155 Repairing Bleach-Damaged Hair
Figure 9. The initial elastic modulus (A), the breaking stress (B), and the breaking extension (C) of various
hairs. The white bars in the bar charts are the bleached hair samples, untreated or treated, with various
polyphenols (0.9 mM) and copper chlorophyllin (Cu, 4 ppm) at ambient temperature for 24h. See the
experimental section for details. A t-test was used to compare between the two groups, which are shown with
the arrows. The difference was assessed with two-side test. A total of 60 hair fibers (20 fibers from each of 3
persons) were tested. The asterisk indicates a significant difference (p 0.01).

156 JOURNAL OF COSMETIC SCIENCE
of the polyphenol which has two catechol-like moieties connected with a hydrophilic acid/
ester backbone (Figure 1), the bidentate polyphenol acts efficiently on the cuticle keratin
to cure the bleached hair, even in the low concentration. The previous report suggests that
the large polyphenol may hardly penetrate the matrix (the cortex cellular region) through
the thick layer of the cuticular cells of the hair.23
CONCLUSION
First, the model proteins (lysozyme and keratin) were converted to higher molecular
weight-proteins by treating with the polyphenol (catechol, hydroquinone and chicoric acid)
in the presence of copper (II) chlorophyllin (4ppm). The amino acid analysis and the thiol
group-quantification revealed that the polyphenol treatment induced the decrease in the
contents of the lysine, histidine and cysteine residues of proteins. Second, the pale yellow,
bleached, straight hair, which was made from black natural hair, was similarly treated
with the polyphenols in the presence of the copper salt. The resulting light brown hair
was examined for the amino acid analysis and the fluorescence characteristics to indicate
that the amino acid residues were also decreased in a similar manner to the model proteins
treated with polyphenol in the presence of the copper salts. It also appears that through
treatment, especially with chicoric acid, the bleached hair was repaired at the levels
comparable to that of the natural hair with the following characteristics: subdued cuticle
scale lifting, small swelling degree, and large mechanical properties (the breaking stress
and the initial elastic modulus). The results were explained by a formation of the quinone-
crosslinking bond between the protein molecules as displayed schematically in Figure 7.
The present treatment was conducted under mild conditions, and may be applied to hair-
care technology for bleached hair damages.
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