Also going by the names hen of the woods, sheep's head, and ram's head, this polypore mushroom can be found growing in forests on the trunks of trees near the ground. The most common name, maitake, stems from its Japanese roots where it is one of the most popular mushrooms to eat. In China it is also regularly eaten. In the U.S., it is primarily found at Asian supermarkets and alternative medicine and health food stores.
The overall amount of antioxidants in maitake is low but the same can be said about almost all varieties of fungi. Rather what mushrooms are prized for are certain phytonutrients which are not found elsewhere in the animal or plant kingdom. Most notably in the maitake mushroom is an enzyme called cyclooxygenase which has been shown to possibly inhibit the occurance of angiogenesis (the process through which new blood vessels grow from those already existing) (1). Angiogenesis is a major problem in the growth of tumors, as the new vessels deliver nutrients to them. For this reason, maitake have been studied as possibly offering anti-cancer benefits and for treatments which might be developed from them.
USDA Database for the Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods, Release 2 - Prepared by Nutrient Data Laboratory, Beltsville Human Nutrition Research Center (BHNRC), Agricultural Research Service (ARS), U.S. Department of Agriculture (USDA) - May 2010