Link 14-Melanin, Pheomelanin: from benzopyrrole to benzothiazinone 


                        New Hampshire chicken Pheomelanin                       Pheochromes of a napolitan boy

                     and pheochromes of the feathers. The crest hemoglobin  .







 Marsupial pigments are probably triptophane derivatives




                           The pigment of red hairs





               The chromophore


Pheomelanins are pigments of feathers, hair and furs. Pheomelanins are formed starting from cysteinyldopa (1) (2). Pheomelanins are divided into two groups:
Pheochromes, yellow, reddish crystallizable, dilute HCl soluble pigments
Pheomelanins, red-brown, brown, amorphous, dilute HCl insoluble pigments.
Pheochrome cis-
D2,2'-Bi(5-hydroxy-7-alanyl-2H-1,4-benzothiazine)-3-carboxy-3'-one (I) together with gallopheomelanin-1, have been isolated from New Hampshire chicken feathers and characterized. Cysteinyldopa is the biological precursor of (I), a yellow-orange compound recovered as crystals. Its chromophore system is responsable of the  carrot-red hair of the young Neapolitan boy see in the photography. The structure of pheomelanins is not well understood but the structure (I) may be part of gallopheomelanin-1 (1-21).
The  pheochromes (other names like trichosiderins, trichochromes, are reported in litterature) obtained during acid extracion of feathers and hair are artifacts. The chromophores may be (II) (III) (IV) type (32). Melanin, Pheomelanin, Pheochromes may coexist in Nature.
Pheomelanins and  pheochromes  as  radical-polaron structure are  biological electric conductors. The EPR spertra is similar to that of melanin. 
Actually, DOPA a versatile aminoacid, precursor of melanins and alkaloids, provides benzopyrrole, benzothiazine and isoquinoline skeleton to eumelanin, pheomelanin and neuromelanin, respectively.

The red, orange, brown pigments of some rodents and kangoroo furs are probably tryptophane derivatives.


1. G. Prota, M. Piattelli, R. A. Nicolaus “Preliminary results in the study of phaeomelanins” Rend. Acc. Sci. Fis. Mat. Vol.XXXIII, 146 (1966).

2. R. A. Nicolaus “Melanins” Hermann Paris 1968; R.A. Nicolaus "Melanins" pag. 190-199 in Methodicum Chimicum, vol 11 part.3, Eds. F. Korte, M. Goto, AP Tokyo 1978.

3. G. Prota, R. A. Nicolaus “Struttura e Biogenesi delle feomelanine. Nota 1. Isolamento e proprietà dei pigmenti delle piume” Gazz. Chim. Ital. 97 665 (1967).

4. G. Prota, G. Scherillo, E. Napolano, R. A. Nicolaus “Struttura e biogenesi delle feomelanine. Nota II. Sulla reazione tra o.chinoni e cisteina” Gazz. Chim. Ital., 97, 1457 (1967).

5. L. Minale, E. Fattorusso, G. Cimino, S. De Stefano, R. A. Nicolaus “Struttura e biogenesi delle feomelanine. Nota III. Prodotti di degradazione” Gazz. Chim. Ital 97, 1636, (1967).

6. R. A. Nicolaus “Melanins” Chemistry of Natural Products, Series editied by Edgar Lederer, Hermann, Paris 1968.

7. G. Prota, G. Scherillo, R.A. Nicolaus “Struttura e biogenesi delle feomelanine. Nota IV. Sintesi e proprietà della 5-S-cisteinildopa” Gazz. Chim. Ital. 98, 495, (1968).

8. E. Fattorusso, L. Minale, S. De Stefano, G. Cimino, R. A. Nicolaus “Struttura e biogenesi delle feomelanine. Nota V. Sulla struttura della gallofeomelanina-1” Gazz. Chim. Ital. 98, 1443 (1968).

9. D. Sica, C. Santacroce, R. A. Nicolaus “Sintesi di 2H-1,4-tiazine” Gazz. Chim. Ital. 98, 17, (1968).

10. C. Santacroce, D. Sica, R. A. Nicolaus “Sintesi di 1,4-benzotiazine” Gazz. Chim. Ital. 98, 85, (1968).

11. D. Sica, C. Santacroce, R. A. Nicolaus “Restringimento dell’anello di alcune 3,5-diaril-2H-1,4-tiazine per idrogenolisi” Gazz.Chim.Ital. 98, 488 (1968).

12. G. Prota, G. Scherillo, R. A. Nicolaus “On the structure of tricosiderins” Rend.Acc.Sci.Fis.Mat.XXXV, 326, (1968).

13. E. Fattorusso, L. Minale, G. Cimino, S. De Stefano, R. A. Nicolaus “Struttura e biogenesi delle feomelanine. Nota VI. Sulla struttura della gallofeomelanina –1” Gazz. Chim. Ital. 99, 29 (1969).

14. R.A.Nicolaus, G.Prota, C.Santacroce, G.Scherillo, D.Sica “Struttura e biogenesi delle feomelanine. Nota VII. Sulla struttura delle tricosiderine”  Gazz. Chim. Ital. 99 323, (1969).

15. L.Minale, E.Fattorusso, G.Cimino, S.De Stefano, R.A. Nicolaus “Struttura e biogenesi della feomelanina. Nota VIII. Sulla struttura della gallofeomelanina- 1” Gazz. Chim. Ital. 99, 431 (1969).

16. E.Fattorusso, L.Minale, S.De Stefano, G.Cimino, R.A.Nicolaus “Struttura e biogenesi delle feomelanine. Nota IX. Feomelanine biosintetiche” Gazz. Chim. Ital. 99, 969, (1969).

17. G.Prota, G.Scherillo, O.Petrillo, R.A.Nicolaus, “Struttura e biogenesi delle feomelanine. Nota X. Sulla struttura delle tricosiderine”Gazz. Chim. Ital. 99, 1193 (1969).

18. G.Misuraca, R.A.Nicolaus, G.Prota, G.Ghiara, “Cytochemical study of Phaeomelanin Formation in Feather Papillae of New Hampshire Chick Embryos” Experientia 25, 920 (1969).

19. L.Minale, E.Fattorusso, S.De Stefano, R.A.Nicolaus “Struttura e biogenesi delle feomelanine. Nota XI. Ulteriori ricerche sulla biogenesi delle feomelanine” Gazz. Chim. Ital. 100, 461 (1970).

20. L.Minale, E.Fattorusso, S.De Stefano, S.Magno, G.Cimino, R.A.Nicolaus “Struttura e biogenesi delle feomelanine, nota XII. Modelli sintetici in relazione alla struttura delle feomelanine” Gazz. Chim. Ital. 100, 870 (1970).

21. E.Fattorusso, L.Minale, S.De Stefano. R.A. Nicolaus, “Struttura e biogenesi delle feomelanine. Nota XIII- Sulla struttura della gallofeomelanina-I”. Gazz. Chim. Ital. 100, 880 (1970).

22. G.Prota, S.Crescenzi, G.Misuraca, R.A.Nicolaus, “New Intermediates in Phaeomelanogenesis in vitro”. Experientia, 26, 1058 (1970).

23. E.Fattorusso, L.Minale, G.Sodano “Feomelanine ed eumelanine da nuove fonti naturali” Gazz. Chim. Ital. 100, 452, (1970).

24. G.Prota, A.Suarato, R.A.Nicolaus “The isolation and Structure of Trichosiderin B” Experientia 27, 1381 (1971).

25. R.A. Nicolaus “The Nature of Mammalian Colors” Chim.Ind. 54, 27 (1972).

26. R.H. Thomson “The pigments of reddish hair and feathers” Angew. Chim. Int. Ed. English 13, 305 (1974).

27. G.Prota, R.H. Thomson “Melanin pigmentation in Mammals” Endeavour XXXV, 32 (1976).

28. F.Chioccara, R.A.Nicolaus, E.Novellino, G.Prota, “Ring-expansion of benzothiazolines into 1,4-benzothiazines” Chim. Ind. 58, 546, (1976).

29. R.A.Nicolaus “Melanine” Quaderni della Accademia Pontaniana n°4, Napoli 1984.

30. G.Prota “Melanins and Melanogenesis” AP, San Diego (1992).

31. C.Costantini, G.Testa, O.Crescenzi, M.D’Ischia “Photochemical Ring Contraction of Dihydro –1,4-benzothiazines” Tetrahedron Letters 35, 3365 (1994).

32. B. L. Kaul  295. Studies on Heterocyclic Colouring Matters. Part II: D2,2'-Bi(2H-1,4-benzothiazines), Helv. Chem. Acta 57, 2664 (1974).

33. C. Santacroce, D.Sica, G.Prota, R.A.Nicolaus  D2,2'-Bi(5-hydroxy-7-methyl-8- (2-hydroxy-4-methylphenoxy)-2H-1,4-benzothiazine Rend. Acc. Sci. Fis. Mat. XXXV, (1968).

34. A. Bolognese "Sul cromoforo delle tricosiderine" Tesi di laurea, relatore Prof. C. Santacroce, Facoltà di Scienze, Università di Napoli, Napoli, 21 novembre, 1968.

35. E.M.Nicholls "Marsupials Pigments" pag.142 in Pigment Cell Vol.II, Eds.V.J.McGovern, P.Russel. S.Karger,Basel 1973.

36. F.Giordano,L.Mazzarella, G.Prota, C.Santacroce, D.Sica,  "Synthesis and stereochemistry of D2,2'-bi(2H-1,4-benzothiazine) derivatives.Crystal structures of cis- and trans- D2,2'-bi(3-p-bromophenyl)-2H-1,4-benzothiazines" J.Chem.Soc. (C) 2610 (1971).

37. L.Mosca, C.Blarzino, R.Coccia, C.Foppoli, M.A.Rosei "Melanins from tetrahydroisoquinolines spectroscopic characteristic, scavenging activity and redox transfer properties" Free Radical Biol..Med. 24, 161, (1998).

38. L.Musaio  "Prodotti metabolici derivati dal triptofano via Chinurenina"  in Biogenesi delle Sostanze Naturali, Accademia Nazionale dei Lincei, pag.259, Roma (1964)

Revised , Naples September 2003