Mimosine

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Mimosine is an alkaloid, β-3-hydroxy-4 pyridone amino acid. It is a toxic non-protein free amino acid. Renz (1936) isolated mimosine from Mimosa pudica and named it mimosine. Later, it was also isolated by Bickel and Wibaut (1946) from Mimosa pudica. The chemical structure of mimosine was determined by Bickel et al. (1947a, 1947b). Its chemical structure is similar to that of the amino acid tyrosine. In ruminants, mimosine is degraded to 3,4 and 2,3 dihydroxy pyridone. It occurs in a few mimosa and all species of the closed allied genus Leucaena (Kumar 1999). Although toxicosis occurred in Australia (Jones, 1975, 1985), Papua New Guinea (Holmes, 1979, 1980, 1981), Africa (Compre, 1959; Vohradsky, 1972, Ostesile and Akpokoje, 1986; Akpokoje and Ostesile, 1987; Semenye, 1990) and Florida (Hammond et al., 1989), it was not found in any other tropical and subtropical areas throughout the world (Hammond, 1995). However, goats in Myanmar lost hair, when they were fed to diet containing 50 % of leucaena (Tin Ngwe, personal communication). Henke (1958) noticed that there was no adverse effects of leucaena for ruminants in Hawaii and Jones (1981) provided the evidence that goats and cattle in Hawaii had the ability to degrade the 3,4-DHP ruminally. After noting the differences in the tolerance to leucaena by animals in different geographic areas, it was proposed that tolerance might be related to the presence or absence of microbes tolerant to mimosine and 3,4-DHP (Jones et al., 1981). Subsequently, Jones and Megarrity (1983) conducted experiments with goats in Australia and Hawaii to improve the proposed differences in the ruminal degradation of 3,4-DHP between the locations, Hawaiian goats, but not Australian goats, could degrade 3,4-DHP ruminally.

The initial population of bacteria inoculated was not a pure culture. From this mixed culture, pure colonies of bacteria with ability to degrade the two isomers of DHP, 3,4 and 2,3 were isolated (Jones, 1985; Jones and Megarrity, 1986b). At first they named it strain 78-1 (ATCC 49833). It is extremely anaerobic when growing, can be stored at 20 ºC and will tolerate temperature up to 50 ºC. Between 50 and 55 ºC, the bacteria are killed (Jones, 1985). Detailed works in the USA on the substrates, they ferment, on their cell wall composition and rRNA sequences, have clearly shown that the bacteria are not closely related to any other rumen bacteria. Allison et al. (1990) isolated 3,4-DHP degrading bacteria which was assigned to a new genus and species Synergestes jonesii (Allison et al., 1992) in honour of R. J. Jones. Domiguez-Bello and Stewart (1990) isolated other types of ruminal bacteria that can degrade 3, 4-DHP from sheep and cattle in Venezuela. Furthermore, Chhabra et al. (1998) have found other type in India.