D-fraction is a water-soluble protein-bound β-1,3/ β -1,6-glucans (proteoglucan) extracted from the fruiting body of Maitake mushroom (Grifola frondosa).

1. β -1,3/ β -1,6-glucans contained in D-fraction have a greater degree of branching compared to β -glucans from other mushrooms or yeast. Researchers found that the branching frequency of β -glucans is an important factor related to its immune activity. This is one of the reasons why D-fraction is more active than glucans from other mushrooms or yeast.
2. D-fraction is a proteoglucan (or protein-bound β -glucans), not pure β -glucans. It is an optimal form for oral administration.
3. A number of studies on the mycelium of Maitake mushroom were conducted in the past years, however, there has been no report to suggest that the mycelium contains D-fraction.