Advances in the Treatment of Hepatitis with Flavonoids

Anda WEI, Hua ZHU, Fengfeng XIE, Miao ZHANG, Piaoling HUANG, Wenqi YANG

Guangxi University of Chinese Medicine, Nanning 530200, China

Abstract Flavonoids are important compounds in natural medicines. They have a wide range of pharmacological activity and have important research value and development prospects. In this article, literature on the treatment of hepatitis with flavonoids is searched, and research reports on the treatment of hepatitis with flavonoids in the past ten years are sorted out, in order to provide a basis for the in-depth research and further development of flavonoids in the treatment of hepatitis.

Key words Flavonoid, Hepatitis, Research progress

1 Introduction

Flavonoids are secondary metabolites of plants. From the point of view of structural characteristics, the basic nucleus of their chemical structure is benzopyrone (C6-C3-C6). According to the oxidation degree of the middle three-carbon chain, whether the three-carbon chain is cyclic, the position of the phenyl group,etc., flavonoids are divided into different types, including flavonols, flavonoids, dihydroflavonoids, dihydroflavonols, dihydroisoflavones, isoflavones, chalcones. Flavonoids have a wide range of pharmacological activity. They have effect on the cardiovascular system, reproductive system, digestive system, endocrine system,etc[1-2]. Numerous studies have shown that natural flavonoids can protect the liver, and they have certain effect on acute and chronic hepatitis, hepatitis C, fatty liver and toxic liver injury, in which flavonoids, flavonols, dihydroflavonoids,etc.play a major role. The efficacy of flavonoids is closely related to the structure[3].

The hesperidin (HDN), dihydroquercetin and naringenin isolated from a medicinal plant in Mexico can be used to treat jaundice and chlorhepatitis[4]. An experiment on duck hepatitis A virus (DHAV-1) was conducted. The efficacy of the flavonoid compound baicalin-linalin-cikalin-nosine glycoside R1 (BLIN) in the prescription on DVH was evaluated. It was found that in duck embryo liver cells, at 20 μg/mL, the inhibition rate of BLIN on DHAV-1 was 69.3%. The survival rate of ducklings after BLIN treatment was about 35.5%, which was significantly higher than that of virus control. After the treatment with BLIN, the liver damage and oxidative stress of the infected ducklings were all relieved. This shows that BLIN has a significant effect on DVH. It is expected that BLIN can be used as a new drug for the clinical treatment of DVH.

2 Hesperidin (HDN)

HDN is a derivative of dihydroflavonoid. It is a glycoside formed by hesperetin and rutin. In the study of the mechanism of hesperidin on lipid metabolism and inflammation in rats with alcoholic fatty liver, Sun Jingetal.[5]compared the expression of PPAR-γmRNA, TNF-α, and NF-κBP65m RNA in rat liver, and found that HDN enhanced the expression of PPAR-γmRNA and inhibited the expression of TNF-α and NF-κBP65m RNA in rats. HDN could significantly reduce the fatty and inflammation degree of liver cells, which might be achieved by enhancing the expression of PPAR-γ and reducing the expression of TNF-α and NF-κBP65.

Baietal.found that hesperetin can block bile acid-induced rat hepatocyte apoptosis and cytokine-induced inflammation. The results of TUNEL test and serum AST and ALT detection show that in ConA and D-GalN/lps-induced severe hepatitis, HDN improved the histology of the liver, protected liver cells from damage, and reduced the expression of inflammatory marker iNOS and the expression of tumor necrosis factor α (TNF-α) and IFN-γ, the main mediators of fulminant hepatitis cytotoxicity[6].

3 Flavonols

Quercetin is an effective ingredient in many natural medicines, with molecular formula of C15H10O7. It is widely found in vegetables, fruits and medicinal plants. Modern research shows that quercetin has anti-inflammatory, anti-oxidant, anti-tumor and other pharmacological effects. It can be used for the treatment of liver injury, tumor and other diseases. Miltonprabu[7]pointed out that quercetin is a major flavonoid compound commonly found in apples, berries and other fruits and cruciferous plants. It can be used for the treatment of various liver diseases, and is a promising active substance for the treatment of hepatitis. In the study of the active ingredients of Herba Hyperici Japonici, Zheng Chaoetal.[8]screened out the compounds with the highest anti-hepatitis B virus activityinvitro, including quercetin and quercetin structurally similar compounds. It can be seen that quercetin has a strong anti-hepatitis B effect. Jigucao Ganyan granules are a commonly used medicine for the treatment of hepatitis. It has a significant effect on acute jaundice or non-jaundice hepatitis, with fast efficacy, and can also reduce the sequelae of hepatitis patients. In the granules, quercetin is an important active substance[9]. Ganyankang capsules are a commonly used in-hospital preparation and are mainly used to treat hepatitis. Research on the quality standards of Ganyankang capsules shows that quercetin is the main indicator for the quality control of Ganyankang capsules, and is the material basis for curative effect[10].

Li Jianboetal.[11]studied the therapeutic effect and mechanism of quercetin on non-alcoholic steatohepatitis in rats. The results show that compared with the high-fat model group, the serum LDL-C, TC and AST levels in different doses of quercetin groups were significantly reduced. After treatment with quercetin, liver steatosis and inflammatory cell infiltration in NAS rats were significantly reduced. At the same time, the expression of TNF-α, IL-6 and IL-1β mRNA and NF-κBp65 proteins was significantly inhibited. The mechanism of action may be related to the inhibition of lipid deposition in liver cells and the regulation of the NF-κB pathway.

Liu Minghaoetal.[12]found that high dose of quercetin could reduce inflammatory cell infiltration, significantly improve liver lipid deposition and liver fibrosis, significantly reduce the expression of NF-κB, and increase the expression of PI3K and AKT in rats. Quercetin improved the degree of fatty degeneration of liver tissue in rats with non-alcoholic steatohepatitis. The mechanism of reducing liver inflammation may be achieved by regulating the PI3K/AKT/NF-κB signaling pathway.

Wuetal.[13]studied the protective effect and mechanism of quercetin on ConA-induced hepatitis in mice, and observed that quercetin significantly affected the expression of Bax, Bcl-2, Beclin-1, LC3, P62 and caspase 9. In the experiment, quercetin was used to treat ConA-induced hepatitis in mice, and the expression of TRAF6 and p-JNK decreased in the quercetin group. The results show that quercetin could inhibit ConA-induced autoimmune hepatitis cell apoptosis and autophagy. Lietal.[14]studied the effect of quercetin on ConA-induced hepatitis in mice and its potential molecular mechanism. It was observed that quercetin treatment significantly reduced ConA-induced plasma transaminase concentration and liver necrosis in mice, as well as reduced serum TNF-α, interferon (IFN)-γ and interleukin (IL)-4 levels. The mechanism might be weakening the HMGB1-TLRs-NF-κB signaling pathway.

Wei[15]studied the protective effect and mechanism of quercetin on liver injury caused by triptolide (TP). It was found that the use of quercetin (QE) before the administration of TP can restore the changes caused by TP within a certain dose range, indicating that QE can inhibit the liver damage caused by TP. QE also significantly reduced the expression levels of Th17-related pro-inflammatory cytokines, such as IL-17 and IL-6, and Th17 transcription factor retinoic acid-related orphan receptor-γt (ROR-γt). The mechanism may be regulated by Tim-3 and TLR4-MyD88-NF-κB signaling pathways, making the transfer of Th17 and Treg cells from Th17 dominant to Treg dominant balanced.

Elbeetal.[16]studied the effect of quercetin-streptozotocin (STZ)-induced experimental diabetic liver cell damage. It was found that quercetin significantly changed the histopathology, including cell glycogen depletion, hyperemia, sinus dilation, inflammation in the diabetic group and fibrosis. Quercetin increased the activity of CAT and level of GS, and reduced the levels of H and MDA in diabetic rats. In short, quercetin significantly reduced the liver cell damage of experimental diabetes induced by STZ.

4 Flavonoids

4.1 BaicalinBaicalin is one of the effective ingredients ofScutellariabaicalensis, a plant of the Lamiaceae family. It has a wide range of pharmacological activity such as anti-inflammatory, inhibiting HBV replication, scavenging free radicals, regulating immune function and protecting the liver. It is often used clinically to treat hepatitis, usually in combination with other drugs[17-18].

Song Xinwenetal.[17]conducted clinical research on the treatment of 50 cases of chronic hepatitis B with baicalin combined with IFN. It was found that the cure rate of baicalin combined with IFN treatment group was significantly higher than that of single IFN treatment group. At the same time, it was found that baicalin and IFN could promote HBeAg and HBVDNA to turn negative, thereby resisting inflammation and liver fibrosis. Li Xinchengetal.[18]explored the efficacy of baicalin combined with IFN-α in the treatment of chronic hepatitis B and its influence on cellular immunity. The results show that the ratio of CD4+T and NK cells in the combination treatment group was significantly higher than that in the control group, and the proportion of CD8+T cells in the control group was significantly higher than that in the combination group. Baicalin and IFN have a synergistic effect in fighting liver fibrosis, improving cellular immune status, and promoting the conversion of HBeAg and HBV-DNA to negative.

Li Xiaohuaetal.[19]explored the effect of baicalin combined with lamivudine on cellular immunity in the treatment of chronic hepatitis B. The results show that the ALT, AST and TBil levels in the treatment group were reduced after treatment, all lower than those before treatment and those of the control group. The negative conversion rate of HBeAg and HBV-DNA and the seroconversion rate of HBeAg/HBeAb of the patients were significantly higher than those of the control group; the CD4+cell subset, CD4+/CD8+ratio and NK cell level of the treatment group were higher than those of the control group. The combined use of baicalin and lamivudine can improve cellular immunity.

Ping Jianetal.[20]conductedinvitroexperiment on the anti-hepatitis B virus and anti-liver fibrosis of oxymatrine and baicalin. It was found that the drug combination inhibited the secretion of hepatitis B virus antigen, and the transcription and translation levels of α-SMA and the expression level of type I collagen were significantly better than the treatment with oxymatrine alone. It indicates that baicalin has an inhibitory effect on the secretion of hepatitis B virus antigens by HepG2.2.15 cells and the expression of α-SMA and type I collagen in HSC-T6 cells. Ai Zhenglinetal.[21]explored the anti-inflammatory effect of baicalin in the treatment of non-alcoholic steatohepatitis in rats. After treatment with different doses of baicalin, the serum ALT and AST levels, liver tissue TNFα, IL-1β and IL-6 contents, and interlobular inflammatory cell infiltration in NASH mice were all reduced. Pathology shows that liver cell steatosis was gradually reduced. The mechanism may be increasing the activity of GSH and SOD enzymes and reducing the production of TNFα, IL-1β and IL-6 inflammatory factors, thereby alleviating liver inflammation. Li Jinkeetal.[22]observed clinically that the alanine aminotransferase recovery rate and HBV-DNA and hepatitis B antigen negative conversion rates of the combination of baicalin capsules and IFN were significantly higher than those of IFN alone. It shows that baicalin has obvious transaminase-reducing and antiviral effect. Chenetal.[23]proposed that baicalin (BA) has a strong antiviral effect, but its solubility is very poor. They modified BA with phospholipid complex to obtain BA phospholipid complex (BAPC), and carried out duck hepatitis A virus type 1 (DHAV-1) experiment. The results show that BAPC’s ability to inhibit DHAV-1 was stronger than baicalininvitroandinvivo, and BAPC enhanced antioxidant and immune enhancement capabilities through inhibiting the adsorption, replication and release of DHAV-1.

4.2 LuteolinLuteolin is a flavonoid compound that exists widely in natural medicines. It has pharmacological effects such as anti-inflammatory, immune regulation and promotion of tumor cell apoptosis. Nong Yunhongetal.[24]studied the effect of luteolin on HBV replication and transcriptioninvitro. It was found that luteolin effectively inhibited the secretion of HBsAg and HBeAg by hepG2.2.15 cells. Moreover, it was observed that the inhibition of luteolin on HBV replication was concentration-dependent.

Bai[25]found that luteolin could reduce the replication of HBV DNA in HepG2.2.15 cells, and effectively inhibit the expression of nuclear factor 4α in liver cancer cells and the cell reproduction of HepG2.2.15 hepatitis B virus promoter. Luteolin could inhibit the replication of hepatitis B virus, suggesting that it could be used for clinical anti-HBV treatment.

4.3 ApigeninApigenin has a molecular formula of C15H10O5. It belongs to the class of bioflavonoids, and is widely found in fruits, vegetables, spices and other plants. Studies have shown that apigenin can block ConA-induced T cell cycle in the G0/G1 phase, and inhibitinvitroactivation, proliferation and apoptosis, suggesting that it can be used to treat ConA-induced autoimmune hepatitis disease in model mice. At the same time, it is found that apigenin can inhibit the proliferation, NO secretion and phagocytosis of RAW264.7 stimulated by LPS[26]. Shao Yidanetal.[27]explored the inflammatory response of apigenin on the non-alcoholic steatohepatitis (NASH) model of L02 cells stimulated by free fatty acids and observed its therapeutic activity on insulin resistance. It was found that apigenin adjusted the lipidosis rate of cells and the contents of IL-8, TNF-α,etc.At the same time, it was observed that it significantly improved the insulin resistance and inflammatory response of the L02 cell NASH model induced by FFA.

Shi Tingtingetal.[28]explored the effect of apigenin on the expression of peroxisome proliferator-activated receptors (PPARs) in liver tissues of rats with non-alcoholic steatohepatitis. The results show that apigenin inhibited fatty degeneration and inflammatory necrosis of the liver, significantly improved insulin resistance and glucose and lipid metabolism, and reduced the levels of serum related indicators (e.g.TC, TG and FBG) in mice, indicating that apigenin can be used to treat non-alcoholic steatohepatitis.

Hicksetal.[29]pointed out that apigenin is a compound with anti-fiber activity, and it could dose-dependently reduce the type I collagen of human HSC line. By identifying the proteins that mediate the action of apigenin, the characteristics of 122 unique genes in HSCs were observed, and 160 genes known to encode proteins that interact with apigenin were listed. The genes encoding C1Q TN F2 and complement C1Qtu were identified. C1Q TN F2 was observed to inhibit alcoholic liver injury in mice during the activation of hepatic stellate cells, suggesting that it may have a protective effect in the progression of liver cirrhosis.

5 Other flavonoids

At present, silymarin is the most commonly reported flavonoid for the treatment of hepatitis. Silymarin has the effects of clearing away heat and dampness, detoxifying and removing jaundice. It has a wide range of pharmacological activity such as anti-free radicals, anti-lipid peroxidation, anti-lipoxygenase, anti-tumor and lowering blood lipids. The effect of silymarin derivatives on hepatitis C virus was first discovered on the basis of cell culture, and silymarin was found to be able to block viral infections. Research on silymarin and silymarin derivatives at home and abroad has proved that they have clear antiviral effectinvivoandinvitro, but the mechanism of action is still unclear. Regarding silymarin in the treatment of HCV, its mechanism of action and pharmacokinetics and pharmacodynamics has made good progress. Studies have shown that silymarin can induce two stages of HCV RNA decline. This indicates that its antiviral effect may have dual mechanisms: by inhibiting RNA polymerase to achieve direct antiviral activity and by inhibiting virus from entering liver cells or inhibiting its release process. Silymarin has a bright future in the treatment of hepatitis, but its side effects and high price may create obstacles[30]. Neha[31]fully discussed the role of silymarin in chronic diseases. It was found that silymarin regulates cell signaling and has obvious effects in various diseases such as liver disease, inflammatory disease, cancer, nervous system disease, skin disease and hypercholesterolemia. It provides new possibilities for the treatment of hepatitis, but more in-depth research is needed.

Han Mingetal.[32]observed the clinical efficacy of silymarin combined with simvastatin in the treatment of non-alcoholic steatohepatitis. It was observed that the serum ALT level of the two groups of patients was significantly reduced after treatment, and the blood lipid indexes of the patients in the case group were significantly improved after treatment. The important thing is that there were no obvious adverse reactions in the two groups of patients during the medication. This shows that silymarin combined with simvastatin has a significant effect on non-alcoholic steatohepatitis and is safe to use.

Zheng Shengetal.[33]clinically observed the efficacy of silymarin capsules combined with polyene phosphatidylcholine on non-alcoholic fatty liver. The contents of alanine aminotransferase, aspartate aminotransferase and total cholesterol in the observation group of drug combination were lower than those of the control group, and the improvement of liver steatosis was more obvious. It can be seen that Feili Ganning capsule combined with Yishanfu has a good clinical effect in the treatment of non-alcoholic steatohepatitis, and the two have a synergistic effect. Xu Hongetal.[34]found that silymarin has an effect on anti-tuberculosis drug-induced hepatitis, mainly manifested as restricting the penetration of certain hepatotoxic substances into the cell interior, enhancing the resistance of the liver, and promoting the repair and regeneration of liver cells by accelerating protein synthesis. Large amounts of data have proved that while fighting tuberculosis, silymarin can reduce the incidence of drug-induced hepatitis, and moreover, it is safe, so it is applicable to anti-tuberculosis treatment, especially to combined use in the intensive period.

Wan Zhonghuietal.[35]discussed the mechanism of intervention of silymarin on non-alcoholic steatohepatitis. Rat NASH models were induced with a high-fat diet. The liver index, total cholesterol, aspartate aminotransferase, alanine aminotransferase, serum triacylglycerol, fasting insulin and TNF-α levels were significantly lower than the control group. The mechanism might be that silymarin inhibited the occurrence and development of NASH by promoting the mRNA expression of liver peroxisome proliferator-activated receptor α. Xing Lingxiangetal.[36]studied the preventive effect of silymarin on non-alcoholic steatohepatitis in rats and its mechanism. It was found that compared with the normal control group, the serum ALT, TG, TC and MDA levels of the model group were significantly increased, while those of the silymarin group were significantly decreased. At the same time, it was found that the SOD level in serum and liver tissue was significantly increased, and the expression of PPARα and mRNA in liver tissue was increased. It can be seen that silymarin has curative effect on experimental non-alcoholic fatty liver rats. The mechanism of action may be to promote the expression of PPARα in liver.

Liu[37]developed high-bioavailability silybin nanoparticles (SB-NPs). Experiments have found that SB-NP efficie treatment severely limits the transmission of HCV from cells to cells, and oral administration of SB-NPs has no obviousinvivotoxicity to rodents. Pharmacokinetic studies have shown that SB-NP effectively reduces HCV infection of human primary hepatocytes. SB-NP has enhanced bioavailability, effective anti-liver cancer activity and overall liver protection, and is worthy of being widely used and evaluated in the treatment of hepatitis C. Federico[38]pointed out silymarin has significant biological effects. Due to anti-oxidation, anti-inflammatory and anti-fibrosis abilities, it can be used for different liver diseases, especially chronic liver disease, cirrhosis and hepatocellular carcinoma. The antioxidant and anti-inflammatory effects of silymarin are aimed at reducing virus-related liver damage, softening through the cascade of inflammation and regulating the immune system. Silymarin has an important biological effect on non-alcoholic fatty liver. It can be used to regulate liver cirrhosis and hepatocellular carcinoma of different molecular patterns.

Tao[39]found that the total flavonoids (TFs) of roxburgh rose have a protective effect on liver injury and cerebral ischemia reperfusion (I/R) injury. The results of RT-PCR show that TFs down-regulated the levels of inflammatory factors including IL-1β, IL-6 and TNF-α. Further studies have shown that TF-induced liver protection is accomplished by inhibiting TLR4/MyD88 and activating S to complete the infrared 1/Nrf2 signaling pathway. TFs inhibited transcriptional activity and inflammatory response of NF-κB and AP-1 through blocking the TLR4 pathway. These findings confirm the cure effect of TFs on liver I/R damage.

Duetal.[40]explored the therapeutic effect of prescription combining flavonoids and polysaccharides on duck viral hepatitis (DVH). The results show that the prescription significantly reduced the mortality rate, reduced the severity of liver damage, reduced the score of liver pathology severity and reduced the DHAV gene expression level in blood, indicating that HRS prescription has a significant hepatoprotective effect. Bose[41]found that rutin can significantly inhibit the combination of HCV-LP and liver cancer cells and the early entry stage b of HCV life cycle to directly act on virus particles, and it is non-toxic to liver cancer cells. Rutin is a promising candidate for the development of anti-HCV therapeutic drugs to treat HCV infection.

Flavonoids are known for their broad-spectrum pharmacological activities. They provide new possibilities for the treatment of hepatitis. For example, quercetin, baicalin, silymarin,etc.have shown significant effects on hepatitis ininvitroexperiments and clinical trials. The mechanism of action is diversified, and the regulation of PI3K/AKT/NF-κB, TLR4 and other signal pathways has been reported frequently. To further clarify the structure-activity relationship and to study the preparation of anti-hepatitis drugs using flavonoids as raw materials is the direction of future research.