For nearly three decades, a pair of mysterious molecules from rye pollen sat in scientific limbo — promising enough to catch researchers' attention, but impossible to pin down. Now, chemists at Northwestern University have finally cracked the case, and the breakthrough could open new doors in cancer research.
The story starts in the 1990s, when scientists discovered that rye pollen — a substance from the cereal crop grown for grain — seemed to slow tumor growth in animal studies. The findings hinted at something powerful, but researchers hit a wall: they couldn't figure out the exact shape of the molecules responsible. Without knowing how the molecules were built, they couldn't study them properly or develop them into treatments.
That changed when Karl A. Scheidt, a chemistry professor at Northwestern, and his team took on the challenge. By building the molecules from scratch in the lab — a painstaking process called total synthesis — they determined the precise three-dimensional structures of secalosides A and B for the very first time. Their work was published in the Journal of the American Chemical Society.
"In preliminary studies, other researchers found that rye pollen could help different animal models clear tumors through some unknown, non-toxic mechanism," Scheidt said. "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 therapy."
The team had to get creative to solve the puzzle. Traditional lab techniques couldn't fully reveal how the molecules' key parts were arranged. Scientists had spent decades debating between two possible models that looked almost identical — the same atoms connected the same way, but with one critical region flipped like a mirror image. That subtle difference matters enormously, just like how a left-handed glove won't fit a right hand.
"It's like your hands," Scheidt explained. "They are mirror images of each other, but you need a different glove for each."
To settle the debate, the Northwestern team built both versions in the lab and compared them with molecules extracted from actual rye pollen. Only one matched perfectly.
The work wasn't easy. The molecules contain an extremely rare, tightly packed 10-membered ring at their core — a structure that is notoriously difficult to assemble. The researchers solved it by first building a larger, more flexible ring and then triggering a chemical reaction that transformed it into the smaller, strained ring in a single step.
This discovery puts rye pollen on a path well-trodden by other natural compounds that became important medicines. Morphine comes from poppies. Taxol, a widely used chemotherapy drug, was first found in Pacific yew trees. Statins, which help lower cholesterol, 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."
Rye pollen extract is already sold as a dietary supplement for prostate health, but it has never been developed into a pharmaceutical treatment. With a clear molecular blueprint now in hand, that could change. Scheidt is already looking for collaborators in immunology to push the research forward.
"We've demonstrated we can make the core of this natural product," he said. "Now, we're trying to find potential collaborators in immunology who could help us translate this to a possible clinical endpoint."