Effect of reaction pH and CuSO4 addition on the formation of catechinone due to oxidation of (+)-catechin.
Int J Cosmet Sci
; 35(4): 362-7, 2013 Aug.
Article
em En
| MEDLINE
| ID: mdl-23574395
ABSTRACT
A novel hair dyeing technique being milder and safer for a human body is desired. The oxidation product of (+)-catechin, catechinone, was invented as a safer dyestuff for hair colouring under such the situation. The preparation of catechinone by a chemical oxidation is a practical way and the objective of the study is clarify the effect of the solution pH and in the presence or absence of Cu(2+) on the formation rate and yield of catechinone in order to improve the efficiency of the dye formation. The catechinone formation was monitored by ultraviolet-visible spectroscopy. Catechinone was prepared chemically from (+)-catechin in aqueous solution with O2 gas introduced over a pH range of 7.1-11.7. The rate and amount of the dye formation increase with increasing pH. Dissociation of the hydroxyl group of the catechol part of (+)-catechin is significant for the oxidation of (+)-catechin and promotes the dye production. This is because the deprotonated (+)-catechin has a higher reactivity with O2 . The production of catechinone is accelerated by the addition of CuSO4 and the production rate reaches the maximum at pH = 8.8. (+)-Catechin - Cu(2+) complexes are formed and the formation promotes the oxidation of the catechol part of (+)-catechin at pH ≤ 8.8. On the other hand, the complex becomes too stable to proceed for the oxidation reaction at pH > 8.8.
Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Catequina
/
Sulfato de Cobre
/
Concentração de Íons de Hidrogênio
Idioma:
En
Revista:
Int J Cosmet Sci
Ano de publicação:
2013
Tipo de documento:
Article
País de afiliação:
Japão