Commonly used mushrooms are wood ear, shiitake, and oyster mushrooms. Mushrooms, especially dried shiitake, are sources of umami flavor from guanylate. The Shanghai variation also contains shiitake mushrooms and onion. Bolete mushrooms are sometimes also used as pizza topping, not unlike champignons, shiitake, or portobellos. Cucumbers, radishes, and shiitake mushrooms were among the vegetables used in this period. In Asia, seafoods, tofu, and shiitake mushrooms may also be used. Logs from the poplar provide a growing medium for shiitake mushrooms. Medicinal mushrooms like Reishi and Shiitake are herbal products with a long history of use. Softwood should not be used to cultivate shiitake mushrooms. The kelp and/or shiitake dashi serve as a vegetarian soup stock. Eritadenine is a chemical compound found in shiitake mushrooms. Ingredients are sea bream, abalone, shiitake, mitsuba and shiso. Lentinan has been reported to cause shiitake mushroom dermatitis. Lentinan is a polysaccharide isolated from the fruit body of shiitake mushroom ("Lentinula edodes" mycelium). The beech tree is usually unsuitable for cultivation of the shiitake mushroom.