Enzymatic production of oroxylin A and hispidulin using a liverwort flavone 6‐ O ‐methyltransferase

Oroxylin A and hispidulin, compounds which are abundant in both Scutellaria and liverwort species, are important lead compounds for the treatment of ischemic cerebrovascular disease. Their enzymatic synthesis requires an O ‐methyltransferase able to interact with the related flavonoid's 6‐ OH group, but such an enzyme has yet to be identified in plants. Here, the gene encoding an O ‐methyltransferase (designated PaF6 OMT ) was isolated from the liverwort species Plagiochasma appendiculatum . A test of alternative substrates revealed that its strongest preferences were baicalein and scutellarein, which were converted into, respectively, oroxylin A and hispidulin. Allowed a sufficient reaction time, the conversion rate of these two substrates was, respectively, 90% and 100%. PaF6 OMT offers an enzymatic route to the synthesis of oroxylin A and hispidulin.