FIGURE 15.42 Biotransformation of germacrone (118) by Cunninghamella blakeseeana and Curcuma zedoaria cells.
Aspergillus niger biotransformed germacrone (118, 3g) to very unstable 3b-hydroxygermacrone (123), and 4,5-epoxygermacrone (119) which was further converted to two guaiane sesquiterpenoids (121) and (122) through trans-annular-type reaction (Takahashi, 1994). The same substrate was incubated in the microorganism, Cunninghamella blakeseeana to afford germacrone-4,5-epoxide (119) (Hikino et al., 1971) while the treatment of 118 in the callus of Curcuma zedoaria gave four metabolites 121, 122, 125, and 126 (Sakamoto et al., 1994) (Figure 15.42).
The same substrate (118) was treated in plant cell cultures of Solidago altissima (Asteraceae) for 10 days to give various hydroxylated products (121, 127, 125, 128-132) (Sakamoto et al., 1994). Guaiane (121) underwent further rearrangement C4-C5, cleavage and C5-C10 trans-annular cycl-ization to the bicyclic hydroxyketone (128) and diketone (129) (Sakamoto et al., 1994) (Figure 15.43).
Curdione (120) was also treated in Aspergillus niger to afford two allylic alcohols (133, 134) and a spirolactone (135). Curcuma aromatica and Curcuma wenyujin produced spirolactone (135) which might be formed from curdione via trans-annular reaction in vivo was biotransformed to spirolactone diol (135) (Asakawa et al., 1991; Sakui et al., 1992) (Figure 15.44).
Aspergillus niger also converted shiromodiol diacetate (136) isolated from Neolitsea sericea to 2b -hydroxy derivative (137) (Nozaki et al., 1996) (Figure 15.45).
Twenty strains of filamentous fungi and four species of bacteria were screened initially by thin layer chromatography (TLC) for their biotransformation capacity of curdione (120). Mucor spinosus, Mucor polymorphosporus, Cunninghamella elegans, and Penicillium janthinellum were found to be able to biotransform curdione (120) to more polar metabolites. Incubation of curdione with Mucor spinosus, which was most potent strain to produce metabolites, for 4 days using potato medium gave five metabolites (134, 134a-134d) among which compounds 134c and 134d are new products (Ma et al., 2006) (Figure 15.46).
Many eudesmane-type sesquiterpenoids have been biotransformed by several fungi and various oxygenated metabolites obtained.
b-Selinene (138) is ubiquitous sesquiterpene hydrocarbon of seed oil from many species of Apiaceae family; for example, Cryptotenia canadensis var. japonica, which is widely used as vegetable for Japanese soup. b -Selinene was biotransformed by plant pathogenic fungus Glomerella
cingulata to give an epimeric mixtures (1:1) of 1ß,11,12-trihydroxy product (139) (Miyazawa et al., 1997a). The same substrate was treated in Aspergillus wentii to give 2a,11,12-trihydroxy derivative (140) (Takahashi et al., 2007).
Eudesm-11(13)-en-4,12-diol (141) was biotransformed by Aspergillus niger to give 3ß-hydroxy derivative (142) (Hayashi et al., 1999).
a-Cyperone (143) was fed by Collectotrichum phomoides (Lamare and Furstoss, 1990) to afford 11,12-diol (144) and 12-manool (145) (Higuchi et al., 2001) (Figure 15.47).
The filamentous fungi Gliocladium roseum and Exserohilum halodes were used as the bioreactors for 4ß-hydroxyeudesmane-1,6-dione (146) isolated from Sideritis varoi subsp. cuatrecasasii. The former fungus transformed 146 to 7a-hydroxyl- (147), 11-hydroxy- (148), 7a ,11-dihydroxy- (149), 1a,11-dihydroxy- (150), and 1a,8a-dihydroxy derivatives (151) while Exserohilum halodes gave only 1a-hydoxy product (152) (Garcia-Granados et al., 2001) (Figure 15.48).
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