What is the d-fraction in Maitake Mushrooms?

One of the most exciting new mushrooms to emerge is maitake, Grifola frondosa. A choice edible that is highly prized by wild mushroom hunters, maitake is now being cultivated thereby insuring a steady supply for the first time. A mushroom without the common cap and gills, this polypore has multiple branching stems with flowery ruffled caps. Although there is scant evidence of use in traditional Chinese medicine, recent scientific research in Japan has shown maitake to contain significant active polysaccharides.

The search for active compounds in natural products leads to the processing of raw herbs into numerous extract fractions. These extract fractions are individually tested for activity, which if significant, may allow the filing of patents or the eventual development of a new drug. Such was the case with the polysaccharide ‘lentinan’ from shiitake mushroom. It should be noted that for a compound to be developed into a drug, it must be a pure, singular compound. Many mushroom extracts with high activity are protein-bound polysaccharides and therefore not pure compounds. A full spectrum mushroom extract can contain enough of these compounds to be very active and effective.

The active polysaccharides in Maitake have been identified as beta-D-glucans. The most important studies were carried out using nothing more than dried mushroom powder mixed into animal feed. These studies showed that many mushrooms possessed the ability to significantly inhibit various cancer systems when used orally.(1, 2) What this means is that dried mushrooms and mushroom extracts have a high degree of oral effectiveness when used in proper doses. Maitake mushroom powder showed 86% tumor inhibition in these feeding studies. With similar activity was shiitake mushroom powder, which showed 78% tumor inhibition in the same study.
Five hundred grams of dried maitake mushrooms contains:

  • A fraction = 14.5 grams
  • B fraction = 2.95 grams
  • C fraction = 2.3 grams
  • D fraction = 0.8 grams = 1.6 mg./gm

Many maitake polysaccharide fractions have shown anti-tumor activity in laboratory animals when administered by injection. One fraction showed significant activity when administered orally. It is called MT-1 or simply ‘D-fraction’, an alkali-soluble, hot water extractable compound that contains approximately 30% protein, or a ratio of beta-glucan to protein of 7:3. It occurs in a concentration of 1.6 mg. per gram of dried maitake mushrooms or .0016%. (3, 4) The optimum dose in animal experiments performed by Dr. Hiroki Nanba of Japan appears to be 25 mg./kg of body weight.(5) The activity of the ‘D’ fraction corresponds to other scientific evidence that would indicate the relatively higher oral activity of mushroom fractions when the polysaccharide is protein-bound. Like the other mushrooms, Maitake’s action is that of an HDP, or ‘Host Defense Potentiator’. Other activities that have been reported by scientists are the lowering of blood pressure, total cholesterol, and blood sugar concentrations.

  1. Mushroom Science XII, Proceedings of the Twelfth International Congress on the Science and Cultivation of Edible Fungi. Braunschweig, Germany 1987. ‘Antitumor Action of Fruit Bodies of Edible mushrooms Orally Administered to Mice’, Mori, Toyomasu, Namba, Kuroda.
  2. Proceedings of the International Symposium, Scientific and Technical Aspects of Cultivating Edible Fungi. Penn. St. Univ., University Park, PA. 1986. ‘Antitumor Activities of Edible Mushrooms by Oral Admiistration’, Mori, Toyomasu, Nanba, Kuroda.
  3. Chem. Pharm. Bull. 35 (3) 1987 ‘The Chemical Structure of an Antitumor Polysaccharide in Fruit Bodies of Grifola frondosa (Maitake)’, Nanba, Hamaguchi, Kuroda.
  4. Chem. Pharm Bull. 36 (5) 1988 ‘Antitumor Activity Exhibited by Orally Administered Extract from Fruit Body of Grifola frondosa (Maitake)’, Hishida, Nanba, Kuroda.
  5. Chem. Pharm Bull. 35 (1) 1987 ‘Potentiation of Host-Mediated Antitumor Activity in Mice by b-glucan obtained from Grifola frondosa (Maitake)’, Adachi, Nanba, Kuroda.

** Important Note: A company in New Jersey with strong Japanese ties, including affiliations with the Japanese researcher Dr. Hiroaki Namba, has trademarked the name ‘d-fraction’. They sell a product with this name.