<P> Boletus edulis fruit bodies contain about 500 mg of ergosterol per 100 g of dried mushroom . Ergosterol is a sterol compound common in fungi . Additionally, the fruit bodies have about 30 mg of ergosterol peroxide per 100 g of dried mushroom . Ergosterol peroxide is a steroid derivative with a wide spectrum of biological activity, including antimicrobial and anti-inflammatory activity, and cytotoxicity to various tumor cell lines grown in laboratory culture . </P> <P> The mushroom also contains a sugar - binding protein, or lectin, that has affinity for the sugars xylose and melibiose . The lectin is mitogenic--that is, it can stimulate cells to begin the process of cell division, resulting in mitosis . Further, the lectin has antiviral properties: it inhibits the human immunodeficiency virus enzyme reverse transcriptase . Other studies suggest that B. edulis also has antiviral activity against Vaccinia virus and tobacco mosaic virus grown in culture . Antiviral compounds from mushrooms are a subject of interest in biomedical research for their potential to advance the knowledge of viral replication, and as new drugs in the treatment of viral disease . </P> <P> The fruit bodies have a high antioxidative capacity, due probably to a combination of various organic acids (such as oxalic, citric, malic, succinic and fumaric acids), tocopherols, phenolic compounds and alkaloids; the highest antioxidant activity is in the mushroom caps . Furthermore, fruit bodies were determined to have 528 mg of the antioxidant compound ergothioneine per kilogram of fresh mushroom; this value was the highest among many food items tested in one study . Porcini were thought to have anti-cancer properties according to Hungarian research conducted in the 1950s, but later investigations in the United States did not support this . </P>

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