Scientific Reports of Medicinal Plants Used for the Prevention and Treatment of Neurodegenerative diseases

Sunali Lalotra*, J S Vaghela

Bhupal Nobles‘ College of Pharmacy, Udaipur-313001, Rajasthan, India

Received: 21-Nov-2018 , Accepted: 19-Jan-2019

Keywords: Neurodegenerative diseases, Medicinal herbs, Alzheimer’s disease, Parkinson’s disease, Memory loss, Phytocompounds

DOI: http://dx.doi.org/10.20510/ukjpb/7/i1/179297

 

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Abstract

Neurodegenerative diseases are incurable and debilitating conditions that result in progressive degeneration / death of nerve cells or neurons in the human brain. Alzheimer’s disease and Parkinson’s disease are the major Neurodegenerative diseases, which are characterized by progressive loss (and even death) of structure and function of neurons, and have created great burden to the individual and the society. Treatment of these diseases with prolonged administration of synthetic drugs will lead to severe side effects. Therefore herbal treatment is being preferred over conventional treatments. Much attention and so scope is drawn towards herbal remedy of many Neurodegenerative diseases. The present review puts together research on various medicinal plants that have shown promise in reversing the Alzheimer’s and Parkinson’s pathology and highlights importance of phytochemicals of medicinal herbs on neuroprotective function and their mechanism of action.

1 Introduction

Neurons are the building blocks of the nervous system which includes the brain and spinal cord. Neurons normally don’t reproduce or replace themselves, so when they become damaged or die they cannot be replaced by the body. Neurodegenerative diseases are incurable and debilitating conditions that result in progressive degeneration / death of nerve cells or neurons in the human brain. This causes problems with movement (called ataxias), or mental functioning (called dementias).

The actual cause of various neurodegenerative diseases still remains a mystery in healthcare. Some of the commonly studied environmental factors causes for neurodegenerative diseases are protein degradation, oxidative stress, inflammation, environmental factor, mitochondrial defects, familial history, and abnormal protein accumulation in neuron1,2. Ageing is considered as one of the major problem in neurodegenerative diseases3. Examples of neurodegenerative diseases include Parkinson’s, Alzheimer’s, and Huntington’s disease, Motor neurone diseases, Spinocerebellar ataxia (SCA), Spinal muscular atrophy (SMA)4.

2 Alzheimer’s disease (AD)

On the other hand, Alzheimer’s disease is associated with progressive memory loss, as well as judgment and decision making impairments, according to statistics collected by Guttmacher et al (2003)7. It is an age-related neurodegenerative disorder characterized by memory deficits. No cure for Alzheimer`s exists, and the drugs currently available to treat the disease have limited effectiveness.  AD is named after German physician Aloes Alzheimer, who first described it in 1906 and primarily affects the elderly population of over 65 years of age, and is estimated to account for 50 - 60% of the dementia cases. Symptoms typically appear after age 60, and some early-onset forms of the disease are linked to a specific genetic defect. Early disease shows a loss of short-term memory, inability to learn new information, mood swings, difficulty in finding words, forgetting names, and losing items. Frustration, hostility, and irritability are common emotional features exhibited by patients with AD. In severe cases, patients become totally incontinent, memory is completely lost, and sense of time and place disappears5.  

Several studies have revealed that natural antioxidants, such as vitamin E, vitamin C, and beta-carotene, may help in scavenging free radicals generated during the initiation and progression of these disease. The loss of memory is considered to be the result of a shortage of the nerve transmitter acetylcholine. It is possible to increase the level of this transmitter in the brain by inhibiting the activity of the enzyme acetylcholinesterase, which splits or breaks down the transmitter substance. Drugs that inhibit the breakdown of the messenger or transmitter acetylcholine delay the development of the disease6.

3 Parkinson’s disease (PD)

Parkinson’s disease is a progressive disorder which causes slow motion and rigidity in the body. The clinical manifestation includes bradykinesia (having difficulties in initiating movement), hypokinesia, rigidity, rest tremor and non-motor features including depression, psychosis autonomic dysfunction. Other  symptoms  includes  co-ordinate  movements, shuffling  gait, fixed facial expression, lack of blinking, and micrographia, autonomic dysfunction, cognitive, psychiatric  changes, sensory symptoms, Seborrhea and Muscle atrophy.

It is characterized by neuronal loss in the substantia nigra and other brain regions, also associated with the formation of intracellular protein inclusions known as Lewy bodies. The loss of dopaminergic neurons, leads to the reduction of dopamine being released into the striatum. Mitochondrial dysfunction and oxidative insult are considered to be the key culprit. The current therapy available for PD primarily relies on Levodopa that offers the potential of slowing down disease progression to some extent but includes lot of side effects7.In 1817 James Parkinson first described as   paralysis agitans or shaking palsy, the term "Parkinson`s disease" being coined later by Jean-Martin Charcot6

The neurochemical events associated with Parkinson’s disease include increased levels of free radicals, oxidative stress, inflammation, mitochondrial dysfunction, and α-synuclein aggregation. Additionally, increased concentration of redox active metals such as iron and copper, reduced glutathione levels, and increased lipid peroxidation have also been reported. Recent studies have suggested that oxidative stress (OS), produces apoptosis which results in mitochondrial defects, neuroinflammation may also play important roles in its pathogenesis. Various agents as 6-Hydroxydopamine (6-OHDA), 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, Rotenone a neurotoxin commonly and many more are used in models of PD, induces selective catecholaminergic cell death, mediated by reactive oxygen species (ROS) and mitochondrial defects. 

4 Medicinal plants used for the treatment of Alzheimer’s and Parkinson’s disease

A number of scientifc researches have been carried out  on medicinal herbs. Herbal medicine offers several options to modify the progress and symptoms of Alzheimer’s and Parkinson’s disease. Herbal medicines viz. Ginseng, Ashwagandha, Baccopa monnieri, Ginkgo biloba, Valeriana officinalis, Nardostachys jatamansi, Withania somnifera, Centella asiatica have compounds such as flavonoids, celastrol, trehalose, lycopene, sesamol, resveratrol, and curcumin has gained a lot of interest for their therapeutic potential. Phytocompounds from medicinal plants play a major part in maintaining the brain`s chemical balance by acting upon the function of receptors for the major inhibitory neurotransmitters. Herbs have anti-infammatory and antioxidant activities that may be used in the treatment of Alzheimer’s and Parkinson’s disease2.

The present review puts together research on various Ayurvedic medicinal plants that have shown promise in reversing the Alzheimer’s and Parkinson’s pathology. The present review puts together research on various medicinal plants that have shown promise in reversing the Alzheimer’s and Parkinson’s pathology and highlights importance of phytochemicals of medicinal herbs on neuroprotective function and their mechanism of action. The report summarizes information concerning the phytochemical and biological activities of these various plants in order to provide sufficient baseline information that could be used in drug discovery campaigns and development processes, thereby providing new functional leads for Alzheimer’s and Parkinson’s disease. Table 1 and 2 summarizes some of the commonly used Medicinal plants for their neuroprotective effect.  

5 Conclusion 

Medicinal plants served as a platform for ancient Ayurvedic system of medicine. The current review has offered inclusive details of plants used in the treatment of Neurodegenerative diseases special reference to AD and PD. The different phytoconstituents and extracts of various plants demonstrated the protective effect for Neurodegenerative diseases. The existences of bioactive chemicals are mostly responsible for the treatment of AD and PD. However, many other active agents obtained from plants have not been well characterized. It is required to carry out study to assess the mechanism of action of medicinal plants for the treatment of AD and PD.

6 Conflict of interests

None

7 Author’s contributions

SL and JSV collected the data and drafted the manuscript. Both authors have read and approved the final manuscript. 

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