Encyclopedia
Please note this is a comparison between Version 1 by Aly Farag El Sheikha and Version 2 by Rita Xu.
Ganoderma lucidum has a long history of medicinal uses in the Far East countries of more than 2000 years due to its healing properties. Recently, G. lucidum has come under scientific scrutiny to evaluate its content of bioactive components that affect human physiology and has been exploited for potent components in the pharmacology, nutraceuticals, and cosmetics industries. For instance, evidence is accumulating on the potential of this mushroom species as a promising antiviral medicine for treating many viral diseases, such as dengue virus, enterovirus 71, and recently coronavirus disease of 2019 (COVID-19). Still, more research studies on the biotherapeutic components of G. lucidum are needed to ensure the safety and efficiency of G. lucidum and promote the development of commercial functional foods.
- Ganoderma lucidum
- prebiotics
- functional food
- therapeutic properties
1. Introduction
1.1. What Does History Say about Ganoderma lucidum?
“Lingzhi is a miraculous king of herbs”—Chinese people (221–206 BC).
Historically, the Romans considered mushrooms in general as the food of their gods and only served them for great feasts, while the Greeks and the Vikings believed that eating mushrooms gave them strength and enthusiasm before the war. America’s indigenous people have often used mushrooms in age-old rituals (e.g., magical hallucinogens) to cross the body and mental barrier [1]. Considered as one of the main folk medicinal mushrooms, G. lucidum was used for many centuries and reported under several names in China (Lingzhi), Japan (Reishi), and Korea (Mannentake). According to bimillennial beliefs, G. lucidum can promote health and longevity, but it was also considered a combination of spiritual force and a source of immortality [2][3][4]. Moreover, the Japanese people have regarded this mushroom as a “10,000-year” mushroom [5][6][7].
Several researchers have pointed out the long history of traditional medicinal uses of mushrooms, especially G. lucidum, mostly in Far East countries, dating back more than 4000 years [7][8][9][10][11][12][13][14]. This type of mushroom has therapeutic characteristics with medical claims that can be attributed to a well-respected pharmacopeia from the Qin dynasty (221–206 BC) called Shen Nong Ben Cao Jing, or The Divine Farmer’s Materia Medica [13][15]. The ethnomedicinal uses of G. lucidum had reflections on culture, such as the artworks beginning in the Yuan Dynasty (1280–1368 AD) [7][13]. This was not limited to artworks, but the use of G. lucidum images extended to furniture, carvings, paintings, and even women’s accessories [2].
For a long time, G. lucidum has been used as a traditional medicine for treating neurasthenia, debility of prolonged illness, insomnia, anorexia, dizziness, chronic hepatitis, hypercholesterolemia, mushroom poisoning, coronary heart disease, hypertension, prevention of acute mountain sickness, “deficiency fatigue”, carcinoma, and bronchial cough in the elderly [16][17]. Studies on medicinal mushrooms began in Western science more than 30 years ago. These studies have continued until the present via a series of exciting discoveries related to the biological activities of Ganoderma lucidum, including antitumor and anti-inflammatory effects, as well as cytotoxicity to hepatoma cells [18][19].
1.2. Ganoderma lucidum through the Glasses of Botanists, Taxonomists, Economists, and Scientometric Analysis
1.2.1. Through Botanists’ Glasses
Morphologically, lucidum is a word derived from the Latin word lucidus, which means “shiny” or “brilliant”, and describes the varnished look of the mushroom’s surface. Overall, G. lucidum is a large, dark mushroom distinctively characterized by a glossy surface (including a red-varnished and kidney-shaped cap) and a woody texture (see Figure 1). The fresh mushroom is soft, corklike, flat, lacks gills on its underside, and releases its spores via fine pores. The pore color on its underside depends on the age of the mushroom, and maybe white or brown [6][20]. Chen [21] described the nature of G. lucidum’s growth on the bases and stumps of a wide variety of deciduous trees, such as oak, maple, elm, willow, sweetgum, magnolia, and locust, and less frequently found on coniferous trees (e.g., larix, ptea, pinus) in Europe, Asia, and North and South America, especially in temperate rather than subtropical regions.
Figure 1. Image of Ganoderma lucidum.
1.2.2. Through Taxonomists’ Glasses
Ganoderma lucidum (Curtis) P.Karst. was first described by Curtis [22] based on material from England, and the description was sanctioned by Fries [23]. The first scientific record of G. lucidum from China was made by Teng [24] when he incorrectly identified a Lingzhi specimen as G. lucidum. Geographically, the G. lucidum sensu stricto (Curtis) Karst mushroom is native to Europe and some parts of China [25]. According to the Index Fungorum (2016) (http://www.indexfungorum.org, accessed on 16 February 2022), Ganoderma lucidum (Curt: Fr.) Karst. belongs to Basidiomycota (phylum), Polyporales (order), and Ganodermataceae (family), as classified by the taxonomist Nahata [5]:
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Kingdom: Fungi
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Division: Basidiomycota
Figure 2. Wide-scale applications of mushrooms including Ganoderma lucidum; i.e., pharmaceuticals, nutraceuticals, and cosmetics. Source: Reprinted from Wu et al. [31]. Licensed under CC BY 4.0.
Table 1. Some of the cosmetic products are produced commercially from the G. lucidum mushroom worldwide *.
| Commercial Product Name/Producing Country | Uses |
|---|
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It converts food to nutrients;
| CV Skinlabs Body Repair Lotion, USA | Wound healing and anti-inflammatory |
| Dr. Andrew Weil for Origins Mega-Mushroom Skin Relief Face Mask, USA |
- G
- .
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G. lucidum contains 3.5 g of dietary fiber per 100 g of mushroom (d/w).
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G. lucidum contains significant amounts of major minerals (e.g., phosphorus, sulfur) and other trace mineral contents; i.e., Cu, Mg, and Fe.
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As also mentioned in Table 2, G. lucidum is a highly rich source of vitamins such as riboflavin, niacin, thiamin, etc. Additionally, Ahmad [62] reported that several vitamins have been found in G. lucidum, such as vitamins B1, B2, B6, β-carotene, C, D, and E.
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Based on the nutritional profile of G. lucidum, this mushroom possesses a high nutrient potential that reflects positively on its health benefits.
Through this vision, the G. lucidum mushroom is increasingly becoming one of the natural and untapped medicine resources, which should be of interest to pharmaceutical, nutraceutical, and cosmetics manufacturers and consumers worldwide [63]. Ganoderma lucidum contains myriad biologically active compounds (over 400 compounds), including polysaccharides, triterpenoids, steroids, fatty acids, amino acids, nucleosides, proteins, and alkaloids [64]. Still, how do these bioactive compounds reflect their medical properties? The following section will discuss the therapeutic impacts of these bioactive compounds.
2.1. Ganoderma lucidum Is a Factory of Biologically Active Useful Compounds
“Mushroom of immortality & symbol of traditional Chinese medicine”—Chen et al. [65].
The biologically active molecules of G. lucidum rely on their chemical composition, with polysaccharides, peptidoglycans, and triterpenes being the three major bioactive compounds [58][62][64][65][66][67]. Additionally, this mushroom contains other constituents with distinct biological functions, such as minerals (e.g., germanium), proteins, lectins, crude fibers, phenols, enzymes, sterols, and long-chain fatty acids [6][68][69][70][71]. Table 3 shows the major bioactive compounds and their biological effects. Snapshots of these bioactive compounds could be found as follows.
Table 3. The major bioactive compounds of G. lucidum and their biological effects.
| Bioactive Compounds | Biological Effects | References |
|---|---|---|
| Triterpenoids | ||
| Anti-inflammatory properties | ||
- The human gut, via epithelial cell walls, assists in the absorption process of nutrients into the blood;
| Moon Juice Spirit Dust, USA |
- The human gut inhibits toxic and strange particles from entering the bloodstream.
Consequently, and directly, any gut malfunction has adverse effects on human health. In this regard, functional foods, including pre- and probiotics, have become increasingly important due to their positive role in human gut health.
1.3.4. Ganoderma lucidum as a Functional Food: How?
Historically, mushrooms, including Ganoderma lucidum, were traditionally consumed due to their nutritional and culinary values, and for their medical benefits when used in folk medicine. This historical heritage has recently been translated through molecular research to explore the present bioactive components and unlock mushrooms’ nutrition and therapeutic values [46][47]. Among these health benefits, mushrooms could help prevent diseases; e.g., hypertension, diabetes, hypercholesterolemia, and cancer, as mentioned in many reports. Hence, mushrooms can be considered a curative food [8][48]. Mushrooms are still untapped sources of bioactive substances such as glycoproteins, polysaccharides, mainly β-glucans, and secondary metabolites; i.e., nucleotide analogs, metal-chelating agents, terpenoids, polyphenols, alkaloids, lactones, and sterols. These biologically active components possess several therapeutic implications, such as antiviral, anticancer, hepatoprotective, immunopotentiating, and hypocholesterolemic agents [47][48][49][50][51].
The present papentryr critically discusses the benefits of G. lucidum, from nutritional value to medicinal impacts, and sheds light on its potential as a source of nutraceuticals and functional food. Moreover, this rentryview provides answers with a critical vision to many questions, such as why the bioactive compounds of G. lucidum need to be further studied in vitro and in vivo, and what secrets are still behind them. Is it important to ensure G. lucidum’s quality and safety, as well as the best method to achieve that? With the potential of G. lucidum, will the future carry researcherus to the possibility of commercial widescale use of G. lucidum and its products as new functional foods and medicines?
Despite that Ganoderma lucidum is not edible in its raw state due to its higher content of bitter compounds, its palatability can be increased by turning it into manufactured products such as powders, supplements, and tea [52]. The nutritional value of G. lucidum will be tackled in-depth in the following section.
2. The Nutritional Profile of Ganoderma lucidum
“Medicines and food have a common origin”—Kaul [53].
For thousands of years, mushrooms have been valued throughout the world as food and medicine [8]. Nevertheless, mushrooms are still largely untapped resources in producing effective pharmaceutical products, nutrients, and cosmetics. Indeed, only approximately 150,224 species have been described [54] out of the estimated 2.2–3.8 million fungal species worldwide [55]. About 3000 species that belong to Macrofungi are safe for human consumption, such as edible mushrooms [56].
From the nutritionist’s point of view, generally, fresh mushrooms contain both soluble and insoluble fibers; the soluble fiber is mainly β-glucanpolysaccharides and chitosans [57]. However, a question comes to mind: does G. lucidum that is grown naturally or wild differ from that grown artificially in its nutritional components? According to the research in this regard, the answer is yes, as it was found that the quantities of crude protein, carbohydrates, and crude fiber were greater in the artificially grown variety [58]. Few studies have revealed the nutritional profile of G. lucidum. Roy and others [59] reported the nutritional value and mineral composition of G. lucidum. Through an analytical view of the nutritional profile of the G. lucidum mushroom (Table 2), several important conclusions can be reached.
Table 2. Physicochemical properties and chemical composition of Ganoderma lucidum mushroom.
| Constitute | Content | DRIs * (g/day) | Value in 100 g Mushroom/DRIs × 100 | |||||
|---|---|---|---|---|---|---|---|---|
| Value | g/100 g Mushroom (Wet-Weight Basis) | g/100 g Mushroom (Dry-Weight Basis) | ||||||
| Moisture % | 47 | |||||||
| Total solids (TS) % | 53 | |||||||
| Ganoderic acids, lucidumol, lucialdehyde, lucidenic acids, ganodermic, ganolucidic acids, ganoderals, ganoderiols | Anticancer | Wachtel-Galor et al. | [6 | |||||
| ] | , El Mansy | [69] | pH value | |||||
| Triterpenoids | 5.6 | Antidiabetic | Ahmad [62], Ma et al. [72] | |||||
| Energy (kcal) | 238.98 ** | Men: 2215 *** | 10.79 | |||||
| Ganoderic acids T-Q and lucideinic acids A, D2, E2, and P | Anti-inflammatory | El Mansy [69] | Women: 2025 | 11.80 | ||||
| Triterpenes | Antioxidant | El Mansy [69] | Water-soluble proteins % | 19.5 | 36.80 | Men (total proteins) ****: 56 | 34.82 | |
| Ganoderic acids, ganodermin, ganoderic acid A, ganodermadiol, ganodermanondiol, lucidumol B, ganodermanontriol, ganoderic acid B, ganolucidic acid B | Antimicrobial | Cör et al. [64], Sudheer et al. [67] | Women (total proteins): 46 | 42.39 | ||||
| Triterpenoids, ganoderic acid, ganoderiol F, ganodermanontriol | Antiviral | Bishop et al. [13], Zhang et al. [73], Zhu et al. [74] | Total lipids % | 3.00 | 5.66 | 44–77 ***** | 3.90–6.82 | |
| Polysaccharides | Total ash % | |||||||
| 1→3, 1→4, and 1→6-linked β and α-D (or L)-glucans, GLP-2B | Anticancer | Wachtel-Galor et al. [6], Ferreira et al. [ | 6.3 | |||||
| 75 | ] | Reducing sugars % | 4.39 | |||||
| Polysaccharides | Antidiabetic | Ahmad [62], Ma et al. [72] | ||||||
| Polysaccharides | Antioxidant | El Mansy [69] | ||||||
| Polysaccharides | Antimicrobial | Cör et al. [64] | ||||||
| Polysaccharides (ganopoly) | ||||||||
- ]
- .
Many other bioactive compounds have been isolated from G. lucidum, including:
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Enzymes; e.g., a metalloprotease that delays clotting time [6].
- Class: Agaricomycetes
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Order: Polyporales
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Family: Ganodermataceae
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Genus: Ganoderma
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Species: G. lucidum
1.2.3. Through Economists’ Glasses
Ganoderma-based products attract a great deal of interest in many countries within Europe and North America, although South Asia (Malaysia, Singapore, China, Japan, and Korea) are the principal producers/providers of these food products [26]. In the past, consumption of G. lucidum was restricted to the wealthy only, and therefore there was no need to expand its cultivation, and what was grown in the wild was sufficient. Recently, however, the consumption of this mushroom has increased through multiple societal groups as an effective alternative to modern medicine or alongside it, and this is what has called for the expansion of its cultivation [27][28]. With over 110,000 ton/year, China is the biggest producer and exporter of G. lucidum [29]. Therefore, G. lucidum-based products play a pivotal role in the Chinese economy as a source of foreign-exchange flow through increasing exports and as promising products at the food and medical levels.
Generally, the mushroom’s ingredients possess a wide variety of biological properties, including pharmaceutical, nutraceutical, and cosmetic, as shown in Figure 2 [8][30][31]. As such, regarding the G. lucidum mushroom, there are three types of products that are produced from it: nutraceuticals, pharmaceuticals, and cosmetics [31]. Different parts of G.
| Immune system | |
| Estée Lauder Re-Nutriv Sun Supreme Rescue Serum sun care product, USA | Triple-action repair technology to enhance the skin’s own natural defenses against the visible effects of sun exposure and sun-stressed skin |
| Four Sigma Foods Instant Reishi Herbal Mushroom Tea, UK | Immunity boost |
| Kat Burki Form Control Marine Collagen Gel, UK | Boosting collagen, improving elasticity, and providing hydration |
| Tela Beauty Organics Encore Styling Cream, UK | Providing hair with sun protection and preventing color fading |
| Menard Embellir Refresh Massage, France | Skin antiaging |
| Yves Saint Laurent Temps Majeur Elixir De Nuit, France |
Antiaging |
| Pureology NanoWorks Shineluxe, France | Antiaging and antifading |
| Hankook Sansim Firming Cream (Tan Ryuk SANG), Korea |
Making skin tight and vitalized |
| La Bella Figura Gentle Enzyme Cleanser, Italy | Antioxidants and vitamin D |
| DXNGanozhi Moisturizing Micro Emulsion, Malaysia | Hydrating and nourishing the skin |
| Guangzhou Bocaly Bio-Tec. Ganoderma Cell-Repairing Antiaging Face Mask, China | Antiwrinkle, firming, lightening, moisturizer, and nourishing, pigmentation corrector; pore cleaning and whitening |
| Nanjing Zhongke Pharmaceuticals Ganoderma Face Cream Set (day/night cream and eye gel set), China | Immunity boost and antifatigue |
| Shenzhen Hai Li Xuan Technology HailiCare Skin Whitening Cream, China | Removing freckles and whitening |
| Menard Embellir Night Cream, Japan | Eliminating toxins and helping repair skin damage associated with overexposure to UV radiation and free radicals |
| MAVEX Rejuvenating Treatment, Hong Kong | Antioxidant action and deep cellular renewal; fight degenerative processes and the negative action of free radicals |
* Sources: Wu et al. [31], Taofiq et al. [34], Hapuarachchi et al. [35], www.vegamebeljepara.com, www.dazzlinggroup.com, www.dxnmalaysia.com, and www.vegamebeljepara.com (accessed on 16 February 2022) Adapted from Wu et al. [31]. Licensed under CC BY 4.0. Adapted with permission from Taofiq et al. [34]. 2022, Elsevier.
1.2.4. Scientometric Analysis
During the last decade, the G. lucidum mushroom has attracted multiple research fields, including biochemistry, genetics and molecular biology, agricultural and biological sciences, pharmacology, toxicology, pharmaceutics, and medicine. Figure 3 illustrates the increasing interest in multidisciplinary utilization of G. lucidum based on the number of research articles in the past 10 years.
Figure 3. A scientometric analysis of increasing interest in Ganoderma lucidum over the last 10 years. Reprinted with permission from Scopus. 2020, Elsevier.
1.3. Why Should Mushrooms, including Ganoderma lucidum, Be Considered Functional Foods?
1.3.1. How to Define Functional Food?
In the early 1980s, the idiom “functional food” first appeared in Japan. Functional food is a broad term that includes several concepts [36]; for example, the definition of functional food provided by the Food and Agriculture Organization (FAO) states that “the functional food is the source that provides the human body with the necessary quantities of nutrients, i.e., proteins, carbohydrates, fats, vitamins, minerals, and others to keep it healthy. In addition, functional food can be cooked or prepared using ‘artificial intelligence technology’ [37]. In addition, the European Food Safety Authority (EFSA) defined functional food as “a food, which beneficially affects one or more target functions in the body, beyond adequate nutritional effects, in a way that is relevant to either an improved state of health and well-being and/or reduction of risk of disease” [38]. As described by the Functional Food Center (FFC) in the United States, functional foods are “real or processed foods that contain known or unknown biologically active compounds that, efficient, in defined and non-toxic quantities, recorded health benefit or provide a scientifically validated using unique biomarkers for the prevention, treatment or control of chronic disease or its symbiotic diseases” [39]. According to the definition of the Institute of Food Technologists (IFT), functional foods are those with ingredients that have health benefits in addition to basic nutrition, which is similar to the definition published by the International Life Sciences Institute (ILSI) [40][41].
Comprehensively, functional food can be defined as “a whole ingredient or a part of food that is used as food. It is part of a standard diet and is consumed on a regular basis, in normal quantities. It has proven health benefits that reduce the risk of specific chronic diseases or beneficially affect target functions beyond its basic nutritional functions” [42][43].
1.3.2. What Do the Definitions of Functional Foods Conclude?
The use of the term “ingredient” means that functional food is not only conventional food but also could be a part of other food or food ingredients. In addition, the above-mentioned definitions of functional foods allow for adaptation to cultural differences, including widely differing “standards” among cultures and countries. Moreover, the use of the term “health benefits” is not restrictive. It refers to physiological, psychological, and biological advantages [43][44].
1.3.3. Functional Foods and Their Relation with Gut Health
Among the important health effects of foods including the functional ones are those associated with gut health, a major determinant of an individual’s overall health. Several diseases are related in this context; e.g., gluten-therapy-resistant celiac, Crohn’s disease, ulcerative colitis, and irritable bowel syndrome. These adverse effects are caused by overgrowth and imbalance of intestinal bacteria linked to an individual’s food system [45]. The question that comes to mind is, what are the roles of the human gut in the body? These can be summarized as follows [45]:
| 8.28 | ||||||||
| Nonreducing sugars % | ||||||||
| 1.02 | 1.92 | |||||||
| Total sugars % | 5.41 | 10.21 | 130 | 4.16 | ||||
| Crude fibers % | 3.5 | Men: 38 | 9.21 | |||||
| Cardiovascular problems | Chan et al. | [76] | Women: 25 | 14.00 | ||||
| Proteins, Glycoproteins, and Peptidoglycans | Polyphenols “as gallic acid” | 0.04 | 0.08 | 1 ****** | 7.5 | |||
| Glycopeptides and peptidoglycans | Anticancer | Wachtel-Galor et al. [6], Sudheer et al. [67], Ferreira et al. [75], | Mineral | Mineral content (mg/100 g mushroom) | DRIs (mg/day) | Value in 100 g mushroom/DRIs × 100 | ||
| Protein Ling Zhi-8 (LZ-8), lectin, ribosome-inactivating proteins, antimicrobial proteins, glycopeptides/glycoproteins, peptidoglycans/proteoglycans, ganodermin A, ribonucleases, proteinases, metalloproteases, laccases | Immunomodulatory, anticancer, and antitumor | Wachtel-Galor et al. [6], El Mansy [69] | Major minerals | |||||
| Proteoglycans, proteins (LZ-8) | Antidiabetic | Ahmad [62], Ma et al. [72] | Potassium | 432 | 4700 | 9.19 | ||
| Phosphorus | 225 | 700 | 32.14 | |||||
| Polysaccharide–peptide complex | Antioxidant | Mehta [77] | ||||||
| Phenolic compounds | Sulfur | 129 | ||||||
| Phenolic components, phenolic extracts | 200–1500 | Antioxidant | 8.60–64.50 | |||||
| Mehta | [ | 77] | Magnesium | 7.95 | Men: 400 | 2.00 | ||
| Saponins | Women: 310 | 2.60 | ||||||
| Sodium | 2.82 | 1500 | 0.20 | |||||
| Calcium | 1.88 | 1000 | 0.20 | |||||
| Trace minerals | ||||||||
| Copper | 26 | 0.9 | 2889 | |||||
| Manganese | 22 | Men: 2.3 | 956.52 | |||||
| Women: 1.8 | 1222.22 | |||||||
| Iron | 2.22 | Men: 8 | 27.75 | |||||
| Anticancer and antioxidant | Lee et al. | [78] | ||||||
| Sterols; e.g., ergosterol | Provitamin D2 | Wachtel-Galor et al. [6] | ||||||
| Long-chain fatty acids | Antitumor | Gao et al. [79] | Women: 18 | 12.33 | ||||
| Zinc | 0.7 | Men: 11 | 6.40 | |||||
| Women: 8 | 8.75 | |||||||
| Vitamin | Vitamin content (mg/100 g mushroom) | DRIs (mg/day) | Value in 100 g mushroom/DRIs × 100 | |||||
| Thiamine (B1) | 3.49 | Men: 1.2 | 290.83 | |||||
| Women: 1.1 | 317.27 | |||||||
| Riboflavin (B2) | 17.10 | Men: 1.3 | 1315.38 | |||||
| Women: 1.1 | 1554.54 | |||||||
| Niacin (B3) | 61.9 | Men: 16 | 386.87 | |||||
| Women: 14 | 442.14 | |||||||
| Pyridoxine (B6) | 0.71 | Men: 1.4 | 50.71 | |||||
| Women: 1.2 | 59.16 | |||||||
| Ascorbic acid | 32.2 | Men: 90 | 35.77 | |||||
| Women: 75 | 42.93 | |||||||
2.2. Polysaccharides and Peptidoglycans
Polysaccharides, such as ganoderans, represent diverse biological macromolecules with a broad range of biological properties [58]. Additionally, G. lucidum is a source of polysaccharides, glycopeptides, and polysaccharide crude extracts, as indicated by several studies [80]. In addition, these components of G. lucidum mushroom showed strong biological activities, including, for example, antioxidant, anti-tumor, and antibacterial activities due to its content of sugars, glycoproteins, and polysaccharide extracts obtained from the fruiting bodies [75][81][82][83]. Anti-inflammatory, hypoglycemic, antitumorigenic, and immunostimulating activities are among the multiple biological roles of polysaccharides extracted from G. lucidum [84][85][86][87][88][89]. Free radical scavenging abilities, reducing power, and chelating on ferrous ions are among the reported antioxidant properties [90][91]. Ospina et al. [92] reported that the isolated chitosan from G. lucidum has promising and desirable characteristics in specialized sectors such as biomedicine, pharmaceutics, and cosmetics, beyond the food industry. Regarding the peptidoglycans, G. lucidum contains a proteoglucan (GLPG) that has antiviral activity [93].
2.3. Triterpenes
Several triterpenes extracted from G. lucidum have been reported (around 100 types of triterpenes), with half of these types being novel and unique to G. lucidum [18]. Ganoderic and lucidenic acids are the major triterpenes produced by G. lucidum, while other triterpenes have been identified; e.g., ganodermic, ganoderiols, and ganoderal acids [58][94][95][96][97][98][99][100][101].
2.4. Other Bioactive Compounds
2.4.1. Germanium
The element germanium has brought some attention to G. lucidum. Germanium is one of the most prevalent elements in wild G. lucidum. With 489 μg/g, germanium occupied the fifth-highest rank among the other detected minerals in terms of concentration [102]. This element possesses significant biological activities; i.e., antimutagenic, antitumor, immune-potentiating, and antioxidant [103]. There is no rigorous proof linking germanium with the specific health benefits of G. lucidum.
2.4.2. Proteins
Some bioactive proteins purified from G. lucidum have been found to contribute to the medicinal properties of this mushroom; for example:
