PHARMACOLOGICAL EFFECTS OF MEDICINAL MUSHROOMS
The antioxidant activity of edible mushrooms could be directly applied to daily life because it is associated with natural prevention of oxidative str ess which is often as a result of lifestyle habits (Sakano et al., 2009). A number of in vitro and in vivo studies have reported antioxidant potentials of various mushroom species that enable them to neutralize free radicals (Ferreira et al., 2009). Assays involving chromogen compounds (e.g., ABTS and DPPH methods) are the most commonly used methods to measure mushrooms antioxidant activity (Sánchez, 2016). The findings of those studies demonstrated that the antioxidant components are found in fruit bodies, mycelium and culture both of the mushrooms. These often show good activity as a scavenger of DPPH radical and reactive oxygen species (hydroxyl radical, superoxide radical, and hypochlorous acid). They also act as an xanthine oxidase inhibitor which has indications for various therapeutic procedures, including cancer therapy since inhibition of Xanthine Oxidase can inhibit the oxidation of 6-mercaptopurine and potentiate antitumor properties (Pacher et al., 2006; Ribeiro et al., 2007). The metabolites responsible for the antioxidant activities include polysaccharides, phenolic compounds, carotenoids, ergosterol, tocopherols, ascorbic acid and many others (Sánchez, 2016; Zhang et al., 2016a).
IMMUNOMODULATORY AND ANTITUMOR ACTIVITIES
Immunomodulators, also known as BRMs, are compounds used to regulate or normalize the immune system (Jong and Yang, 1999). BRMs have been isolated from the fruiting bodies of mushrooms as well as the stalk, spores, and mycelium. They can also be isolated from fermentation broth when cultivated in submerged culture, hi some studies, BRMs were applied simultaneously with conventional chemotherapy and radiotherapy during cancer treatment to increase their efficiency. Mushroom BRMs have been classified into four main categories according to then chemical structure:
- 1. lectins
- 2. terpenoids
- 3. polysaccharides
- 4. fungal immunomodulator proteins (El Enshasy, 2010).
Cancer is one of the leading causes of death all over the world especially in low and middle- income countries where resources available for diagnosis, prevention, and treatment of cancer is limited. For many years, treatment of cancer was limited to chemotherapy in conjunction with radiotherapy. However, development of resistance to chemotherapy and severe side effects linked to the therapy became major pitfalls for these treatments (Brenner and Stevens, 2010). Some of the reported side effects include reduced caloric intake and decreased absorption of nutrients that could endanger the life of cancer patients (Shervington and Lu, 2008). In addition, chemotherapy often results in damage and weakening of patient’s natural immunological defenses (Orsine et al., 2012).
All these led to the consideration of using natural products for the prevention and treatment of various chronic diseases. For over three decades, scientific and medical research studies have confirmed the bioactive compounds which can be extracted from mushrooms and are usefill in the management and treatment of cancer and other related diseases (Lee et al., 2013). Mushrooms are judged to strengthen the immune system by applying their effects on cellular activities through secondary production of chemical compounds that boost the immune system (El Enshasy, 2010). Mushrooms polysaccharides (mainly a- or 0-glucans and glycoproteins) demonstrated immunomodulatory activities through:
- 1. activation of cytotoxic lymphocyte, that is, natural killer (NK) cells
- 2. regulation of cytokines production (i.e.,IL-10,IL-12p70, and IL-12p40) by dendritic cells
- 3. increased production of TNF-a, IL-1, IL-6, IL-8, IL- 12p40, and NO, and expression of iNOS by macrophages (Borchers et al., 2008).
Compounds of mushrooms in crude and pure form have effectively demonstrated antitumor and immunomodulatory activities (Krishnamoorthy and Sankaran, 2016; Vetvicka et al., 2008) coupled with anti-angiogenesis properties (Liu et al., 2012). One of the mechanisms by which mushrooms exert protection against cancer is through stimulation of the immune system response. This is because 0-glucan polysaccharide activates immune cells that destroy tumor cells (Vetvicka et al., 2008). However, an intact T-cell component is required for the antitumor action of 0-glucan polysaccharides since their activity is controlled by a thymus-dependent immune mechanism (Vetvicka et al., 2008).
Drugs prepared from mushroom polysaccharides which were applied as immunotherapeutic agents have shown positive results from in vitro and in vivo studies on cancer treatment (Lee and Kim, 2014; Liu et al., 2012). The anticancer role of mushrooms can be described from the following mechanisms:
- 1. Cell cycle arrest
- 2. Induction of cell apoptosis to prevent cancer cell proliferation (Song et al., 2013).
Mushrooms with demonstrated anticancer properties include the following genus: Agaricus, Albatrellus, Antrodia, Calvatia, Clitocybe, Cordyceps, Flam-mulina, Fomes, Funlia, Ganodenna, Inocybe, Inonotus, Lactarius, Phellinus, Pleurotus, Schizophyllum, Russula, Suillus, Trametes, and Xerocomus.