Effect of hydroxylamine, p-aminobenzoic acid and p-aminosalicylic acid on the oxidation of o-dihydroxy- and trihydroxyphenols by mushroom tyrosinase

The effect of hydroxylamine (NH2OH), p-aminobenzoic acid (PABA) and p-amino salicylic acid (PASA) on the spectrum of the final product(s) formed when o -dihydroxy- and trihydroxyphenols were oxidized by tyrosinase was examined. New pigmented product(s), probably oximes, were formed by the interaction of NH2OH with the o-quinones of 4-methyl catechol, 3, 4-dihydroxyphenylacet ic acid (DOPAC) and 3,4-dihydroxyphenylpropionic acid (3, 4-DPPA) but not w ith the o-quinones of catechol or protocatechuic acid. Interaction of PABA or PASA with the o-quinones of catechol, 4-methyl catechol, protocatechuic acid, DOPAC and 3,4-DPPA also yielded pigmented oximes. The interaction of the o-quinones of trihydroxyphenols with NH2OH, PABA or, PASA had little effect on the spectrum of the final product(s), suggesting that oximes are not formed in these reactions.