The origin of ISODONIS HERBA in the Japanese standards for non-Pharmacopoeial crude drugs 2018 is the aerial parts of Isodon japonicus H. Hara (Plectranthus japonicus Koidzumi, Rabdosia japonica H. Hara) and Isodon trichocarpus Kudô (Plectranthus trichocarpus Maximowicz, Rabdosia trichocarpa H. Hara) (Labiatae). This herb is used as an ingredient for gastrointestinal agents, health foods, and cosmetics. ISODONIS HERBA contains ent-kaurane diterpenoids such as enmein. Enmein is a characteristic compound in ISODONIS HERBA.

In order to help better understanding and facilitate quality control of ISODONIS HERBA, methods for quantitative analyses of enmein in ISODONIS HERBA were elaborated.

A phytochemical investigation of the underground parts of Eremurus robustus was performed using column chromatography and preparative HPLC. As a result, five phenolic compounds (1 - 5), including one new compound (1), were obtained. The structural characterization of 1 was established mainly based on NMR spectroscopic analysis. Compounds 1 - 5 were evaluated for their cytotoxic activity against SBC-3 human small cell lung cancer cells. Compound 1 exerted potent cytotoxicity and induced apoptotic cell death.