Isolation and characterization of melanin from Osmanthus fragrans seeds

Melanin derived from Osmanthus fragrans' seeds was isolated from O. fragrans' seeds by alkaline extraction, acid hydrolysis, and repeated precipitation with a yield of 0.34 g/100 g (wet weight basis). Physical and chemical properties of the melanin revealed that the melanin derived directly from O. fragrans' seeds were similar to typical melanin. The melanin was stable under ultraviolet light or room-light, stable in the range of 25-100 degrees C, relatively stable in alkaline solution, reducer and salt, but was bleached by strong oxidants (KMnO4, K2Cr2O7 and NaOCl). The metal-ion of Ca2+, Cu2+, Fe3+ and Zn2+ had the function of color increase or color preservation to the melanin. Although Mg2+, Al3+ and Na+ reduce pigment color, it was not obvious. Amino acid and organic acid did not affect the melanin, while sugar, starch, and glucose affected it slightly. (C) 2005 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.