Ginseng is most commonly used in the West to boost energy (increasingly in energy drinks) and to support the immune system. But there is already some evidence of its benefits to the brain. A small Chinese trial reported two years ago found that a ginseng compound improved memory scores of people suffering from stroke-induced dementia.
In the new study, a team from Baylor College of Medicine in Houston, US, investigated whether a purified form of ginseng, in which some of the herb's active chemicals had been concentrated, could protect rats from the effects of a toxin that caused severely impaired movement and loss of neurons.
The chemical used was designed to mimic the degenerative process seen in Huntington's disease, but the rat model could also be relevant to other degenerative diseases like Parkinson's.
The rats received either the purified ginseng extract, rich in the ginsenosides known as Rb(1), Rb(3), or Rd, or a preparation from the whole root of American ginseng. A third group were given a preparation of ground leaves and stems, which contains greater levels of ginsenosides than ground root.
The concentrated extract had the most benefit. It significantly reduced the induced motor impairment and cell loss in the striatum, and it completely prevented any mortality, write the researchers in this month's issue of the Annals of Neurology (vol 57, pp642-648).
"A partial purification of whole ginseng to concentrate the neuroprotective components may have utility as a neuroprotective agent," concluded the researchers.
Rats given the preparation of ground leaves and stems gained some protection - an improved behavioural score and less damage to the striatum. But pretreatment with a preparation from the whole root of American ginseng had no protective effects and even increased mortality.
This suggests that some components need to be taken out of the whole ginseng root in order to isolate the useful ones and make it safe for future trials in humans.
It is thought that certain ginsenosides may act as antioxidants against the oxidative damage thought to contribute to conditions like Huntington's and Parkinson's disease. The latter is thought to affect 1 per cent of people over the age of 65 worldwide.