title: Structural Characterization of Melanin Pigments from Commercial Preparations of the Edible Mushroom Auricularia auricula.
abstract: Many of the most widely consumed edible mushrooms are pigmented, and these have been associated with some beneficial health effects. Nevertheless, the majority of the reported compounds associated with these desirable properties are non-pigmented. We have previously reported that melanin pigment from the edible mushroom Auricularia auricula can protect mice against ionizing radiation, although no physicochemical characterization was reported. Consequently, in this study we have characterized commercial A. auricula mushroom preparations for melanin content and carried out structural characterization of isolated insoluble melanin materials using a panel of sophisticated spectroscopic and physical/imaging techniques. Our results show that approximately 10% of the dry mass of A. auricula is melanin and that the pigment has physicochemical properties consistent with those of eumelanins, including hosting a stable free radical population. Electron microscopy studies show that melanin is associated with the mushroom cell wall in a manner similar to that of melanin from the model fungus C. neoformans. Elemental analysis of melanin indicated C, H, and N ratios consistent with 5,6-dihydroxyindole-2-carboxylic acid/5,6-dihydroxyindole and 1,8-dihydroxynaphthalene eumelanin. Validation of the identity of the isolated product as melanin was achieved by EPR analysis. A. auricula melanin manifested structural differences, relative to the C. neoformans melanin, with regard to the variable proportions of alkyl chains or oxygenated carbons. Given the necessity for new oral and inexpensive radioprotective materials coupled with the commercial availability of A. auricula mushrooms, this product may represent an excellent source of edible melanin.
authors.forename: Rafael
authors.initials: R
authors.lastname: Prados-Rosales
authors.forename: Stacy
authors.initials: S
authors.lastname: Toriola
authors.forename: Antonio
authors.initials: A
authors.lastname: Nakouzi
authors.affiliation: Department of Chemistry, Graduate Center and Institute for Macromolecular Assemblies, City University of New York , New York, New York 10031-9101, United States.
authors.forename: Subhasish
authors.initials: S
authors.lastname: Chatterjee
authors.affiliation: Department of Chemistry, Graduate Center and Institute for Macromolecular Assemblies, City University of New York , New York, New York 10031-9101, United States.
authors.forename: Ruth
authors.initials: R
authors.lastname: Stark
authors.forename: Gary
authors.initials: G
authors.lastname: Gerfen
authors.affiliation: Goodwin and Wells , New York, New York 10065, United States.
authors.forename: Paul
authors.initials: P
authors.lastname: Tumpowsky
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Dadachova
authors.forename: Arturo
authors.initials: A
authors.lastname: Casadevall
mesh_terms: D001487:Basidiomycota / Q000737:chemistry*; D002473:Cell Wall / Q000737:chemistry; D003455:Cryptococcus neoformans / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D007211:Indoles / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008543:Melanins / Q000032:analysis / Q000737:chemistry* / Q000302:isolation & purification; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D009284:Naphthols / Q000737:chemistry; D011208:Powders / Q000737:chemistry
chemical_list: D007211:Indoles; D008543:Melanins; D009284:Naphthols; D011208:Powders; C041877:eumelanin; C030692:5,6-dihydroxy-2-indolylcarboxylic acid; C041660:1,8-dihydroxynaphthalene
keywords: Auricularia auricula; melanin; mushroom; radiotherapy