Purification, characterisation and analysis of melanin extracted from Tuber melanosporum Vitt.

A new method for the purification of melanin extracted from Tuber melanosporum Vitt. with KOH under nitrogen was developed. The physical and chemical properties of the resulting dark pigment were determined, including its elemental composition and ultraviolet (UV) and infrared (IR) spectra. The results of this study were calibrated using data obtained with synthetic dihydroxyphenylalanine (DOPA) melanin and indicate that (1) purification with chloroform gave the best results, as shown by elemental and infrared analysis; and (2) the synthetic and natural melanins have the same physical and chemical properties, with the same percentage of nitrogen, the same functional groups and the same degree of polymerisation. However, they showed large differences in: (1) the time necessary to become decolorised by oxidizing agents (NaOCl and H2O2); (2) the slope of log absorbance vs wavelength. These results and data found in the literature lead to a proposal that melanin of T. melanosporum is derived from a new nitrogen precursor.