Isolation of melanin from testae of Prunus ameniaca Linn.

Melanin was extracted from testae of Prunus ameniaca first and the effective extraction of melanin was explored.The result showed the melanin was suitable to be extracted twice with 0.5 mol/L NaOH at 60 ℃ for 12 h,and the operation should be carried out under nitrogen to avoid excessive oxidation.After acid hydrolysis,further purification with organic solvents and repeated precipitation,4.73% yield of melanin was obtained.The melanin from testae of Prunus ameniaca contained higher total phenolic content,about 262 mg gallic acid equivalents per gramme.The physicochemical properties of the melanin from testae of Prunus ameniaca showed a strong similarity to these of synthetic DOPA melanin.They were insoluble in both water and common organic solvents but dissolved only in alkali,while precipitated in alkaline FeCl3 and when pH is below 3,and were bleached in KMnO4,K2Cr2O7,NaClO and H2O2,and produced a blue color with FeSO4/ferricyanide.In the ultraviolet and visible range of wavelengths the melanin absorption spectrum represents the decreasing line.The infrared spectra had the same strong absorption peaks as the broad band at 3 400 cm-1 and at 1650-1620 cm-1,respectively.