CHAPTER 5: EXTRACTION, DEVELOPMENT AND CHEMISTRY OF ANTI-CANCER COMPOUNDS FROM MEDICINAL MUSHROOMS Synopsis The main antitumour compounds presently isolated from mushroom fruit-bodies, submerged cultural mycelial biomass or liquid culture broth have been identified as either water soluble β-D-glucans with heterosaccharide chains of xylose, mannose, galactose or uronic acid or β-D-glucan-protein complexes – proteoglycans. Methods of extraction and purification are outlined. Levels of anti-cancer activity are related to molecular weight, degree of branching and solubility in water of the respective molecules. The main medically important polysaccharide compounds to have achieved clinical relevance, viz. Lentinan, Schizophyllan, PSK and PSP, and Grifron-D are discussed. Hot water extracts of many mushrooms used in traditional Chinese medicine and other folk medicines have long been said to be efficacious in the treatment of various diseases including many forms of cancer. The use of medicinal mushroom extracts in the fight against cancer is well known and documented in China, Japan, Korea, Russia and now increasingly in the USA (Mizuno et al., 1995). However, it is only within the last three decades that chemical technology has been able to isolate the relevant compounds and use them in controlled experiments. They have been extensively screened for medical properties especially for anticancer application (Mizuno, 1999). Many species of mushrooms have been found to be highly potent immune system enhancers, potentiating animal and human immunity against cancer (Wasser and Weis, 1999a, Borchers et al., 1999, Kidd, 2000; Ikekawa, 2000; Feng et al., 2001). While at least 30 mushroom species have yielded compounds with pronounced anticancer actions in xenographs only a small number have taken the next step, viz. objective clinical assessment for anticancer potential in humans.