Agaritine from Agaricus bisporus is capable of preventing melanin formation

Agaritine [(beta-N-(gamma-L(+)-glutamyl)-4-hydroxymethylphenylhydrazine] wa s isolated and purified from the mushroom Agaricus bisporus. The prevention of melanin formation by agaritine is reported here for the first time. Thi s compound, characteristic for the Agaricus genus, was a nucleophile in its deprotonated state which was able to remove the, either enzymatically or c hemically generated, o-quinones from the assay medium. The disappearance of these o-quinones followed first order kinetics through a decreasing uniexp onential. The dependencies of the apparent rate constant (k(q)) for the dis appearance of the o-quinone, as well as the o-quinone concentration removed from the assay medium ([Q](0)) were studied as a function of proton, agari tine and o-quinone initial concentrations. k(q) increased linearly with aga ritine concentration, decreased non-linearly with proton concentration and was independent of the initial o-quinone concentration. [Q](0) showed a lin ear increase with initial o-quinone concentration, a non-linear decrease wi th proton concentration and was independent of the initial agaritine concen tration. Taking into account the effect of agaritine on o-quinones, this pa per calls for caution in the use of agaritine in experiments with o-quinone accumulation. Moreover, a possible role for agaritine in the browning of m ushrooms is discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.