The Iron Pigment of Red Hair and Feathers

Abstract

In the 25 years since Rothman and Flesch isolated trichosiderin, the iron pigment of human red hair (1, 2), little progress has been made in this field. That a similar pigment may be found in red chicken feathers was suggested (3, 4), but the data as given are hard to evaluate. Later Barnicot (5), instead of extracting pigment with boiling acids, incubated human red hair at room temperature with dilute alkali. The resulting yellow solution, upon 5 minutes' boiling with acids, assumed the characteristic red color and absorption spectrum of trichosiderin. Thus it is evident that trichosiderin is not the natural form of the pigment, a belief noted earlier (6, 2). Barnicot's finding also demolished the allegation that trichosiderin may be an artifact produced by the acid hydrolysis of horny structures (7).In our recent attempts to characterize this unique pigment, two goals were set: The first objective was to isolate the pigment of red chicken f athers and compare it with trichosiderin, with a view toward eventual use as a chemical model. Feathers, being loose structures, would yield the pigment more easily than hair. The second aim was to isolate different forms of the pigment for structural analyses.Extraction of the hair with boiling 0.1 NHC1 was performed as previously described (1, 2). The hair was pretreated with chloroform and acetone; feathers from Rhode Island red chickens were thoroughly washed with chloroform and dried before extraction.In contrast to red hair, feathers give up most of their red pigment within 10 minutes' boiling with acids. After an initial yellow color, the resulting solution turns wine-red, much more deeply colored than extracts of equal amounts of hair. Further purification of the pigments was achieved by precipitation at pH 7, washing with water and repeated solution in acids with subsequent precipitation (2).In all tests performed so far, the red pigments of hair and feathers behaved in the same way. Both pigments reversibly change to yellow above pH 2, precipitate at pH 7, and may be dissolved in alkalis with a yellow color; both have the sameabsorption spectra in the visible and ultraviolet (Fig. 1); both contain firmly attached iron in varying amounts. Both may be obtained under milder conditions of extraction as