Production of Two Novel Methoxy-Isoflavones from Biotransformation of 8-Hydroxydaidzein by Recombinant Escherichia coli Expressing O-Methyltransferase SpOMT2884 from Streptomyces peucetius

Abstract

Biotransformation of 8-hydroxydaidzein by recombinant Escherichia coli expressing O-methyltransferase (OMT) SpOMT2884 from Streptomyces peucetius was investigated. Two metabolites were isolated and identified as 7,4′-dihydroxy-8-methoxy-isoflavone (1) and 8,4′-dihydroxy-7-methoxy-isoflavone (2), based on mass, 1H-nuclear magnetic resonance (NMR) and 13C-NMR spectrophotometric analysis. The maximum production yields of compound (1) and (2) in a 5-L fermenter were 9.3 mg/L and 6.0 mg/L, respectively. The two methoxy-isoflavones showed dose-dependent inhibitory effects on melanogenesis in cultured B16 melanoma cells under non-toxic conditions. Among the effects, compound (1) decreased melanogenesis to 63.5% of the control at 25 μM. This is the first report on the 8-O-methylation activity of OMT toward isoflavones. In addition, the present study also first identified compound (1) with potent melanogenesis inhibitory activity.

Production and Anti-Melanoma Activity of Methoxyisoflavones from the Biotransformation of Genistein by Two Recombinant Escherichia coli Strains

“…Based on these spectral data and a comparison of the 1 H-NMR and 13 C-NMR data with literature values [ 10 ], compound 2 was characterized as 5,7,3′-trihydroxy-4′-methoxyisoflavone. These results—together with our previous study [ 7 , 8 ] and the study performed by Lee et al [ 6 ]—reveal that genistein was first converted into 3′-hydroxygenistein by the recombinant E. coli expressing B. megaterium tyrosinase, and then the resulting 3′-hydroxygenistein was further transformed by recombinant E. coli expressing S. peucetius O -methyltransferase into 5,7,4′-trihydroxy-3′-methoxyisoflavone or 5,7,3′-trihydroxy-4′-methoxyisoflavone. Scheme 1 shows a diagram of the biotransformation of genistein by the two recombinant E. coli strains.…”

“…The search for new melanogenesis inhibitors for use in skin-whitening cosmetics is an interesting topic [ 8 , 11 , 12 ]. In the assay for evaluating melanogenesis inhibitory activity, mouse B16 melanoma cells are used [ 12 , 13 ].…”

“…S. peucetius O -methyltransferase belongs to the class I O -methyltransferases (also known as caffeoyl coenzyme A OMTs or CCoAOMTs), which are involved in methylation of phenolic hydroxyl residues [ 20 ]. The enzyme has been shown to catalyze many flavonoids, including flavonols (quercetin, rutin), flavones (7,8-dihydroxyflavone, luteolin), a flavanone (naringenin), and isoflavonoids (daidzein, 8-hydroxydaidzein, and formononetin) [ 8 , 19 ]. Based on the results of the previous studies, it is highly possible that the two-step biotransformation process developed in the present study could also be applied to other flavonoids or even simple phenolic compounds.…”

“…Both recombinant E. coli expressing B. megaterium tyrosinase and recombinant E. coli expressing S. peucetius O -methyltransferase were constructed in our laboratory per our previous work [ 7 , 8 ]. We purchased both mouse B16-F10 melanoma cells BCRC 60031 and mouse normal fibroblast cells BCRC 60203 from the Bioresources Collection and Research Center (BCRC, Food Industry Research and Development Institute, Hsinchu, Taiwan).…”

“…The biotransformation system was also successfully applied to catalyze the ortho -hydroxylation of the soy isoflavone glycosides daidzin and genistin [ 7 ]. On the other hand, a recombinant E. coli expressing O -methyltransferase from Streptomyces peucetius was demonstrated to catalyze the O -methylation of ortho -dihydroxyisoflavone [ 8 ]. Based on the results of these previous studies, it is possible to use the two recombinant E. coli strains to conduct dual modifications, including hydroxylation and O -methylation, on soy isoflavones.…”