(Z)-Anethole

(Z)-Anethole is the minor isomer of anethole. It occurs only in trace amounts in anise and fennel oils, generally below one percent.

Injection. Acute intraperitoneal LD50 is 135 mg/kg in mice and 93 mg/kg in rats. The (Z)-isomer is markedly more toxic than the (E)-isomer.

Carcinogenicity. Four intraperitoneal injections of a 90 percent (Z)/10 percent (E)-anethole mixture given prior to weaning did not produce hepatomas in mice at 18 months. (Z)-Anethole is not classified as carcinogenic.

Because concentrations in essential oils are very low, the compound does not raise practical safety concerns at typical use levels.

(Z)-Anethole may form when (E)-anethole is exposed to light or air over time. Its level tends to rise as essential oils age.