## 2 Biologically Active Polysaccharides--Structure and Function
### Fungal polysaccharides  
Several members of the Basidiomycota division (as well as some of the Ascomycota), often referred to as the \"higher fungi\", can produce immunomodulating, hepatocyte, antimicrobial, antioxidant, hypoglycemic, and hypolipidic substances, which are usually \(\beta\)-glucanas, but also heteroglycans or proteoglycans [81; 82; 83; 84]. Numerous mushroom polysaccharides are considered biological response modifiers (BRMs) [85]. Fungal polysaccharides may be used as a non-invasive form of cancer treatment due to their ability to induce a non-specific response of the immune system against cancer cells. Further, this capacity is also evident against viral and bacterial infections and inflammation [86]. They stimulate macrophages, T lymphocytes, and NK cells to produce cytokines (TNF-\(\alpha\), I-1b, IFN-\(\gamma\)), which have the ability to inhibit cancer cell proliferation and apoptosis [87]. The best polysaccharides tested for immunomododulatory properties were branched \(\beta\)-(1-3)-D-glucans, containing a backbone of \(\beta\)-(1,3)-D-glucose residues to which \(\beta\)-(1,6)-D-glucose side groups are linked via glycosidic linkages. The most well-studied immunomododulating branched \(\beta\)-D-glucans are lentinan from _Lentiunala edodes_[88; 89; 90] and schizophrenyllan isolated from _Schizophyllum commune_[91; 92]. The structures of lentinan and schizophrenia are similar, but the molar mass of lentinan is significantly higher: lentinan has an average molecular weight of around 500 kDa, while schizophrenyllan is in the range of 100-200 kDa. Both \(\beta\)-glucans acquire a triple helical conformation in solutions. They are also both used as immunological adjuvants during chemotherapy, radiotherapy, radio-chemotherapy, and hormone therapy for various malignant tumors. Although they do not have a direct cytotoxic effect on cancer cells, they are effective in treating cancer of the stomach, colon, lung, breast, and cervix in combination with conventional medications. Both glucans are non-toxic. Their action is more effective if given in the early stage of neoplastic disease development [93]. Many other fungi can biosynthesize immunoassay, branched \(\beta\)-D-glucans, mainly constituting the building blocks of their cell wall. They include: _Ganoderma luculum_ (ganodera) [94; 95; 96], _Pleurotus ostreatus_ (pleuran) [97; 98]_Grifola fondosa_ (grifolan) [99], and several others. In addition to the above-described immunoassay, branched \(\beta\)-D-glucans, fungi produce numerous biologically active polysaccharides with different monosaccharide composition and types of glycosidic bonds: homo- and heteroglycans. For example, [PERSON] et al. determined the structure of a immunoassay proteoglycan isolated from _G. lucidum_ fruiting bodies, with a main chain of 1,6-\(\alpha\)-galactopyranoside-, 1,2,6-trisubstituted-\(\alpha\)-galactopyranoside-, 1,3-disubstituted-\(\beta\)-glucopyranoside-, and 1,4,6-tri-substituted-\(\beta\)-glucopyranoside-groups, with branches of 1-\(\beta\)-glucopyranoside- and 1-\(\alpha\)-tropyransoide- residues [100]. In turn, two immunostainingitating heteroglycans have been isolated from _Agaricus blazei_ fruiting bodies, which are composed of glucose, galactose, and mannose [101]. Moreover, _A. blazei_ mycelium cultivated in liquid cultures excretes an extracellular antitumor proteoglycan with high molecular weight (1000-10,000 kDa), which was composed of mannose, glucose, galactose, and ribose groups [102]. One of the most successful therapeutic mushroom polysaccharides, which has been marketed as an anticancer drug (in combination with chemotherapy), krestin (polysaccharide-K, PSK) derives from the edible mushroom _Coriolous versicolor_ (_Trametes versicolor_) [103]. It is a low-molecular-weight proteoglycan, containing glucose as a major monosaccharide, but other sugar residues are also present, such as mannose, fucose, xylose, and galactose.