| Budget Amount *help |
¥16,170,000 (Direct Cost: ¥15,300,000、Indirect Cost: ¥870,000)
Fiscal Year 2007: ¥3,770,000 (Direct Cost: ¥2,900,000、Indirect Cost: ¥870,000)
Fiscal Year 2006: ¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 2005: ¥9,500,000 (Direct Cost: ¥9,500,000)
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| Research Abstract |
The hippopotamus' skin produces a colorless viscous sweat over its entire hairless body from unknown big subdermal glands. The colorless secretion changes its color to red within a few minutes, and then brown as the pigment polymerizes about within a few hours. Tow unstable pigments, red and orange, responsible to the red coloration were isolated and called hipposudoric acid and norhipposudoric acid, respectively.
In order to study these structures more precisely, chemical synthesis was performed. Starting from 2,5-dimethoxytoluene and 2,5-dimethoxybenzaldehyde through coupling reaction and then Pscorr reaction, the fluorenone core, the common intermediate for the both pigments, was synthesized. Several steps led this intermediate to the corresponding unstable dihydroquinones which were oxidized to the unstable diquinones using air with copper(II) as the catalyst. Using a model compound, the tautomeric structures of these pigments both in an aqueous (polar) and an organic (lesspolar) solvents were revealed. The red sweat has been said to be a medicine for the hippopotamus, that is, the sweat protect hippo from strong sunlight and also from infection of microbes. These stories based on the following observations; (1) some adult albino hippos are survived, although these mutants are usually short-lived (2) hippos are always injured by quarrel, however, the wounds are smoothly cured, in spite of their living in the mud. These pigments were proved to absorb the UV light (280-400nm) and also exhibited antimicrobial activities against some gram-negative bacteria, Pseudomonas aeruginosa and Krebsiella pneumoniae.
From the colorless sweat, homogentisic acid was isolated and when it was mixed with polymer portion of the sweat, the pigments were produced. Accordingly, the acid was proved to be the precursor of the pigments and the reaction was proved to be catalyzed by an enzyme.
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