Biotransformation of Hydroxychalcones as a Method of Obtaining Novel and Unpredictable Products Using Whole Cells of Bacteria

Abstract

The aim of our study was the evaluation of the biotransformation capacity of hydroxychalcones—2-hydroxy-4′-methylchalcone (1) and 4-hydroxy-4′-methylchalcone (4) using two strains of aerobic bacteria. The microbial reduction of the α,β-unsaturated bond of 2-hydroxy-4′-methylchalcone (1) in Gordonia sp. DSM 44456 and Rhodococcus sp. DSM 364 cultures resulted in isolation the 2-hydroxy-4′-methyldihydrochalcone (2) as a main product with yields of up to 35%. Additionally, both bacterial strains transformed compound 1 to the second, unexpected product of reduction and simultaneous hydroxylation at C-4 position—2,4-dihydroxy-4′-methyldihydrochalcone (3) (isolated yields 12.7–16.4%). During biotransformation of 4-hydroxy-4′-methylchalcone (4) we observed the formation of three products: reduction of C=C bond—4-hydroxy-4′-methyldihydrochalcone (5), reduction of C=C bond and carbonyl group—3-(4-hydroxyphenyl)-1-(4-methylphenyl)propan-1-ol (6) and also unpredictable 3-(4-hydroxyphenyl)-1,5-di-(4-methylphenyl)pentane-1,5-dione (7). As far as our knowledge is concerned, compounds 3, 6 and 7 have never been described in the scientific literature.

Combinatory Library of Microorganisms in the Selection of Reductive Activity Applied to a Ketone Mixture: Unexpected Highlighting of an Enantioselective Oxidative Activity

“…This approach makes it possible to discover new enzymatic activities with the formation of unexpected products. For example, substitution on the quinone ring by ethanolamine, decyanation, oxidative intramolecular cyclization and Michael reaction was observed during the biotransformation of ilimaquinone [15], 1-benzylpyrrolidine-2,5-dicarbonitrile [16], guttiferone A [12] and hydroxychalcones [17], respectively. A microorganism's abilities in biotransformation processes are dependent on its growing and incubation conditions.…”

Regiospecific Hydrogenation of Bromochalcone by Unconventional Yeast Strains

“…The scientific literature shows that microorganisms are less effective in converting 2 -hydroxychalcones than compounds not substituted with a hydroxyl group [16,17,37]. This is probably due to the formation of hydrogen bonds between the electron pair present on the carbonyl oxygen and the hydrogen of the hydroxyl group [19].…”