Mimosine concentration in <i>Leucaena leucocephala</i> under various environmental conditions
Keynote paper presented at the International Leucaena Conference, 1‒3 November 2018, Brisbane, Queensland, Australia.
Leucaena leucocephala (leucaena) is a multipurpose tropical tree-legume that is highly resistant to many biotic and abiotic stresses. Leucaena is used primarily as an animal fodder owing to its protein-rich foliage. However, leucaena foliage also contains mimosine, a toxic non-protein amino acid that can cause alopecia, goiter and other thyroid problems, infertility, and fetal death. Considering its toxicity and abundance in leucaena, it is important to quantify the mimosine concentrations in leucaena under different environmental conditions. Mimosine was extracted from various types of leucaena tissue exposed to a range of environmental conditions and then quantified by HPLC. The mimosine concentrations in leucaena treated with NaCl increased after 6 days of treatment and remained relatively high when treatment continued for 18 days. Interestingly, leucaena exposed to complete darkness for up to 5 days had a higher mimosine concentration than control plants exposed to normal light/dark photoperiods. On the other hand, drying leucaena leaflets or macerating them in an alkaline buffer significantly lowered their mimosine concentration. Mature leaflets that had fallen off the plant and dried out also contained significantly less mimosine than fresh leaflets. The results of this study indicate that mimosine concentrations in leucaena are affected by environmental conditions and this knowledge can assist in managing to prevent toxicity.