Essential oil composition
The bitter principle of the horehound is marrubiin (volatile oil), a diterpene lactone. In addition, horehound
contains a sterolin, an esterfied form and a sesquiterpene. Flavonoids isolated from horehound include apigerin, luteolin,
apigerin 7-glycoside, luteolin 7-glycoside, quercetin 3-rhamnoglycoside and quercetin 3-glycoside.