1. Echinacea purpurea (L.) Moench

Echinacea purpurea (L.) Moench is an endemic plant in the U.S. Great Plains and the Canadian prairies of North America. The indigenous traditional healers from North American tribes of Cheyenne, Choctaw, Dakota, Delaware, Fox Kiowa, Montana, Omaha Pawnee, Ponca, Sioux, and Winnebago indicated Echinacea preparations for the healing of wounds, skin inflammatory conditions, infectious diseases, coughs and chest conditions, sore throat and thrush, and also as an antidote against snakebites and poisons, and as a pain reliever ^[1][2]. Even though Echinacea originates in North America, the traditional knowledge of this plant’s beneficial effects was introduced to European settlers and it has spread beyond the Atlantic Ocean. In modern times, the plant’s traditional description was changed from “anti-infective” to immunomodulatory active ^[3][4]. It is worth to mention that the immunomodulatory activity might be related to antimicrobial and antiviral activities due to the synergistic effect on the host immune system ^[3][5]. The immune-enhancing effects of Echinacea purpurea (L.) Moench preparations are well documented and the underlying mechanisms have been widely investigated ^[6][7][8][9]. The plant’s important components are caffeic acid derivatives, alkylamides, flavonoids, polysaccharides, lipoproteins and polyacetylenes. Among them, the caffeic acid derivatives and alkylamides were proved to have effects of immunoregulation ^[10]. At their highest concentration, polysaccharides are typically present in aqueous or fresh pressed juice extracts, while alkylamides (as major constituents) are more likely to be found in ethanolic extracts ^[10].

2. Hemagglutinins (lectins)

Hemagglutinins (lectins) are natural bioactive proteins and glycoproteins that have the capability to specifically bind sugars ^[11]. These sugar-binding proteins are of non-immune origin, and can agglutinate cells or precipitate glycoconjugates ^[12]. Previously, numerous lectins have been isolated from various sources such as plants, algae, and fungi. Plants’ lectins are known to have immunomodulatory activity. They are capable of modulating the secretion of cytokines and the production of other immune mediators, such as reactive oxygen species (ROS) and reactive nitrogen intermediates (RNI), in order to improve the host’s resistance to microbial infections ^[13]. Plants’ lectins have the ability to bind to specific carbohydrate residues, which are present in the membrane of both the bacterial and immune cells of the host. Plants’ lectins are mitogens that have the ability to stimulate lymphocytes to undergo mitosis in a calcium-dependent manner ^[11]. This stimulation is a result of the interaction between the plants’ lectins and the surface’s sugar moieties present on the surface of lymphocytes. T lymphocytes’ cell proliferation is an essential factor to monitor the different adaptive immune reactions. In a variety of studies, authors used spleen, mainly of mice, to investigate the mitogenic power of lectins. Splenocytes encompass macrophages, dendritic cells, and B and T cells; these splenic populations are capable of generating innate and adaptive immune responses ^[10].

Lactose-, D-mannose-, and D-galactose-specific glycoproteins (~40 kDa) were extracted and purified from fresh Echinacea purpurea (L.) Moench root. The purified glycoproteins were identified by LS-MS/MS as a two LysM (lysine motif) domain that contains lectins. The LysM domain, which contained lectins, demonstrated hemagglutinating activity ^[14]. There are no data on Echinacea purpurea (L.) Moench’s lectin effect on the immune response in vivo. Therefore, in the present study we investigated the effects of Echinacea purpurea (L.) Moench (EP) fresh roots’ tincture, and purified (from Echinacea purpurea (L.) Moench fresh root) glycoproteins with the LysM domain in a mouse model by analyzing samples of blood and spleen.

This entry is adapted from the peer-reviewed paper 10.3390/plants10050936