PMID- 23256922
OWN - NLM
STAT- MEDLINE
DCOM- 20130828
LR  - 20130205
IS  - 1096-0309 (Electronic)
IS  - 0003-2697 (Linking)
VI  - 434
IP  - 2
DP  - 2013 Mar 15
TI  - High-performance liquid chromatography estimation of cross-linking of 
      dihydroxyindole moiety in eumelanin.
PG  - 221-5
LID - S0003-2697(12)00620-3 [pii]
LID - 10.1016/j.ab.2012.12.005 [doi]
AB  - Eumelanin pigments consist of various ratios of 5,6-dihydroxyindole-2-carboxylic 
      acid (DHICA) and 5,6-dihydroxyindole (DHI). On alkaline hydrogen peroxide 
      oxidation, these indole moieties give rise to pyrrole-2,3,5-tricarboxylic acid 
      (PTCA) and pyrrole-2,3-dicarboxylic acid (PDCA), respectively. In a recent study, 
      we detected considerable amounts of other pyrrole acids, 
      pyrrole-2,3,4,5-tetracarboxylic acid (PTeCA) and pyrrole-2,3,4-tricarboxylic acid 
      (isoPTCA), among the oxidation products of fossil ink sacs more than 160 million 
      years old. PTeCA and isoPTCA arise from the cross-linking of the DHI moiety of 
      eumelanin at the C2 and/or C3 positions. We mimicked the process of cross-linking 
      by heating synthetic eumelanins prepared from various ratios of DHICA and DHI at 
      100  degrees C for 18 days (or at 40  degrees C for 180 days). The heated eumelanins were 
      analyzed after alkaline peroxide oxidation as PTCA, PDCA, PTeCA, and isoPTCA by 
      high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection. On 
      heating, PTCA decreased rapidly due to decarboxylation, whereas PDCA decreased 
      gradually. Concurrently, PTeCA increased gradually to levels close to PTCA. 
      IsoPTCA also increased gradually at lower levels. Similar changes were observed 
      at 40 degrees C at a much slower rate. These findings suggest that the PTeCA/PTCA ratio 
      may serve as a good indicator of aging (cross-linking) of eumelanin.
CI  - Copyright (c) 2012 Elsevier Inc. All rights reserved.
FAU - Ito, Shosuke
AU  - Ito S
AD  - Department of Chemistry, Fujita Health University School of Health Sciences, 
      Toyoake, Aichi 470-1192, Japan. sito@fujita-hu.ac.jp
FAU - Wakamatsu, Kazumasa
AU  - Wakamatsu K
FAU - Glass, Keely
AU  - Glass K
FAU - Simon, John D
AU  - Simon JD
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20121219
PL  - United States
TA  - Anal Biochem
JT  - Analytical biochemistry
JID - 0370535
RN  - 0 (Cross-Linking Reagents)
RN  - 0 (Indoles)
RN  - 0 (Melanins)
RN  - 12627-86-0 (eumelanin)
RN  - Z3OC8499KG (5,6-dihydroxyindole)
SB  - IM
MH  - Chemistry Techniques, Analytical/*methods
MH  - *Chromatography, High Pressure Liquid
MH  - Cross-Linking Reagents/*chemistry
MH  - Fossils
MH  - Indoles/*chemistry
MH  - Melanins/*chemistry
EDAT- 2012/12/22 06:00
MHDA- 2013/08/29 06:00
CRDT- 2012/12/22 06:00
PHST- 2012/08/30 00:00 [received]
PHST- 2012/10/31 00:00 [revised]
PHST- 2012/12/04 00:00 [accepted]
PHST- 2012/12/22 06:00 [entrez]
PHST- 2012/12/22 06:00 [pubmed]
PHST- 2013/08/29 06:00 [medline]
AID - S0003-2697(12)00620-3 [pii]
AID - 10.1016/j.ab.2012.12.005 [doi]
PST - ppublish
SO  - Anal Biochem. 2013 Mar 15;434(2):221-5. doi: 10.1016/j.ab.2012.12.005. Epub 2012 
      Dec 19.