L-Mimosine

Table 1 The tyrosinase inhibitory activities of compounds 3-7, as compared to the standard inhibitors (kojic acid and L-mimosine) [43]...

Non-protein amino acids Phytohemagglutinins (lectins) Selenocystathionin, L-mimosine... 

Heterocyclic compoimds such as L-mimosine (Fig. 11.10) cause hair loss in mules, horses, and sheep. Mimosine interferes with the enzyme that forms cysteine from methionine. Cysteine, in turn, is needed in growing hair follicles. Mimosine has been tried as a defleecing agent in sheep. After 2 days of intravenous infusion of mimosine, it takes 15 days for a sheep to drop its entire fleece (Reis etal., 1975). However, it has not yet proven practical in sheep ranching. 

Because of its bioisosteric similarity to the normal physiological substrate L-dopa (4), L-mimosine (5) inhibits catechol oxidation by the enzyme tyrosinase (7). These compounds exemplify a situation in which bioisosteresdis-play opposite pharmacologic effects at the same receptor. 

Khan et al. (2005) performed and reported tyrosinase inhibition studies of a combinatorial library of 2,5-disubstituted-l,3.4-oxadiazoles (25-43) [47]. The library of oxadiazoles was synthesized under microwave irradiation [47]. The synthetic steps involved for these compounds are shown in Scheme 2. Among the compounds from the library, 29 (30-[5-(40-bromophenyl)-1,3,4-oxadiazol-2-yl]pyridine, for structure see Fig. 6) exhibited the most potent (ICso = 2.18 xM) inhibition against tyrosinase, which has found to be more potent than the standard potent inhibitor L-mimosine (IC50 = 3.68 [xM, for structure see Fig. 1) [47]. 

Aromatic AA and L-mimosine in extracts of plant seeds and nonprotein AA... 

Nonprotein Amino Acids Derived from Aspartic Acid Lysine-Derived Nonprotein Amino Acids Pipecolic Acid and Related Compounds L-Mimosine Homoserine L-Canavanine Canaline... 

L-Mimosine (18) (Fig. 13.5) is a toxic heterocyclic amino acid that has been reported from several legumes. Among the plants that contain mimosine are Mimosa pudica and Leucaena leucocephala. The latter is often cultivated in tropical countries as a windbreak, a forage crop, and as a shade crop for coffee, tea and cacao (Rosenthal, 1991). This native of Mexico is capable of fixing nitrogen and is a quite agres-sive species. 

NO2, 1,4-Cyclohexadiene-l-glycine, 40B, 1092 iNOg, Lycoperdic acid, 44B, 435 2N202f L-Prolyl-L-alanyl cyclodipeptide, 45B, 2N2O8S 1.5 H2O, L-Mimosine sulfate hydrate. 

The pyridine (dihydropyridine) derived amino acid P-(3-hydroxy-4-pyridon-l-yl)-L-alanine, L-mimosine (2-62), is thyreotoxic (causes over-activity of the thyroid gland) to nonruminant animals. It occurs in the subfamily Mimosoideae of the legume family Fabaceae, in plants of the genera Mimosa and Leucaena. Leucaena leucocephala (syn. Mimosa glauca) is native to the tropical and subtropical Americas, known as White Leadtree, and is used as livestock fodder. The mimosine content in seeds can reach up to 5% of dry matter (see Section 10.3.2.7.1). The amino acid pyridosine arising from lysine in the Maillard reaction can also be considered a dihydropyridine derivative (see Section 4.7.5.12.3). 

An important amino acid toxic to Hvestock is L-mimosine, P-(3-hydroxy-4-pyridone-l-yl)-L-alanine (see 2-62). It occurs in plants of genera Leucaena and Mimosa of the family Mimosaceae. Its quantity in the fodder plant L. leucocephala can reach up to 30-50 g/kg of dry matter. 

Figure 4.20 Structures of selected HIF-stabilizers (1-6) and sirtuin activators (7-9) isoquinoline model substance (1), isoquinoline model substance (2), 2-oxoglutarate (3), oxalyl glycine (4), 3,4-dihydroxybenzoic acid (5), L-mimosine (6), resveratrol (7), SRT-1720 (8), and SRT-1460 (9).

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