Compounds from two Nigerian vegetables found to inhibit enzymes implicated in neurodegenerative diseases
12/24/2020 / By Evangelyn Rodriguez
Neurodegenerative disease is a term used for conditions that affect the function of neurons in the human brain. Unlike other cells in the body, neurons, or nerve cells, are incapable of cell reproduction. Once neurons are injured, degenerate or die, the body cannot replace them with new ones. This is why neurodegenerative diseases are debilitating and very difficult to cure.
Parkinson’s disease and Alzheimer’s disease are two of the most common neurodegenerative diseases in the world. Alzheimer’s, in particular, is the most common cause of dementia — an umbrella term for conditions that cause memory loss — accounting for 60 to 80 percent of dementia cases.
Although the cause of dementia is unknown in many cases, abnormal brain changes and neurodegeneration are believed to trigger the gradual worsening of symptoms experienced by people with dementia.
In a recent study, researchers at the Federal University of Technology Akure in Nigeria investigated the potential of two commonly consumed vegetables in southern Nigeria to help with the management of neurodegenerative diseases. Specifically, they looked at the modulatory effects of alkaloids isolated from these vegetables on the activities of enzymes involved in neurodegeneration.
The researchers reported their findings in an article published in the Journal of Dietary Supplements.
Alkaloids from two African vegetables can inhibit enzymes that break down neurotransmitters
Plants produce alkaloids as part of their defense mechanism against herbivores. Alkaloids are known to have pharmacological properties that benefit human health. According to recent studies, these properties include analgesic, anti-hyperglycemic, antiarrhythmic, antibacterial and anti-cancer activities.
For their experiment, the researchers extracted alkaloids from Lasianthera africana, locally known as editan, and Gongronema latifolium, also known as utazi, and explored their ability to regulate the activities of enzymes involved in neurodegeneration. Specifically, they examined how these alkaloids affected the activity of cholinesterases (e.g., acetylcholinesterase [AChE] and butyrylcholinesterase [BChE]) and the enzyme monoamine oxidase (MAO) in vitro.
AChE is an enzyme found in neuromuscular junctions. Its function is to break down acetylcholine, the chief neurotransmitter (chemical messenger) of the parasympathetic nervous system, thereby terminating impulse transmission between nerves. Low levels of acetylcholine have been found in patients with Alzheimer’s dementia. Inhibiting AChE activity, on the other hand, has been shown to cause improvements in cognition.
BChE is a non-specific enzyme that catalyzes the breakdown of choline-based esters, including the neurotransmitter acetylcholine. Patients with Alzheimer’s have increased cortical levels of this cholinesterase. Because it also lowers acetylcholine levels in the brain, BChE is often targeted together with AChE for the treatment of Alzheimer’s disease. (Related: Can oxygen treatments help prevent neurodegenerative disease?)
MAO is an enzyme involved in the degradation of monoamines released by neurons and other types of brain cells. It is also involved in neurodegeneration because it triggers oxidative stress, which can cause cell damage, impair the DNA repair system and induce mitochondrial dysfunction. All of these events have been linked to the development of neurodegenerative diseases like Alzheimer’s and Parkinson’s.
The researchers also looked at the ability of editan and utazi alkaloids to chelate iron II (Fe2+) and scavenge free radicals — activities performed by antioxidants. They then used gas chromatography coupled with flame ionization detector (GC-FID) to develop an alkaloid profile.
The researchers found that the alkaloids from editan and utazi inhibited AChE, BChE and MAO in a concentration-dependent manner. In particular, the alkaloid from utazi showed a higher inhibitory activity for all three enzymes than the alkaloid from editan. GC-FID analysis revealed an abundance of choline in both extracts, which could be a reason for their cognitive effects.
Because of the ability of editan and utazi extracts to inhibit enzymes implicated in neurodegeneration, the researchers believe these African vegetables would make great dietary supplements for the management of neurodegenerative diseases.
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