The Pigments of Reddish Hair and Feathers

Despite sporadic investigations over many years the structures of the pigments responsible for most of the yellow, orange, and brown colors of mammalian hair, and of feathers, have remained unknown. However, recent work has shown that the major reddish‐brown pigments, gallophaeomelanins, are polymers containing benzothiazole and tetrahydroisoquinoline units. The yellow‐orange and violet trichochromes are minor pigments based on a new chromophore, Δ2,2′‐bi(1,4‐benzothiazine). Both groups arise in vivo from tyrosine and cysteine by a deviation from the biogenetic pathway which normally leads to the formation of eumelanins, the black pigments.