Pseudostellaria heterophylla: Antioxidant Activity and Its Mechanism of Action

Huiqing PAN, Yanda ZHANG*, Yufang MA, Qi ZHAO

1. Fujian Beidi Pharmaceutical Co., Ltd., Ningde 355300, China; 2. Municipal Enterprise Technical Center of Fujian Beidi Pharmaceutical Co., Ltd., Ningde 355300, China; 3. College of Animal Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China

Abstract The tonic traditional Chinese medicine Pseudostellaria heterophylla both medicinal and nutritional effects. It has been applied to research in the field of modern aquaculture, and its anti-oxidant clinical trials have also become a hot spot. Through searching domestic and foreign literature databases to sort out related literature, the anti-oxidation property of P. heterophylla was reviewed systematically from the three levels of in vitro chemical method, biological method and animal experiment method. On this basis, the functional mechanism of the anti-oxidant activity of P. heterophylla explored, in order to provide a reference for the follow-up in-depth research on the anti-oxidation of P. heterophylla and the discovery and development of feed and health care value of P. heterophylla the field of modern animal breeding.

Key words Pseudostellaria heterophylla, Antioxidant, Mechanism

1 Introduction

Radix Pseudostellariae is the dry root ofPseudostellariaheterophylla, and was first recorded in theNewCompilationofMateriaMedicain the Qing Dynasty. It is mainly produced in Fujian, Guizhou and Jiangsu[1], with the largest yield in Zherong[2].P.heterophyllahas both medicinal and nutritional effects, and its medicinal ingredients are dominated by polysaccharides, saponins and cyclic peptides[3]. The content of polysaccharides is about 25%-35%, and the content of total amino acids is about 7.67%-11.95%[4]. Clinical trials have proved thatP.heterophyllahas the effects of invigorating the spleen and lung[5], anti-oxidation[6], anti-inflammation[7]and enhancing immunity[8].P.heterophyllahas been applied to research in the field of modern aquaculture. Pan Shuleietal.[9]reported the research and application ofP.heterophyllapolysaccharides in modern animal husbandry industry. Ruan Shaojiangetal.[10]added Radix Pseudostellariae extract with a concentration of 0.5%-1.0%to the feed ofPseudosciaenacroceaand observed that the survival rate and growth rate ofP.croceawere significantly improved. Yao Yongetal.[11]found that the addition ofP.heterophyllato the feed could improve the immunity of prawns. Wu Binetal.[12]found that polysaccharides fromP.heterophyllacan significantly improve the non-specific immune function of Cyprinus carpio. Wu Jianhuaetal.[13-14]reported thatP.heterophyllaand its preparations can improve the immunity, improve and prolong the antibody against swine fever, and reduce diarrhea rate of piglets. Pan HQetal.[15]reported that the extract ofP.heterophyllacan promote the growth of probioticBacillusfor livestock and poultryinvitro. The previous research of the research group found that the extract ofP.heterophyllahad a certain inhibitory effect on theinvitroproliferation of duck H9N2 influenza virus on MDCK cells[16]. In summary,P.heterophylla, a traditional Chinese medicine for tonic, has a positive market prospect in modern animal breeding and health care. Oxidative stress of animals in the breeding process is the oxidative damage caused by the disorder of the oxidation and antioxidant system of the animal body due to endogenous or exogenous stimulation[17]. It often causes a decrease in the immunity of the animal’s body and inflammatory disease. At present, Chinese herbal medicine resources are mostly used in the research on antioxidation of animal body[18]. The research on antioxidation ofP.heterophylla, a traditional Chinese medicine for tonic, has also become a hot spot[6, 18-21].Through the previous literature review, it was found that the literature selected few anti-oxidant indexes and index detection and evaluation methods, and the research was relatively isolated and scattered. To this end, in this article, the domestic and foreign databases (CNKI, Wanfang, Weipu, Web of Science, Elsevier,etc.) were searched to sort out the literature on anti-oxidation ofP.heterophylla(the retrieval time was from the time of database establishment to April, 2021), and the antioxidation ofP.heterophyllawas reviewed systematically from three levels ofinvitrochemical method, biological method and animal experiment method, and on this basis, the mechanism of anti-oxidant activity ofP.heterophyllaexplored, in order to provide reference for discovery and development of feed and health care value ofP.heterophyllain the field of modern animal breeding.

2 Active components for antioxidant activity of P. heterophylla

After searching the databases and reviewing, organizing, sorting and counting the literature on antioxidation ofP.heterophylla, it is found that the antioxidant active substances in Radix Pseudostellariae include crude extract, polysaccharides, saponins and cyclic peptides (Table 1).Among them, the crude extract ofP.heterophylla(alcoholic extract and water extract ofP.heterophylla) and polysaccharides are researched frequently and hotly. In addition, the differences in extraction process and test concentration ofP.heterophyllacomponents have significant effects on the antioxidant activity of the components.

Table 1 Antioxidant components and main antioxidant indices of Pseudostellaria heterophylla

3 Research progress on antioxidant activity of P. heterophylla

3.2 Antioxidant effect based oninvitrobiological method

Invitrobiological evaluation of the antioxidant activity of Chinese herbal medicines mainly includes the evaluation of the inhibition of lipid peroxidationinvitroand the evaluation of the antioxidant activity ofinvitrocell models. This method has obvious advantages overinvitrochemical method, and in particular, the test target cells of theinvitrocell model method are closer to the body environment. This method can simulate the environment in the real animal body, taking into account the metabolic activity of cells, and its test results are more credible and convincing[21].

3.2.1Lipid peroxidationinvitro. Theinvitrolipid peroxidation-inhibiting experiment ofP.heterophyllaextract focuses on red blood cells.NG TBetal.[6]found that the water extract ofP.heterophyllahas a certain inhibitory effect on red blood cell hemolysis. Zhang Zhenmingetal.[26]reported that the alcohol extract ofP.heterophyllahas a significant inhibitory effect oninvitrohemolysis of red blood cells, and the inhibitory effect is dose-dependent on the alcohol extract. Xiong Hejianetal.[22]observed that thatP.heterophyllaextracts can inhibit H2O2- induced hemolysis of erythrocytes, and among them, the water extract, alcohol extract and crude saponin extract ofP.heterophyllashowed an inhibitory rate of over 20%. In summary, the extract ofP.heterophyllahas an inhibitory effect on the hemolysis of red blood cellsinvitro, and under oxidative stress, it can inhibit lipid peroxidation to achieve the protection function for erythrocyte membrane and improve the antioxidant level of red blood cells.

3.3 Antioxidant effect based on animal experimentTaking experimental animal as research object, the animal experiment method analyzes and investigates the target animal’s serum indices and tissue indices separately for evaluation. Serum biochemical indices can reflect the changes in the functional status of the body’s life activities, and the internal biochemical indices of tissues can best reflect the body’s health level and the body’s repair level. Liu Xiangxiangetal.[28]reported thatP.heterophyllapolysaccharides have a protective effect on rats with myocardial ischemia, and they can reduce the serum MDA content and increase the SOD level in rats. Xu Xianxiangetal.[32]reported thatP.heterophyllapolysaccharides can reduce the MDA content and increase the SOD level in the serum of diabetic mice. Yuan Yimingetal.[33]found that the alcohol extract ofP.heterophyllacan increase the serum GSH-Px level of natural aging model rats. In summary, the extract ofP.heterophyllacan improve the antioxidant function of target animals by enhancing the activity of antioxidant enzymes SOD and GSH-Px and inhibiting lipid peroxidation in the animal’s serum.

Zhang CLetal.[19]found that the extract ofP.heterophyllacan increase the SOD and GSH-Px levels and significantly reduce the MDA content in muscle tissue of rats with exercise fatigue. Zhang Zhenmingetal.[24]concluded that the water extract ofP.heterophyllacan enhance the antioxidant capacity of aging model mice, and increase the SOD and GSH-Px levels and reduce the MDA content in the heart tissue, kidney tissue and liver tissue. The finding of Li Zhihuaetal.[29]show thatP.heterophyllapolysaccharides can improve the SOD level and GSH-Px level and reduce the MDA content in the brain tissue of model mice. In summary,P.heterophyllaextract can improve and enhance the antioxidant function of animals by activating and enhancing the activity of antioxidant enzymes SOD and GSH-Px and inhibiting lipid peroxidation in animal tissues.

4 Antioxidant mechanisms of P. heterophylla

The antioxidant mechanisms of Chinse herbal antioxidants of different composition, types and structures are different. Based on the review above, the antioxidant mechanism ofP.heterophyllais analyzed and explained. The antioxidant mechanisms ofP.heterophyllamainly include scavenging free radicals directly, inhibiting lipid oxidation, activating antioxidant enzyme activity, inhibiting oxidase activity, and enhancing cell protection. The specific mechanism of action can be seen in Fig.1.

4.2 Inhibiting lipid peroxidationUnder normal conditions, the oxygen free radical reaction and lipid peroxidation reaction in the animal body are in a steady-state dynamic balance. Under oxidative stress, it is easy to cause chain reaction of oxygen free radicals to produce LPO and MDA, among which MDA is one of the end products of lipid peroxidation with strong virulence[30]. It has been mentioned above that the extract ofP.heterophyllacan significantly reduce the MDA content, and inhibit lipid peroxidation. In addition, Pang Haiyueetal.[31]reported that both water extract and alcohol extract ofP.heterophyllasignificantly inhibit the activity of oxidase LOX. In theory, the reduction of LOX activity can reduce ROS production and further slow down the lipid peroxidation reaction, thereby reducing MDA. Xiong Hejianetal.[22]also found that the scavenging rate of ethanol extract and crude saponin extract ofP.heterophyllato inhibit oxidation of linoleic acid reached 24.2% and 26.9%, respectively.

4.4 Enhancing cell protectionAntioxidants can also play an anti-oxidant effect by improving cell activity, cellular immunity, and cell structural integrity[37]. Red blood cell hemolysis can reflect the degree of lipid peroxidation of cell biofilms[6, 22, 26]. Under certain circumstances, it can also reflect the structural integrity of cells. Pang Haiyueetal.[31]reported that the alcohol extract ofP.heterophyllacan better reduce the DNA fragmentation of plasmid DNA after UVB and H2O2damage, and has a certain DNA protection function, suggesting thatP.heterophyllaextract has a certain auxiliary effect on cell repair under oxygen stress. Wang Zetal.[21]also reported that both ginsenosides and polysaccharides can increase the activity of target cells in a dose-dependent manner, reduce the content of intracellular MDA and increase the activity of SOD. At the same time, Wang Jiakui[38]found that the total saponins and crude polysaccharides ofP.heterophyllacan promote the immune function of red blood cells.

4.5 Other mechanisms of actionThe antioxidant effect ofP.heterophyllacan be achieved by regulating the intracellular antioxidant system. Wang Qietal.[39]reported thatP.heterophyllapolysaccharides can activate the liver’s Nrf2 antioxidant system and interfere with the inhibition of inflammatory signals. Nrf2 is the body’s oxidative stress sensor. It plays a key role in cellular anti-oxidative stress. Under oxidative stress in animals, Nrf2 can specifically bind to antioxidant element (ARE) to regulate the expression of antioxidant enzymes[40]. In addition, You Setal.[7]found thatP.heterophyllapolysaccharides can help restore the integrity of the intestinal mucosa and the meristem of intestinal goblet cells, and they have a significant effect on supporting the intestinal flora. At the same time, they show anti-inflammatory activity by activating the TLR4 signaling pathway. Modern studies have found that animal intestinal integrity and normal intestinal flora structure directly affect the balance of redox state and the production of intestinal bacterial ROS. Thus, the above two approaches provide new ideas or research directions for explaining the anti-oxidation mechanism ofP.heterophylla.

5 Conclusions

P.heterophyllais a tonic Chinese herbal medicine, with complex composition and both medicinal and nutritional functions. It has been applied to research in the field of modern aquaculture, and its antioxidation clinical trials have also become a hot spot. The article reviews the literature on antioxidation ofP.heterophyllafrom three levels, includinginvitrochemical methods, and explores the mechanism of antioxidation ofP.heterophyllafor the first time. The results show thatP.heterophyllahas good antioxidant activity. Its mechanism of action mainly includes five aspects, such as scavenging free radicals directly. With the development of modern "reducing resistance" and "no resistance" breeding trends and the demand for green, healthy and efficient Chinese veterinary drugs or new feed additives, the research of Chinese herbal medicine resources will become more abundant, and the research on health care and the development of formulations of the tonic traditional Chinese medicineP.heterophyllawill also receive constant attention.