Łużny Mateusz, Tronina Tomasz, Kozłowska Ewa, Kostrzewa-Susłow Edyta, Janeczko Tomasz
Department of Chemistry, Wrocław University of Environmental and Life Sciences, Norwida 25, 50-375 Wrocław, Poland.
J Agric Food Chem. 2021 Apr 7;69(13):3879-3886. doi: 10.1021/acs.jafc.1c00136. Epub 2021 Mar 29.
5,7-Dimethoxyflavone, a chrysin derivative, occurs in many plants and shows very low toxicity, even at high doses. On the basis of this phenomenon, we biotransformed a series of methoxy-derivatives of chrysin, apigenin, and tricetin obtained by chemical synthesis. We used entomopathogenic fungal strains with the confirmed ability of simultaneous hydroxylation/demethylation and glycosylation of flavonoid compounds. Both the amount and the place of attachment of the methoxy group influenced the biotransformation rate and the product's amount nascent. Based on product and semi-product structures, it can be concluded that they are the result of cascading transformations. Only in the case of 5,7,3',4',5'-pentamethoxyflavone, the strains were able to attach a sugar molecule in place of the methoxy substituent to give 3'--β-d-(4″--methylglucopyranosyl)-5,7,4',5'-tetramethoxyflavone. However, we observed the tested strains' ability to selectively demethylate/hydroxylate the carbon C-3' and C-4' of ring B of the substrates used. The structures of four hydroxyl-derivatives were determined: 4'-hydroxy-5,7-dimethoxyflavone, 3'-hydroxy-5,7-dimethoxyflavone, 3'-hydroxy-5,7,4',5'-tetramethoxyflavone, and 5,7-dimethoxy-3',4'-dihydroxyflavone (5,7-dimethoxy-luteolin).
5,7-二甲氧基黄酮是一种白杨素衍生物，存在于许多植物中，即使在高剂量下也显示出极低的毒性。基于这一现象，我们对一系列通过化学合成获得的白杨素、芹菜素和三羟黄酮的甲氧基衍生物进行了生物转化。我们使用了具有已证实的对黄酮类化合物同时进行羟基化/去甲基化和糖基化能力的昆虫病原真菌菌株。甲氧基的数量和连接位置影响了生物转化率和新生产物的量。根据产物和半产物的结构，可以得出它们是级联转化的结果。只有在5,7,3',4',5'-五甲氧基黄酮的情况下，这些菌株能够在甲氧基取代基的位置连接一个糖分子，生成3'-β-d-(4″-甲基吡喃葡萄糖基)-5,7,4',5'-四甲氧基黄酮。然而，我们观察到受试菌株能够选择性地对所用底物B环的C-3'和C-4'碳进行去甲基化/羟基化。确定了四种羟基衍生物的结构：4'-羟基-5,7-二甲氧基黄酮、3'-羟基-5,7-二甲氧基黄酮、3'-羟基-5,7,4',5'-四甲氧基黄酮和5,7-二甲氧基-3',4'-二羟基黄酮（5,7-二甲氧基木犀草素）。
