The incidence of neurodegenerative diseases (NDs) such as Alzheimer’s and Parkinson’s diseases are growing in developed countries. Occurring in tandem with an increasing lifespan and growing rates of chronic disease, the medical community is calling out for novel treatments to reduce this soaring epidemic.
Herbal medicines have unique properties such as antioxidant, anti-inflammatory and cognition-enhancing actions which may be beneficial in the treatment of NDs. Many can cross the blood-brain barrier, exerting neuroprotective effects on neurological tissues.[1,2,3]
Panax ginseng (Korean ginseng) is one such herb. In an animal study, oral administration of an extract of Korean ginseng (G115 - standardised to 4mg ginsenosides) significantly reduced dopaminergic cell loss, microgliosis, and accumulation of alpha-synuclein aggregates, suggesting that this herb may be useful in neurological conditions such as Parkinson’s disease.
Ginkgo biloba (ginkgo) has been extensively investigated for its effect on Alzheimer’s disease and mild cognitive impairment. The most recent systematic review and meta-analysis conducted on this herb included a review of 21 clinical trials, with most using 120 or 240mg per day of standardised extract.
Treatment periods were from two to 52 weeks (majority were 22-26 weeks) and ginkgo was used as an adjunct to pharmaceutical medications (memantine, donepezil, galantamine, rivastigmine) in many of the trials. It was found that when used as an adjunct to orthodox medications, ginkgo improved Mini-Mental State Examination (MMSE) (p<0.0001), mild cognitive impairment (MCI) (p<0.00001) and Activity of Daily Living (ADL) (p=0.0002) scores at 24 weeks in Alzheimer’s disease subjects compared with use of conventional medicine alone.
Another herb which exhibits neuroprotective properties is Withania somnifera (withania). Used for centuries as a nerve tonic and nootropic agent, recent research shows withania’s active constituents, including withaferin A, and withanolides A, B and D, exhibit neuroprotective benefits via N-methyl-d-aspartate (NMDA) receptor mediated excitotoxicity, which is implicated in many NDs. Withania also demonstrates promise for Parkinson’s disease, via dopaminergic neuroprotection.
Other herbal active constituents with the potential for treatment of NDs via neuroprotective mechanisms include berberine from Berberis vulgaris (barberry), Phellodendron amurense (phellodendron) and Hydrastis canadensis (golden seal) and honokiol from Magnolia officinalis (magnolia).[1,6] Berberine exerts this activity via antioxidant, anti-inflammatory and anti-apoptopic activities, whilst honokiol is thought to aid neuroprotection for NDs via antioxidant activity, amelioration of excitotoxicity related to the blockade of glutamate receptors and reduction in neuroinflammation.[1,3]
- Talarek S, Listos J, Barreca D, et al. Neuroprotective effects of honokiol: from chemistry to medicine. Biofactors 2017;43(6):760-769. [Abstract]
- Van Kampen JM, Baranowski DB, Shaw CA et al. Panax ginseng is neuroprotective in a novel progressive model of Parkinson’s disease. Exp Gerontol 2014;50:95-105. [Abstract]
- Lin X, Zhang N. Berberine: pathways to protect neurons. Phytother Res 2018;32(8):1501-1510. [Abstract]
- Yang G, Wang Y, Sun J, et al. Ginkgo biloba for mild cognitive impairment and Alzheimer’s disease: a systematic review and meta-analysis of randomized controlled trials.Curr Top Med Chem 2016;16(5):520-528. [Abstract]
- Kumar G, Patnaik R. Exploring neuroprotective potential of Withania somnifera phytochemicals by inhibition of GluN2B-containing NMDA receptors: An in silico study. MedHypotheses 2016;92:35-43. [Abstract]
- Prakash J, Chouhan S, Yadav SK, et al. Withania somnifera alleviates parkinsonian phenotypes by inhibiting apoptotic pathways in dopaminergic neurons. Neurochem Res 2014;39(12):2527-2536. [Abstract]