*4.1.5 Antiviral properties of mushrooms*

Diseases caused by viruses are not treated by common antibiotics and therefore require target-specific drugs. Antiviral properties have been studied not only for whole extracts of mushrooms but also for isolated secondary metabolites derived compounds. These antiviral compounds may act directly through the inhibition of viral enzymes, synthesis of viral nucleic acids, or adsorption and uptake of viruses into the mammalian cells [87, 95]. The direct antiviral activities are effectively demonstrated by smaller molecules. Indirect antiviral activities are due to the immune-stimulating


#### **Table 3.**

*Mushroom antitumor polysaccharide and polysaccharide-protein complexes that have passed clinical trials.*

#### *Medicinal Mushroom of Potential Pharmaceutical Toxic Importance: Contribution… DOI: http://dx.doi.org/10.5772/intechopen.103845*

activity of polysaccharides or other complex compounds [33]. Small molecular bioactive compounds with antiviral properties, several triterpenes from *Ganoderma lucidum* such as ganoderiol F, ganodermanontriol, ganoderic acid B, all act as antiviral agents against human immunodeficiency virus IHIV) type 1 (HIV-1) [9, 51, 82]. *In vitro* antiviral activity for influenza viruses type A and B was shown for mycelial extracts of *Kuehneromyces mutabilis* [14], and two isolated phenolic compounds from *Inonotus hispidus* [64, 96] and also ergosterol peroxide identified in several mushrooms.

#### *4.1.6 Mushrooms as antibacterial and antifungal agents*

Mushrooms are capable of producing antibacterial and antifungal secondary bioactive compounds as an adaptive defense system to survive in their natural environment. Therefore, they are potential sources of natural antibiotics and many of the external bioactive compounds from extracellular secretions by the mycelium, that can inhibit bacteria [72] and viruses [3, 19]. Several metabolites compounds extracted from mushrooms have been demonstrated to have antifungal and antibacterial properties, especially against *Escherichia coli*, *Staphylococcus aureus*, and *Bacillus subtilis* [24, 49, 79]. The European-derived *Ganoderma* species, *Ganoderma pfeifferi* are known to inhibit the growth of methicillin-resistant *S. aureus* and other bacteria by a new compound sesquiterpenoid hydroquinones [19]. It has also been demonstrated that whole aqueous extracts of this mushroom can inhibit the growth of microorganisms linked to skin problems, such as *Staphylococcus epidermidis*, *Pityrosporum ovale*, and *Propionibacterium acnes* [33].

Infectious diseases caused by microorganisms, such as bacteria, viruses, fungi, or parasites, are among the most serious agents of global morbidity and mortality [23]. Currently, many pathogenic infections are often caused by multi-resistant microorganisms resulting in disease resistance and difficulty for drug therapy; with a well-known example like coronavirus (COVID-19), which is the latest pandemic killing millions of people worldwide. Consequently, the pharmacoeconomic of healthcare costs are on a rapid increase, and of public health concern in many countries [9, 24]. This pandemic situation has led to an increasing search for new chemical entities (lead compounds) of antimicrobial agents from different sources. Several researchers have studied the antimicrobial potential of natural or synthetic compounds of pharmaceutical importance [27]. Thus, natural sources of bioactive compounds mushrooms, are constantly on investigation for finding novel antimicrobial bioactive compounds [23, 38].

In the food industry, contaminants by bacteria and fungi may be a result of exposure to sources of contamination during post-harvest processing (harvesting, processing, and/or packaging process) [12, 64]. Food additives are now widely used in the food industries to enhance and increase the shelf life of food and to prevent the optimal proliferation conditions of microorganisms [14]. It is for this reason that natural antimicrobials, including those isolated from mushrooms, are increasingly popular as potential alternatives to synthetic preservatives, whose safety and impact on human health are still challenging [19, 78]. However, proof of the safety of many natural antimicrobials has been generally recognized in Europe, USA, and in Asia as opposed to sub-Saharan Africa where research is limited [34, 72].

#### *4.1.7 Mushrooms as anti-inflammatory agents*

Studies on the ethanolic extracts and a proteoglycan from *P. linteus* have shown potential anti-inflammatory activity some *in vitro* tests, such as in the collagen-induced arthritis, the croton oil-induced ear edema test in mice, and antinociceptive effect in the writhing test [69, 71, 83]. Other bioactive compounds effectively elucidated in the writhing test include the ganoderic acids A, B, G, and H, isolated from *G. lucidum*. These compounds demonstrated a stronger anti-inflammatory activity in the animal model than acetylsalicylic acid [12, 45]. Methanolic extract of *Pleurotus pulmonarius* fruiting bodies at doses (500 and 1000 mg/kg) reduced carrageenan-induced and formalin-induced paw edema in mice. The activity was comparable to the reference diclofenac (10 mg/kg). The IC50 value for hydroxyl-radical scavenging was recorded as 476 mg/ml and for lipid peroxidation inhibition 960 mg/ml [11, 89]. The edible mushroom *Gaylussacia frondosa* is known to contain ergosterol, ergosta-4-6-8, 22-tetraen3 one, and 1-oleoyl-2-linoleoyl-3-palmitoylglycerol, which can potentially inhibit cyclooxygenases I and II activity [76].
