The team from the University of Newcastle upon Tyne said that based on the results, both herbs are worth pursuing as potential treatments for both cognitive and non-cognitive symptoms caused by dementia.
Alzheimer's is the most common form of dementia and affects an estimated 10 million people worldwide. Many of the current drugs taken to treat the disease, such as donepezil, have unpleasant side effects and doctors are keen to find alternatives. The ageing population presents an urgent need for better treatments.
Both sage and lemon balm have previously been shown to improve memory and/or reduce agitation, and possess a range of relevant cholinergic and non-cholinergic activities.
The Newcastle researchers prepared plant extracts with the best possible standardised bioactivity, and tested them in controlled trials in normal volunteers and in Alzheimer's patients.
In controlled trials in normal volunteers, both extracts improved memory, and lemon balm also improved mood. Lemon balm reduced agitation and improved quality of life in people with Alzheimer's.
The effects of sage on the disease are currently under investigation, and preliminary data indicate significant effects on attention and behaviour. Both species of plant were extremely well tolerated both by volunteers and Alzheimer's patients, and there were minimal, or no, side effects, reported the researchers, speaking at a Faculty of the Psychiatry of Old Age annual meeting in Liverpool.
Newcastle researchers have previously reported that healthy, young adults who took sage oil capsules performed significantly better in a word recall test than those who took placebo pills.
And last year researchers from King's College London said they had found four compounds isolated from an extract of sage root to be acetylcholinesterase inhibitors. This is the same pharmacological action as drugs marketed to treat Alzheimer's disease.