The determination of mimosine and 3,4-dihydroxypyridine in biological material

Abstract

A simple, specific method is described for the determination of mimosine and 3,4-dihydroxypyridine (DHP) in extracts of leaves and seeds of Leucaena glauca Benth. and in urine. Plant material is extracted with cold 0.1 N hydrochloric acid, and interfering substances are removed by chromatography on a cation-exchange resin. Organic cations are displaced from the resin with 2N ammonium hydroxide and the concentrated eluate chromatographed in one direction with the use of mesityl oxide : formic acid : water (41 : 7 : 6 by volume). The spots of mimosine and DHP, revealed with a ferric chloride spray, are cut out and the colour fully developed and measured. Urines are analysed in the same way except for a preliminary hydrolysis of the conjugated DHP. The method is satisfactory for estimating amounts of mimosine and DHP in the range 10–160 µg applied to the paper. Recoveries of these substances added to various extracts and to urine have varied between 98–102%. Appreciable destruction of mimosine, with the formation of some DHP, occurred when fresh L. glauca leaves were dried even under mild conditions. In fresh material no loss of mimosine occurred when it was placed immediately in 0.1 N hydrochloric acid. The ready hydrolysis of mimosine to DHP by boiling 0. I N hydrochloric acid has been demonstrated for the first time.