Neuroprotective activities of acai berries (Euterpe sp.) against monosodium glutamate induced toxicity in neural cells

Alnasser, Maryam (2023) Neuroprotective activities of acai berries (Euterpe sp.) against monosodium glutamate induced toxicity in neural cells. PhD thesis, University of Nottingham.

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Although L-glutamate (L-Glu) is not an essential amino acid, it is a vital excitatory

neurotransmitter that plays a critical role in brain function. An excess of L-Glu levels

over 1 mM within excitatory synaptic cleft has been linked to neurotoxicity in

neurodegenerative diseases (NDDs) and stroke. Monosodium glutamate (MSG) is a

highly used food enhancer and food additive worldwide, and excessive consumption of it

can cause extreme levels of L-Glu to build up in the cerebrospinal fluid (CSF), leading to

neuronal death.

The native South American palm berry known as the acai berry (Euterpe sp.) is a

potential nutraceutical that contains several bio-active phytochemicals with multi�pharmacological effects. Several studies in recent years have shown that acai berries and

their bioactive contents can relieve inflammation, act as antioxidants, prevent

carcinogenesis, and protect the nervous system.

The first thesis aim was to conduct a systematic review of existing literature to examine

how L-Glu affects neuronal viability and its implications for NDDs. A systematic review

of 71 studies that met eligibility criteria found that exposure to L-Glu in vitro or in vivo is

associated with multiple pathogenic mechanisms that affect neuronal viability, including

oxidative stress, antioxidant defence decline, neuroinflammation, neurotransmitter levels

dyshomeostasis, aberrant protein aggregation, excitotoxicity, mitochondrial malfunction,

calcium level dyshomeostasis, and abnormalities in neuronal histology, cognitive

function, and animal behaviour. Thus, identifying and understanding these diverse

mechanisms might enable the design of more effective and efficient agents targeting

multiple L-Glu-based pathways for NDDs.

Moreover, the following research project aimed to evaluate L-Glu (0.137 - 100 mM), acai

aqueous and ethanolic extracts (0.001 µg/mL - 1000 µg/mL) toxicity and investigate the

neuroprotection effects of acai berry extracts. The evaluation was carried out using

various methods, including dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT)

and lactate dehydrogenase (LDH) assays to assess cell viability, and to assess

mitochondrial function the adenosine 5′-triphosphate (ATP) bioluminescent, and


mitochondrial membrane potential (MMP) measurements as well as oxidative stress

measurement using the 2,7-dichlorodihydrofluorescein diacetate (DCFHDA) assay. A

whole-cell patch-clamp assay was conducted to investigate the effects of L-Glu and acai

berry extracts on NMDARs. This study investigated human neuroblastoma cells SH�SY5Y and differentiated human rhabdomyosarcoma cells TE671. The impact of acai

berry extracts and L-Glu toxicity was also investigated in differentiated SH-SY5Y cells

and human cortical neural progenitor cells (ReNcell CX) via MTT assay. L-Glu caused a

significant reduction in cell viability (p < 0.01 - p < 0.0001), ATP levels (p < 0.05 - p <

0.0001), and MMP level (p < 0.05 - p < 0.0001) and increased ROS production (p < 0.05

- p < 0.0001) in human undifferentiated SH-SY5Y and differentiated TE671 cells.

Whole-cell patch-clamp recordings showed that L-Glu and glycine (Gly) administration

did not activate currents in SH-SY5Y cells, while activated currents were observed in

differentiated TE671 cells. Although acai berry extracts alone had some adverse effects

high concentration at 1-1000 µg/mL reduced cell viability, ATP, and MMP level and

increased ROS production in undifferentiated SH-SY5Y and differentiated TE671 cells.

However, the co-application of acai berry extracts to L-Glu provided neuroprotection

against L-Glu with sustained cell viability, decreased LDH production, restored ATP

levels, preserved MMP levels and reduced ROS levels. Moreover, the results of this

thesis showed novel results that the acai berry aqueous extract significant inhibits (0.001,

100, 1000 µg/mL, p < 0.001, p < 0.0001, and p < 0.0001, respectively) L-Glu + Gly�activated currents in differentiated TE671 cells in a concentration-dependent manner.

Furthermore, differentiated SH-SY5Y cells showed no significant reduction in viability

after exposure to L-Glu (0.137 - 100 mM), but ReNcell CX cells experienced significant

(p < 0.0001) toxicity impacts after exposure to L-Glu at concentration range 0.03 - 100

mM. In ReNcell CX cells, aqueous acai berry extract (0.0001 - 100 µg/mL) co-applied to

neurons exhibited significant (p < 0.05 - p < 0.0001) neuroprotection against L-Glu.

Thus, this study showed that acai berries contain nutraceuticals with antioxidant and anti�excitotoxicity properties, making them a potentially beneficial dietary component to

prevent pathological deficits caused by excessive levels of L-Glu.


The third project in this dissertation is designed to evaluate the potential nutraceutical

benefits of acai berry extracts in vitro by examining their ability to inhibit cholinesterase

enzymes (ChE) and scavenging free radicals by using 2,2-diphenyl-1-picryl-hydrazyl�hydrate (DPPH) and 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS)

assays. Furthermore, several antioxidant effects were assessed, including hydrogen

peroxide (H2O2) or hydroxyl radical (OH•

) scavenging, nitric oxide radical (NO•


scavenging, lipid peroxidation (LPO) inhibition, and ferric ion reduction (Fe+3). Total

polyphenols (TPC) and flavonoids (TFC) were determined in both acai extracts. In

addition, acai berry extracts were fractionated and analyzed by liquid chromatography

mass spectrometry (LC-MS) to identify phytochemicals that may possess anti�cholinesterase and antioxidant properties. Acai berry extracts showed novel action in

their ability to inhibit acetyl- and butyryl-cholinesterase with estimated IC50 of 0.001

µg/mL, and 6.378 mg/mL, respectively. Moreover, both acai extracts exhibited effective

concentration-dependent antioxidant and free radical scavenging properties. The acai

ethanolic extract showed the most potent antioxidant capability and exhibited the highest

phenolic and flavonoid contents 101.39 ± 4.61 milligram gallic acid equivalents/gram of

acai berry extracts (mg GAE/g) and 11.78 ±1.42 milligram quercetin equivalents/gram of

extract (mg QUER E/g), respectively. Fractionation and analysis of acai berry extracts

with LC-MS identified several phytochemicals that may have provided antioxidants and

anti-cholinesterase effects. Therefore, acai berry extracts could be a potentially dietary

supplements that reduce the pathogenic impairments seen in AD.

Taken together, the data in this thesis suggest that excessive L-Glu intake has adverse

effects, including neuronal tissue degradation, similar pathomechanisms found in NDDs

and stroke. Moreover, this thesis reveals that acai berry extracts may include

neuroprotective compounds and could be exploited to develop drugs to treat NDDs and

strokes, which are linked to excessive buildup and toxicity of L-Glu. In addition, acai

extracts may present a novel approach for prospective AD therapy if further fractionated

due to their novel anti-cholinesterase and antioxidant properties. However, it is still

necessary to validate these findings using human primary cell lines, 3D neuronal models,

and in vivo models to explore the influences of L-Glu and acai berry extracts exposure in


Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Mellor, Ian
Carter, Wayne
Keywords: Acai berry; Euterpe sp; Excitotoxicity; L-Glutamate; Neuroprotection; NMDA receptor; Oxidative stress; Stroke
Subjects: Q Science > QP Physiology
Faculties/Schools: UK Campuses > Faculty of Medicine and Health Sciences > School of Life Sciences
Item ID: 74850
Depositing User: AL-NASSER, Maryam
Date Deposited: 13 Dec 2023 04:40
Last Modified: 13 Dec 2023 04:40

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