Structural characterization of melanin pigments from commercial preparations of the edible mushroom Auricularia auricula

Rafael Prados-Rosales, Stacy Toriola, Antonio Nakouzi, Subhasish Chatterjee, Ruth Stark, Gary Gerfen, Paul Tumpowsky, Ekaterina Dadachova, Arturo Casadevall

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18 Scopus citations

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 nonpigmented. 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.

Original languageEnglish (US)
Pages (from-to)7326-7332
Number of pages7
JournalJournal of Agricultural and Food Chemistry
Volume63
Issue number33
DOIs
StatePublished - Aug 26 2015

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Keywords

  • Auricularia auricula
  • Melanin
  • Mushroom
  • Radiotherapy

ASJC Scopus subject areas

  • Chemistry(all)
  • Agricultural and Biological Sciences(all)

Cite this

Prados-Rosales, R., Toriola, S., Nakouzi, A., Chatterjee, S., Stark, R., Gerfen, G., Tumpowsky, P., Dadachova, E., & Casadevall, A. (2015). Structural characterization of melanin pigments from commercial preparations of the edible mushroom Auricularia auricula. Journal of Agricultural and Food Chemistry, 63(33), 7326-7332. https://doi.org/10.1021/acs.jafc.5b02713