Polysaccharides (complex sugars) are carbohydrate molecules composed of long chains of smaller monosaccharides (simple sugars) linked by glycosidic bonds. These natural compounds have a wide range of functions in nature, such as storing energy, cellular messaging, and structural support.

Medicinal mushrooms contain many different polysaccharides, but one specific type called beta-d-glucans are responsible for most of their proposed health benefits. Because polysaccharides are water-soluble, they are typically extracted by using the hot water extract method.