Project description:Members of the genus Equisetum are often referred to as “living fossils”, partly because they are the only extant representatives of the Equisetidae, a subclass that was once prominent in late Paleozoic forests. Several classes of specialized metabolites have been reported to occur in the genus Equisetum. However, while steady progress is being made with identifying individual novel metabolites of Equisetum, few if any analyses have focused on assessing the chemical diversity across the genus. The present study focused on three species: E. hyemale subsp. affine (rough horsetail or scouring rush), which is native to the temperate to artic portions of North America; E. arvense (common horsetail), which is endemic to the arctic and temperate regions of the northern hemisphere; and Equisetum telmateia subsp. braunii (Milde) Hauke (giant horsetail), which is native to western North America. Both below-ground rhizome and above-ground shoot material was harvested from each species, extracted with aqueous methanol, and subjected to non-targeted HPLC-QTOF-MS analysis. This research project was designed to lay the foundation for continued research to capture the metabolic capabilities in the ferns and fern allies.