Study on Echinacea Extract for Inflammation

Echinacea purpurea is a perennial herbaceous flowering plant in the Asteraceae family, native to North America. Echinacea purpurea is rich in a variety of pharmacologically active ingredients and has outstanding anti-infective and immunomodulatory effects. With the continuous improvement of extraction technology, this plant and its active ingredients have gradually attracted the attention of scholars at home and abroad [1]. Some preclinical studies have shown that Echinacea purpurea has anti-inflammatory, antibacterial, antiviral, antitumor and immunomodulatory effects, but further clinical studies are needed to confirm its effects in humans. Some studies have shown that the active ingredients and extracts of Echinacea have made some progress in anti-inflammatory research. Therefore, we summarize the mechanism of action and the main related signal pathways of the active ingredients and extracts of Echinacea in anti-inflammatory research, to provide a reference for further research on the anti-inflammatory effect of Echinacea.

Inflammation is a series of stress responses of the body to harmful stimuli, and is a defensive and protective response. Among the many inflammatory factors present in the body, nitric oxide (NO) is a key factor mediating the inflammatory response, and is synthesized by inducible nitric oxide synthase (iNOS) [2-3]. Interleukin 6 (IL-6) is the most potent endogenous pro-inflammatory factor that initiates a systemic inflammatory response. It is an important indicator of the severity of inflammation and disease in the body. Interleukin-1β (IL-1β) is a cytokine that regulates natural immunity. It can induce the secretion and release of other inflammatory response mediators in various cells. Prostaglandin E2 (PGE2) is a metabolic product of arachidonic acid in the body. It is closely related to physiological activities such as fever and inflammatory responses in the body. It is mainly synthesized by cyclooxygenase-2 (COX-2). Tumor necrosis factor alpha (TNF-α) is produced by activated macrophages/monocytes and is an important inflammatory factor in the clinic, participating in a variety of physiological and pathological processes in the human body[4] .

1 Anti-inflammatory effect of Echinacea active ingredients

According to domestic and foreign research reports, Echinacea contains a variety of bioactive ingredients, including polysaccharides (Echinacea purpurea polysaccharides, EPPS), glycoprotein components, caffeic acid derivatives, alkylamides and essential oil components. Polysaccharides and glycoproteins are important active ingredients in Echinacea purpurea; caffeic acid derivatives (CADs) are the main polar components of Echinacea purpurea's active ingredients, among which caffeic acid and chrysanthemic acid are the main phenolic acid components in Echinacea purpurea extracts; alkyl amides are the most common lipophilic compounds among Echinacea purpurea's active ingredients. The anti-inflammatory effects of these components have been well demonstrated in preclinical studies.

1.1 Echinacea polysaccharides

The polysaccharides isolated from Echinacea purpurea are mainly composed of inulin, as well as xyloglucan, pectin-like polysaccharides, 4-methoxyl-glucurono-arabino-xylan, acidic arabinose-rhamnose-galactan, and fructan. Some sources report that the EPPS component can inhibit edema and reduce the infiltration of inflammatory cells. Xu Tianli et al. [6] obtained Echinacea polysaccharides by water extraction and alcohol precipitation, and purified them using DEAE-cellulose and dextran G-100 gel chromatography. The three types of Echinacea polysaccharides obtained after purification all had an inhibitory effect on the swelling of mice's ears induced by xylene.

Jia Qinghui [7] also confirmed the anti-inflammatory effect of Echinacea polysaccharides through animal experiments. BALB/C mice were intranasally administered lipopolysaccharide (LPS), which caused pathological damage to the lung tissue and a significant increase in pro-inflammatory factors such as TNF-α, IL-6 and IL-1β. After the mice were administered Echinacea polysaccharides, it was found that Echinacea polysaccharide can significantly inhibit the secretion and mRNA expression of TNF-α, IL-6 and IL-1β. In addition, when mouse alveolar macrophages RAW264. 7 was pretreated with LPS, the expression of nuclear factor κB (NF-κB) protein was elevated, and Echinacea polysaccharide could effectively inhibit its expression. Since the activation of NF-κB is an important pathway in the process of cell inflammation response and immune response [8-9], it was found that Echinacea polysaccharide may exert anti-inflammatory effects by inhibiting the activation of NF-κB. Fast et al. [10] also showed that the polysaccharides in the aqueous extract of Echinacea purpurea root inhibit the secretion of TNF-α by human monocyte THP-1 cells induced by triacyl lipopeptide (Pam3Csk4).

In addition, Hou et al. [11] found that Echinacea polysaccharides have anti-hyaluronidase activity. Zhang Hongying et al. [12] showed that Echinacea polysaccharides can inhibit cell adhesion of pathogenic Escherichia coli.

1.2 Caffeic acid derivatives

Caffeic acid substances are the main active ingredients in Echinacea purpurea. Caffeic acid, methyl caffeate, ethyl caffeate, chicoric acid, chlorogenic acid, echinacoside, caffeoyl tartaric acid, and cinnamic acid can be isolated by solvent extraction and chromatography. Caffeic acid and its derivatives are widely distributed in the plant world. They have a simple structure and multiple biological activities, making them a type of natural active ingredient with broad application prospects.

1.2.1 Caffeic acid

Caffeic acid, with the molecular formula C9 H8 O10 and molecular weight 180.16, is a natural phenolic compound with the structure of hydroxyphenolic acid. It can remove oxygen free radicals released by neutrophils and macrophages during inflammatory reactions, significantly improving leukopenia, oxidative stress and inflammatory reactions[13]. In addition, CA enhances the body's anti-inflammatory effect by inhibiting the activation of NF-κB and reducing the expression of pro-inflammatory factors [14]. Coughlan and Nedic et al. confirmed [15-16] that caffeic acid can inhibit the inflammatory response of macrophages induced by LPS. The expression of p38 Mitogen-activated protein kinase (p38MAPK) and NF-κB was found to be reduced by detecting the expression of related kinases in cells by western blot. Su Guoying[17] confirmed that caffeic acid can inhibit the chronic inflammatory response caused by advanced glycation end products (AGEs) by inhibiting the reactive oxygen species (ROS)/MAPK/NF-κB signaling pathway.

1.2.2 Chicoric acid

Chicoric acid (CA), with the molecular formula C22 H18 O22 and molecular weight 474.37, is an important and representative compound among the derivatives of caffeic acid. It is widely used in pharmaceuticals, nutritional supplements and health foods. Cichoric acid can regulate the LPS-induced inflammatory response in different animal models. Asun Xian et al. [18] found that cichoric acid inhibits the inflammatory response of yak peripheral blood mononuclear cells (PBMC) by promoting the synthesis of anti-inflammatory factors and inhibiting the expression of pro-inflammatory factors. In another study, Asung Xian found that chicoric acid inhibited the inflammatory response by suppressing the expression of key genes and proteins in the Toll-like receptor 4 (TLR4) signaling pathway in yak peripheral blood mononuclear cells (PBMCs) [19]. Li et al. [20] reported that chicoric acid alleviates acute liver injury by inhibiting MAPK and NF-κB to relieve inflammation. Wang et al. [21] found that chicoric acid can improve swelling, inflammation and pathological changes in the ankle joints of rats, and is a potential anti-gout drug. It can also inhibit the activity of some viruses, such as rhinoviruses and influenza viruses, as well as some pathogenic respiratory bacteria such as H1N1 and HSV [22-23]. Reinke et al. [24] found that chicoric acid is a non-competitive and reversible inhibitor of HIV integration in vitro.

Liu et al. [25] found that chicoric acid can significantly inhibit the decrease in BV2 microglial cell viability induced by LPS. Another study [26] found that chicoric acid can inhibit macrophage-induced apoptosis, significantly improve mitochondrial function, regulate redox homeostasis-related signal pathways such as MAPK and phosphatidylinositol-3 kinase (PI3K)/AKT, increase the expression of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) and sirtuin 1 (SIRT1), enhance the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK), and promote energy metabolism to reduce the inflammatory response of neurons. The results of Park et al. [27] showed that luteolin and chicoric acid treatment could inhibit NF-κB and AKT phosphorylation, reduce cellular NO and PGE2 production and expression, inhibit iNOS and COX-2 expression, and also reduce the levels of pro-inflammatory cytokines, TNF-α and IL-1. In addition, different doses of chicoric acid can significantly inhibit acute liver damage caused by lipopolysaccharide and galactosamine in a dose-dependent manner [20].

1.2.3 Other caffeic acid derivatives

Over the years, many scholars have synthesized many derivatives to enhance the anti-inflammatory effects of natural molecules in Echinacea purpurea. Zhang Jie [28] designed and synthesized a group of caffeic acid ester derivatives, four of which showed strong inhibitory effects on the formation of induced rat macrophages and can be used for further research on anti-inflammatory activity. Wang Yinghong et al. [29] confirmed that caffeic acid phenethyl ester can reduce damage to microglial cells by inhibiting the expression of inflammatory factors. Its anti-inflammatory effect may be achieved by inhibiting the inflammatory response mediated by the NF-κB signaling pathway.

1.3 Essential oil composition

Echinacea purpurea was identified by GC-MS analysis, and 68 compounds were initially identified. The essential oil of Echinacea purpurea contains fatty acids, unsaturated fatty acids and their esters. Zeng et al. [30] used a combination of traditional reflux extraction and solid-phase microextraction (SPME) to isolate a variety of aliphatic compounds from the dried roots of Echinacea purpurea. Xue Yafeng [31] used a method combining water vapor distillation and GC-MS to extract Echinacea buds and identified a variety of compounds such as alkenes and organic acids. In addition, it was found that Echinacea contains flavonoids, alkaloids, steroidal compounds and various inorganic elements. Oláh et al. [32] showed in vitro and clinical trials that emulsions made from alkylamides in Echinacea can treat atopic eczema (AE). The alkylamides in the Echinacea purpurea extract regulate the expression of TNF-α mRNA in human macrophages and monocytes through the cannabinoid 2 (CB2) receptor, and also inhibit the expression of TNF-α stimulated by LPS, thereby exerting an anti-inflammatory effect. The volatile oil in the roots of Echinacea purpurea has anthelmintic effects. Canlas et al. [23] reported that Echinacea purpurea extract can inhibit the proliferation of parasites in the body and can better control inflammation caused by parasitic infections.

1.4 Alkylamides

Alkylamides are the most common lipophilic compounds among the active ingredients of Echinacea. They can inhibit cyclooxygenase and block the synthesis of prostaglandins, thereby reducing pain, fever and inflammation [5]. Alkylamides in Echinacea can synergistically damage the fungal cell wall/membrane complex, thereby exerting antifungal activity.

2. Anti-inflammatory effect of Echinacea extract

The advantages of Echinacea extract are its broad-spectrum activity, which minimises the production of resistant mutants, as well as its high efficacy and lack of cytotoxicity. Studies have shown that Echinacea ethanol extract contains a variety of different ingredients that can regulate the production of cytokines by macrophages to varying degrees. Mo Qiufen et al. [33] concluded that Echinacea extract can inhibit the release of pro-inflammatory factors such as TNF-α and IL-1β. Cheng Yongxue et al. [34] determined through mouse experiments that Echinacea flowers have good anti-inflammatory activity. Yu Yinx[35] research confirmed that: Echinacea root extract can increase the IL-2 content in canine peripheral serum, reduce the release of IL-6, and increase the lysine content, which has a certain anti-inflammatory effect.

2.1 Anti-bacterial

Studies on the use of Echinacea purpurea to treat diseases associated with bacterial infections have been reported, and many studies have now confirmed the antibacterial activity of Echinacea purpurea and its preparations. Tribess et al. [36] reported that applying an Echinacea purpurea leaf infusion to the outside of infected cells had an anti-infective effect, without specifying the type of infection. Rizzello et al. [37] tested the extract against Escherichia coli, Klebsiella pneumoniae, Enterococcus faecalis, Yersinia enterocolitica, etc. using the disc diffusion and broth microdilution tests. The results showed that the extract had an inhibitory effect on the growth of most strains, without mentioning the plant parts used. Jeschke et al. [38] reported that that an Echinacea syrup can be prescribed for the treatment of fever, acute upper respiratory tract infections and acute pharyngitis. Sharma et al. [39] confirmed the effect of fresh Echinacea ethanol extract against respiratory tract infection strains using the dark-light method.

Stanisavljevic et al. [40] confirmed the antimicrobial properties of the extract by demonstrating its inhibitory effect on most bacteria, including Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus, using both conventional and ultrasonic extraction methods. Wei Xiuli et al. [41] found that the combined use of Echinacea purpurea extract and enrofloxacin has a synergistic effect on the antibacterial effect on some Escherichia coli, which can significantly reduce the dosage of enrofloxacin. Han Xiaoxia et al. found that the application of Echinacea extract alone can significantly inhibit the inflammation caused by multidrug-resistant Staphylococcus aureus in mouse mammary tissue, and is dose-dependent.

2.2 Antiviral

Echinacea has immunomodulatory and antiviral effects, and can effectively reduce the risk of respiratory tract infections and their complications. Echinacea preparations can completely or partially reverse viruses such as herpes simplex virus, influenza A virus, adenoviruses 3 and 11, reduce the secretion of pro-inflammatory cytokines, and may alleviate other respiratory diseases. Experiments have shown that Echinacea modulates multiple signaling pathways of different cell receptors (ICAM-1 and LDL) and transcription factors, reducing the secretion of pro-inflammatory factors. In human bronchial and pulmonary epithelial cells infected with rhinovirus, Echinacea inhibits the expression and secretion of pro-inflammatory cytokines and chemokines such as IL-1, IL-6, IL-8 and TNF-α. Echinacea extract not only suppresses colds caused by viruses, but also effectively prevents recurrent infections, and can be recommended as a preventive measure against the common cold. A large number of studies on the prevention or treatment of the common cold with echinacea have been reported, and these studies have been critically summarized [23].

2.3 Anti-other microorganisms

2.3.1 Clostridium difficile

Clostridium difficile is a Gram-positive spore-forming anaerobic intestinal bacterium that has been increasingly associated in recent years with the prevalence of diarrhea and pseudomembranous colitis, especially with intestinal infections caused by intestinal flora disorders after long-term use of antibiotics in patients. Oral administration of appropriate Echinacea extracts or some teas made from EP may be beneficial for infected patients, but current research is unclear as to how significant this change is.

2.3.2 Parasites

Leishmaniasis and trypanosomiasis are diseases caused by the protozoan parasites Leishmania and Trypanosoma, respectively, which belong to the kinetoplastida family. These two parasites cause hundreds of thousands of new cases every year. Although drugs are available for the treatment of the various stages of the disease, they often cause serious side effects. Recent studies have tested the anti-parasitic properties of several plant extracts with promising results. Three different Echinacea preparations were prepared and evaluated for their ability to inhibit the growth of organisms and anti-inflammatory activity in vitro. All three preparations showed dose-dependent anti-leishmania and trypanocidal activity after incubation for 24, 48 and 72 hours [23]. Certain Echinacea preparations can control the growth of these parasites and inhibit the inflammatory activity caused by them [23].

In addition, it was found that Echinacea extract can significantly reduce the number of tachyzoites in the abdominal fluid and liver of mice infected with Toxoplasma gondii strains. The research results further confirmed the protective effect of Echinacea extract against infection with different Toxoplasma gondii strains.

3 Summary

Echinacea has a long history of medicinal use due to its outstanding anti-infective and immunomodulatory effects. Echinacea extracts have attracted considerable attention both domestically and abroad as immunomodulators and immunostimulants. Currently, some studies use extracts from different plant parts and with different extraction methods, which may lead to significant differences in their chemical composition and biological activity. Therefore, some studies have concluded that echinacea is effective in anti-inflammation, while some studies have shown a lack of effectiveness. Despite the divergent opinions, the overall trend in the therapeutic effects of echinacea preparations is beneficial.

Echinacea extracts have been widely used in clinical trials abroad, but due to the complex active ingredients in echinacea, research on the active ingredients in echinacea is not yet comprehensive and in-depth enough. In China, although research on the pharmacological activity of Echinacea is still limited to veterinary medicine and the laboratory stage, and it will take some time before it is applied clinically, some regions have successfully introduced species of Echinacea with medicinal value, and research on the active ingredients of domestically produced Echinacea is gradually being carried out. This will lay the foundation for the research and development of domestically produced Echinacea and related drugs and their application in clinical practice, and help promote the development of China's healthcare industry.

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