O-Methylation of phenylphenalenone phytoalexins in Musa acuminata and Wachendorfia thyrsiflora

• Published in: Phytochemistry (Oxford) 2010-02, Vol.71 (2), p.206-213
• Main Authors: Otálvaro, Felipe, Jitsaeng, Kusuma, Munde, Tobias, Echeverri, Fernando, Quiñones, Winston, Schneider, Bernd
• Format: Article
• Language: English
• Subjects: biochemical pathways; Biological and medical sciences; Chemical constitution; Elicitor; Fundamental and applied biological sciences. Psychology; Haemodoraceae; isotope labeling; Labelling; methoxycinnamic acid; Methylation; methylenedioxycinnamic acid; Musa acuminata; Musaceae; NMR; phenylphenalenone; Phenylphenalenones; Phytoalexins; Plant physiology and development; polycyclic aromatic hydrocarbons; Wachendorfia thyrsiflora
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/j.phytochem.2009.10.019

Labelled precursors were used to study biosynthetic O-methylation in various positions of the backbone of phenylphenalenones by NMR spectroscopic methods. The inducible formation of (methoxy)phenylphenalenones after treatment with jasmonic acid and copper chloride has been shown. Biosynthetic O -methylation at various sites along the backbone of inducible phenylphenalenones in Musa acuminata var. “Williams” (Musaceae) and Wachendorfia thyrsiflora (Haemodoraceae) was investigated using 13C-labelled precursors. The inducibility of O-methylated metabolites was demonstrated in both species and the origin of methoxyl group from [ methyl- 13C] l-methionine was confirmed. In addition to known phenylphenalenones, a methoxylated metabolite, 4-(4-hydroxy-3-methoxy-phenyl)-benzo[ de]isochromene-1,3-dione, was detected and its structure elucidated mainly by NMR spectroscopic techniques. The experiments were used to discriminate methionine-derived and artificial methoxy groups formed during methanolic extraction. Finally, demethylation of 4′-methoxycinnamic acid and subsequent conversion to 3′,4′-methylenedioxycinnamic acid was demonstrated in M. acuminata.