Enzymatic Modification of 7,8-Dihydroxyflavone by Methylation and Glycosylation

다국어 초록 (Multilingual Abstract)

Methylation and glycosylation are two different but vital modification processes in plants to generate diversified secondary metabolites. Methylation increases the lipophilicity of compounds whereas glycosylation enhances the solubility. Most of the methylated and prenylated natural compounds are significantly active against cancers. 7, 8-dihydroxyflavone is a member of a flavonoid family of chemicals, which are abundant in fruits and vegetables. The compound’s selective effects suggest that it could be the founder of a new class of brain-protecting drugs as it can cross the blood-brain barrier by triggering tyrosine kinase B (TrkB) proving it could be a powerful anti-oxidant and neuroprotectant drug. In this study, we used E. coli BL21 (DE3) expressing SPOMT 2884, a Streptomyces peucetius ATCC 27952 derived O-methyltransferase, cell as a biocatalyst for the production of methylated derivative of 7, 8-Dihydroxy flavone. The supplementation of 0.2 mM of 7, 8-dihydroxyflavone in the growing induced culture of E. coli BL21 (DE3) harboring pET28-SPOMT2884 recombinant resulted in the production of a mono methylated compound which was confirmed by HPLC (Rt:17 min) and high resolution LC-QTOF-ESI/MS (m/z+ 269.08). Further, this enzymatically synthesized methylated derivative of 7, 8-DHF was purified in large amount and used as a substrate for in-vitro glycosylation by Yjic, a glycosyltransferase from Bacillus licheniformis DSM13. This reaction mixture analysis revealed the presence of glycosylated product which was analyzed by TLC and HPLC. Further structural elucidation is necessary for the confirmation of methylation and glycosylation positions. However, this study reveals a method that might be useful for the enzymatic biosynthesis of the methylated compound and subsequent modification of the same by glycosylation.