Rosemary has long been linked to memory—Shakespeare even wrote, “There’s rosemary, that’s for remembrance.”
Now, modern science is giving us new reasons to believe in rosemary’s power to help the brain. Researchers at Scripps Research have studied a compound called carnosic acid, found in rosemary and sage, and discovered that it might help fight Alzheimer’s disease.
Alzheimer’s is the leading cause of dementia and the sixth leading cause of death in the United States. It slowly destroys memory and thinking skills. One of the key problems in Alzheimer’s is inflammation in the brain, which can damage nerve cells and make symptoms worse.
Carnosic acid is a natural substance known for its antioxidant and anti-inflammatory effects. However, it breaks down too quickly to be used as a medicine. To solve this problem, scientists at Scripps Research created a more stable version called diAcCA. When taken by mouth, diAcCA turns into carnosic acid in the gut and then enters the bloodstream.
In a study published in February 2025 in the journal Antioxidants, researchers tested diAcCA in mice with Alzheimer’s disease. The mice showed big improvements in memory and brain health. They had more synapses—connections between brain cells—which are important for learning and memory. In Alzheimer’s, synapses often disappear, leading to cognitive decline.
The treated mice also had lower levels of brain inflammation. Interestingly, the drug only becomes active in areas of the brain where there is inflammation. This targeted action means fewer side effects. Since carnosic acid is already on the FDA’s “generally regarded as safe” list, this could help speed up the process for human trials.
The lead researcher, Dr. Stuart Lipton, said that the drug not only reduced inflammation and oxidative stress, but also decreased harmful brain proteins like amyloid-β and phosphorylated tau. These proteins are linked to Alzheimer’s and are used as markers to track the disease.
Lipton’s team had previously found that carnosic acid can enter the brain and activate protective genes. But because it breaks down easily, they worked with chemist Dr. Phil Baran to create new versions. They chose diAcCA as the best option because it was stable, absorbed well by the body, and had good drug-like properties.
In the study, mice were treated with diAcCA for three months. They performed better on memory and learning tests. When researchers looked at their brains under the microscope, they saw more healthy connections between neurons and fewer harmful protein clumps.
The drug also had other benefits. It reduced inflammation in the stomach and was better absorbed than regular carnosic acid. The mice’s bodies used about 20% more carnosic acid from diAcCA than from the natural form.
Dr. Lipton believes diAcCA could be used along with current Alzheimer’s treatments. It might reduce side effects from other drugs and boost their effectiveness. It may also help treat other diseases linked to inflammation, such as type 2 diabetes, heart disease, and even Parkinson’s disease.
Because of its safety and effectiveness in animals, researchers are hopeful that diAcCA can be tested in humans soon.
If you care about brain health, please read studies about how the Mediterranean diet could protect your brain health, and Omega-3 fats and carotenoid supplements could improve memory.
For more information about brain health, please see recent studies about antioxidants that could help reduce dementia risk, and higher magnesium intake could help benefit brain health.
The study is published in Antioxidants.
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