Relieving Two Headaches with One Process: Acetaminophen from Lignin

by Jill Sakai (Great Lakes Bioenergy Research Center) With a new method to synthesize a popular pain-relieving medication from plants rather than fossil fuels, researchers at the Great Lakes Bioenergy Research Center have found a way to relieve two headaches at once.

A team led by John Ralph, a professor of biochemistry at the University of Wisconsin–Madison, has been awarded a patent for a method to synthesize acetaminophen—the active ingredient in Tylenol—from a natural compound derived from plant material. The approach offers a renewable alternative to the current manufacturing process, which uses chemicals derived from coal tar. It also creates a useful product from an abundant but difficult-to-manage component of plant cell walls called lignin.

“Lignin is an extremely complex, messy polymer. No two molecules in a plant are exactly the same,” Ralph says. “It’s very effective for providing structure and defense for the plant, but it’s challenging for us to break down into useable materials.”

The lignin in bioenergy crops, such as poplar, can create a headache for bioenergy researchers due to its recalcitrant tendencies, Ralph says. Once plant sugars are used to produce biofuels, the lignin that remains is typically burned for energy.

The patent application, filed by the Wisconsin Alumni Research Foundation, describes a way to convert a molecule found on lignin into acetaminophen. It was awarded in May to Ralph, Steven Karlen of UW–Madison, and Justin Mobley, a former GLBRC postdoctoral fellow who is now at the University of Kentucky.

“Although lignin itself is a challenge to break down, the p-hydroxybenzoate is fairly easy to clip off as a quite pure stream,” Ralph says.

From there, the researchers devised a short series of chemical reactions to convert the molecule into acetaminophen. The method is inexpensive and builds on a biomass pretreatment process previously developed at GLBRC.

In addition to charting a way to synthesize acetaminophen from a renewable, sustainable source material, the newly patented process improves the overall bottom line for biorefining—that is, producing fuels and other industrial materials from plants.

Acetaminophen and related molecules are also useful as commodity chemicals, the industrial building blocks used to make products including other pharmaceuticals, plastics and fuels.

The researchers are now working on refining the process to improve the yield and purity of the plant-derived acetaminophen. READ MORE