Eupatorium rotundifolium explained

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.^[1] It is found in low, moist habitats such as wet savannas and bogs.^{[2] [3]}

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.^[2]

Taxonomy

Three varieties of Eupatorium rotundifolium are recognized. They are:

• 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,^[4] and molecular evidence also suggests that these plants may be different enough from E. rotundifolium to recognize them as a species, Eupatorium pilosum.

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.^[5]

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.^{[6] [7]}

Notes and References

1. http://bonap.net/MapGallery/County/Eupatorium%20rotundifolium.png Biota of North America Program 2014 county distribution map
2. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242416533 Flora of North America, Eupatorium rotundifolium Linnaeus, 1753. Roundleaf thoroughwort
3. Web site: Flora of the Southern and Mid-Atlantic States . Alan Weakley . 2015.
4. Web site: 18. Eupatorium pilosum Walter .
5. American Journal of Botany . 93 . 2 . 319–325 . 2006 . Molecular confirmation of the hybrid origin of Eupatorium godfreyanum (Asteraceae) . Kunsiri Chaw Siripun . Edward E. Schilling . amp . 10.3732/ajb.93.2.319 . 21646192.
6. Tetrahedron Lett. . June 1968. 9 . 31 . 3517–3520 . Eupachlorin acetate, a novel chloro-sesquiterpenoid lactone tumor inhibitor from Eupatorium rotundifolium . Kupchan SM, Kelsey JE, Maruyama M, Cassady JM . 5649802 . 10.1016/S0040-4039(01)99098-7 .
7. The isolation and structural elucidation of euparotin acetate, a novel guaianolide tumor inhibitor from Eupatorium rotundifolium . Kupchan SM, Hemingway JC, Cassady JM, Knox JR, McPhail AT, Sim GA . J Am Chem Soc . 18 January 1967. 89 . 2 . 465–466 . 6031638 . 10.1021/ja00978a061 .