Eupatorium japonicum

Carries an alpha-methylene-gamma-lactone ring that alkylates protein thiols. It inhibited nitric oxide production in stimulated macrophages with an IC50 of 7.53 micrograms per mL and was cytotoxic to HepG2, MCF-7 and NTERA-2 cancer stem cells at IC50 values of 0.94, 1.22 and 0.88 micrograms per mL, killing NTERA-2 cells through caspase-3-dependent apoptosis. Its window is narrow: at the 4 micrograms per mL that gave 93.8 per cent nitric oxide inhibition, macrophage viability had already fallen to 43.3 per cent. The same reactive lactone is the hapten behind Compositae contact allergy, so potency and allergenicity travel together.

A tigloyloxy-substituted eudesmanolide, one of seventeen compounds isolated in the first phytochemical study of this species. Assayed head to head with eupatoriopicrin it was inactive, with IC50 values above 100 micrograms per mL against all three cancer cell lines and only 48 per cent nitric oxide inhibition at that concentration. A useful negative control: not every sesquiterpene lactone in this plant is potent.

Together with its methyl ester this is the component that carries the bone effect of the stem extract: both suppressed adipocyte differentiation and raised alkaline phosphatase and osteoblast markers in C3H10T1/2 and primary bone marrow cells. This is a stem finding and should not be read onto the leaf or flower.

Bulk triterpenes of the leaf. The isolating authors attribute part of the extract's overall anti-inflammatory behaviour to this group rather than to the sesquiterpene lactone alone, on the basis of published nitric oxide, TNF-alpha and COX-2 effects for these amyrins.

The phenolic fraction of the leaf, and the constituents named alongside the amyrins and phytosterols as contributing to the anti-inflammatory activity of the crude extract. Ordinary, widely distributed phenolics rather than species-specific markers, so they cannot be used to authenticate the drug.

Recorded here as an open question rather than a confirmed constituent. Intermedine, lycopsamine, their N-oxides, retronecine, seneciphylline and senkirkine were all found in Eupatorium fortunei, at exposures far above the 1.0 microgram per day limit the European Medicines Agency sets for herbal products, and intermedine N-oxide impaired neural progenitor cells at 10 micromolar. Whether material sold as Eupatorium japonicum carries the same load has not been measured; absence of an assay is not evidence of absence.

Records this species under the Chinese name Bai Tou Po as a folk drug of the eastern provinces, kept separate from the official Pei Lan of the Pharmacopoeia. It has never held a monograph of its own in the national Pharmacopoeia.

Relevant by exclusion. The Pharmacopoeia drug Pei Lan is defined as the aerial part of Eupatorium fortunei, not of this species. Since Kew's 2024 treatment proposes sinking Eupatorium fortunei into Eupatorium japonicum, a record filed under this binomial can silently swallow the Pei Lan monograph; the two should be kept as separate entries until the taxonomy settles.