avenanthramide D

Avenanthramide D is a neutral hydroxycinnamic acid amide and a member of the avenanthramide group of phenolic alkaloids. It is a conjugate derived from p-coumaric acid and anthranilic acid. Naturally occurring primarily in oat grain (Avena sativa), it was originally characterized as a phytoalexin. The compound exhibits diverse biological activities, including anti-inflammatory, antioxidant, anti-itch, anti-irritant, anti-fibrotic, and antiatherogenic effects [360].

The metabolic engineering strategy for avenanthramide D production involves the expression of tyrosine ammonia lyase (TAL) to convert tyrosine into p-coumaric acid, followed by activation of the resulting hydroxycinnamic acid by 4-coumarate A ligase (4CL). The final conjugation step is catalyzed by an anthranilate N-hydroxycinnamoyl/benzoyltransferase (HCBT) [360]. Precursor availability can be further enhanced through engineering of the shikimate pathway, including overexpression of anthranilate synthase (trpEG) and deletion of anthranilate phosphoribosyltransferase (trpD), thereby promoting accumulation of the anthranilate precursor pool [360]. Furthermore, type III polyketide synthases have been employed as biosensors to identify gene knockdown targets, including pabA and zwf, whose modification increases precursor availability and consequently improves avenanthramide D production [64].