ARS | Publication request: Phytotoxicity of Constituents of Glandular Trichomes and the Leaf Surface of Camphorweed, Heterotheca subaxillaris

Submitted to: Phytochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 26, 2008
Publication Date: January 20, 2009
Citation: Morimoto, M., Cantrell, C.L., Libous Bailey, L.M., Duke, S.O. 2009. Phytotoxicity of Constituents of Glandular Trichomes and the Leaf Surface of Camphorweed, Heterotheca subaxillaris. Phytochemistry. 70:69-74.

Interpretive Summary: Camphorweed, Heterotheca subaxillaris, has a camphor-like odor, and its leaf surfaces contain glandular trichomes of the type that contains high levels of bioactive terpenoids in other plant species. Phytotoxic compounds (calamenene-type sesquiterpenes, borneol, and methylated flavones) were isolated from the dichloromethane wash of camphorweed shoots. Of the compounds isolated, 2-methoxycalamenene-14-carboxylic acid, had the strongest plant growth inhibitor against bentgrass, lettuce, and duckweed. It was as potent as some commercial herbicides.

Technical Abstract: Camphorweed, Heterotheca subaxillaris (Lam.) Britt. & Rusby has a camphor-like odor, and its leaf surfaces contain glandular trichomes of the type shown to contain high levels of isoprenoids in other species. Phytotoxic calamenene-type sesquiterpenes (1-4, 8-10), borneol (11) and methylated flavones (12-15) were isolated from the dichloromethane rinsate of camphorweed aerial parts. The strongest plant growth inhibitor against Agrostis stolonifera and Lactuca sativa seedlings, as well as duckweed (Lemna pausicostata), was the 2-methoxycalamenene-14-carboxylic acid (1). Esterification of calamenene carboxylic acids decreased their biological activity.