An herb traditionally used in the ancient Hindu system of healing known as Ayurveda improved memory in a mouse model for Alzheimer's disease, Oregon Health & Science University researchers have found.
Gotu kola, also used in Chinese medicine as a nerve tonic and memory-enhancing agent, appeared to normalize the behavior of mice bred to express a protein mutation that causes Alzheimer's-like symptoms, according to the study by OHSU and Portland Veterans Affairs Medical Center neurologists.
"The gotu kola-treated Alzheimer mice were very similar to wild-type mice, with no significant deficits" on behavioral tests, said the study's lead author, Joseph Quinn, M.D., associate professor of neurology, and cell and developmental biology, OHSU School of Medicine and the Portland VA Medical Center He also is an investigator at OHSU's Layton Aging and Alzheimer's Disease Center.
The behavioral changes may be the result of gotu kola's possible anti-oxidant qualities. A study in cell culture also showed the herb reduced an oxidant known as nitric oxide, which is triggered by the build-up in the brain of beta-amyloid plaques associated with Alzheimer's.
Study co-author Amala Soumyanath, Ph.D., associate professor of neurology, OHSU School of Medicine, said she wasn't surprised by the positive results.
"The herb was selected for study based on its traditional use as a memory enhancer and not just randomly, so the results were not entirely out of the blue," said Soumyanath, an expert in the study of medicines derived from botanicals. "However, we were delighted that there was an effect in the models we had selected."
The results were presented this month at the Society for Neuroscience's 35th annual meeting in Washington, D.C.
Gotu kola, which goes by the Latin name Centella asiatica, is a slender plant with fan-shaped leaves that is found primarily in the swampy regions of India, Madagascar and other tropical climates, including the southern United States. It is often prepared as a tea and can be dried for use in capsules; dietary supplement retailers describe it as an energy and vitality booster that promotes circulation to the brain and throughout the body. The validity of those claims is uncertain, and the research at OHSU is aimed at clarifying the facts surrounding this and other botanical therapies.
To prepare the plant material for testing, the OHSU team boiled dry gotu kola leaves in water, then filtered away and discarded the plant material, as is done with tea. The water was evaporated off to leave a solid residue or "aqueous extract."
The extract was then added daily to the drinking water of the transgenic Alzheimer's mice, with each mouse receiving about 6 milligrams per day. After two weeks of treatment, the mice performed as well as control mice in behavioral tests, including one that tests memory.
Soumyanath said the next step in the research is to "get a handle" on which components of gotu kola cause the beneficial effects in animals and in cell culture. That way researchers can assure that any herbal products used in trials contain these active ingredients.
"Herbal products are notoriously variable depending on where and when they were grown, and how they were processed, so it's important to ensure that the product used in trials is of high quality and contains the right ingredients," she said.
That way, Quinn added, treatment can be standardized and blood plasma levels of relevant components of the herb can be monitored during therapy. "If we proceed to human studies without this info, a negative result in human subjects may be completely meaningless," he said.
It is possible some Alzheimer's patient already are using gotu kola, particularly those who typically experiment with botanical dietary supplements, Soumyanath said. However, "it is not as well known as ginkgo biloba and it is unlikely that many patients are being directed to this herb by their health care professionals."
But that could change in the coming years, particularly if scientists continue to show gotu kola's beneficial effects in the lab. OHSU scientists are seeking financial support for additional "preclinical" studies to gather the evidence necessary to justify and design a rational clinical trial in human subjects.
The study was funded by the National Institutes of Health and the U.S. Department of Veterans Affairs. Other collaborators included Bruce Gold, Ph.D., associate professor of neurology, OHSU School of Medicine; Teri Wadsworth, PhD., OHSU Department of Physiology and Pharmacology; Yong-Ping Zhong, research assistant, OHSU Center for Research in Occupational and Environmental Toxicology; and Edward Henson, research assistant, OHSU Layton Aging & Alzheimer's Disease Center.
Dr. Soumyanath is the director of research and development for Oregon's Wild Harvest, the manufacturer of investigational products used in this research This potential conflict was reviewed and a management plan approved by the OHSU Conflict of Interest in Research Committee was implemented.