A pretty plant native to California may hold the key to curing Alzheimer’s disease, according to new research.
It is named Yerba santa – Spanish for ‘holy herb’ – in honour of its remarkable medicinal properties.
Now scientists have found the main active compound, known as sterubin, has powerful neuro-protective and anti-inflammatory effects.
In experiments, the chemical destroyed rogue ‘amyloid beta’ proteins that accumulate in the brains of dementia patients.
These develop into clumps, killing neurons and leading to memory loss and confusion.
The breakthrough offers hope of turning it into a drug that actually treats the cause of the devastating neurological disorder, rather than the symptoms.
Corresponding author Dr Pamela Maher, of The Salk Institute for Biological Studies, San Diego, said it could also be turned into treatments for other neurological illnesses.
She said: “Alzheimer’s disease is a leading cause of death in the United States.
“And because age is a major risk factor, researchers are looking at ways to counter ageing’s effects on the brain.
“Our identification of sterubin as a potent neuroprotective component of a native California plant called Yerba santa is a promising step in that direction.”
The shrub’s scientific name is (Eriodictyon californicum). It is known for its beautiful blue flowers, similar to bluebells or forget-me-nots.
Dr Maher’s team identified sterubin in a series of tests to identify natural plant extracts that could reverse symptoms of neurological disease.
Using nerve cells of mice, they found it boosted their energy and survival by reducing toxicity, mutated versions of amyloid beta that misfold and join together.
In particular, sterubin had a potent anti-inflammatory impact on brain cells known as microglia. All these processes are believed to lead to Alzheimer’s.
It also effectively removed iron which can builds up in neurons as people get older, triggering neuro-degenerative diseases.
Overall, the compound was effective against multiple inducers of cell death in the nerve cells, said Dr Maher.
She said: “This is a compound that was known but ignored.”
Her researchers applied a screening technique used in drug discovery to a commercial library of 400 plant extracts with known pharmacological properties.
The lab had previously used this approach to identify other plant chemicals, called flavonoids, that have anti-inflammatory and neuro-protective properties.
Added Dr Maher: “Not only did sterubin turn out to be much more active than the other flavonoids in Yerba santa in our tests, it appears as good as, if not better than, other flavonoids we have studied.”
The lab is now planning to test sterubin in living mice with a rodent form of Alzheimer’s, then determine its drug-like characteristics and toxicity levels in them.
With that data, it might be possible to test the compound on humans.
It would be critical to use sterubin derived from plants grown under standardised, controlled conditions, said Dr Maher.
It is also likely the team will generate synthetic derivatives of sterubin, she added.
Today, herbal extracts of Yerba santa can be found in herbal medicine stores. It was also used as a smoke plant by American Indians, which was said to help those with asthma. In addition to smoking, the leaves can be chewed upon for pleasure.
Apparently, bees who visit the flowers make a deliciously spicy amber honey.
Dr Maher said: “We show for the first time that the most significant neuroprotective flavonoid in Yerba santa is the flavanone sterubin.
“Although sterubin has long been known to be present in Yerba santa, it has remained remarkably unstudied with most reports focusing on the other flavonoids, eriodictyol or homoeriodicytol.
“Yerba santa has long been known to have medicinal properties. For example, a treatise published in 1902 on plants used by the native people in Mendocino County, California states that ‘No plant is more highly valued as a medicine by all the tribes of Mendocino County.’
“Historically, it was used to treat a variety of indications including various respiratory conditions and fever as well as bruises, infections and pain including headaches.
“Thus, its anti-inflammatory properties are well documented, consistent with the potent anti-inflammatory effects of sterubin in our tests.”
She added: “We believe sterubin deserves further examination in the context of Alzheimer’s disease, as well as other neuro-degenerative diseases.”
There are about 850,000 people living with Alzheimer’s and other forms of dementia in the UK, alone. This figure is set to rise to 2 million by 2050 because of the ageing population. There is no cure.
Globally, as many as 44 million people are living with the disorder. It typically impacts one in ten people over the age of 65, although that number increases to one in three for those over 85.
By Mark Waghorn
