Rosemary has long been linked to memory. In Shakespeare’s Hamlet, the character Ophelia says, “There’s rosemary, that’s for remembrance.”
Now, modern science is taking a closer look at this connection.
A team of researchers from Scripps Research has studied a natural compound called carnosic acid, found in rosemary and sage, to see if it can help treat Alzheimer’s disease.
Alzheimer’s is the main cause of dementia and ranks as the sixth leading cause of death in the United States.
One of the key problems in Alzheimer’s is brain inflammation, which leads to memory loss and cognitive decline.
Carnosic acid has antioxidant and anti-inflammatory properties. It works by triggering the body’s own defense system. However, in its natural form, it is unstable and breaks down easily, making it difficult to use as a medicine.
To solve this, scientists developed a new version called diAcCA, which is stable and turns into carnosic acid in the gut before entering the bloodstream.
The researchers published their findings in the journal Antioxidants in February 2025. They tested the new compound in mice with symptoms similar to Alzheimer’s disease. After three months of treatment, the mice showed better memory and had more synapses in the brain.
Synapses are the connections between brain cells, and having more of them is linked to better brain function. In Alzheimer’s, the loss of synapses is closely tied to worsening memory, so this is a major step forward.
The team also found that inflammation in the brain was reduced. Interestingly, the drug only becomes active in parts of the brain where inflammation is already happening. This means fewer side effects, since it doesn’t affect healthy areas.
Because carnosic acid is already on the FDA’s “generally regarded as safe” list, the path to clinical trials could be quicker.
Dr. Stuart Lipton, the lead researcher, explained that diAcCA not only reduced inflammation but also helped remove harmful proteins like amyloid-β and phosphorylated-tau, which are linked to Alzheimer’s. These proteins form plaques and tangles in the brain that damage nerve cells and are key signs of the disease.
Previously, Lipton’s team discovered that carnosic acid activates a protective pathway in the brain known as Nrf2, which helps turn on genes that fight inflammation and damage. But because regular carnosic acid breaks down quickly, they needed a more stable version. Working with chemist Dr. Phil Baran, the team created and tested several compounds. DiAcCA turned out to be the best candidate because it was more stable, easy to absorb, and acted like a drug.
The mice given diAcCA performed better in memory tests and had more healthy connections between brain cells. Their brain tissue also showed fewer signs of damage. The compound was well tolerated and even helped reduce inflammation in other parts of the body, like the esophagus and stomach.
One important finding was that diAcCA helped deliver 20% more carnosic acid into the bloodstream than if the mice had taken plain carnosic acid. Since regular carnosic acid breaks down before it can be absorbed, the new compound works more effectively.
Dr. Lipton believes diAcCA could also help improve current Alzheimer’s drugs. Some of the new treatments for Alzheimer’s, like amyloid antibody therapies, can cause dangerous side effects such as brain swelling or bleeding. DiAcCA might reduce these risks and make those treatments safer.
Because of its safety profile, Lipton hopes diAcCA can be tested in people soon. He also sees potential for this compound to help with other diseases involving inflammation, such as type 2 diabetes, heart disease, Parkinson’s disease, and other brain conditions.
This study provides new hope that a natural compound from rosemary could one day become a powerful tool in the fight against Alzheimer’s and other diseases that affect the brain.
If you care about Alzheimer’s disease, please read studies about the protective power of dietary antioxidants against Alzheimer’s, and eating habits linked to higher Alzheimer’s risk.
For more health information, please see recent studies that oral cannabis extract may help reduce Alzheimer’s symptoms, and Vitamin E may help prevent Parkinson’s disease.
The study is published in Antioxidants.
