The sugar compositions of yellow and white pearles were compared, since it being concluded in the previous paper that the pigments resulting from the interaction of conchiolin-like substances and some sugar derivatives are responsible for the yellow color of pearl.
The pigments extracted from the decalcified nacres of pearls with 1
N HC1-methanol and the residual conchiolin were hydrolysed with 4
N H
2SO
4 in a boiling water bath separately. Each of the resulting bydrolyzates was fractionated into neutral and basic fractions using ion exchange resins. After trimethylsilylation, both fractions were subjected into GLC for sugar analysis.
Xylose, fucose, mannose, galactose, and glucose were found in the neutral fraction of the yellow pearl pigments. On the basis of their peak areas, the relative amounts of xylose and mannose were found to be larger than those of fucose, galactose, and glucose. Sugars of the same sort as those in the yellow pearl were also found in the neutral fraction of the white pearl pigments. Fucose was present in relatively larger amounts than were the other sugars. The basic fraction of the yellow pearl pigments contained the amino sugars, galactosamine and glucosamine, while white pearl contained only glucosamine.
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