Pengfei SONG, Jianxue GANG, Sujun ZHAO, Wenqiang YANG, Xiuling YU

College of Pharmacy, Linyi University, Linyi 276000, China

Abstract Resveratrol is a non-ketone polyphenolic compound containing a stilbene structure. It exists in many common medicinal plants. It has many pharmacological activities such as anti-tumor, antioxidant, antibacterial and cardiovascular protection. In this paper, the advances in research of pharmacological activities of resveratrol in recent years were reviewed, to provide a reference for its further development and utilization.

Key words Resveratrol, Pharmacological activities, Advances in research

1 Introduction

As a plant-derived polyphenol compound containing a stilbene structure, Resveratrol (Res) was isolated for the first time from the root ofVeratrumgrandiflorumin the Liliaceae family. Extensive studies have shown that resveratrol has various pharmacological activities, such as anti-tumor, antibacterial, and cardiovascular protection, so it is highly valued by researchers both at home and abroad. In China, the extract of resveratrol has been made into capsules with functions such as regulating blood lipids; at the same time, Canada and Japan have also taken resveratrol as health food. With the continuous deepening of research, many pharmaceutical companies have used resveratrol to develop new drugs for the treatment of type 2 diabetes. Resveratrol has significant effects and good clinical application prospects.

2 Physical and chemical properties

The chemical name of resveratrol includes trans-3,5,4’-trihydroxystilbene and (E)-5-(4-Hydroxystyryl)benzene-1,3-diol, the molecular formula is C14H12O3, and the relative molecular mass is 228.4. Its structural formula is illustrated in Fig.1. Resveratrol can produce fluorescence under ultraviolet light with a wavelength of 365 nm, and can react with ferric chloride-potassium Ferrocyanide (FeCl3-K4[Fe (CN)6]·3H2O). Under natural conditions, resveratrol has cis and trans isomers. There are more trans-resveratrol than cis-resveratrol, and the physiological activity of the trans-isomer is stronger than that of the cis-isomer.

Fig.1 Structural formula of resveratrol

3 Pharmacological activities

3.1 Anti-tumor effectsPrevious studies have shown that both cis and trans isomers of resveratrol have anti-tumor activity, and its action mechanism is to inhibit the activity of protein-tyrosine kinases in the stage of cancer. Extensive medical studies have found that resveratrol can inhibit a variety of malignant tumors, such as liver cancer, stomach cancer, bowel cancer, prostate cancer, leukemia, ovarian cancer, skin cancer,etc.Resveratrol is an indirect activator of silent mating type information regulation 2 homolog-1 (Sirt1)[1]. It can inhibit the occurrence of some precancerous lesions and reduce the probability of cell cancer. Using statistical methods, Shi Jieetal.[2]found that the concentration of 50 μmol/L resveratrol is an effective concentration for studying Sirt1 on ovarian granulosa cell apoptosis.

Some studies have found that resveratrol can slow down the growth and spread of hepatocellular carcinoma when the cells in the liver have become cancerous. It can lay a good foundation for the late treatment of hepatocellular carcinoma caused by chronic HCV (Hepatitis C virus) infection[3-4]. Resveratrol, the main component of grape extract, can kill stem cells of colorectal cancer[5]. Through an experiment, Zeng Yuhua[6]tested the effects of resveratrol on the proliferation and apoptosis of colon cancer cells, and the results showed that resveratrol can inhibit the proliferation of colon cancer cells and induce their apoptosis. Therefore, resveratrol can be used as a potential drug candidate for the treatment of colon cancer.

Qiu Yanxin[7]took human tongue squamous cell carcinoma Tca8113 cells as the research object of resveratrol for the first time and found that resveratrol can effectively inhibit the migration activity of human tongue squamous cell carcinoma Tca8113 cells in a concentration-dependent manner. In addition, resveratrol also can inhibit ribonucleotide reductase, which makes it have a more significant inhibitory effect on the proliferation of many cells. Wen Bingjunetal.[8]found that resveratrol can activate caspase-6 and promote the apoptosis of rat nasopharyngeal carcinoma cell CNE-2Z to achieve anti-cancer effects.

According to findings of He Leietal.[9], resveratrol has the effect of reducing the expression activity of Ki-67 and p21ras protein in cancer cells, making it abnormal in the division period, that is, unable to proliferate normally. Furthermore, resveratrol has a high antioxidant activity and can reduce cell damage caused by free radicals, thereby reducing the rate of cell carcinogenesis. There is a large correlation between abnormal activation and abnormal phosphorylation of JAK2-STAT3 and tumor formation. Resveratrol can significantly inhibit the expression of JAK2 (Janus Kinase 2) signal transducer and activator of transcription 3 (STAT3). The inhibitory effect has a strong correlation with the time and concentration of resveratrol treatment. Resveratrol indirectly hinders the normal functioning of the STAT3 pathway by inhibiting the abnormal phosphorylation of JAK2, and then plays an anti-cancer effect. With the function of inducing differentiation, resveratrol can affect the G2/M phase of the cell cycle of human promyelocytic leukemia cells (HL60), slow down their growth and make them develop in a benign direction. Resveratrol can also effectively inhibit the mutation of typhimurium TM677 strain under the action of 7,12-dimethylbenzanthracene (DMBA) to achieve anti-tumor effect[10].

Resveratrol can fix HL60 cells in the S phase of the cell cycle, making it unable to complete the replication of the genetic material DNA in the cells, so as to prevent cell proliferation. However, this effect is reversible. After removing the resveratrol in the system, the cells restore their normal ability to divide and proliferate[11]. Through treating the glioma cell A172 culturedinvitrowith resveratrol, it was found that its effect of inhibiting the proliferation of cancer cells is achieved by inhibiting the activity of DNA synthetase in cancer cells, and this effect has a high correlation with time and dose. Some scholars pointed out that resveratrol can also inhibit the normal expression of cell growth factor, and transform growth factor and their corresponding receptors to inhibit cell growth and achieve anti-cancer effects[12].

3.2 Antibacterial effectsBacteria in nature have natural drug resistance. Due to the long-term use of antibiotics such as penicillins and cephalosporins, methicillin-resistantStaphylococcusaureus(MRSA) has appeared widely and become the primary problem in clinical treatment[13]. Using the borth microdilution method, Li Yongjunetal.[14]measured the minimum inhibitory concentration (MIC) of the tested strainsinvitroand found that the MIC50and MIC90of resveratrol to MRSA were 0.256 and 0.512 g/L, respectively. Yan Xiaojuanetal.[15]selected water extracts of commonly used antibacterial Chinese medicines such as Coptidis Rhizoma, Sophorae Flavescentis Radix, Forsythiae Fructus and Rhei Radix Et Rhizoma to determine the MIC of MRSA, and found that the MIC values of Anemarrhenae Rhizoma , Raw Rehmannia Root and Sophorae Flavescentis Radix for MRSA were ≥100 g/L, and the MIC values of Coptidis Rhizoma, Rhei Radix Et Rhizoma and Forsythiae Fructus for MRSA were ≤50 g/L. Compared with traditional Chinese medicine, resveratrol has obvious antibacterial effects on MRSA.

3.3 Antioxidant effectsThrough structural analysis, it was found that the polyphenolic structure in resveratrol has the functions of internal antioxidant free radicals, scavenging free radicals and affecting the catabolism of arachidonic acid, and has obvious preventive and therapeutic effects on common diseases of the elderly. Studies in recent years have proved that free radicals can destroy hyaluronic acid and change the pathogenesis of rheumatoid arthritis. Hung Limanetal.[16]found that resveratrol can scavenge free radicals in the body, reduce the formation of free radicals, reduce DNA damage, and protect joints and cartilage.Invitro, a small dose of resveratrol can receive a signal from a class of detoxifying enzymes;invivo, resveratrol can increase the plasma antioxidant effect and reduce the occurrence of peroxidation. This is closely related to reducing the prevalence of coronary artery disease and myocardial infarction[17].

Tamakietal.[18]found that resveratrol can reduce oxidative stress and alveolar bone resorption in a rat periodontitis model. Cristinaetal.[19]confirmed that resveratrol can enhance cell proliferation and eliminate most of the reactive oxygen species (ROS), and prevent oxidative stress induced bone loss. Resveratrol can not only scavenge free radicals, but also inhibit lipoxygenase from producing pro-inflammatory factors by chelating metal compounds, reducing the accumulation of hydrogen oxides, thereby inhibiting the the peroxidative degradation of low-density lipoprotein (LDL)[20-22]. In addition, resveratrol can inhibit the autophagy and apoptosis of granular cells induced by oxidized low-density lipoprotein (LOX-1) by regulating the expression of oxidized low-density lipoprotein[23].

3.4 Anti-inflammatory effectsResveratrol is an inflammatory inhibitor and can directly inhibit the inflammatory reaction process[24]. Studies have shown that resveratrol has a certain anti-inflammatory effect. The action mechanism is related to reducing the activity of white blood cells, removing oxygen free radicals, reducing the production of cyclooxygenase metabolites, prostaglandins and other inflammatory factors, so that arachidonic acid can play a role and achieve anti-inflammatory effect.

Besides, resveratrol can not only inhibit the expression and secretion of matrix metalloproteinase-13 (MMP-13) in osteoblasts caused by lipopolysaccharide ofPorphyromonasendodontalis, but also decrease the expression of some inflammatory factors[25-27]. Wang Pengetal.[28]proved that resveratrol has a certain dose-dependent effect on the inhibition of acute gouty arthritis. Through further experiment, Yang Qibinetal.[29]found that resveratrol can inhibit gout inflammation by regulating the expression of Sirtuin 1 in peripheral blood mononuclear cells of primary gout arthritis.

Sawdaetal.[30]conducted an experimental study on Alzheimer’s disease (AD) patients and found that resveratrol can restrict the penetration of inflammatory mediators such as interleukins into the brain by reducing the permeability of the blood-brain barrier (BBB). According to findings of Meng Xuelian[31], resveratrol can effectively inhibit the toxic factors released by over-activated microglia and has a protective effect on nerve cell damage caused by activated microglia. Using Western blot detection, Lin Qinqinetal.[32]found that resveratrol can inhibit the expression of high mobility group protein 1 (HMGB1) and the expression of inflammasomes containing NLR family Pyrin domain protein 3 (NLRP3), and reduce the inflammatory stress state caused by one-time exhaustive exercise.

Sheng Lietal.[10]treated the mouse model of autoimmune encephalomyelitis and orally administered with resveratrol at a dose of 100 mg/kg daily, observed and found that its clinical symptoms and inflammation were significantly reduced, and significant apoptosis occurred to the inflammatory cells in the bone marrow. At the same time, the levels of TNF-α, IFN-γ, IL-2, IL-9, IL-12, MCP-1, RANTES, Eotaxin and other cytokines and chemokines contained in the serum were significantly reduced.

Resveratrol can significantly inhibit the activity of inducible nitric oxide synthase in macrophages and hinder the formation of inflammatory factor nitric oxide, thereby exerting an anti-inflammatory effect. Through treating human monocytes treated with phorbol esters with resveratrol, it was shown that the presence of resveratrol inhibited the activity of activator protein 1, affected the transcription of interleukin-8 gene, so that the interleukin-8 synthesis process was hindered, thereby reducing the inflammatory response. Furthermore, through the treatment of severe acute pancreatitis rat model with resveratrol, it was found that the pathological damage of the rat model was significantly reduced. Further study has shown that the reason for the reduction of pathological damage in rats is that the presence of resveratrol inhibits the activity of nuclear factor κB (NF-κB), ultimately leading to a relatively significant drop in the levels of tumor necrosis factor α (TNFα) and interleukin-8. In summary, the anti-inflammatory effect of resveratrol may be achieved by reducing the content of cytokines to inhibit the activity of certain substances[33].

3.5 Immunomodulatory effectsLei Yupengetal.[34]found that resveratrol may promote the M2-type polarization of RAW264.7 macrophages stimulated by lipopolysaccharide. As found by Liu Yingbo[35], resveratrol can stimulate the proliferation of splenic lymphocytes, play an immunomodulatory role, and increase the secretion of immune cytokines by up-regulating the expression of lymphocyte mRNA, thereby enhancing the immune function of lymphocytes. Through experiment, Zuninoetal.[36]found that resveratrol has an inhibitory effect on the proliferation and activity of B cells, and has a certain dose-dependent effect on gene expression in B cells. Gao Xiaohuaetal.[37-38]found that resveratrol not only has a higher inhibition rate on the proliferation of antigen-activated T cells, but also can stimulate the specific lethality of cytotoxic T cells. Zhao Hongyue[39]confirmed that resveratrol can improve the bone repair microenvironment by reducing the secretion of inflammatory cytokines by T lymphocytes, thereby promoting bone repair by human umbilical cord mesenchymal stem cells. Li Minjingetal.[40]found that resveratrol can down-regulate the expression of inducible nitric oxide synthase (iNOS) and IL-6, it can inhibit the transport of HMGB1 and the phosphorylation of IκBα. According to findings of An Lifengetal.[11], in the immunosuppressed mouse model treated with resveratrol, the lethality of NK cells, the transformation of T lymphocytes, and the release of antibodies were significantly increased. Thus, resveratrol can indeed increase the humoral and cellular immune response levels of immunosuppressed mice, and it is also involved in the secretion of cytokines, and regulate the immune system at multiple levels to improve immune function.

3.6 Hepatoprotective effectsAccording to findings of Wu Yanbingetal[41], resveratrol can effectively inhibit the increase of serum transaminase in mice after exhaustive exercise liver injury, and the presence of resveratrol can effectively reduce the inflammation of the liver, thereby effectively preventing further liver damage. As found by Liu Yingetal[42], the presence of resveratrol can significantly reduce the levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) contained in rat serum, increase the content of superoxide dismutase (SOD) and reduce the content of malondialdehyde (MDA), accordingly protecting the normal shape and function of the liver.

Guo Xuehong[43]treated the rat liver cells isolated byinsituperfusion with vitamin E to make comparison, and used different concentrations of resveratrol to treat the liver cells damaged by CCl4. After using hepatic stellate cells (HSC) and ferric nitrilotriacetate to stimulate them to produce oxygen stress at the same time, the activities of malondialdehyde (MDA) and alanine aminotransferase (ALT) contained in the cells were further measured, the cell survival rate was counted, and HSC was observed. The results show that resveratrol can significantly increase the survival rate of damaged liver cells, reduce the activity of MDA and ALT, effectively inhibit the proliferation of HSC and also reduce the production of type I collagen, and ultimately preventing liver fibrosis[43].

Resveratrol can further increase the activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in liver cells, and further reduce the consumption of reduced glutathione, thereby indirectly reducing the formation and oxidation of nitric oxide, and reducing the toxic effects of oxides on liver cells[11].

3.7 Protective effect on cardiovascular systemWith the development of economy and the improvement of people’s living standards, cardiovascular disease has become a key health prevention and treatment project in the world. Hypertension and malignant arrhythmia are common cardiovascular diseases. Resveratrol can effectively inhibit the normal aggregation of platelets in the blood, participate in the process of lipid metabolism regulation, promote moderate expansion of blood vessels, and reduce the infarct size, to protect the cardiovascular system[44]. The biological activity of resveratrol is related to the regulation of nuclear factor, deacetylase, protein kinase and other signal conversions. Through regulating the expression of these signal conversions, resveratrol exerts anti-atherosclerosis and anti-thrombotic functions, so as to reduce the disease incidence of cardiovascular system.

3.7.1Protective effect on blood vessels. Blood vessels are the key targets of hypertension which is mainly manifested as atherosclerosis and is a common disease threatening human health. Resveratrol increases the expression of eNOS by activating SIRT1, increases the synthesis and release of NO, promotes vasodilation and prevents the occurrence of endothelial nitric oxide synthase (eNOS) uncoupling, prevent the generation of superoxide free radicals from damaging the function of blood vessels[45-46].

3.7.2Inhibitory effect on atherosclerosis. Common pathological manifestation of cardiovascular diseases such as atherosclerosis and hypertension is vascular calcification, which is also an important cause of morbidity and death. Yang Juhongetal.[47]established a model of resveratrol to treat vascular calcification and found that resveratrol can effectively reduce blood pressure and improve heart function in rats with vascular calcification. Liu Xun[48]stated that resveratrol can increase the secretion of anti-atherosclerotic factor NO, reduce the expression of atherosclerotic factor mRNA, and play an anti-atherosclerotic effect. Jia Xuelingetal.[49]found that resveratrol can reduce the expression of inflammatory factors by regulating the long-chain non-coding RNA MALAT1, and reduce arterial plaque and foam cells, so as to play a protective effect on atherosclerosis.

The existing studies have shown that oxidized low-density lipoprotein (oxLDL) plays a key role in the early and developmental stages of atherosclerosis. It mainly causes the apoptosis of vascular endothelial cells and further increases the possibility of thrombosis. Therefore, to preventing or reduce the formation of thrombus, it is necessary to prevent the apoptosis of vascular endothelial cells as much as possible. Further research results on umbilical vein endothelial cells culturedinvitroshow that the main reasons for the apoptosis of umbilical vein endothelial cells are as follows: (i) generation of reactive oxygen species (ROS) under oxidative stress, (ii) release of mitochondrial cytochrome C caused by fluctuations in the concentration of Ca2+, and (iii) activation of caspase-3 protein. The release of mitochondrial cytochrome C activates caspase-3, ultimately leading to cell apoptosis. However, after treatment with resveratrol, the number of cell apoptosis was significantly reduced. Therefore, it can be inferred that resveratrol can protect the cardiovascular system by preventing cell apoptosis[50].

3.7.3Inhibitory effect on platelet aggregation. Endogenous adenosine diphosphate (ADP) is an important factor affecting platelet aggregation. Experiments have proven that resveratrol has a certain inhibitory effect on the secretion of endogenous ADP and ATP induced by thrombin, and it exhibits aspirin-like effects, inhibiting the activity of cyclooxygenase 1, thereby reducing the generation of thromboxane[51-52]. Resveratrol can reduce blood lipid levels and inhibit platelet aggregation in rats with high blood lipid levels[53]. Another study has shown that the mechanism of resveratrol in reducing platelet aggregation is to block lipid peroxidation and ensure the integrity of endothelial cells by reducing blood lipid levels, affecting the synthesis of nitric oxide, and maintaining the stability of thromboxane and prostaglandin in plasma or tissues and calcium ions inside and outside the cells[54].

3.8 Prevention of neurodegenerative diseasesNeurodegenerative disease, as a chronic disease, is characterized by progressive dysfunction, gradual loss and death of specific populations of neurones. Autophagy dysfunction has an important effect on neurodegenerative diseases. As an activator of SIRT1, resveratrol can accelerate the clearance of pathological proteins through regulating the autophagy, and thus preven neurodegenerative diseases to some extent[55]. Besides, resveratrol can effectively eliminate pathological proteins through inducing cell autophagy, protect dopamine neurons, inhibit striatal dopamine degeneration, and play the neuroprotective effects[56-57]. According to findings of Chen Yueetal[58], resveratrol can effectively reduce the expression of β-amyloid precursor protein (APP) and improve memory ability, and has a certain preventive effect on AD. Some studies have shown that abnormal accumulation of neurofibrils is positively correlated with the severity of AD. Dermautetal.[59-60]further found that resveratrol can reduce the highly phosphorylated tua protein in neurofibrillary tangles to prevent abnormal aggregation in the later stage. Excessive reactive oxygen species produced in mitochondria will aggravate oxidative stress and promote AD. Resveratrol has an antioxidant effect, can effectively remove damaged mitochondria and reduce the production of reactive oxygen species, thereby reducing neuronal oxidative stress damage and protecting patients with AD[61]. In summary, the effect of resveratrol on AD is mainly manifested in interfering with the formation of β-amyloid peptide, reducing the production of tua protein and improving the antioxidant effect, thereby protecting the nervous system.

4 Prospects

In conclusion, resveratrol has broad application prospects. It can kill cancer cells, and has a therapeutic effect on cardiovascular and cerebrovascular diseases. Due to a wide range of sources, low toxicity, resveratrol is suitable for long-term use. However, the existing research is still at the preliminary stage, and the research on drug efficacy is still limited toinvitroanimal experiments. Thus, its clinical application prospects, safety and effectiveness have potential research value. Considering the antioxidant properties of resveratrol, it is feasible to develop resveratrol cosmetics and health products that can delay aging and remove free radicals for the skin, it will have high economic benefits.