title: Isolation, fractionation and characterization of melanin-like pigments from chestnut (Castanea mollissima) shells.
abstract: Melanins are known as versatile biopolymers, but the utilizations are restricted by their poor solubilities. Therefore, well soluble ones or their analogs are much desired. In this article, a new procedure was developed for fractionation of the pigments isolated from chestnut (Castanea mollissima) shells, and 3 fractions (Fr. 1, Fr. 2, and Fr. 3) were obtained. The solubilities of all the fractions in waters of different pH and in common organic solvents were studied. The physicochemical properties of the fractions were characterized for the first time on the basis of combined chemical analyses and spectroscopic methods including ultraviolet-visible (UV-Vis), Fourier transform infrared (FT-IR), electron spin resonance (ESR), and solid-state ¹³C nuclear magnetic resonance (¹³C-NMR). All the fractions could be bleached by NaOCl and H₂O₂ and give a positive reaction for polyphenols, which are usually used as typical tests for allomelanins. Their UV-Vis, FT-IR, and ESR spectra resembled those of synthetic and some natural melanins. Elemental data and quantitative analyses of ¹³C-NMR spectra revealed that pigment-bound proteins and polysaccharides were the most abundant in Fr. 1, while Fr. 2 was presented with the highest aromaticity.
  
  
  CONCLUSIONS
  We provided a new, simple, and inexpensive method to fractionate the melanin-like pigments from chestnut shells. This technique can be used to produce natural melanin-like food colorants with different solubilities from chestnut shells.
authors.affiliation: Key Laboratory for Forest Resource Conservation and Utilization in the Southwest Mountains of China, Ministry of Education, Southwest Forestry Univ, Kunming 650224, China. zengyuyao@126.com
authors.forename: Zengyu
authors.initials: Z
authors.lastname: Yao
authors.forename: Jianhua
authors.initials: J
authors.lastname: Qi
authors.forename: Lihua
authors.initials: L
authors.lastname: Wang
mesh_terms: D057886:Bleaching Agents / Q000737:chemistry; D005591:Chemical Fractionation; D055598:Chemical Phenomena; D002681:China; D004578:Electron Spin Resonance Spectroscopy; D029962:Fagaceae / Q000737:chemistry*; D005505:Food Coloring Agents / Q000032:analysis / Q000737:chemistry* / Q000191:economics / Q000302:isolation & purification*; D005525:Food-Processing Industry / Q000191:economics; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste / Q000032:analysis / Q000191:economics; D008543:Melanins / Q000032:analysis / Q000737:chemistry / Q000191:economics / Q000302:isolation & purification; D019906:Nuclear Magnetic Resonance, Biomolecular; D009754:Nuts / Q000737:chemistry*; D010860:Pigments, Biological / Q000032:analysis / Q000737:chemistry* / Q000191:economics / Q000302:isolation & purification*; D010936:Plant Extracts / Q000737:chemistry / Q000302:isolation & purification; D012995:Solubility; D012997:Solvents / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D057886:Bleaching Agents; D005505:Food Coloring Agents; D007220:Industrial Waste; D008543:Melanins; D010860:Pigments, Biological; D010936:Plant Extracts; D012997:Solvents