Isolation and identification of pigments from oyster mushrooms with black, yellow and pink caps

The genus Pleurotus, namely oyster mushroom, is widely cultivated and consumed worldwide. Cap color is an important commercial trait for oyster mushroom. Diverse color is determined by various pigment constituents. However, the pigments of oyster mushrooms are still ambiguous. In this study, we extracted and identified pigments of oyster mushroom species with black, yellow and pink cap color. The extracted pigments appearing the three color types correspondingly to the cap color, which were all identified as melanin using a panel of spectroscopic and physical/imaging techniques. Nevertheless, HPLC and elemental analysis indicated that the melanin in oyster mushrooms was actually a mixture of eumelanin and phaeomelanin. Differences in the quantities and relative proportions of eumelanin and phaeomelanin resulted in the color variation in oyster mushroom caps. Electron microscopy studies showed that the melanin units are likely located in the cell wall, as reported in other fungi. The pigments in oyster mushrooms with three different cap color were extracted and identified for the first time in this study, which provided fundamental knowledge for future studies on the mechanism of color formation in mushrooms.