduction in the DNA replication rate with aphidicolin (0.4 µM) or hydroxyurea (40 µM) created smaller and rounder EBs and altered the expression levels of Wnt3a, Tbx6, and Cyp26a1 in a manner similar to trans-resveratrol. Consistently, trans-resveratrol significantly reduced the rate of EdU incorporation in P19C5 cells. These results suggest that a reduction in the DNA replication rate is one of the mechanisms by which trans-resveratrol impacts EB development. This study provides mechanistic insight for further investigations on the developmental toxicity of trans-resveratrol.