Herbs hold clue to curing dementia

MEDICAL scientists have enlisted the help of a classics scholar to comb ancient texts on herbs in an effort to find potential leads for new drugs. The unique collaboration has already identified two plants whose extracts appear to have neurochemical effects similar to drugs used for treating Alzheimer's disease.

The work is being done at the newly established Medicinal Plant Research Centre at the University of Newcastle. The centre's director, Professor Elaine Perry, an expert in the biochemistry of neurological disorders, said: "Over the past few years I have become interested in whether or not there might be traditional approaches to treating memory disorders with plants and whether we could take these plants and look closely at their biological activity."

Professor Perry discovered that the university had a botanical garden that could grow herbs for experiments, and that in its classics department was a plant enthusiast who was one of a handful of people in the country capable of translating scientific Latin texts: Dr Elizabeth Lazenby.

"While you can glean information from the currently available herbal texts, it may be of limited value in that most of the herbals have in turn obtained their information from others," Professor Perry said. "It's important to trace the origin of statements so that they can be validated."

Professor Perry asked Dr Lazenby to search herbal literature for references to mood and memory disorders.

"This was difficult," said Dr Lazenby, "because these were very abstract concepts to the ancient world, and such ailments were generally considered merely an indication of advancing age. So I searched for terms such as insania, concitatio, animi perturbatio, oblivio, immemor ingenum - mania, hysteria and memory loss."

Eventually, three plants emerged as possible contenders: sage, balm and rosemary.

Paracelsus (1493-1541), the Swiss physician, sold balm to kings as an elixir of life and as a safeguard against early senility, while Avicenna, a doctor in 10th-century Syria, proclaimed that the herb "maketh the heart merry and strengtheneth the vitall spirits".

Sage was said by the English herbalist Gerard in 1597 to be "good for the head and brain, it quickeneth the senses and memory", a sentiment echoed by Culpeper ("excellent ... to help the memory"). An old English proverb states that "He that would live for aye/Must eat sage in May". And The Grete Herball of 1526 suggested that rosemary was a good cure "for weyknesse of ye brain".

The three plants were grown in the botanic garden and taken to the laboratory for analysis. Rosemary did not appear to have any significant activity in test-tube experiments, but sage and balm did.

The clinical treatment of Alzheimer's focuses on a molecule in the brain called acetylcholine, which plays a central role in transmitting nerve signals. There are two fundamental ways of increasing the activity of this neurotransmitter: to inhibit the naturally occurring enzyme, acetylcholinesterase, which breaks down acetylcholine; or to increase the activity of the receptors on nerve cells that bind acetylcholine.

"In the laboratory we tested the effect of the plant extracts on the enzyme and the receptors," Professor Perry said. "We found that the extract of sage inhibited acetylcholinesterase in a similar way to Aricept, the drug which is used for this purpose. While balm extract did not have an effect on the enzyme, it did stimulate the receptors."

Chemists are now working on the plants to identify which compounds in the extracts are biologically active. There may be a single chemical responsible for the activity, or several may be working together.

Once the compounds are identified, Professor Perry hopes to set up clinical trials, using either the actual plant material, whole extracts or the biologically active compounds alone. She stresses, however, that the work is in its early stages: "Before people start rushing out and consuming vast quantities of these plants it is important to await the outcome of carefully controlled clinical trials."

Dr Lazenby has been asked by a dermatologist to identify plants with potential anti-inflammatory properties. "Drugs do not just come out of the ether, and many drugs that are prescribed now are derived from plant-based substances," she said. "We are trying to find things that have been perhaps missed or lost."