BIOSYNTHESIS OF PODOPHYLLUM LIGNANS - I. CINNAMIC ACID PRECURSORS OF PODOPHYLLOTOXIN IN PODOPHYLLUM HEXANDRUM

Article abstract of DOI:10.1016/S0031-9422(00)82603-5

Feeding experiments in Podophyllum hexandrum plants have established that phenylalanine, cinnamic acid and ferulic acid are good precursors of the two major aryltetralin lignans podophyllotoxin and 4'-demethylpodophyllotoxin.Sinapic and 3,4,5-trimethoxycinnamic acids were poorly utilized, showing that the substitution pattern of the pendent aryl ring is built up after coupling of the two phenylpropane units.Degradation studies on podophyllotoxin derived from <3-O(14)CH3> ferulic acid show that the two halves of the lignan molecule are equally labelled supporting a biosynthetic sequence involving oxidative coupling of two similar phenylpropane precursors having the substitution pattern of ferulic acid.Although 3,4-methylenedioxycinnamic acid was readily incorporated, degradative studies prove that this compound is not incorporated intact, but via a metabolic sequence in which the methylenedioxy carbon atom enters the C1-pool and then labels the methylenedioxy and methoxyl substituents of podophyllotoxin.The rest of the skeleton is incorporated via ferulic acid, presumably by way of caffeic acid.Key Word Index - Podophyllum hexandrum; Podophyllaceae; aryltetralin; lignans; biosynthesis; podophyllotoxin.