Hands-On Demonstration of Natural Substance Fluorescence in Simple Tree Extracts: Sycamore

Sycamore wood is a source of a blue, fluorescent, aqueous extract that exhibits dramatic pH dependence. The sycamore tree has two most prevalent species in the eastern USA, the native American sycamore (Platanus occidentalis) and the more globally present hybrid London planetree (Platanus x acerifolia), both being equally amenable to the demonstration. The primary fluorescent substance in the aqueous extract of the wood is scopoletin (6-methoxy-7-hydroxycoumarin), a secondary metabolite of the tree generated in response to the injury of harvesting a specimen from the live tree. The fluorescence responds well to black light (365 nm) and violet (405 nm) excitation. The easy, attractive, and inexpensive demonstration of the extraction and fluorescence is described, and it is adaptable to hands-on activities like that described for narra wood (Pterocarpus indicus) earlier in this Journal. Updated information is provided on Pterocarpus wood species that exhibit excellent fluorescence in a similar manner.