A new meta-study done by researchers from the School of Public Health at China Medical University has confirmed that the plant constituent called Huperzine A can significantly improve cognitive function among Alzheimer’s disease patients.
The researchers found and analyzed 42 clinical studies that have investigated Huperzine A. They eliminated all studies that did not fit inclusion criteria for quality research. The researchers were left with eight high-quality placebo-controlled and randomized studies — five being double-blind and three being single-blind – involving more than 10 human subjects each.
In all, the eight studies followed 733 patients with Alzheimer’s disease. The fewest number of patients in a study was 28 and the most was 197. The studies ranged from 8 weeks to 24 weeks long.
All of the studies used the mini-mental state examination (MMSE) and the activities of daily living scale (ADL) to measure the results of the plant extract. These two tests are standardized tests that gauge the cognitive, consciousness and lifestyles of dementia patients. They are often used to diagnose Alzheimer’s disease and other types of dementia. The MMSE test gauges orientation, repetition, attention, recall, language and complex commands.
The meta-analysis calculations of these studies found that Huperzine A significantly increased cognition among those patients compared to those taking the placebo.
The average drop in MMSE scores among the Huperzine A groups compared with the placebo groups — indicating improved condition — was 4.84 points.
Among those subjects with vascular dementia, the rate of improvement in MMSE scores was similar — dropping 4.92 in comparison with the placebo group.
The point system on the MMSE goes up to 30, with the higher scores being indicative of cognitive decline. An improvement of nearly 5 out of 30 points is a significant change — though its percentage change does not necessarily indicate a straight-line relationship.
Activities of daily living scale (ADL) scores also were significantly better among the Huperizine A groups. The difference between the Huperzine A and placebo groups among the vascular dementia cases was a significant 10.24 points lower.
The researchers added:
“The results from our meta-analysis of eight randomized controlled trials showed that Huperzine A could significantly improve the MMSE and ADL score of AD patients.”
Just what is Huperzine?
Huperzine A is extracted from the firmoss plant (Huperzia serrata and other Huperzia species). There are numerous varieties of firmosses that grow on different continents.
Huperzine A, and its more newly-found molecular relatives Huperzine B and Huperzine U, is a sesquiterpene that has a mechanism of blocking the enzyme acetylcholinesterase. Acetylcholinesterase will break down acetylcholine, an important neurotransmitter that allows information to be carried from one nerve to another.
Excess acetylcholinesterase has been observed among a number of cognitive disorders, including Alzheimer’s, Parkinson’s and other dementia forms.
As mentioned, Huperzine B and U have similar properties. A recent study from India’s Integral University found that the acetylcholinesterase-inhibiting properties of Huperzine B provides a more intelligent “docking” potential with acetylcholinesterase compared with pharmaceutical acetylcholinesterase-inhibitors, which can come with significant side effects including dizziness.
Studies on Huperzine A have indicated a history of safety, with the few side effects noted as minor stomach upsets.
Other medicinal plants contain natural acetylcholinesterase-inhibitors. These include alkaloids such as quinolizidine, isoquinoline and indoles. Salix alba L. — Willow — for example, was found to have a 50% inhibition for acetylcholinesterase.
Researchers from Turkey’s Gazi University found that Heptaptera triquetra — also named Colladonia triquetra, a Mediterranean flowering plant in the parsley family — inhibited acetylcholinesterase over 80% in their laboratory studies.
Shu-huai Xing, Chun-xiao Zhu, Rui Zhang, and Li An, “Huperzine A in the Treatment of Alzheimer’s Disease and Vascular Dementia: A Meta-Analysis,” Evidence-Based Complementary and Alternative Medicine, vol. 2014, Article ID 363985, 10 pages, 2014. doi:10.1155/2014/363985
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Konrath EL, Passos Cdos S, Klein LC Jr, Henriques AT. Alkaloids as a source of potential anticholinesterase inhibitors for the treatment of Alzheimer’s disease. J Pharm Pharmacol. 2013 Dec;65(12):1701-25. doi: 10.1111/jphp.12090