marrubiin

Marrubiin is a natural product classified as a diterpene lactone that has been isolated from the herb Marrubium vulgare, commonly known as white horehound, and from other species in the Lamiaceae family. It is one of the major constituents reported in the non-volatile fraction of these plants and is often used as a chemotaxonomic marker in studies of Marrubium species.

Chemically, marrubiin belongs to the labdane-type diterpenes and contains a lactone ring within its core structure. Specific stereochemistry and ring system have been described in structural studies, but the compound is typically referred to by its general diterpene lactone characteristics rather than a single universal formula in common texts.

Biological and pharmacological research has investigated marrubiin for a range of activities in vitro and in vivo, including anti-inflammatory, antimicrobial, bronchodilatory, and spasmolytic effects, as well as some cardiovascular effects in preclinical models. However, results have varied and there is no established clinical use or approved therapeutic indication based on marrubiin alone. Its activity is often reported in the context of crude plant extracts rather than as a pure, approved medicine.

Biosynthesis of marrubiin is consistent with its classification as a diterpene, arising from the mevalonate or non-mevalonate pathways to build the 20-carbon skeleton that is elaborated to incorporate the lactone moiety.

Safety and toxicity data for pure marrubiin are limited; as with many plant-derived diterpenoids, high-dose exposure could carry risks, and interactions with other herbal constituents have not been fully characterized.