The bioactive components in Ganoderma lucidum that mediate their anti-aging or anti-aging-related functions mainly include polysaccharides, triterpenes, peptides, and polysaccharide peptides. We will first outline their general characteristics and describe their lifespan extension and related effects.

Polysaccharides are the most important contributors to the bioactivity and medical application of Ganoderma lucidum. It has been reported that these polysaccharides have antioxidant and immunomodulatory properties. Considering the structure of the polysaccharides extracted from Ganoderma lucidum, they are made up of glucose, mannose, galactose, fucose, xylose, and arabinose.

Even different Ganoderma lucidum share a distinct glycosidic linkage, allowing the polysaccharides to bind with various protein or peptide residues to form polysaccharide-protein or -peptide complexes. Based on the distinct structure and water solubility of polysaccharides, their extraction pattern differs from each other.

Generally, the extracting processes include crude extraction, precipitation, and purification. The most common methodology for primary extraction is hot water extraction with other techniques involving a microwave, ultrasonic, ultrasonic/microwave, and enzymatic treatments. The crude solution is precipitated by adding alcohol, methanol, or acetone. Finally, the purification process (chromatographic techniques, such as ion exchange, gel filtration, and affinity chromatography) aids in obtaining pure polysaccharides.

Studies have revealed that the polysaccharides in Ganoderma lucidum possessing prominent lifespan extension effects mainly include the Reishi Polysaccharide Fraction 3 (RF3) and Ganoderma lucidum polysaccharides I, II, III, and IV (GLPI, GLPII, GLPIII, and GLPIV). RF3 is a water-soluble glycol-conjugate fraction of Ganoderma lucidum. At the same time, Ganoderma lucidum polysaccharides I, II, III, and IV (GLPI, GLPII, GLPIII and GLPIV) are extracted from Ganoderma lucidum mycelium using fermented soybean curd residue as a growth medium, which is a new technique for extracting Ganoderma lucidum polysaccharides.

The traditional production of Ganoderma lucidum polysaccharides is mostly extracted from G. lucidum fruit bodies, which require a long incubation time with a low yield. The new technique used in extracting GLPI, GLPII, GLPIII, and GLPIV not only saves and cuts down the production time of Ganoderma lucidum polysaccharides but also increases the utilization of agricultural waste and subsequently decreases the cost of extraction. RF3, GLPI, GLPII, GLPIII, and GLPIV have all been reported to have immunomodulatory effects. RF3 have also demonstrated specific anti-aging effects, while GLPI, GLPII, GLPIII, and GLPIV may induce lifespan extension through their antioxidant properties.

Bioactive peptides are a class of peptides with molecular masses of less than 6 kDa; the relatively small molecular weight enables them to be easily absorbed by the human intestine. Ganoderma lucidum peptide (GLP) is the bioactive peptide of Ganoderma lucidum. It has been reported that GLP is the major antioxidant component of Ganoderma lucidum, and this property makes it a probable candidate for anti-aging.

Since the individual polysaccharides and peptides from Ganoderma lucidum are candidates for mediating its anti-aging effect, combining these components may have similar functions. The Ganoderma polysaccharide peptide (GLPP) has been shown to possess antioxidant and immunomodulatory effects, thus exerting an anti-aging effect. Its average molecular weight is 520 kDa. The polysaccharides in GLPP are D-rhamnose, D-xylose, D-fructose, D-galactose, and D-glucose with molar ratios of 0.549: 3.614: 3.167: 0.556: 6.89 and are linked by β-glycosidic linkages. GLPP contains 16 amino acids, Asp 8.49, Thr 3.58, Ser 3.93, Glu 5.81, Gly 3.50, Ala 3.84, Cys1.06, Val 2.68, Met 5.33, Iso-Leu 0.25, Leu 1.5, Phe 1.99, Lys 3.30, His 1.21, Arg 3.94, Pro 1.22 (mg/g). The polysaccharides to peptides ratio in GLPP is approximately 95:5.

Ganoderma lucidum triterpene is another major bioactive constituent of Ganoderma lucidum besides polysaccharides. More than 140 distinct triterpenes have been extracted from Ganoderma lucidum. They have been reported to have anti-oxidation, anti-radiation, anti-tumor, and immunomodulatory effects. No reports directly link the anti-aging effect of Ganoderma lucidum triterpene, but its antioxidant property suggests that Ganoderma lucidum triterpene would have a potential lifespan extension effect. The anti-tumor effect of Ganoderma lucidum triterpenes has been shown in many different types of tumors, such as breast, lung, and cervical cancers. The triterpenes in Ganoderma lucidum associated with anti-aging are total triterpene and Ganoderic acid C1. Total triterpenes are isolated from the fruit bodies of Ganoderma lucidum.

Dissolving the ethanol extract of Ganoderma lucidum fruit bodies in chloroform allows one to collect the soluble fraction. It is then concentrated and eluted with petroleum ether, chloroform, methanol, or a combination of these solvents. Fractions are finally screened for characteristics of triterpene to obtain total triterpenes of Ganoderma lucidum. Ganoderic acid C1 (GAC1) is a triterpenoid isolated from G. lucidum. It has been suggested that GAC1 is the most potent triterpenoid of Ganoderma lucidum, which could inhibit the release of cytokines to the similar extent as G. lucidum polysaccharides to modulate the immune cascade.

1 Lifespan extension by bioactive components from Ganoderma lucidum

Among the bioactive components from Ganoderma lucidum, only RF3 has been reported to possess the ability to extend lifespan. RF3 could bind to a membrane-bound receptor to increase the expression of Toll-interleukin 1 receptor intracellular domain (TIR-1). TIR-1 is associated with aging and innate immunity in Caenorhabditis elegans, so RF3 exerts its anti-aging effect by upregulating TIR-1. Furthermore, RF3 could bind to an uncertain membrane surface receptor to activate the MAPK signaling pathway, thereby increasing the transcription of rab-1/pmk-1, which induces the expression of lifespan and longevity-related transcription factor DAF-16 to extend lifespan subsequently. Since TIR-1 could also inhibit rab-1transcription, it is supposed that RF3 may upregulate TIR-1 and RAB-1 through the different mechanisms in the process of lifespan elongation. Acetic acid could inhibit the expression of the trans-membrane receptor DAF-2 and indirectly increase the level of DAF-16 to induce lifespan extension in Caenorhabditis elegans. Therefore, the combination of acetic acid and RF3 could strengthen the anti-aging effect of RF3 by 30-40% compared with using RF3 alone.

2 Anti-aging-related effects of bioactive components from Ganoderma lucidum

2.1 Antioxidant activity

Evidence has shown that Ganoderma lucidum polysaccharides GLP-I, GLP-II, GLP-III, GLP-IV, Ganoderma lucidum total triterpenes, Ganoderma lucidum peptide, and Ganoderma polysaccharide peptide possess antioxidant properties. The antioxidant enzymes and GSH help protect cells against oxidative stress. SOD, CAT, and GPx aid in clearing ROS, while GSH protects against protein oxidation. Under oxidative stress conditions, the hydroxyl radicals could cross the cell membranes and react with almost all the intracellular molecules leading to cellular functional disorder and finally causing cell death.

The antioxidant activity of GLP-I, GLP-II, GLP-III, and GLP-IV are measured in vitro by hydroxyl radical scavenging activity, metal chelating activity, DPPH radical scavenging activity, SOD-like activity assay, and reducing powder test. It is proven that GLP-I, GLP-II, GLP-III, and GLP-IV have differing levels of hydroxyl radical scavenging: GLP-III > GLP-IV > GLPI > GLP-II.

Transition metals could act as catalysts to promote the production of radicals and finally lead to radical-mediated oxidative chain reactions. GLP-I, GLP-II, GLP-III, and GLP-IV also possess metal chelating activities, decreasing the number of transition metals available. GLP-III and GLP-IV have more robust metal chelating capability vs. GLP-I and GLP-II.

Two of the four polysaccharides have strong scavenging activities concerning the DPPH radical in a concentration-dependent manner. The DPPH scavenging activity of GLP-IV is the strongest, followed by GLP-III, GLP-II, and GLP-I. Further, the 2,2′-azinobis (3-ethylbenzothiazolin-6-sulphonic acid) (ABTS) assay can be used to evaluate the total antioxidant power of a substance with GLP-IV possessing the strongest ABTS scavenging ability followed by GLP-III, GLP-I, and GLP-II. These polysaccharides also have SOD-like activities and act as potent reducing agents.

As the binding of Ganoderma polysaccharides to peptides, Ganoderma polysaccharide peptide (GLPP) could decrease the level of oxidative enzyme NADPH and NADPH-dependent ROS production and attenuate the MDA level in a model of renal ischemia-reperfusion, while simultaneously increasing antioxidative enzymes SOD, Mn-SOD, CAT, GSH, and GSH-Px. Moreover, it protects the mitochondria in macrophages against tert-butyl hydroperoxide (t-BOOH)-induced injury, improves mitochondria dysfunction, and attenuates apoptosis induced by mitochondrial stress. Furthermore, GLPP could decrease low-density lipoprotein (LDL) oxidation by decreasing its relative electrophoretic mobility and ox-LDL level caused by CuCl2.

Ganoderma lucidum triterpenes were shown to increase the levels of SOD, CAT, GPx, and GSH in liver and brain tissues. Administration of G. lucidum triterpenes could protect the body against oxidative-stress-induced protein and lipid peroxidation.

2.2 Immunomodulatory effect

The immunomodulatory effect of the bioactive components in Ganoderma lucidum includes stimulating the proliferation of immune cells and cytokine expression. RF3, GLP-I, GLP-II, GLP-III, GLP-IV, and GAC1 have been reported to possess immunomodulatory effects independent of any disease circumstances. In contrast, the immunomodulatory effect of GLPP is seen in effectively treating rheumatoid arthritis.

RF3 exerts its immunomodulatory effect by stimulating mice’s spleen cell proliferation and cytokine (especially IL-1, IL-2, and IFN-γ) expression. RF3 could also regulate immunophenotypic expression in mononuclear cells. Treating mononuclear cells with RF3 increased the populations of CD14+CD26+ monocyte/macrophage, CD83+CD1a+ dendritic cells and CD16+CD56+ NK-cells. Furthermore, NK cells in UCB play an important role in immune surveillance against cancer. RF3 in umbilical cord blood (UCB) could significantly increase the cytotoxicity of CD56+ NK cells.

GLP-I, GLP-II, GLP-III, and GLP-IV could stimulate macrophage proliferation and induce NO production in macrophages. NO is a highly reactive free radical, which is involved in the formation of oxidation products. Since NO is significant in the activation of non-specific host defense, it can be used to measure macrophage activation. The relative potential of GLPs on NO production is ranked as follows GLP-IV > GLP-III > GLP-II > GLP-I.

GLPP’s immunomodulatory is seen in its effectiveness in treating rheumatoid arthritis. IL-8 and MCP-1 are key inducers of rheumatoid arthritis. The downregulation of fibroblastic IL-8 and MCP-1 could attenuate leukocyte aggregation and activation and decrease chemokine production. GLPP could activate the NF-κB signal transduction pathway to reduce IL-8 and MCP-1 production, thereby exerting its anti-inflammation and immunomodulatory effects.

GAC1 was demonstrated to inhibit the release of TNF-α in LPS-stimulated murine macrophages and asthma patients’ peripheral blood mononuclear cells (PBMNCs). In asthma, GAC1 inhibits TNF-α secretion through the NF-κB pathway. Besides asthma, GAC1 also activates macrophages and decreases the secretion of inflammatory cytokines, including TNF-α, IFN-γ, and IL-17α in PBMNCs and a colonic biopsy of patients with Crohn’s disease. Excessive TNF-α production could directly mediate or exacerbate several inflammatory diseases, including Crohn’s disease, rheumatoid arthritis, and asthma. A series of anti-TNF-α medications are currently used to treat inflammatory diseases. The inhibition of TNF-α secretion by GAC1 is important concerning its immunomodulatory effect.