Estragole

The robust wild tarragon, often sold in plant nurseries as Russian tarragon, has a harsh and uninteresting flavor, while the relatively fragile cultivated form, “French” tarragon, has a distinctive aroma thanks to the presence of a phenolic compound called estragole from the French name for the plant, estragon in oil cavities alongside the leaf veins. ❋ Harold McGee (2004)

Noted carcinogen authority Bruce Ames of the University of California estimated that one cup of comfrey tea was about as risky as eating one peanut butter sandwich, which has traces of estragole, a natural carcinogen. ❋ Earl Mindell (2008)

Avocado Leaf Mexican races of the avocado tree (Persea americana) have leaves with a distinct tarragon aroma, thanks to the same volatiles that flavor tarragon and anise (estragole, anethole). ❋ Harold McGee (2004)

A related sweet aromatic is estragole methyl chavicol, which is most prominent in sweet basil and tarragon. ❋ Harold McGee (2004)

Fennel contains an estrogen-like substance (estragole) and may thereby increase sexual drive in women. ❋ Abacus Chinese Translation Services (2009)

Chervil Chervil Anthriscus cerefolium has small, pale, finely divided leaves, and a delicate flavor that comes from relatively small amounts of the tarragon aromatic estragole; it’s best used raw or barely warmed, since heat drives away its flavor. ❋ Harold McGee (2004)

“Mexican tarragon” is a marigold-like New World native, Tagetes lucida, whose leaves do indeed contain a mixture of anise-like anethole and tarragon’s estragole. ❋ Harold McGee (2004)

(Well, OK, in tarragon it's anethole's close cousin, estragole. ❋ Unknown (2010)