Eutrochium purpureum (L.) E. E. Lamont - Asteraceae - trumpet weed, gravel root, Joe-Pye weed

Perennial herb, up to 2m tall, native to southeastern North America; leaves vanilla-scented when crushed, pinnately veined, ovate; flowers purple.
Eutrochium purpureum (L.) E. E. Lamont var. purpureum = Eupatorium purpureum L. (leaves glabrous)
Eutrochium purpureum var. holzingeri = Eupatorium holzingeri Rydb. (leaves puberulent to villous)
http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=250066769

„… the crude ethanolic extract of the anti-rheumatic herbal drug gravel root (rhizome of Eupatorium purpureum), was identified as a potent inhibitor of some beta 1 and beta 2 integrin-mediated cell adhesions. The active principle of gravel root has now been isolated and identified as 5-acetyl-6-hydroxy-2,3-dihydro-cis-2-isopropenyl-3-tiglinoyloxybenzofuran.“
[Cistifolin, an integrin-dependent cell adhesion blocker from the anti-rheumatic herbal drug, gravel root (rhizome of Eupatorium purpureum)., Habtemariam, S., Planta medica, Vol.64(8), 1998, 683-685]

„Previous reports from this laboratory revealed that cistifolin from the antirheumatic herbal drug, gravel root (rhizome of Eupatorium purpureum), showed activity both in in vitro and in vivo models of inflammation. Data are now presented to show that, in addition to the LFA-1 and other integrin-mediated leucocyte adhesions, cistifolin inhibits the Mac-1 (CD11b/CD18)-dependent monocyte adhesion to fibrinogen in a concentration-dependent manner. Further phytochemical analysis of the crude extract also led to the isolation of three known benzofurans, euparin, euparone, 6-hydroxy-3β-methoxytrematone and a new benzofuran, 5-acetyl-6-hydroxy-2-(1-oxo-2-acetoxy-ethyl)-benzofuran. None of these compounds were active in suppressing integrin-mediated monocytic U937 cell adhesions in vitro.“
[Antiinflammatory activity of the antirheumatic herbal drug, gravel root (Eupatorium purpureum): further biological activities and constituents., Habtemariam, S., Phytotherapy Research, Vol.15(8), 2001, 687-690]

Millspaugh, C.F., American medicinal plants, vol. 1: t. 78 (1892)
http://plantgenera.org/species.php?id_species=1147711