Biosynthesis of oat avenanthramide phytoalexins

The biosynthesis of oat phytoalexins, avenanthramides, was investigated: by administering labeled putative precursors to oat leaf segments treated with the elicitor, penta-N-acetylchitopentaose. Among the compounds tested, oat leaf segments incorporated [ring-UL-C-14]anthranilic acid, [2,3,4,5,6-H-2]L-phenylalanine and [1,2-C-13]p-coumaric acid into avenanthramides, but not [2,6-H-2]L-tyrosine. These findings suggested that avenanthramides were de novo synthesized from primary metabolites after elicitor treatment and that phenylpropanoid metabolism is involved in their biosynthesis. In addition to L-phenylalanine and p-coumaric acid, sodium [C-13(2)]-acetate was incorporated into avenanthramide L, which indicated that the avenalumoyl (5-(4-hydroxyphenyl)-2,4-pentadienoyl) moiety of avenanthramide L was biosynthesized from p-coumaric acid by elongation of its side chain with an acetate unit. (C) 1998 Elsevier Science Ltd. All rights reserved.