The invention provides a method for extracting
melanin from Stizolobium capitatum seed coats. The method comprises the steps: carrying out an extractive process: subjecting the Stizolobium capitatum seed coats to water cooking so as to remove impurities, then, adding the Stizolobium capitatum seed coats into a NaOH solution in accordance with that the material /
liquid ratio is 1g: (6 to 9)ml, carrying out extraction for 10 to 14 hours in a
nitrogen gas environment, then, adding a HCl solution into the solution so as to adjust the pH to be smaller than 2.5, and carrying out centrifugal collecting, so as to obtain gelatinous precipitates; carrying out a purifying process: suspending the collected gelatinous precipitates in a HCl solution, of which the volume is 15 to 25 times that of the gelatinous precipitates, carrying out
hydrolysis in boiling water bath for 2 to 6 hours, carrying out cooling, and then, carrying out centrifugal collecting, so as to obtain
solid granules; washing the collected
solid granules with
ethanol,
ethyl acetate and
acetone sequentially, and then, carrying out repeated
precipitation by using the NaOH solution and the HCL solution, thereby obtaining
melanin granules. According to the method, the operation is simple, the ratio of extraction of the
melanin from the Stizolobium capitatum seed coats is high, the purity of the melanin is high, the degree of oxidation of the melanin is low, and the extraction cycle is short; in addition, the cost is low, so that the method is suitable for being used for carrying out large-scale extraction on the melanin of the Stizolobium capitatum seed coats; the economic value of Stizolobium capitatum is increased, and the field of application of the Stizolobium capitatum is widened.