Protective effects of pinostilbene, a resveratrol methylated derivative, against 6-hydroxydopamine-induced neurotoxicity in SH-SY5Y cells

Induction of Semaphorin 3A by Resveratrol and Pinostilbene via Activation of the AHR-NRF2 Axis in Human Keratinocytes

Semaphorin 3A (SEMA3A), a nerve-repellent factor produced by keratinocytes, has an inhibitory effect on nerve extension to the epidermis. Epidermal innervation is involved in pruritus in inflammatory skin diseases such as atopic dermatitis (AD) and dry skin. We previously reported that tapinarof, a stilbene molecule, upregulates SEMA3A in human keratinocytes. We also showed that this mechanism is mediated via the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor, and the nuclear factor erythroid 2-related factor 2 (NRF2) axis. Since some stilbenes activate AHR and NRF2, we attempted to identify other stilbenes that upregulate SEMA3A. We analyzed normal human epidermal keratinocytes (NHEKs) treated with 11 types of stilbenes and examined SEMA3A expression. We found that resveratrol and pinostilbene, antioxidant polyphenols, upregulated SEMA3A and increased nuclear AHR and NRF2 expression. In addition, AHR knockdown by small interfering RNA (siRNA) transfection abolished the NRF2 nuclear expression. Furthermore, AHR and NRF2 knockdown by siRNA transfection abrogated resveratrol- and pinostilbene-induced SEMA3A upregulation. Finally, we confirmed that resveratrol and pinostilbene increased SEMA3A promoter activity through NRF2 binding using ChIP-qPCR analysis. These results suggest that resveratrol and pinostilbene upregulate SEMA3A via the AHR-NRF2 axis in human keratinocytes.

Stilbenes: a journey from folklore to pharmaceutical innovation

In modern times, medicine is predominantly based on evidence-based practices, whereas in ancient times, indigenous people relied on plant-based medicines with factual evidence documented in ancient books or folklore that demonstrated their effectiveness against specific infections. Plants and microbes account for 70% of drugs approved by the USFDA (U.S. Food and Drug Administration). Stilbenes, polyphenolic compounds synthesized by plants under stress conditions, have garnered significant attention for their therapeutic potential, bridging ancient wisdom with modern healthcare. Resveratrol, the most studied stilbene, initially discovered in grapes, red wine, peanuts, and blueberries, exhibits diverse pharmacological properties, including cardiovascular protection, antioxidant effects, anticancer activity, and neuroprotection. Traditional remedies, documented in ancient texts like the Ayurvedic Charak Samhita, foreshadowed the medicinal properties of stilbenes long before their modern scientific validation. Today, stilbenes are integral to the booming wellness and health supplement market, with resveratrol alone projected to reach a market value of 90 million US$ by 2025. However, challenges in stilbene production persist due to limited natural sources and costly extraction methods. Bioprospecting efforts reveal promising candidates for stilbene production, particularly endophytic fungi, which demonstrate high-yield capabilities and genetic modifiability. However, the identification of optimal strains and fermentation processes remains a critical consideration. The current review emphasizes the knowledge of the medicinal properties of Stilbenes (i.e., cardiovascular, antioxidant, anticancer, anti-inflammatory, etc.) isolated from plant and microbial sources, while also discussing strategies for their commercial production and future research directions. This also includes examples of novel stilbenes compounds reported from plant and endophytic fungi.

Protective Effect of Resveratrol Combined with Levodopa Against Oxidative Damage in Dopaminergic Neurons

Levodopa (L-3,4-dihydroxyphenylalanine, L-Dopa) alleviates the symptoms of Parkinson's disease (PD), yet prolonged usage may give rise to severe adverse effects. Resveratrol (RSV) is a potent antioxidant, anticancer and anti-inflammatory agent. And a variety of polyphenol antioxidant compounds derived from RSV combined with levodopa have demonstrated neuroprotective activity against neuronal cell death. The purpose of this study was to examine the impact of this combination of RSV and L-Dopa on the survival rate, growth status, and reactive oxygen species (ROS) of MES23.5 dopamine (DA) neuron cells. In this study, we induced MPP+ in MES23.5 dopamine neuron cells and observed their survival rate, growth status, ROS content, as well as the effect of RSV combined with L-Dopa on cell survival. We also measured malondialdehyde (MDA) levels and superoxide dismutase (SOD) activity levels as indicators of mitochondrial function, oxidative stress, and oxidative damage in the cells. Our results indicated that the MES23.5 dopamine neurons had decreased survival, poor growth status, and increased ROS content after MPP+ induction. Moreover, we found that MDA levels were elevated, and SOD activity levels were decreased, suggesting that the cells experienced abnormal mitochondrial function. However, when RSV was combined with L-Dopa, the cells showed a reduced level of MPP + -induced oxidative damage, with a more significant inhibitory effect observed in the RSV group at a concentration of 50 μmol/L. In conclusion, we found that the effects of co-administration of RSV with L-Dopa (100 μmol/L) was more effective than L-Dopa administered at the high dose. Thus, we found that RSV has the potential to reduce the dose of L-Dopa required to improve PD symptoms.

The effects of curcumin-piperine supplementation on inflammatory, oxidative stress and metabolic indices in patients with ischemic stroke in the rehabilitation phase: a randomized controlled trial

BACKGROUND

Stroke is a leading cause of death worldwide, which is associated with a heavy economic and social burden. The purpose of this study was to investigate the effects of supplementation with curcumin-piperine combination in patients with ischemic stroke in the rehabilitation stage.

METHODS

In this randomized controlled trial, 66 patients with stroke were randomized into two groups receiving curcumin-piperine tablets (500 mg curcumin + 5 mg piperine) and matched placebo tablets for 12 weeks. High-sensitivity C-reactive protein (hs-CRP), carotid intima-media thickness (CIMT), thrombosis, total antioxidant capacity (TAC), lipid profile, anthropometric indices, blood pressure, and quality of life were assessed before and after the intervention. Statistical data analysis was done using SPSS22 software.

RESULTS

A total of 56 patients with a mean age of 59.80 ± 4.25 years completed the trial. Based on ANCOVA test, adjusted for baseline values, curcumin-piperine supplementation for 12 weeks resulted in significant reductions in serum levels of hs-CRP (p = 0.026), total cholesterol (TC) (p = 0.009), triglycerides (TG) (p = 0.001), CIMT (p = 0.002), weight (P = 0.001), waist circumference (p = 0.024), and systolic and diastolic blood pressure (p < 0.001), and a significant increase in TAC (p < 0.001) in comparison to the placebo. Pain score significantly increased in both groups; however, its increase was significantly higher in the placebo group compared with the intervention group (p = 0.007). No significant changes were observed between the two groups in terms of serum fibrinogen, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and quality of life indices.

CONCLUSION

Curcumin-piperine supplementation had beneficial effects on CIMT, serum hs-CRP, TC, TG, TAC, and systolic and diastolic blood pressure in patients with ischemic stroke in the rehabilitation stage.

Pinostilbene inhibits full-length and splice variant of androgen receptor in prostate cancer

Prostate cancer is the most prevalent cancer in men worldwide and is promoted by the sex hormone androgen. Expression of androgen from the testis can be significantly reduced through castration. However, as most prostate cancer patients acquire castration resistance, additional therapeutic solutions are necessary. Although anti-androgens, such as enzalutamide, have been used to treat castration-resistant prostate cancer (CRPC), enzalutamide-resistant CRPC (Enz-resistant CRPC) has emerged. Therefore, development of novel treatments for Enz-resistant CRPC is urgent. In this study, we found a novel anti-androgen called pinostilbene through screening with a GAL4-transactivation assay. We confirmed that pinostilbene directly binds to androgen receptor (AR) and inhibits its activation and translocalization. Pinostilbene treatment also reduced the protein level and downstream gene expression of AR. Furthermore, pinostilbene reduced the protein level of AR variant 7 in the Enz-resistant prostate cancer cell line 22Rv1 and inhibited cell viability and proliferation. Our results suggest that pinostilbene has the potential to treat Enz-resistant CRPC.

Pterostilbene Enhances Thermogenesis and Mitochondrial Biogenesis by Activating the SIRT1/PGC-1α/SIRT3 Pathway to Prevent Western Diet-Induced Obesity

SCOPE

Sirtuin 1/peroxisome proliferator-activated receptor gamma co-activator 1 alpha (SIRT1/PGC-1α) pathway activation is known to promote thermogenesis and mitochondrial biogenesis. Pterostilbene (PSB) and pinostilbene (PIN), the methylated analogs of resveratrol, are potential candidates to enhance thermogenesis and mitochondrial biogenesis.

METHOD AND RESULTS

A model of Western diet-induced obesity in mice is designed. Either PSB or PIN is supplemented in the diet for 16 weeks. Both samples can significantly reduce body weight gain but only PSB can decrease inguinal adipose tissue weight. Besides, both samples can promote lipolysis but only PSB supplementation activates the SIRT1/PGC-1α/SIRT3 pathway to enhance mitochondrial biogenesis and thermogenesis in the inguinal adipose tissue. In addition, although both samples exert a modulatory effect on gut microbiota but significant increments in fecal isobutyric acid, valeric acid, and isovaleric acid are only observed in the PSB group, functioning as gut microbial metabolites.

CONCLUSION

Overall, these findings suggest PSB and PIN as potential candidates for the improvement of obesity and gut microbiota dysbiosis. With its higher stability, PSB exerts a greater effect than PIN by promoting thermogenesis and mitochondrial biogenesis via SIRT1 activation.

Molecular Dynamics Simulations of Selected Amorphous Stilbenoids and Their Amorphous Solid Dispersions with Poly(Vinylpyrrolidone)

Amorphous solid dispersions (ASDs) are one of the promising strategies to improve the solubility and dissolution rate of poorly soluble compounds. In this study, Molecular Dynamics simulations were used to investigate the interactions between three selected stilbenoids with important biological activity (resveratrol, pinostilbene and pterostilbene) and poly(vinylpyrrolidone). The analysis of the pair distribution functions and hydrogen bond distributions reveals a significant weakening of the hydrogen bond network of the stilbenoids in ASDs compared to the pure (no polymer) amorphous systems. This is accompanied by an increase in the mobility of the stilbenoid molecules in the ASDs, both in the translational dynamics determined from the molecular mean square displacements, and in the molecular reorientations followed by analysing several torsional distributions.

Conjugation, Prodrug, and Co-Administration Strategies in Support of Nanotechnologies to Improve the Therapeutic Efficacy of Phytochemicals in the Central Nervous System

Phytochemicals, produced as secondary plant metabolites, have shown interesting potential therapeutic activities against neurodegenerative diseases and cancer. Unfortunately, poor bioavailability and rapid metabolic processes compromise their therapeutic use, and several strategies are currently proposed for overcoming these issues. The present review summarises strategies for enhancing the central nervous system's phytochemical efficacy. Particular attention has been paid to the use of phytochemicals in combination with other drugs (co-administrations) or administration of phytochemicals as prodrugs or conjugates, particularly when these approaches are supported by nanotechnologies exploiting conjugation strategies with appropriate targeting molecules. These aspects are described for polyphenols and essential oil components, which can improve their loading as prodrugs in nanocarriers, or be part of nanocarriers designed for targeted co-delivery to achieve synergistic anti-glioma or anti-neurodegenerative effects. The use of in vitro models, able to simulate the blood-brain barrier, neurodegeneration or glioma, and useful for optimizing innovative formulations before their in vivo administration via intravenous, oral, or nasal routes, is also summarised. Among the described compounds, quercetin, curcumin, resveratrol, ferulic acid, geraniol, and cinnamaldehyde can be efficaciously formulated to attain brain-targeting characteristics, and may therefore be therapeutically useful against glioma or neurodegenerative diseases.

Curcumin, Resveratrol and Cannabidiol as Natural Key Prototypes in Drug Design for Neuroprotective Agents

Nowadays, neurodegenerative diseases (NDs), such as Parkinson's disease (PD), Alzheimer's disease (AD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS), represent a great challenge in different scientific fields, such as neuropharmacology, medicinal chemistry, molecular biology and medicine, as all these pathologies remain incurable, with high socioeconomic impacts and high costs for governmental health services. Due to their severity and multifactorial pathophysiological complexity, the available approved drugs for clinic have not yet shown adequate effectiveness and exhibited very restricted options in the therapeutic arsenal; this highlights the need for continued drug discovery efforts in the academia and industry. In this context, natural products, such as curcumin (1), resveratrol (2) and cannabidiol (CBD, 3) have been recognized as important sources, with promising chemical entities, prototype models and starting materials for medicinal organic chemistry, as their molecular architecture, multifunctional properties and single chemical diversity could facilitate the discovery, optimization and development of innovative drug candidates with improved pharmacodynamics and pharmacokinetics compared to the known drugs and, perhaps, provide a chance for discovering novel effective drugs to combat NDs. In this review, we report the most recent efforts of medicinal chemists worldwide devoted to the exploration of curcumin (1), resveratrol (2) and cannabidiol (CBD, 3) as starting materials or privileged scaffolds in the design of multi-target directed ligands (MTDLs) with potential therapeutic properties against NDs, which have been published in the scientific literature during the last 10 years of research and are available in PubMed, SCOPUS and Web of Science databases.

6-C-(E-Phenylethenyl)-naringenin, a Styryl Flavonoid, Inhibits Advanced Glycation End Product-Induced Inflammation by Upregulation of Nrf2

Styryl flavonoids can be formed during the thermal processing of meats and flavonoid-enriched foods, showing high potentials in the prevention of different diseases. In this study, the protective effects of several styryl flavonoids against advanced glycation end product (AGE)-induced inflammation were evaluated, with 6-C-(E-phenylethenyl)-naringenin (6-PN) showing the strongest activity among them. The results indicated that 6-PN significantly ameliorated AGE-induced damages in human umbilical vein endothelial cells, including inhibition of pro-inflammatory cytokines and reactive oxygen species (ROS) production through downregulating the protein levels of the receptor for AGEs (RAGE) and NADPH oxidase. Notably, 6-PN possessed a much higher bioavailability than its parental compound, naringenin. Furthermore, 6-PN also promoted the activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway that was suppressed by AGEs, and the anti-inflammatory effects of 6-PN disappeared when the cells were treated with ML385, a Nrf2 inhibitor. Hence, 6-PN might inhibit AGE-induced inflammation by the RAGE/ROS/Nrf2 signaling pathway.

Neuroprotective Effects of Resveratrol in In vivo and In vitro Experimental Models of Parkinson's Disease: a Systematic Review

Parkinson's disease (PD) is currently the second most common neurodegenerative disease, being characterized by motor and non-motor symptoms. The therapeutic options available for its treatment are limited, do not slow the progression of the disease, and have serious side effects. For this reason, many studies have sought to find compounds with neuroprotective properties that bring additional benefits to current therapy. In this context, resveratrol is a phenolic compound, found in many plant species, capable of crossing the blood-brain barrier and having multiple biological properties. Experimental studies in vitro and in vivo have shown that it can prevent or slow the progression of a variety of diseases, including PD. In this systematic review, we summarize the effects of resveratrol in experimental in vivo and in vitro models of PD and discuss the molecular mechanisms involved in its action. The bibliographic search was performed in the databases of PubMed, Web of Science, SciELO, and Google Scholar, and based on the inclusion criteria, 41 articles were selected and discussed. Most of the included studies have demonstrated neuroprotective effects of resveratrol. In general, resveratrol prevented behavioral and/or neurological disorders, improved antioxidant defenses, reduced neuroinflammatory processes, and inhibited apoptosis. In summary, this systematic review offers important scientific evidence of neuroprotective effects of resveratrol in PD and also provide valuable information about its mechanism of action that can support future clinical studies.

Grafting Resveratrol onto Mesoporous Silica Nanoparticles towards Efficient Sustainable Immunoregulation and Insulin Resistance Alleviation for Diabetic Periodontitis Therapy

The treatment of diabetic periodontitis (DP) has become a tough challenge in dental clinic mainly due to the intrinsic drawbacks of conventional therapy strategy and currently unclear mechanisms to elucidate...

Targeting the Wnt Signaling Pathway in Liver Fibrosis for Drug Options: An Update

Liver fibrosis is a life-threatening disease, with challenging morbidity and mortality for healthcare systems worldwide. It imparts an enormous economic burden to societies, making continuous research and informational updates about its pathogenesis and treatment crucial. This review's focus is on the current knowledge about the Wnt signaling pathway, serving as an important pathway in liver fibrosis development and activation of hepatic stellate cells (HSCs). Two types of Wnt pathways are distinguished, namely the ß-catenin-dependent canonical and non-canonical Ca²⁺ or planar cell polarity (PCP)-dependent pathway. The dynamic balance of physiologically healthy liver and hepatocytes is disturbed by repeated liver injuries. Activation of the ß-catenin Wnt pathway prevents the regeneration of hepatocytes by the replacement of extracellular matrix (ECM), leading to the appearance of scar tissue and the formation of regenerated nodular hepatocytes, lacking the original function of healthy hepatocytes. Therefore, liver function is reduced due to the severely advanced disease. Selective inhibition of ß-catenin inhibits inflammatory processes (since chemokines and pro-inflammatory cytokines are produced during Wnt activation), reduces growth of activated HSCs and reduces collagen synthesis and angiogenesis, thereby reducing the progression of liver fibrosis in vivo. While the canonical Wnt pathway is usually inactive in a physiologically healthy liver, it shows activity during cell regeneration or renewal and in certain pathophysiological conditions, such as liver diseases and cancer. Targeted blocking of some of the basic components of the Wnt pathway is a therapeutic approach. These include the frizzled transmembrane receptor (Fz) receptors using the secreted frizzled-related protein family (sFRP), Fz-coreceptors low-density LRP 5/6 through dickkopf-related protein 1 (DKK1) or niclosamide, glycogen kinase-3 beta (GSK-3β) using SB-216763, cyclic-AMP response element-binding protein (CBP) using PRI-724 and ICG-001, the lymphoid enhancer binding factor (LEF)/T cell-specific transcription factor (TCF) system as well as Wnt inhibitory factor 1 (WIF1) and miR-17-5p using pinostilbene hydrate (PSH). Significant progress has been made in inhibiting Wnt and thus stopping the progression of liver fibrosis by diminishing key components for its action. Comprehending the role of the Wnt signaling pathway in liver fibrosis may lead to discovery of novel targets in liver fibrosis therapeutic strategies' development.

Inhibitory Effects of Pinostilbene on Adipogenesis in 3T3-L1 Adipocytes: A Study of Possible Mechanisms

Resveratrol is a phytoalexin with multiple bioactive properties, including antioxidative, neuroprotective, cardioprotective, and anticancer effects. However, resveratrol exhibits structural instability in response to UV irradiation, alkaline pH, and oxygen exposure. Thus, resveratrol derivatives have attracted considerable research interest. In this study, we aimed to evaluate the anti-adipogenic effects of pinostilbene hydrate (PH), a methylated resveratrol derivative, in 3T3-L1 cells. We also evaluated the mechanisms underlying the effects of PH on adipogenesis in 3T3-L1 adipocytes. Oil Red O staining, lipid accumulation assay, and triglyceride (TG) content assay revealed that PH significantly inhibited lipid and TG accumulation without cytotoxicity. In addition, we determined that PH decreased the expression of adipogenesis-related transcription factors, such as PPARγ, C/EBPα, SREBP-1c, and FABP4, and the phosphorylation of MAPK and protein kinase B (AKT). Moreover, PH attenuated the expression of CREB and C/EBPβ, while increasing the phosphorylation of AMPK and ACC, and decreasing the expression of fatty acid synthase and FABP4. Based on these results, we suggest that PH suppresses adipogenesis in 3T3-L1 cells via the activation of the AMPK signaling pathway and the inhibition of the MAPK and AKT insulin-dependent signaling pathways.

Emerging roles of oxidative stress in brain aging and Alzheimer's disease

Reactive oxygen species (ROS) are metabolic byproducts that are necessary for physiological function but can be toxic at high levels. Levels of these oxidative stressors increase gradually throughout the lifespan, impairing mitochondrial function and damaging all parts of the body, particularly the central nervous system. Emerging evidence suggests that accumulated oxidative stress may be one of the key mechanisms causing cognitive aging and neurodegenerative diseases such as Alzheimer's disease (AD). Here, we synthesize the current literature on the effect of neuronal oxidative stress on mitochondrial dysfunction, DNA damage and epigenetic changes related to cognitive aging and AD. We further describe how oxidative stress therapeutics such as antioxidants, caloric restriction and physical activity can reduce oxidation and prevent cognitive decline in brain aging and AD. Of the currently available therapeutics, we propose that long term physical activity is the most promising avenue for improving cognitive health by reducing ROS while promoting the low levels required for optimal function.

Rational Design of Resveratrol O-methyltransferase for the Production of Pinostilbene

Pinostilbene is a monomethyl ether analog of the well-known nutraceutical resveratrol. Both compounds have health-promoting properties, but the latter undergoes rapid metabolization and has low bioavailability. O-methylation improves the stability and bioavailability of resveratrol. In plants, these reactions are performed by O-methyltransferases (OMTs). Few efficient OMTs that monomethylate resveratrol to yield pinostilbene have been described so far. Here, we report the engineering of a resveratrol OMT from Vitis vinifera (VvROMT), which has the highest catalytic efficiency in di-methylating resveratrol to yield pterostilbene. In the absence of a crystal structure, we constructed a three-dimensional protein model of VvROMT and identified four critical binding site residues by applying different in silico approaches. We performed point mutations in these positions generating W20A, F24A, F311A, and F318A variants, which greatly reduced resveratrol's enzymatic conversion. Then, we rationally designed eight variants through comparison of the binding site residues with other stilbene OMTs. We successfully modified the native substrate selectivity of VvROMT. Variant L117F/F311W showed the highest conversion to pinostilbene, and variant L117F presented an overall increase in enzymatic activity. Our results suggest that VvROMT has potential for the tailor-made production of stilbenes.

Methylated Metabolites of Chicoric Acid Ameliorate Hydrogen Peroxide (H2O2)-Induced Oxidative Stress in HepG2 Cells

Chicoric acid (CA) can display health benefits as a dietary polyphenol. However, as CA is widely metabolized in vivo, the actual compounds responsible for its bioactivities are not entirely known. Herein, the major methylated metabolites of CA were isolated from an in vitro co-incubation system, and their structures were elucidated. The antioxidant activities of the monomethylated metabolites (M1) and dimethylated metabolites (M2) of CA were evaluated against H₂O₂-induced oxidative stress damage in HepG2 cells and compared to CA. The results indicated that both M1 and M2 had better antioxidant capacities than CA by increasing cell viability, improving mitochondrial function, and balancing cellular redox status. These compounds also prevented oxidative stress by mediating the Keap1/Nrf2 transcriptional pathway and downregulating enzyme activity. The current research indicates that the methylated metabolites of CA could potentially be the candidates that are responsible for the biological efficacies attributed to CA.

Vina-Ginsenoside R4 from Panax ginseng Leaves Alleviates 6-OHDA-Induced Neurotoxicity in PC12 Cells Via the PI3K/Akt/GSK-3β Signaling Pathway

Vina-ginsenoside R4 (VGN4) is the first example of protopanaxatriol saponin possessing sugar chains located at C-3 and C-20 of aglycone. However, to the best of our knowledge, no report has been published on the neuroprotective effect of VGN4. In the present work, we investigated the neuroprotective effect of VGN4 against 6-hydroxydopamine (6-OHDA)-induced toxicity and its potential mechanism. Pretreatment of PC12 cells with VGN4 attenuated 6-OHDA-induced cell damage and cell apoptosis, which was correlated with the decrease of reactive oxygen species and the increase of antioxidant enzyme activities including superoxide dismutase and catalase. In addition, VGN4 markedly decreased nuclear translation of the nuclear factor-κB and PI3K/Akt/GSK/3β signaling pathway including p85, PDK1, Akt, and GSK-3β. Further studies revealed that PI3K siRNA attenuated the neuroprotective effect of VGN4 on caspase-3 activity. These data indicate that VGN4 might have the potential to be developed as a new neuroprotective functional food.

Pinostilbene hydrate suppresses hepatic stellate cell activation via inhibition of miR-17-5p-mediated Wnt/β-catenin pathway

BACKGROUND

In the development of liver fibrosis, activated hepatic stellate cells (HSCs) contribute to the synthesis and deposition of extracellular matrix (ECM) proteins. HSC activation is considered as a central driver of liver fibrosis. Recently, microRNAs (miRNAs) have been reported to act as key regulators in HSC activation.

PURPOSE

Pinostilbene hydrate (PSH), a methylated derivative of resveratrol, has demonstrated anti-inflammatory, antioxidant and anti-tumour activities. However, the effects of PSH on HSC activation remain unclear.

METHODS

The effects of PSH on HSC activation were examined. Moreover, the roles of WNT inhibitory factor 1 (WIF1) and miR-17-5p in the effects of PSH on HSC activation were examined.

RESULTS

PSH induced a significant reduction in HSC proliferation. PSH also effectively inhibited HSC activation, with reduced α-SMA and collagen expression. Notably, it was found that Wnt/β-catenin signalling was involved in the effects of PSH on HSC activation. PSH resulted in Wnt/β-catenin signalling inactivation, with a reduction in TCF activity as well as β-catenin nuclear translocation. Further studies showed that PSH inhibited Wnt/β-catenin signalling via regulation of WIF1 and miR-17-5p. Reduced HSC activation caused by PSH could be restored by loss of WIF1 or miR-17-5p mimics. Luciferase reporter assays further confirmed that WIF1 was a target of miR-17-5p.

CONCLUSION

PSH has a significant protective effect against HSC activation. In addition, we demonstrate that PSH enhances WIF1 expression and inhibits Wnt/β-catenin signalling via miR-17-5p, contributing to the suppression of HSC activation.

Antioxidants Targeting Mitochondrial Oxidative Stress: Promising Neuroprotectants for Epilepsy

Mitochondria are major sources of reactive oxygen species (ROS) within the cell and are especially vulnerable to oxidative stress. Oxidative damage to mitochondria results in disrupted mitochondrial function and cell death signaling, finally triggering diverse pathologies such as epilepsy, a common neurological disease characterized with aberrant electrical brain activity. Antioxidants are considered as promising neuroprotective strategies for epileptic condition via combating the deleterious effects of excessive ROS production in mitochondria. In this review, we provide a brief discussion of the role of mitochondrial oxidative stress in the pathophysiology of epilepsy and evidences that support neuroprotective roles of antioxidants targeting mitochondrial oxidative stress including mitochondria-targeted antioxidants, polyphenols, vitamins, thiols, and nuclear factor E2-related factor 2 (Nrf2) activators in epilepsy. We point out these antioxidative compounds as effectively protective approaches for improving prognosis. In addition, we specially propose that these antioxidants exert neuroprotection against epileptic impairment possibly by modulating cell death interactions, notably autophagy-apoptosis, and autophagy-ferroptosis crosstalk.

Inhibitory Effects of Pinostilbene Hydrate on Melanogenesis in B16F10 Melanoma Cells via ERK and p38 Signaling Pathways

Melanin protects our skin from harmful ultraviolet (UV) radiation. However, when produced in excess, it can cause hyperpigmentation disorders, such as melanoma, freckles, lentigo, and blotches. In this study, we investigated the effects of pinostilbene hydrate (PH) on melanogenesis. We also examined the underlying mechanisms of PH on melanin production in B16F10 cells. Our findings indicated that PH significantly inhibits melanin content and cellular tyrosinase activity in cells without causing cytotoxicity. In addition, Western blot analysis showed that PH downregulated the protein levels of microphthalmia-associated transcription factor (MITF), tyrosinase, and other melanogenic enzymes, such as tyrosinase-related protein-1 (TRP-1) and tyrosinase-related protein-2 (TRP-2). Although PH activated the phosphorylation of extracellular signal-regulated kinase (ERK), it inhibited p38 mitogen-activated protein kinases (p38). Furthermore, the inhibition of tyrosinase activity by PH was attenuated by treatment with PD98059 (a specific ERK inhibitor). Additionally, p-AKT was upregulated by PH treatment. Finally, the inhibitory effects of PH on melanin content and tyrosinase activity were confirmed in normal human melanocytes. These results suggest PH downregulates melanogenesis via the inhibition of MITF expression, followed by the MAPKase signaling pathways. Thus, PH may be used to treat or prevent hyperpigmentation disorders and in functional cosmetic agents for skin whitening.

Pinostilbene Hydrate Inhibits the Migration and Invasion of Human Nasopharyngeal Carcinoma Cells by Downregulating MMP-2 Expression and Suppressing Epithelial-Mesenchymal Transition Through the Mitogen-Activated Protein Kinase Signaling Pathways

Background: Nasopharyngeal carcinoma (NPC) is one of the most common head and neck cancers in East and Southeast Asia. During the past decades, advances in radiotherapy and chemotherapy had shown the improvement in tumor control with fewer side effects. Nevertheless, metastasis of NPC causes treatment failure and is often associated with poor clinical outcome and cancer mortality.

Hypothesis/Purpose: Pinostilbene hydrate (PSH) was recently demonstrated to have anti-metastatic properties on human oral cancers. However, the effects of PSH on NPC cells remain unknown.

Methods and Results: This study aims to investigate the anti-cancer ability of PSH on human NPC by wound healing, transwell assays, zymography assay, and Western blot assay to explore the possible underlying mechanisms. PSH significantly reduced the migrated distance of NPC cells in a dose-dependent manner and the abilities of cancer cell migration and invasion were markedly inhibited. The activity and the expression of MMP-2 were also significantly decreased after treatment with PSH. Furthermore, combined treatment of PSH with ERK1/2 inhibitor (U0126) caused significant elevation of the activity and the expression of MMP-2. Additionally, PSH upregulated the expression levels of E-cadherin and Claudin-1 while downregulating that of N-cadherin and vimentin on both NPC cell lines.

Conclusion: Our research illustrates that PSH inhibits the migration and invasion of human NPC cells. After exposure to PSH on NPC, the expression of MMP-2 is downregulated and EMT is suppressed through MAPK signaling pathways. These observations suggest that PSH could be a potential anti-metastatic agent for patients with NPC.

Antioxidant Activity of Selected Stilbenoid Derivatives in a Cellular Model System

The stilbenoids, a group of naturally occurring phenolic compounds, are found in a variety of plants, including some berries that are used as food or for medicinal purposes. They are known to be beneficial for human health as anti-inflammatory, chemopreventive, and antioxidative agents. We have investigated a group of 19 stilbenoid substances in vitro using a cellular model of THP-1 macrophage-like cells and pyocyanin-induced oxidative stress to evaluate their antioxidant or pro-oxidant properties. Then we have determined any effects that they might have on the expression of the enzymes catalase, glutathione peroxidase, and heme oxygenase-1, and their effects on the activation of Nrf2. The experimental results showed that these stilbenoids could affect the formation of reactive oxygen species in a cellular model, producing either an antioxidative or pro-oxidative effect, depending on the structure pinostilbene (2) worked as a pro-oxidant and also decreased expression of catalase in the cell culture. Piceatannol (4) had shown reactive oxygen species (ROS) scavenging activity, whereas isorhapontigenin (18) had a mild direct antioxidant effect and activated Nrf2-antioxidant response element (ARE) system and elevated expression of Nrf2 and catalase. Their effects shown on cells in vitro warrant their further study in vivo.

Oxyresveratrol exerts ATF4- and Grp78-mediated neuroprotection against endoplasmic reticulum stress in experimental Parkinson's disease

Objectives: Endoplasmic reticulum (ER) stress is one of the key mechanisms contributing to Parkinson's disease (PD) pathology. Pathways triggered by ER stress are protective at early stages and initiate apoptosis when the damage is extensive. Methods: We have previously reported that oxyresveratrol rescues cells from oxidative stress and apoptosis in a cell culture model of PD. The aim of this study was to investigate whether the neuroprotective mechanism of oxyresveratrol extends to PD-associated ER stress. For this purpose, we employed two cellular models; to induce severe ER stress, Mes23.5 cells were treated with 6-hydroxydopamine (6-OHDA) and for ER stress driven by chaperones, human neuroblastoma cells were stably transfected to overexpress familial mutants of α-synuclein (α-syn). Results: Our results indicate that oxyresveratrol exhibits distinct modes of protection in both models. In the 6-OHDA model, it inhibited the transcription of activating transcription factor 4 (ATF4), which controls the fate of pro-apoptotic proteins. On the other hand, in the α-syn model, oxyresveratrol suppressed mutant A30P oligomer formation, thereby facilitating a reduction of the ER-chaperone, 78-kDa glucose-regulated protein (Grp78). Discussion: In summary, oxyresveratrol is protective against ER stress induced by two different triggers of PD. Owing to its wide range of defense mechanisms, oxyresveratrol is an ideal candidate for a multifactorial disease like PD.

Considerations for the Use of Polyphenols as Therapies in Neurodegenerative Diseases

Over the last two decades, the increase in the incidence of neurodegenerative diseases due to the increasingly ageing population has resulted in a major social and economic burden. At present, a large body of literature supports the potential use of functional nutrients, which exhibit potential neuroprotective properties to mitigate these diseases. Among the most studied dietary molecules, polyphenols stand out because of their multiple and often overlapping reported modes of action. However, ambiguity still exists as to the significance of their influence on human health. This review discusses the characteristics and functions of polyphenols that shape their potential therapeutic actions in neurodegenerative diseases while the less-explored gaps in knowledge of these nutrients will also be highlighted.

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.

In vivoformed metabolites of polyphenols and their biological efficacy

The metabolites of polyphenols are antioxidant, anti-inflammatory and anticancer agents. Being bioavailable, they may play an important role in preventing degenerative diseases.

2,3,5,4'-tetrahydroxy-stilbene-2-O-β-D-glucoside attenuates methionine and choline-deficient diet-induced non-alcoholic fatty liver disease

Previous studies have suggested that 2,3,5,4′-tetrahydroxy-stilbene-2-O-β-D-glucoside (TSG) prevents progression of non-alcoholic fatty liver disease (NAFLD) induced by high-fat diet. The present study aimed to evaluate whether TSG could reverse NAFLD induced by a methionine and choline-deficient (MCD) diet and identify the possible mechanism of action. C57BL6/J mice were fed a MCD diet and were treated with TSG, fenofibrate, and resveratrol for 9 weeks. Regulatory effects of several cytokines and enzymes, including Nod-like receptor protein 3, apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain (ASC), caspase-1, interleukin (IL)-18, IL-1β, and gut microbiota balance were investigated. TSG significantly reduced NAFLD biochemical indexes, including total cholesterol, triglyceride, low density lipoprotein cholesterol, very low density lipoprotein cholesterol, aspartate aminotransferase and free fatty acid. Middle dosage (TSG.M, 35 mg/kg) of TSG reduced the expression of ASC and caspase-1. Furthermore, TSG displayed gut microbiota regulatory effects on MCD-induced NAFLD mice. The results of the present study suggested that TSG prevented the occurrence and development of MCD diet-induced NAFLD. The data further indicated that TSG may serve as a promising lead compound that may aid with intervention in NAFLD therapy.

Alkylated resveratrol prodrugs and metabolites as potential therapeutics for neurodegenerative diseases

Resveratrol is a naturally occurring stilbene which has shown promising results as treatment for several neurodegenerative diseases. However, its application is limited due to its low efficacy and bioavailability. Here, we have designed and synthesized alkylated resveratrol prodrugs combining structural modification to improve antioxidant and anti-inflammatory properties and the preparation of prodrugs to extend drug bioavailability. For comparison we also studied resveratrol prodrugs and alkylated resveratrol derivatives. Methylated and butylated resveratrol derivatives showed the best in vitro neuroprotective and anti-inflammatory activity. The glucosyl- and glucosyl-acyl- prodrugs of these derivatives showed lower toxicity on zebra fish embryo. When neuroprotection was examined on pentylenetetrazole challenged zebra fish, they were capable of reverting neuronal damage but to a lower extent than resveratrol. Nevertheless, 3-O-(6'-O-octanoyl)-β-d-glucopyranoside resveratrol (compound 8) recovered AChE activity over 100% whereas resveratrol only up to 92%. In a 3-nitropropionic acid mice model of Huntington's disease, resveratrol derivative 8 delayed the onset and reduced the severity of HD-like symptoms, by improving locomotor activity and protecting against weight loss. Its effects involved an equal antioxidant but better anti-inflammatory profile than resveratrol as shown by SOD2 expression in brain tissue and circulating levels of IL-6 (11 vs 18 pg/mL), respectively. Finally, the octanoyl chain in compound 8 could be playing a role in inflammation and neuronal development indicating it could be acting as a double-drug, instead of as a prodrug.

Resveratrol and pinostilbene confer neuroprotection against aging-related deficits through an ERK1/2-dependent mechanism

Age-related declines in motor function may be due, in part, to an increase in oxidative stress in the aging brain leading to dopamine (DA) neuronal cell death. In this study, we examined the neuroprotective effects of natural antioxidants resveratrol and pinostilbene against age-related DAergic cell death and motor dysfunction using SH-SY5Y neuroblastoma cells and young, middle-aged, and old male C57BL/6 mice. Resveratrol and pinostilbene protected SH-SY5Y cells from a DA-induced decrease in cell viability. Dietary supplementation with resveratrol and pinostilbene inhibited the decline of motor function observed with age. While DA and its metabolites (DOPAC and HVA), dopamine transporter, and tyrosine hydroxylase levels remain unchanged during aging or treatment, resveratrol and pinostilbene increased ERK1/2 activation in vitro and in vivo in an age-dependent manner. Inhibition of ERK1/2 in SH-SY5Y cells decreased the protective effects of both compounds. These data suggest that resveratrol and pinostilbene alleviate age-related motor decline via the promotion of DA neuronal survival and activation of the ERK1/2 pathways.

Lipophilization of Resveratrol and Effects on Antioxidant Activities

Resveratrol (R), a polyphenol, was structurally modified via esterification with selected fatty acids to expand its potential application in lipophilic foods, drugs, and cosmetics. The esterification was carried out using 12 different fatty acids with varying chain lengths and degrees of unsaturation (C3:0-C22:6). Two monoesters, two diesters, and one triester were identified by high-performance liquid chromatography-mass spectrometry, and the monoesters (R-3-O-monodocosahexaenoate and R-4'-O-monodocosahexaenoate) were structurally confirmed by nuclear magnetic resonance. The lipophilicity of resveratrol and its alkyl esters was calculated using ALOGPS 2.1. Resveratrol exhibited greater antioxidant activity in both 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation scavenging assays. Resveratrol esters with long-chain fatty acids (C18:0 and C18:1) showed higher antioxidant activity in the DPPH radical scavenging assay, whereas short-chain fatty acid (C3:0, C4:0, and C6:0) showed higher antioxidant activity in the ABTS radical cation scavenging assay. The results may imply that resveratrol derivatives could be used in lipophilic media as health beneficial antioxidants.

Semisynthesis and biological evaluation of prenylated resveratrol derivatives as multi-targeted agents for Alzheimer's disease

A series of prenylated resveratrol derivatives were designed, semisynthesized and biologically evaluated for inhibition of β-secretase (BACE1) and amyloid-β (Aβ) aggregation as well as free radical scavenging and neuroprotective and neuritogenic activities, as potential novel multifunctional agents against Alzheimer's disease (AD). The results showed that compound 4b exhibited good anti-Aβ aggregation (IC₅₀ = 4.78 µM) and antioxidant activity (IC₅₀ = 41.22 µM) and moderate anti-BACE1 inhibitory activity (23.70% at 50 µM), and could be a lead compound. Moreover, this compound showed no neurotoxicity along with a greater ability to inhibit oxidative stress on P19-derived neuronal cells (50.59% cell viability at 1 nM). The neuritogenic activity presented more branching numbers (9.33) and longer neurites (109.74 µm) than the control, and was comparable to the quercetin positive control. Taken together, these results suggest compound 4b had the greatest multifunctional activities and might be a very promising lead compound for the further development of drugs for AD.

Biorelevant physicochemical profiling of (E)- and (Z)-resveratrol determined from isomeric mixtures

Biorelevant, isomer-specific physicochemical parameters of resveratrol, a multifunctional component in red wines, with cardioprotective, anti-Alzheimer and several other pharmacologic activities were determined. The parameters include site-specific basicities, lipophilicities, solubilities and diffusion constants for the two geometric isomers. The protonation equilibria of (E)- and (Z)-resveratrol were monitored by ¹H NMR-pH titrations. Five closely related auxiliary compounds ((E)-pinostilbene, (Z)-pinostilbene, (E)-pterostilbene, (Z)-pterostilbene and resorcinol) were also studied. Combining the datasets, the group-specific protonation constants of resveratrol isomers were determined. The results show that (Z)-resveratrol is more basic at every protonation site than the (E)-isomer. Lipophilicities are quantified in terms of logP values and were determined by octanol/water partition experiments and quantitative NMR spectroscopy: (E)-resveratrol was found to be more lipophilic. Since the molecular geometries of the isomers differ, diffusion ordered NMR spectroscopy (DOSY) experiments were also carried out to quantify the diffusion capabilities of the isomers: (Z)-resveratrol of bent shape has a slightly higher diffusion coefficient than its extended (E) counterpart. A striking 10-fold difference of water solubility was found in favor of the (Z) isomer, due obviously to the reduced water-repellent character in the more compact molecule. This is so far the greatest recorded solubility difference between geometric isomers of any compounds.

Directing group assisted meta-hydroxylation by C-H activation

meta-Hydroxylated cores are ubiquitous in natural products. Herein, we disclose the first template assisted meta-hydroxylation reaction. Experimental and in silico studies helped us to gain valuable mechanistic insights, including the role of the hexafluoroisopropanol (HFIP) solvent, during C-H hydroxylation. The reactive intermediates, prior to the C-H activation, have been detected by spectroscopic techniques. Additionally, the C-O bond formation has been extended to meta-acetoxylation. The preparation of a phase II quinone reductase activity inducer and a resveratrol precursor illustrated the synthetic significance of the present strategy.

Synthesis and cytotoxic activities of E-resveratrol derivatives

The present study was designed to synthesize derivatives of E-resveratrol and evaluate their cytotoxic activity in vitro. Different functional groups were conjugated with the phenolic hydroxyl group of E-resveratrol, and the double bond of E-resveratrol was reduced. The in vitro cytotoxicity of the synthetic derivatives was evaluated against three tumor cell lines (A549, LAC, and HeLa) using the MTT assay. Twenty-six E-resveratrol derivatives were synthesized and their structures were confirmed by (1)H NMR, MS, IR, and elemental analyses. Compounds 1-6, 12, 15-21, and 23-26 were reported for the first time. Among them, Compounds 1, 2, 4, 5, and 9-11, showed significant cytotoxicity against tumor cells; especially, Compound 1 showed an IC50 value of 4.38 μmol · L(-1) in the A549 cells which was 15-fold more active than E-resveratrol; Compound 9 showed an IC50 value of 1.41 μmol · L(-1) in the HeLa cell line which was 90-fold more active than E-resveratrol, and close to adriamycin. The structure-activity relationships were also investigated. Compounds 1, 2 and 9-11 may serve as potential lead compounds for the discovery of new anticancer drugs.

Effects of pterostilbene and resveratrol on brain and behavior

Age is the greatest universal risk factor for neurodegenerative diseases. During aging, these conditions progress from minor loss of function to major disruptions in daily life, loss of independence and ultimately death. Because approximately 25% of the world population is expected to be older than age 65 by 2050, and no treatments exist to halt or reverse ongoing neurodegeneration, the need for effective prevention strategies is more pressing that ever before. A growing body of research supports the role of diet in healthy aging, particularly diets rich in bioactive phytochemical compounds. Recently, stilbenes such as resveratrol (3, 5, 4'-trans-trihydroxystilbene) and its analogue, pterostilbene, have gained a significant amount of attention for their potent antioxidant, anti-inflammatory, and anticarcinogenic properties. However, evidence for the beneficial effects of stilbenes on cerebral function is just beginning to emerge. In this review, we summarize the current knowledge on the role of resveratrol and pterostilbene in improving brain health during aging, with specific focus on antioxidant and anti-inflammatory signaling and behavioral outcomes.

Bioavailability of dietary polyphenols: Factors contributing to their clinical application in CNS diseases

The anatomical location of the central nervous system (CNS) renders it immunologically and pharmacologically privileged due to the blood brain barrier (BBB). Although this limits the transport of unfavorable molecules to the CNS, the ensuing privilege could be disadvantageous for therapeutic compounds. Hence, the greatest challenge in the pharmacotherapy of CNS diseases is to ensure efficient brain targeting and drug delivery. Research evidences indicate that dietary polyphenols have neuroprotective potential against CNS diseases. However, their selective permeability across BBB, poor absorption, rapid metabolism and systemic elimination limit their bioavailability and therapeutic efficacy. Consequently, the beneficial effects of these orally administered agents in the CNS still remain a subject of debate. This has also limited its clinical application either as independent or adjunctive therapy. Improving the in vivo bioavailability by novel methods could improve the therapeutic feasibility of polyphenols and assist in evolving novel drugs and their derivatives with improved efficacy in vivo. Here we review the mechanistic and pharmacological issues related to the bioavailability of polyphenols with therapeutic implications for CNS diseases. We surmise that improving the bioavailability of polyphenols entails efficient in vivo transport across BBB, biochemical stability, improved half-life and persistent neuroprotection in the CNS.

In vitro assessment of antioxidant activity of tyrosol, resveratrol and their acetylated derivatives

Consumption of phenolic compounds is associated with beneficial effects in humans even though many of them are poorly absorbed. The aim of this study was to investigate the in vitro antioxidant activity of tyrosol (T), resveratrol (R) and their acetylated derivatives (AcD), as increased lipophilicity has been reported to improve absorption. The chemically synthesized AcDs were evaluated by their ability to scavenge DPPH radicals, inhibit non-enzymatic linoleic acid peroxidation, inhibit human serum oxidation in the presence of copper ions and inhibit lipoxygenase activity. T showed an inhibitory effect only in serum oxidation, where the T-acetylated at aromatic-OH was the most active. The T-acetylated at aliphatic-OH and 3,5-diacetyl-R exhibited the most powerful effect in non-enzymatic linoleic acid peroxidation with IC50 values 2.4 mM ± 0.21 and 0.055 mM ± 0.0018, respectively. In all other tests R was the most potent among all its AcD and T. Increasing lipophilicity by acetylation improves antioxidant activity of phenolic compounds in non-enzymatic lipid peroxidation assays.

Adaptive cellular stress pathways as therapeutic targets of dietary phytochemicals: focus on the nervous system

During the past 5 decades, it has been widely promulgated that the chemicals in plants that are good for health act as direct scavengers of free radicals. Here we review evidence that favors a different hypothesis for the health benefits of plant consumption, namely, that some phytochemicals exert disease-preventive and therapeutic actions by engaging one or more adaptive cellular response pathways in cells. The evolutionary basis for the latter mechanism is grounded in the fact that plants produce natural antifeedant/noxious chemicals that discourage insects and other organisms from eating them. However, in the amounts typically consumed by humans, the phytochemicals activate one or more conserved adaptive cellular stress response pathways and thereby enhance the ability of cells to resist injury and disease. Examplesof such pathways include those involving the transcription factors nuclear factor erythroid 2-related factor 2, nuclear factor-κB, hypoxia-inducible factor 1α, peroxisome proliferator-activated receptor γ, and forkhead box subgroup O, as well as the production and action of trophic factors and hormones. Translational research to develop interventions that target these pathways may lead to new classes of therapeutic agents that act by stimulating adaptive stress response pathways to bolster endogenous defenses against tissue injury and disease. Because neurons are particularly sensitive to potentially noxious phytochemicals, we focus on the nervous system but also include findings from other cell types in which actions of phytochemicals on specific signal transduction pathways have been more thoroughly studied.