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Sensitivity of the microorganism to (+)-carvone (93) and some of the products prevented yields exceeding 0.35 g/L in batch cultures. The fungus Trychoderma pseudokoningii gave the highest yield of (-)-neoisodihydrocarveol (102d) (Figure 14.110). (+)-Carvone (93) is known to inhibit fungal growth of Fusarium sulphureum when it was administered via the gas phase (Oosterhaven et al., 1995a, 1995b). Under the same conditions, the related fungus, Fusarium solani var. coeruleum was not inhibited. In liquid medium, both fungi were found to convert (+)-carvone (93), with the same rate, mainly to (-)-isodihydrocarvone (101b), (-)-isodihydrocarveol (102c), and (-)-neoisodihydrocarveol (102d).

14.3.4.1.1.1 Biotransformation of Carvone to Carveols by Actinomycetes The distribution of actinomycetes capable of reducing carbonyl group of carvone containing a, b-unsaturated ketone to (-)-trans- (81a') and (-)-cis-carveol (81b') was investigated. Of 93 strains of actinomycetes, 63 strains were capable of converting (-)-carvone (93') to carveols. The percentage of microorganisms that produced carveols from (-)-carvone (93') to total microorganisms was about 71%. Microorganisms that produced carveols were classified into three groups according to the formation of (-)-trans-carveol (81a') and (-)-cis-carveol (81b'): group 1, (-)-carvone-81b' only; group 2, (-)-carvone-81a' only; and group 3, (-)-carvone-mixture of 81a' and 81b'. Three strains belonged to group 1 (4.5%), 34 strains belonged to group 2 (51.1%), and 29 strains belonged to group 3 (44%; of this group two strains were close to group 1 and 14 strains were close to group 2).

Streptomyces, A-5-1 isolated from soil converted (-)-carvone (93') to 101a'-102d' and (-)-trans-carveol (81a'), whereas Nocardia, 1-3-11 converted (-)-carvone (93') to (-)-cis-carveol (81b') together with 101a'-81a' (Noma, 1980). In case of Nocardia, the reaction between 93' and 81a' was reversible and the direction from 81a' to 93' is predominantly (Noma, 1979a, 1979b; 1980) (Figure 14.111).

(-)-Carvone (93') was metabolized by actinomycetes to give (-)-trans- (81a') and (-)-cis-car-veol (81b') and (+)-dihydrocarvone (101a') as reduced metabolites. Compound 81b' was further metabolized to (+)-bottrospicatol (92a'). Furthermore, 93' was hydroxylated at C-5 position and C-8, 9 position to give 5b -hydroxy-(-)-carvone (98a') and (-)-carvone-8,9-epoxide (96'), respectively. Compound 98a' was further metabolized to 5b -hydroxyneodihydrocarveol (100aa') via 5b -hydroxy-dihydrocarvone (99a') (Noma, 1979a, 1979b; 1980) (Figure 14.111).

Metabolic pattern of (+)-carvone (93) is similar to that of (-)-carvone (93') in Streptomyces bottro-pensis. (+)-Carvone (93) was converted by Streptomyces bottropensis to give (+)-carvone-8,9-epoxide

FIGURE 14.109 Possible main metabolic pathways of (-)-carvone (93') and (+)-carvone (93) by Aspergillus niger TBUYN-2. (Modified from Noma, Y. et al., 1985a. Annual Meeting of Agricultural and Biological Chemistry, Sapporo, p. 68.)

(96) and (+)-5a-hydroxycarvone (98a) (Figure 14.112). (+)-Carvone-8,9-epoxide (96) has light sweet aroma and has strong inhibitory activity for the germination of lettuce seeds (Noma and Nishimura, 1982).

The investigation of (-)-carvone (93') and (+)-carvone (93) conversion pattern was carried out by using rare actinomycetes. The conversion pattern was classified as follows (Figure 14.113):

Group 1. Carvone (93)-dihydrocarvones (101)-dihydrocarveol (102)-dihydrocarveol-8,9-

epoxide (103)-dihydrobottrospicatols (105)-5-hydroxydihydrocarveols (100) Group 2. Carvone (93)-carveols (89)-bottrospicatols (92)-5-hydroxy-cis-carveols (12)

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