It is a dimeric polymer of anethole. It is generally obtained by the oxidation of anethole or p-methoxyacetophenone. Upon treatment with potassium hydroxide, estragole converts to anethole. Biosynthesis of the compound is hypothesized to proceed via a NIH shift of anethole. DES can be prepared from anethole, which also happens to be weakly estrogenic. Its essential oils are dominated by anethole. It contains methyl chavicol, anethole, anisaldehyde, limonene, pinene and linalool. It employs the familiar ouzo effect displayed by anethole in many anise-flavored liquors. For example, synthetic anethole is prepared from anisole. Fennel seed oil contains anethole a compound with estrogenic effects. Star anise contains anethole, the same compound that gives the unrelated anise its flavor. Most anethole is obtained from turpentine-like extracts from trees. The insecticidal action of anethole is greater as a fumigant than as a contact agent. Fennel, which contains anethole, has been found to have a galactagogue effect in animals. Anethole trithione is an organosulfur compound, specifically, a dithiole-thione derivative.