Resveratrol
1. Identity: Chemical Name, Botanical Sources, and Common Forms
Chemical Identity
The formal IUPAC name of resveratrol is E-5-(4-hydroxystyryl)benzene-1,3-diol. It is also widely known by its systematic polyphenol name, 3,5,4′-trihydroxy-trans-stilbene. It belongs to the polyphenols' stilbenoids group, possessing two phenol rings linked to each other by an ethylene bridge. Its molecular formula is C₁₄H₁₂O₃.
Resveratrol exists as two geometric isomers: cis-(Z) and trans-(E). The trans form can undergo isomerization to the cis form when exposed to UV irradiation. The trans isomer is regarded as the biologically predominant and more stable form; the trans stereoisomeric form is present in the most commercially used and studied preparations.
Resveratrol is a nonflavonoid polyphenol that naturally occurs as a phytoalexin. It was initially recognized as an antibiotic produced in response to various environmental stresses, such as mechanical damage, microbial infection, UV radiation, heat, and pathogenic conditions.
Botanical Sources
This natural polyphenol has been detected in more than 70 plant species, especially in grape skins and seeds, and was found in discrete amounts in red wines and various human foods. Resveratrol is found in at least 72 species of plants distributed among 31 genera and 12 families, all belonging to the spermatophytes division, including Vitaceae, Myrtaceae, Dipterocarpaceae, Cyperaceae, Gnetaceae, Leguminosae, Pinaceae, Moraceae, Fagaceae, and Liliaceae.
Primary commercial botanical sources include the seeds and skins of grape species such as Vitis vinifera, Vitis labrusca, and Vitis rotundifolia, as well as Polygonum (Giant Knotweed), and in particular Polygonum cuspidatum (Japanese knotweed). Commercially, resveratrol has been extracted from wild Polygonum cuspidatum root (Japanese knotweed), grape skins and seeds (where it has been reported to be between 1.9 and 12.6 mg/L), and the domestic giant knotweed of China, which is the world's largest producer.
Major dietary sources include grapes, wine, peanuts, and soy; however, they can also be introduced into the diet through Itadori tea, which has long been used in Japan and China as a traditional herbal remedy for heart disease and strokes. Additional plant and dietary sources include blueberries, cranberries, mulberries, rhubarb, pistachio, groundnuts, and cocoa.
Discovery and Isolation
Resveratrol was initially extracted from the roots of white hellebore (Veratrum grandiflorum O. Loes.) by Michio Takaoka in 1940. After that, in 1963, it was isolated from Polygonum cuspidatum roots, which are used as antiplatelet and anti-inflammatory agents in traditional Chinese and Japanese medicine. The compound did not maintain much scientific interest for about 50 years until 1992, when Siemann and Creasy suggested that resveratrol was the active ingredient in wines causing reduction of serum lipids.
Commercial Preparations and Forms
Resveratrol is available without prescription as a nutritional supplement in multiple preparations and doses. In human trials, doses of resveratrol have ranged from 20 mg to 5 g daily, but a typical over-the-counter recommended dose is 500 mg twice daily. Supplement forms include standard capsules and tablets (typically standardized to trans-resveratrol content), micronized powders with enhanced bioavailability, and topical preparations.
Even though resveratrol is produced naturally in plants, it is very difficult to extract in commercial quantities because of its low concentration, multiple steps of isolation and purification, and seasonal occurrence. In industry, resveratrol is generally also prepared by chemical or biotechnological synthesis from yeasts of Saccharomyces cerevisiae.
2. Traditional and Historical Use
East Asian Medicine
The molecule, extractable from the roots of Polygonum cuspidatum, is used notably in popular traditional Chinese and Japanese medicine in the treatment of hyperlipemia, arteriosclerosis, inflammatory illnesses, and allergic illnesses. In Chinese medicine, the dried root of Polygonum cuspidatum is known as Hu Zhang (Tiger Cane) and has been used for centuries as part of formulations addressing conditions involving liver disorders, inflammation, and infections.
Resveratrol was later identified in the roots of P. cuspidatum, an oriental plant used in traditional medicine to treat fungal infections, dermatitis, and hyperlipidemic diseases. Itadori tea, prepared from P. cuspidatum, has long been used in Japan and China as a traditional herbal remedy for heart disease and strokes.
Ayurvedic and Mediterranean Traditions
The traditional Ayurvedic medicine darakchasava contains resveratrol in its formulation. In the Ayurveda, a fermented red grape juice is described as being used as a cardiotonic compound. Though practitioners in these traditions were unaware of the specific molecule, the preparations — which included grape-derived fermented beverages — were employed for cardiovascular, digestive, and rejuvenating purposes.
In traditional foodways, folk healers in Mediterranean regions used grape leaves and fermented grape extracts to soothe pharyngitis primarily for their antiseptic qualities. The broader culinary and medicinal use of red wine and grapes across Mediterranean cultures, while not attributed to resveratrol at the time, has attracted scientific attention in retrospect given the compound's concentration in red grape skins.
3. Key Active Constituents and Mechanisms of Action
Principal Compound and Related Stilbenoids
The principal bioactive constituent of resveratrol preparations is trans-resveratrol (3,5,4′-trihydroxystilbene). There are four groups of resveratrol derivatives, including hydroxylated compounds, methoxylated compounds, glycosides, and oligomers. The major oligomers with bioactivities include dimers, trimers, and tetramers. Ninety-two new resveratrol derivatives have been reported from the Leguminosae, Paeoniaceae, Dipterocarpaceae, Vitaceae, Gnetaceae, Cyperaceae, and Polygonaceae families.
Antioxidant Activity
Resveratrol can act as an antioxidant to modulate cellular functions. It scavenges hydroxyl radical, nitric oxide, and superoxide anion. It is a phytoalexin that acts against pathogens including bacteria and fungi. As a natural food ingredient, numerous studies have demonstrated that resveratrol possesses a very high antioxidant potential.
SIRT1 Activation and the NAD⁺/Sirtuin Pathway
The molecular mechanisms behind the health benefits of resveratrol remain enigmatic and controversial. Evidence establishes a chemical-genetic connection between SIRT1 and resveratrol, providing strong evidence that SIRT1 is critical for resveratrol to stimulate mitochondrial biogenesis and a switch toward oxidative muscle fibers. Resveratrol activates SIRT1 by directly binding to SIRT1, and by increasing NAD⁺ levels by upregulating the salvage pathway through Nampt activation, an effect mediated by AMPK.
NF-κB and Anti-Inflammatory Signaling
The anti-inflammatory effects of resveratrol are mediated, at least in part, by suppressing the activation of NF-κB, extracellular signal-regulated kinase-1 and kinase-2, and mitogen-activated protein kinase (MAPK) signaling pathways, which are all important upstream modulators of the production of proinflammatory mediators.
AMPK Activation
Resveratrol activates AMP-activated protein kinase (AMPK). The effect of SIRT1 activators such as resveratrol may not be solely through activation of SIRT1, but also through an integrated effect of SIRT1–LKB1–AMPK. The therapeutic effects of resveratrol are strongly related to the activation of SIRT1 and AMPK. Both proteins act as energy regulators due to their participation in metabolism and mitochondrial function, which makes them suitable targets for the treatment of metabolic diseases.
Nrf2, PI3K/AKT/mTOR, and Other Pathways
Resveratrol modulates several key signaling pathways including NF-κB, SIRT1, AMPK, MAPK, Nrf2, and PI3K/AKT/mTOR. The major mechanisms associated with the neuroprotective effect of resveratrol, in addition to SIRT1, include stimulation of regulation by the microRNA–CREB–BDNF pathway, inhibition of mTOR and AMPK-dependent signaling pathways, inhibition of cholinesterase activity, transcription factor (NF-κB) and apoptotic pathways, and stimulation of cellular autophagy and expression of Nrf2, HO-1, and NQO1.
Estrogenic / Phytoestrogenic Activity
Resveratrol acts as a mixed agonist/antagonist for estrogen receptors alpha and beta. Resveratrol exhibits affinity for both ERα and ERβ, thereby acting as an estrogen agonist to stimulate osteoblastogenesis. The discussion surrounding the hormonal effects of resveratrol revolves around the concept of hormesis, where low doses typically offer protective benefits while high doses may have detrimental effects that worsen disease progression and morbidity.
Bioavailability: The "Resveratrol Paradox"
The so-called "Resveratrol Paradox" — low bioavailability but high bioactivity — is a conundrum not yet solved, in which the final responsible actor for the exerted effects has not been unequivocally identified. The absorption of a dietary-relevant 25 mg oral dose was at least 70%, with peak plasma levels of resveratrol and metabolites of 491 ± 90 ng/mL (about 2 μM) and a plasma half-life of 9.2 ± 0.6 h. However, only trace amounts of unchanged resveratrol (<5 ng/mL) could be detected in plasma. Most of the oral dose was recovered in urine, with metabolic pathways including sulfate and glucuronic acid conjugation of the phenolic groups. Extremely rapid sulfate conjugation by the intestine and liver appears to be the rate-limiting step in resveratrol's bioavailability.
Resveratrol exists in both trans and cis configurations, and the major form found in plasma is a sulfated or glucuronidated conjugate rather than free resveratrol. Although the systemic bioavailability of resveratrol is very low, accumulation of resveratrol in epithelial cells along the aerodigestive tract and potentially active resveratrol metabolites may still produce cancer-preventive and other effects.
4. Scientific Evidence by Area of Use
Overview of the Clinical Evidence Base
Over the last 20 years, there have been almost 200 studies evaluating resveratrol across at least 24 indications, including cancer, menopause symptoms, diabetes, metabolic syndrome, and cardiovascular disease. The greatest number of studies (30) have been conducted for the fundamental purpose of characterising pharmacokinetics, distribution, metabolism, and bioavailability, whilst often simultaneously evaluating safety as an endpoint. The next most common application is in the management of type 2 diabetes mellitus and glucose control (23 studies), followed by cardiovascular disease (21).
Resveratrol has long been proposed as being beneficial to human health across multiple morbidities, yet there is currently no conclusive clinical evidence to advocate its recommendation in any healthcare setting. Scientific evidence obtained from in vitro studies and animal models suggests that resveratrol has antioxidant, anti-inflammatory, and anti-cancer properties; however, the results of clinical trials are not conclusive.
4.1 Cardiovascular Disease
Preclinical evidence: A meta-analysis of 57 preclinical studies involving 1,125 animals showed that resveratrol treatment decreased infarct size in animal models of myocardial ischemia/reperfusion injury (SMD: −5.44; 95% CI [−6.42 to −4.45]; P < 0.01) and myocardial infarction (SMD: −3.41; 95% CI [−4.44 to −2.38]; P < 0.01). These findings are promising but are entirely preclinical.
Clinical evidence (heart failure): In a human clinical trial, 60 outpatients with NYHA class II–III heart failure with reduced ejection fraction were randomized to either 100 mg resveratrol daily or placebo for three months. Echocardiography, a six-minute walk test, spirometry, quality-of-life questionnaire, lab tests, and RNA profile analysis were performed. The systolic and diastolic left ventricular function, as well as the global longitudinal strain, were improved significantly in the resveratrol-treated group.
Clinical evidence (blood pressure and vascular function): In an open-label, controlled RCT involving 57 patients with type 2 diabetes mellitus treated with oral hypoglycemic agents and 250 mg/day of resveratrol for 6 months, there was a significant reduction in systolic blood pressure after resveratrol supplementation compared to baseline (139.71 ± 16.10 vs. 131.14 ± 9.86 mmHg; p = 0.01), and significant reductions in both SBP and DBP comparing the treatment group to control.
Overall strength of cardiovascular evidence: Despite the promise of resveratrol as a treatment for cardiovascular diseases, clinical studies are still limited, and several conflicting results from trials have been reported, which demonstrates the challenges in translating exciting preclinical findings to humans. The results in humans are conflicting, possibly due to interindividual different responses. It is becoming evident that resveratrol may exert cardioprotective benefits through the improvement of inflammatory markers, atherogenic profile, glucose metabolism, and endothelial function, but definitive conclusions cannot yet be drawn.
4.2 Type 2 Diabetes Mellitus and Metabolic Health
Glycemic control: Several clinical trials have suggested that resveratrol has hypoglycemic properties; however, there are other studies in which such an effect has not been observed. A 2022 systematic review and meta-analysis found a dose-dependent pattern: resveratrol decreases glucose levels in subjects aged 45–59 years at doses <250 mg/day (−8.64 mg/dL, p < 0.00001), 250–500 mg/day (−22.24 mg/dL, p = 0.0003), and 500–1,000 mg/day (−28.40 mg/dL, p = 0.0008), while in subjects older than 60 years, it only decreases glucose with doses of 250–500 mg/day.
Negative findings: A significant worsening of glucose and lipid metabolism was observed in a high-dose resveratrol group compared to placebo, reflected by increases in fructosamine (+11.8 μmol/L; P < 0.0113), LDL cholesterol (+0.61 mmol/L; P < 0.006), and total cholesterol (+0.69 mmol/L; P < 0.002). Similarly, a slight increase in total cholesterol and triglycerides was observed with 6-month administration of 500 mg/day, but not 40 mg/day, of resveratrol in adults with type 2 diabetes managed with oral medications.
Overall strength of metabolic evidence: The evidence is mixed, with meta-analyses showing a statistically significant but modest effect on blood glucose in certain subgroups, while other well-designed trials report null or even adverse metabolic effects. A large cohort with high-quality clinical data and clearly defined biomarkers or endpoints is required to draw meaningful conclusions.
4.3 Neurodegenerative Disease (Alzheimer's Disease)
Proposed mechanisms: Preclinical evidence supports the notion that resveratrol may play a role in the treatment and prevention of neurodegenerative diseases, such as Huntington's disease, Parkinson's disease, and Alzheimer's disease. Through SIRT1 activation, resveratrol may protect neurons from reactive oxygen species, hydrogen peroxide free radicals, NO, amyloid-beta (Aβ), and other intra- and extracellular toxins associated with neurodegenerative disorders. Resveratrol-mediated overexpression of SIRT1 markedly reduced NF-κB signaling and Aβ-mediated microglial activation and had strong neuroprotective effects in preclinical models.
Clinical trial data (Alzheimer's disease): In a randomized, double-blind, placebo-controlled trial in subjects with biomarker-confirmed Alzheimer's disease, compared to the placebo-treated group at 52 weeks, resveratrol markedly reduced CSF MMP9 and increased macrophage-derived chemokine (MDC), interleukin (IL)-4, and fibroblast growth factor (FGF)-2. Compared to baseline, resveratrol increased plasma MMP10 and decreased IL-12P40, IL-12P70, and RANTES. These findings indicate modulation of neuroinflammatory markers, though the clinical significance for cognition remains under investigation.
Overall strength of neurological evidence: It has been reported that resveratrol shows effects in in vitro models of epilepsy, Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, and nerve injury. However, human trial data remain sparse, and the evidence base is primarily preclinical at this stage. The mechanisms are still unclear and not fully elucidated. Resveratrol may act on the CNS by inhibiting neuroinflammatory and pro-oxidant mechanisms through multiple action mechanisms that are independent of SIRT1.
4.4 Cancer Chemoprevention
Preclinical evidence: Resveratrol's potential chemopreventive and chemotherapeutic activities have been demonstrated in all three stages of carcinogenesis (initiation, promotion, and progression), in both chemically and UVB-induced skin carcinogenesis in mice, as well as in various murine models of human cancers. Numerous studies have highlighted the multifaceted nature of resveratrol in tumor inhibition, demonstrating its effects through various mechanisms rather than a singular pathway. Resveratrol has been shown to play a role in the development of several cancers, including colon, lung, breast, prostate, liver, and pancreatic cancers.
Anti-proliferative mechanisms: The anti-proliferative properties of resveratrol have been demonstrated in vitro against hormone-dependent and hormone-independent breast cancer cells through the induction of apoptosis via the down-regulation of p53, NF-κB and Bcl-2, the inhibition of ribonucleotide reductase and DNA polymerases, and the suppression of the RhoA/Lats1/YAP signaling axis.
Clinical evidence: Clinical evidence for resveratrol's anti-cancer effects in humans remains very limited and preliminary. A few clinical studies have focused on resveratrol supplementation and predictors for cancer prevention and cancer risk factors in healthy subjects. One study looked at the effects of resveratrol supplementation at doses of 0.5, 1.0, 2.5, and 5 g/day for 29 days (n=10–12/dose) on circulating levels of IGF-1 and IGFBP3, which are associated with tumor formation and metastasis. Since supraphysiological doses of resveratrol used in preclinical studies are not achievable in humans due to low bioavailability, it cannot be concluded that resveratrol's interaction with cellular enzymes is the sole mechanism by which it affords chemoprotection.
Overall strength of cancer evidence: Evidence is predominantly in vitro and animal-model-based. The growing number of preclinical studies have provided encouraging results concerning resveratrol's beneficial properties against cancer, but confirmatory human clinical trial data are lacking for any specific cancer indication.
4.5 Anti-Aging and Longevity
In the laboratory, resveratrol has been reported to exert cardioprotective, neuroprotective, antitumour, antidiabetic, antibacterial, and anti-ageing effects; common to some of these effects is an ability to modulate glucose metabolism, oxidative stress, cell death, and inflammation, amongst numerous potential mechanisms of action. The interest in resveratrol as a longevity compound originates primarily from its activation of sirtuins, which are associated with longevity pathways in model organisms.
Resveratrol attracted a lot of interest in 1992 because of a report demonstrating cardioprotective activity discovered in red wine, spurring the "French Paradox" hypothesis. Currently, attention is being focused on analyzing its properties against neurodegenerative diseases and as an antiaging compound. To date, no large-scale randomized controlled trial has demonstrated a life-extension or aging-reversal effect in humans.
4.6 Hepatoprotection and Liver Health
Resveratrol has been proposed as a treatment for hyperlipidemia and to prevent fatty liver, diabetes, atherosclerosis, and aging. Resveratrol use has been associated with rare instances of serum enzyme elevations during therapy but has not been convincingly linked to episodes of clinically apparent liver injury. Evidence for hepatoprotection in human clinical trials remains preliminary.
4.7 Hormesis: Dose-Dependent Biphasic Response
A growing body of evidence supports the notion that resveratrol exerts a biphasic, dose-dependent response, a phenomenon consistent with hormesis. Low to moderate doses (≤500 mg/day) tend to produce beneficial biological effects, including antioxidant, anti-inflammatory, and metabolic improvements. However, as the dosage exceeds this threshold — particularly at or above 1,000 mg/day — multiple studies have reported a higher incidence of mild to moderate adverse events, predominantly of gastrointestinal origin, such as diarrhea, nausea, and abdominal discomfort. This hormetic behavior complicates the translation of high-dose animal study results to human supplementation.
5. Body Systems Associated with Resveratrol
- Cardiovascular system: Evidence suggests resveratrol exerts cardioprotective benefits through the improvement of inflammatory markers, atherogenic profile, glucose metabolism, and endothelial function.
- Central nervous system: Resveratrol has been identified as an agent that may be useful to treat cancer, pain, inflammation, tissue injury, and other diseases. Neurological effects are under active investigation.
- Metabolic and endocrine system: Associations exist with glucose regulation, insulin sensitivity, and lipid metabolism, operating through SIRT1 and AMPK activation.
- Oncological (cancer biology): Resveratrol is widely studied for its antioxidant, anti-inflammatory, cardioprotective, hepatoprotective, neuroprotective, immunomodulatory, and anticancer properties.
- Skeletal system: Resveratrol exhibits affinity for both ERα and ERβ, thereby acting as an estrogen agonist to stimulate osteoblastogenesis.
- Gastrointestinal tract: Accumulation of resveratrol in epithelial cells along the aerodigestive tract may produce cancer-preventive and other localized effects.
- Skin: The major mechanisms of resveratrol and its derivatives for attenuating cutaneous neoplasia, photoaging, and inflammation are related to its antioxidative activity to scavenge hydroxyl radical, nitric oxide, and superoxide anion.
6. Dosage Forms and Dosages Reported in Studies
Resveratrol is available without prescription as a nutritional supplement in multiple preparations and doses. In human trials, doses have ranged from 20 mg to 5 g daily.
- A clinical trial in heart failure used 100 mg resveratrol daily for three months.
- A cardiovascular/diabetes RCT used 250 mg/day for 6 months.
- Meta-analyses of glycemic control used doses in ranges of <250 mg/day, 250–500 mg/day, and 500–1,000 mg/day.
- A cancer-related human study assessed doses of 0.5, 1.0, 2.5, and 5 g/day for 29 days.
- Six studies utilized 5 g per day, including two trials in cancer patients involving SRT501, a formulation with significantly enhanced bioavailability compared to standard resveratrol.
- Studies on steady-state pharmacokinetics and tolerability of 2,000 mg trans-resveratrol administered twice daily with food showed that trans-resveratrol was well-tolerated by healthy subjects, although diarrhea was frequently observed.
Resveratrol suffers from low water solubility, degradation, and poor bioavailability. The conventional dosage form shows various limitations, such as prolonged therapy requirements, erratic bioavailability, and absence of effective drug concentrations in tissues. Nanocarrier-based delivery systems are being studied to improve the therapeutic potential of poorly soluble molecules by enhancing their bioavailability, solubility, and retention time.
7. Safety Considerations and Drug Interactions
General Tolerability
In general, resveratrol is well tolerated with a robust safety profile. No adverse effects related to resveratrol were reported in clinical studies evaluating doses up to 1 g per day. Resveratrol is well tolerated even at higher doses; however, there is an increase in gastrointestinal side effects at doses exceeding 1 g per day. Human clinical trials have shown resveratrol to generally be safe and well tolerated at doses of up to 5 g, with dose-related gastrointestinal upset reported.
Six patients with hepatic metastases received 5 g per day of resveratrol for 14 days. Resveratrol was generally well tolerated, with the most common adverse effects being mild nausea and diarrhea. Other adverse effects included chills, lethargy, rash, peripheral neuropathy, skin irritation, and vascular flushing, which resolved without sequelae.
Gastrointestinal Effects
Diarrhea or other gastrointestinal symptoms were reported in clinical studies in healthy volunteers at doses of 1,000 mg/day or higher of unmodified resveratrol. Studies do not indicate significant adverse effects below 1,000 mg. In addition, results of metabolic interactions with cytochrome P-450 complex enzymes at doses higher than 1,000 mg/day suggested that this dose of unmodified resveratrol is an upper limit for clinical studies.
Cytochrome P450 Inhibition and Drug Interactions
High doses are associated with inhibition of cytochrome P450 enzymes, specifically CYP3A4, CYP2D6, and CYP2C9, which could result in drug interactions, most concerning for drugs with a narrow therapeutic window. Drug interactions with nicardipine, warfarin, HIV protease inhibitors, antiarrhythmics, calcium channel agonists, antihistamines, and immunosuppressants have been reported in animal models.
Resveratrol has been shown to inhibit several important CYP enzymes, many of which are responsible for the bioactivation of carcinogens. Furthermore, resveratrol induces conjugating enzymes, facilitating the elimination of toxic substances. Due to resveratrol's interactions with drug-metabolizing enzymes and drug transporters, individuals concurrently taking pharmacological doses of resveratrol with other supplements or medications could potentially experience nutrient-drug interactions.
Special Populations and Adverse Findings
With the exception of a patient with multiple myeloma undergoing chemotherapy plus high-dose resveratrol who became dehydrated and developed renal failure (cast nephropathy), other studies of resveratrol in humans have not shown adverse effects on hematologic, hepatic, thyroid, and renal functions.
Atherosclerotic lesion staining in one controlled animal study revealed that resveratrol-treated rabbits had significantly more aortic surface area covered by atherosclerotic lesions, suggesting that resveratrol promoted atherosclerotic development rather than protecting against it, by an independent mechanism. This finding from an animal model underscores the complexity of resveratrol biology and the caution warranted in extrapolating positive findings.
Purity of Commercial Products
In human trials, doses of resveratrol have ranged from 20 mg to 5 g daily. Importantly, the purity of commercial products is rarely well defined, oral bioavailability is poor, and the component responsible for its activity is not known. Safety concerns remain unsolved regarding chronic consumption of high resveratrol doses, especially in medicated people.
References
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