Herbicidal Activity of Mimosine and Its Derivatives

Mimosine [β-[N-(3-hydroxy-4-oxypyridyl)]-α-aminopropionic acid] is a non-protein amino acid, and is a major compound present in all plant parts of Mimosaceae, which includes Leucaena (Leucaena leucocephala), Leucaena glauca, and other legumes belonging to Mimosa spp.. Structurally, mimosine is an analog of dihydroxyphenylalanine with a 3-hydroxy-4-pyridone ring instead of a 3,4-dihydroxy-phenyl ring (Fig. 1). Although Leucaena has a rich protein content and high annual yield, the presence of mimosine has limited the wide use of this plant as animal feed. This compound causes alopecia, growth retardation, cataracts and infertility in animals [1]. Mimosine can be degraded to DHP [3-hydroxy-4(4H)-pyridone] (Fig. 2) by microorganisms in the rumen and bacteria in rhizome nodules of Leucaena, by endogenous enzymes in the Leucaena plants, or by HCl hydrolysis. Although DHP is also toxic, it exerts lower toxicity than mimosine [2]. Mimosine possesses antimitotic activity that blocks the cell cycle in the large G1 phase [3] and inhibits DNA synthesis, which prevents the formation of the replication fork by altering deoxyribonucleotide metabolism [4]. The amino acid may also act as a tyrosine analogue which incorporates biologically vital proteins and, in turn, causes hair loss [1].