Eupatorium rotundifolium

Roundleaf thoroughwort
Conservation status
Secure  (NatureServe)[1]
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Asterids
Order:	Asterales
Family:	Asteraceae
Genus:	Eupatorium
Species:	E. rotundifolium
Binomial name
Eupatorium rotundifolium L.
Synonyms[2]
Synonymy Critonia elliptica Raf. ex DC. Eupatorium marrubium Walter Eupatorium obovatum Raf. Eupatorium ovatum J.Bigelow Eupatorium rotundifolium Fernald 1943 not L. 1753 Eupatorium teucrifolium Willd. Eupatorium verbenaefolium Michaux Eupatorium verbenifolium Reichard Uncasia pubescens (Mühlenb. ex Willd.) Greene Uncasia rotundifolia (L.) Greene Uncasia scabrida (Elliott) Greene Uncasia verbenaefolia (Michaux) Greene Uncasia verbenifolia (Michaux) Greene Eupatorium pubescens Muhl. ex Willd., syn of var. ovatum Eupatorium scabridum Elliott, syn of var. scabridum

Eupatorium rotundifolium, commonly called roundleaf thoroughwort, is a North American species of plant in the family Asteraceae. It native to the eastern and central United States, in all the coastal states from Maine to Texas, and inland as far as Missouri and the Ohio Valley.[3] It is found in low, moist habitats such as wet savannas and bogs.[4][5]

Description

The stems up to 100 cm (40 inches) tall and are produced from short rhizomes. The inflorescences are composed of a large number of small white flower heads, each with 5 disc florets but no ray florets. Plants can be highly variable due to hybridization.[4]

• 
  Detail of stem and leaves. (Photo by Robert H. Mohlenbrock)

Taxonomy

Three varieties of Eupatorium rotundifolium are recognized. They are:[2]

• Eupatorium rotundifolium var. ovatum (Bigelow) Torr.
• Eupatorium rotundifolium var. rotundifolium
• Eupatorium rotundifolium var. scabridum (Elliott) A.Gray

The plants known as Eupatorium rotundifolium var. saundersii have often been treated as a variety of E. rotundifolium. They can be distinguished based on morphology,[6] and molecular evidence also suggests that these plants may be different enough from E. rotundifolium to recognize them as a species, Eupatorium pilosum.[7]

Hybridization

As is common in Eupatorium, E. rotundifolium can form hybrids with other species in the genus. In particular, Eupatorium godfreyanum is a hybrid of E. rotundifolium and Eupatorium sessilifolium.[7]

Chemical constituents

Eupatorium rotundifolium contains sesquiterpene lactones of the guaianolide type including euparotin acetate and eupachlorin acetate, both of which inhibit tumor growth in vitro when isolated from the plant.[8][9]

References

1. "Eupatorium rotundifolium". NatureServe Explorer. NatureServe. Archived from the original on April 15, 2013. Retrieved 2010-09-12.
2. The Plant List, Eupatorium rotundifolium L.
3. Biota of North America Program 2014 county distribution map
4. Flora of North America, Eupatorium rotundifolium Linnaeus, 1753. Roundleaf thoroughwort
5. Alan Weakley (2015). "Flora of the Southern and Mid-Atlantic States".
6. "18. Eupatorium pilosum Walter".
7. Kunsiri Chaw Siripun & Edward E. Schilling (2006). "Molecular confirmation of the hybrid origin of Eupatorium godfreyanum (Asteraceae)". American Journal of Botany. 93 (2): 319–325. doi:10.3732/ajb.93.2.319. PMID 21646192.
8. Kupchan SM, Kelsey JE, Maruyama M, Cassady JM (June 1968). "Eupachlorin acetate, a novel chloro-sesquiterpenoid lactone tumor inhibitor from Eupatorium rotundifolium". Tetrahedron Lett. 9 (31): 3517–3520. doi:10.1016/S0040-4039(01)99098-7. PMID 5649802.
9. Kupchan SM, Hemingway JC, Cassady JM, Knox JR, McPhail AT, Sim GA (18 January 1967). "The isolation and structural elucidation of euparotin acetate, a novel guaianolide tumor inhibitor from Eupatorium rotundifolium". J Am Chem Soc. 89 (2): 465–466. doi:10.1021/ja00978a061. PMID 6031638.