Ganoderma Lucidum (Reishi Mushroom)

Fungi are remarkable for the variety of high-molecular-weight polysaccharide structures that they produce, and bioactive polyglycans are found in all parts of the mushroom. Polysaccharides represent structurally diverse biological macromolecules with wide-ranging physiochemical properties. Various polysaccharides have been extracted from the fruit body, spores, and mycelia of lingzhi; they are produced by fungal mycelia cultured in fermenters and can differ in their sugar and peptide compositions and molecular weight (e.g., ganoderans A, B, and C). G. lucidum polysaccharides (GL-PSs) are reported to exhibit a broad range of bioactivities. Polysaccharides are normally obtained from the mushroom by extraction with hot water followed by precipitation with ethanol or membrane separation.

Structural analyses of GL-PSs indicate that glucose is their major sugar component . However, GL-PSs are heteropolymers and can also contain xylose, mannose, galactose, and fucose in different conformations, including 1–3, 1–4, and 1–6-linked β and α-D (or L)-substitutions .

Branching conformation and solubility characteristics are said to affect the antitumorigenic properties of these polysaccharides . The mushroom also consists of a matrix of the polysaccharide chitin, which is largely indigestible by the human body and is partly responsible for the physical hardness of the mushroom . Numerous refined polysaccharide preparations extracted from G. lucidum are now marketed as over-the-counter treatment.

Terpenes are a class of naturally occurring compounds whose carbon skeletons are composed of one or more isoprene C5 units. Examples of terpenes are menthol (monoterpene) and β-carotene (tetraterpene). Many are alkenes, although some contain other functional groups, and many are cyclic.

Triterpenes are a subclass of terpenes and have a basic skeleton of C30. In general, triterpenoids have molecular weights ranging from 400 to 600 kDa and their chemical structure is complex and highly oxidized.

In G. lucidum, the chemical structure of the triterpenes is based on lanostane, which is a metabolite of lanosterol, the biosynthesis of which is based on cyclization of squalene. Extraction of triterpenes is usually done by means of ethanol solvents. The extracts can be further purified by various separation methods, including normal and reverse-phase HPLC .

The first triterpenes isolated from G. lucidum are the ganoderic acids A and B, which were identified by Kubota et al. (1982). Since then, more than 100 triterpenes with known chemical compositions and molecular configurations have been reported to occur in G. lucidum. Among them, more than 50 were found to be new and unique to this fungus. The vast majority are ganoderic and lucidenic acids, but other triterpenes such as ganoderals, ganoderiols, and ganodermic acids have also been identified (Nishitoba et al. 1984; Sato et al. 1986; Budavari 1989; Gonzalez et al. 1999; Ma et al. 2002; Akihisa et al. 2007; Zhou et al. 2007; Jiang et al. 2008; Chen et al. 2010).

G. lucidum is clearly rich in triterpenes, and it is this class of compounds that gives the herb its bitter taste and, it is believed, confers on it various health benefits, such as lipid-lowering and antioxidant effects. However, the triterpene content is different in different parts and growing stages of the mushroom. The profile of the different triterpenes in G. lucidum can be used to distinguish this medicinal fungus from other taxonomically related species, and can serve as supporting evidence for classification. The triterpene content can also be used as a measure of quality of different ganoderma samples