Treasure on the Sidewalk
The sidewalks around our house are littered with the seedpods of the sweet gum tree (Liquidambar styraciflua). Shaped like miniature Medieval mace heads, these small, spiky pods are the scourge of cyclists and joggers and a frightening projectile when combined with a lawnmower. They are also, however, much-sought-after treasures to my 18-month old daughter, who collects dozens of them on our walks around the neighborhood. Tossing sweet gum pods makes an excellent toddler sport, but could these pods have a value beyond mere child’s play?
L. styraciflua is a sweet gum tree native to American that ranges from Connecticut to Texas. The fruit of the sweet gum tree is a compound fruit composed of several long, slender chambers joined at the base. This gives the fruit the appearance of a spiked ball. As the fruit dries, each chamber opens like bird’s beak to release either mature winged seeds or smaller, immature seeds.
Within the seeds of this common sidewalk obstacle is an important medical compound. Sweet gum seeds, particularly the immature ones, contain shikimic acid. This chemical is used to synthesize the drug Tamiflu, an antiviral that is currently the most promising treatment for H5N1 influenza, also known as avian flu. The majority of this drug is produced using extracts from the fruit of Chinese star anise (Illicium verum). Growing star anise is expensive, and to be honest, there’s just not enough of it to go around. But sweet gum seed pods are super-abundant and have comparable levels of shikimic acid. The bark of the tree also contain the compound. This means that sweet gum trees could be used as a renewable source of medicinal chemicals and become our first line of defense in battling the next pandemic.
So the next time your toddler treasures something they found on the sidewalk, pay attention. They just may have truly found a treasure.
Brian Rutter, PhD, is the cofounder of Thing in a Pot Productions and a postdoctoral researcher in plant biology at Indiana University. Subscribe to our newsletter to receive our “Things About Things – Odd Facts About Plants” and video production tips in your inbox every month!
Works Cited:
Conrad, J. “Sweetbum Balls.” backyardnature.net, 22 July 201, https://www.backyardnature.net/n/w/sweetgum.htm
Deane, G. “Sweet Gum Tree.” eattheweeds.com, 2012, https://www.eattheweeds.com/sweet-gum-tree/
Enrich LB, Scheuermann ML, Mohadjer A, Matthias KR, Eller CF, Newman MS, Fujinaka M, Poon T. Liquidambar styraciflua: a renewable source of shikimic acid. Tetrahedron Letters. 2008 Apr 14;49(16):2503-5.
Martin E, Duke J, Pelkki M, Clausen EC, Carrier DJ. Sweetgum (Liquidambar styraciflua L.): extraction of shikimic acid coupled to dilute acid pretreatment. Applied biochemistry and biotechnology. 2010 Nov;162:1660-8.
Pollack, A. “Is bird flu drug really so vexing? Debating the difficulty of Tamiflu.” nytimes.com, 5 November 2005, https://www.nytimes.com/2005/11/05/business/is-bird-flu-drug-really-so-vexing-debating-the-difficulty-of.html