Biosynthesis of estragole and t-anethole in bitter fennel (Foeniculum vulgare Mill. var. vulgare) chemotypes.: Changes in SAM:phenylpropene O-methyltransferase activities during development

Estragole and t-anethole are the major constituents of the essential oils of bitter fennel chemotypes (Foeniculum vulgare Mill. var. vulgare. Apiaceae). Cell-free extracts from bitter fennel tissues display O-methyltransferase activities able to in vitro methylate chavicol and t-anol to produce estragole and t-anethole, respectively, by utilizing S-adenosyl-L-methionine as a methyl group donor. Analysis of different plant parts of an estragole-rich chemotype, indicated an association between estragole accumulation and chavicol O-methyltransferase activity during development. Young leaves displayed higher levels of O-methyltransferase activity than old leaves. In developing fruits O-methyltransferase activity levels increased until the wasty stage was reached and then dramatically decreased. This chemotype also displayed t-anol O-methyltransferase activity at higher levels than chavicol O-methyltransferase activity although these tissues accumulate mainly estragole. O-methyltransferases activities extracted from a high-t-anethole fennel chemotype also methylated t-anol and chavicol at comparable rates. Thus, although the chemotypes greatly differ in their phenylpropenoids composition, both are efficient in in vitro forming t-anethole and estragole. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.