Transformation of a monoterpene ketone, (R)-(+)-pulegone, a potent hepatotoxin, in Mucor piriformis
1999
Madyastha, K.M. | Thulasiram, H.V.
Biotransformation of a monoterpene ketone, (R)-(+)-pulegone (I), a potent hepatotoxin, was studied using a fungal strain, Mucor piriformis. Eight metabolites, namely, 5-hydroxypulegone (II), piperitenone (III), 6-hydroxypulegone (IV), 3-hydroxypulegone (V), 5-methyl-2-(1-hydroxy-1-methylethyl)-2-cyclohexene-1-one (VI), 3-hydroxyisopulegone (VII), 7-hydroxypiperitenone (VIII), and 7-hydroxypulegone (IX), have been isolated from the fermentation medium and identified. GC analysis of the metabolites indicated that II was the major metabolite formed. The organism initiates transformation either by hydroxylation at the C-5 position or by hydroxylation of the ring methylenes, the former being the major activity. On the basis of the identification of the metabolites, pathways for the biotransformation of (R)-(+)-pulegone have been proposed. The mode of transformation of (S)-(-)-pulegone by this organism was shown to be similar to that of its (R)-(+)-enantiomer. When isopulegone (X) was used as the substrate, the organism isomerized it to pulegone (I), which was then transformed to metabolites II-IX.
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