Highly efficient production of functional substances from synthetic compounds and secondary metabolites by mammal and microbial biotransformation

Abstract

We report herein a highly efficient production of several functional substances from synthetic aromatic compounds and plant secondary metabolites such as chalcones, mono- and sesquiterpenoids by microorganisms and rabbit. The microbial biotransformation was accomplished by four black fungi, Aspergillus niger, A. sojae, A. usami and A. cellulosae in rotatory growth cultures (120 rpm, Czapek-peptone medium at 30 °C for 3-10 days). In the case of biotransformation by mammals, each terpenoid and aromatic compound was orally administered to rabbits, and their collected urines were enzymatically treated to give each metabolite. Aspergillus niger cultured for 10 days in the presence of chalcone (1) (10 g / 200 mL medium) gave dihydrochalcone (2) in 95% isolated yield. The other Aspergillus strains converted chalcone to dihydrochalcone quantitatively. The substrate amount could be scaled up to 25 g / 200 mL medium. 4-Hydroxy- (3) and 4’-hydroxychalcones (4) incubated with the same Aspergillus afforded 4-hydroxydihydro- (5) and 3,4-dihydroxydihydrochalcones (6), and 4’-hydroxydihydro- (7) and 3’,4’-dihydroxydihydrochalcone (8), in good yield, respectively. Thus, Aspergillus strains introduced a hydroxy group directly onto the already substituted benzene ring and very easily reduced the α,β-unsaturated double bond. 1,1-Diphenylmethane (9), 1,3-diphenylacetone (10), 1,3-diphenylpropane (11), bibenzyl (12), (E and Z)-stilbenes (13, 14) and phenylcyclohexane (15), grifolin (16), 6-shogaol (17), 6-gingerol (18), capsaicin (19), and dihydrocapsaicin (20) were also treated by Aspergillus strains to give the direct benzene ring hydroxylated products and ω-hydroxylation products, as well as epoxides, oxo- and hydroxyketo derivatives. (-)-α-Pinene (21) and β-caryophyllene (22) were converted by rabbits to trans-verbenol (23), an insect larvae pheromone, and 14-hydroxy-β-caryophyllene oxide (24), a constituent of mushrooms, in very high yield. Nootkatone (25), contributor to the grapefruit aroma, was obtained almost quantitatively from valencene (26), by a Mucor strain biotransformation. The metabolites of sesquiterpenoids, (+)- and (-)-cyclocolorenones (27, 28), (+)- and (-)-cuparenes (29, 30) and bisbibenzyls from liverworts, as well as the direct biotransformation of the corresponding essential oils are also reported. The presented methods are a cheap and hazard reduced eco-friendly alternative to classical organic synthesis while still reaching the high yields of the metabolites.