Northwestern Chemists Solve 30-Year Rye Pollen Mystery, Opening New Avenues for Cancer Drug Discovery
Key Insights
Northwestern University chemists confirmed the precise three-dimensional structures of secalosides A and B (search) from rye pollen for the first time using total synthesis.
The structural ambiguity had persisted for decades because traditional techniques like NMR spectroscopy could not distinguish between two mirror-image configurations.
Preliminary animal studies showed rye pollen could help clear tumors through an unknown, non-toxic mechanism, making structural confirmation a critical step toward therapeutic development.
Chemists at Northwestern University have definitively solved a three-decade-old structural puzzle surrounding two molecules found in rye pollen — secalosides A and B (search) — by constructing them from scratch in the laboratory. The breakthrough, published in the Journal of the American Chemical Society, provides the first accurate molecular blueprint of these compounds and could pave the way for new approaches to cancer (search) treatment.
"In preliminary studies, other researchers found that rye pollen could help different animal models clear tumors through some unknown, non-toxic mechanism," said Karl A. Scheidt, who led the study. Scheidt is a professor of chemistry at Northwestern's Weinberg College of Arts and Sciences and a professor of pharmacology (by courtesy) at Northwestern University Feinberg School of Medicine. "Now that we confirmed the structure of these molecules, we can find the active ingredient — or what part of the molecule is doing the work. This is an exciting starting point to make better versions of these molecules that could possibly inform approaches to cancer (search) therapy."
A Molecular Puzzle Decades in the Making
For roughly 30 years, scientists could not determine the precise three-dimensional arrangement of secalosides A and B (search). Traditional analytical techniques, including advanced nuclear magnetic resonance spectroscopy, proved insufficient to resolve a critical structural question: two possible models existed, each containing the same atoms connected in the same way, but differing in the spatial orientation of one key region. This subtle mirror-image variation — known as chirality — can dramatically alter how a molecule interacts with biological targets.
"It's like your hands," Scheidt explained. "They are mirror images of each other, but you need a different glove for each. If you had two left-handed gloves, it wouldn't work because your hands can't be superimposed on top of one another."
Total Synthesis Overcomes a Strained Chemical Challenge
To resolve the ambiguity, the Northwestern team employed total synthesis — building the natural molecules step by step in the laboratory. The effort was exceptionally challenging because secalosides A and B (search) contain an extremely rare, highly strained 10-membered ring at their core, a tightly compressed structure that is notoriously difficult to assemble.
The researchers devised an innovative strategy: they first created a larger, more flexible ring, then triggered a chemical reaction that converted it into the smaller strained ring in a single step. After producing both proposed versions of the molecules, the team compared them with samples extracted from rye pollen. Only one version matched perfectly, allowing the researchers to definitively identify the correct structures.
From Natural Product to Potential Cancer Therapy
Rye pollen extract is already sold as a dietary supplement that many people use to support prostate health, but it has never been developed into a pharmaceutical treatment. The lack of a clear picture of the molecules' three-dimensional structures had been a major obstacle.
The discovery places secalosides A and B (search) alongside other nature-derived medicines that have transformed patient care. Morphine, a powerful pain medication, comes from the opium poppy. Taxol, an important chemotherapy drug, was first isolated from the Pacific yew tree. Statins, which lower cholesterol and reduce heart disease risk, originated from fungi.
"Natural products aren't necessarily effective drugs on their own, but they are great leads," Scheidt said. "We can find inspiration in natural products and use chemistry to make better versions that are orally available, survive the metabolism and hit the right targets."
Next Steps Toward Translation
With the structural confirmation in hand, the research team is now actively seeking to advance the work toward biological and clinical investigation. "We've demonstrated we can make the core of this natural product," Scheidt said. "Now, we're trying to find potential collaborators in immunology who could help us translate this to a possible clinical endpoint."
The study, "Synthesis and structural confirmation of secalosides A and B (search)," was supported by the National Institute of General Medical Science, the Chemistry of Life Processes Institute Lambert Fellowship, and the National Science Foundation.