Introduction
Neurodegenerative diseases and cognitive disorders represent a major global public health challenge, particularly among the elderly population. One of the key mechanisms implicated in the pathogenesis of these conditions is oxidative stress, which arises from an imbalance between the production of reactive oxygen species and the body’s antioxidant defenses. This imbalance leads to neuronal damage, impaired synaptic function, and ultimately, cognitive decline.
The brain, a critical organ for perception and environmental adaptation,1 is not immune to aging or degenerative diseases,2,3 which cause the progressive deterioration of nerve cells.
Glutamate, the primary excitatory neurotransmitter in the central nervous system, plays a fundamental role in brain function. However, despite its widespread use as a food additive, monosodium glutamate (MSG) has been shown to exhibit neurotoxic effects in rodents.4,5 Studies confirm that exposure to MSG induces significant neurochemical toxicity, notably through the induction of oxidative stress and neuronal damage.5 It is important to emphasize, however, that these mechanisms differ qualitatively from the complex pathogenic processes involved in Alzheimer’s disease, which involve amyloid protein aggregation, abnormal tau phosphorylation, and specific synaptic alterations. Therefore, direct or simplistic extrapolation of MSG’s neurotoxic effects to Alzheimer’s-like neurodegeneration should be avoided to maintain scientific rigor and preserve the validity of conclusions.6
In the search for new therapeutic strategies, medicinal plants with anthelmintic, antibacterial, antidiabetic, anti-inflammatory, antioxidant, and neuroprotective properties have garnered increasing interest.7Sclerocarya birrea (A. Rich) Hochst (Anacardiaceae), commonly known as marula, is traditionally used in African medicine to treat various ailments, including memory and neurological disorders.8 It also possesses nutritional benefits, supporting its inclusion in local diets.
This species, widely distributed across Saharan and Sub-Saharan Africa,9 exhibits vigorous growth during the dry season and slower growth during the rainy season. Various parts of the plant, particularly the leaves, are used to treat conditions such as sexual impotence, malaria, agalactia, pain, diarrhea, and trypanosomiasis. S. birrea has demonstrated anti-inflammatory, analgesic, antioxidant, antidepressant, antihypertensive, and antipyretic activities.10
Phytochemical analyses of S. birrea root bark have identified the presence of bioactive compounds such as tannins, flavonoids, alkaloids, saponins, and triterpenes, all known for their antioxidant properties.11 Recent studies have shown that aqueous extracts of this bark can mitigate MSG-induced cognitive deficits and oxidative stress in mice. Oral administration of these extracts reverses behavioral disturbances, restores antioxidant enzyme activity, and reduces oxidative brain damage, thus supporting the traditional use of S. birrea in managing neurodegenerative diseases.
This study aimed to further evaluate the neuroprotective and antioxidant effects of orally administered aqueous extracts of S. birrea root bark in a mouse model of MSG-induced oxidative stress and memory impairment. By highlighting the therapeutic potential of this plant, the research seeks to contribute to the development of alternative interventions for cognitive disorders and neurodegeneration.
Materials and methods
Plant material and extract preparation
The root bark of S. birrea was collected in Moundou (Chad) and identified at the National Herbarium of Yaoundé. After grinding, 2.5 g of the powder was boiled in 50 mL of distilled water and then filtered to obtain a stock solution. Evaporation of 23 mL of this solution yielded 0.9435 g of dry extract, with a yield of 37.74%, corresponding to a concentration of 41 mg/mL. The initial administered dose was 410 mg/kg, and two additional doses (205 and 102.5 mg/kg) of the dry extract were subsequently prepared.
Preliminary phytochemical tests of the S. birrea extract were performed using qualitative colorimetric methods to identify the chemical groups.12
These tests showed the presence of alkaloids (white or orange precipitate with Dragendorff’s reagent), tannins (blue-black coloration with FeCl3), flavonoids (orange, red, or purple coloration depending on type), triterpenes or steroids (purple or green-black coloration after treatment with chloroform, H2SO4, and acetic anhydride), anthraquinones (red coloration with petroleum ether/chloroform mixture and NaOH), and phenolic compounds (green or bluish coloration with FeCl3). These results confirm that S. birrea is rich in bioactive molecules that may explain its therapeutic effects.
Assessment of bioactive compound content in S. birrea root bark extract
Polyphenol content
The bioactive compound content of S. birrea root bark extract was evaluated using spectrophotometric methods. Polyphenols were measured using the Folin-Ciocalteu reagent,13 tannins by a vanillin reaction using catechin as a standard,14 and triterpenes following a lupeol-based protocol.15 These analyses allowed quantification of key molecules contributing to the plant’s therapeutic effects.
Determination of plant antioxidant capacity in vitro; Ferric reducing ability of plasma (FRAP) test: quantification of antioxidant potential by reduction of Fe3+ to Fe2+
The FRAP method is based on the ability of an extract to reduce ferric iron (Fe3+) to ferrous iron (Fe2+).16 A fresh FRAP reagent solution was prepared by mixing 2.5 mL of TPTZ (2,4,6-Tris(2-pyridyl)-s-triazine ) solution (10 mM in 40 mM HCl) with 2.5 mL of FeCl3·6H2O (20 mM) and 25 mL of acetate buffer (300 mM sodium acetate, pH adjusted to 3.6 with acetic acid). Then, 900 µL of FRAP reagent, pre-incubated at 37°C, was mixed with 70 µL distilled water and 30 µL of plant extract at different concentrations (0.1 to 0.5 mg/mL). After 30 m of incubation, absorbance was measured at 593 nm at 37°C against the blank. Ascorbic acid was used as a positive control, and its absorbance was measured under the same conditions.
The percentage reducing power of the extract and vitamin C was calculated using the formula:
PR (%) = A0−A1A0×100
where PR is the reducing power, A0 the absorbance of the control, and A1 the absorbance of the sample.Behavioral tests
Naïve white Swiss mice (Mus musculus, Muridae), aged eight to ten weeks, were used to study the effects of S. birrea on memory in an MSG-induced neurotoxicity model. Animals were divided into control and test groups and treated for 15 days with different doses of the plant extract or controls.17 A T-maze test,18 comprising three phases (habituation, acquisition, retention), was conducted to assess exploration, spatial preference, and memory. Parameters measured included latency time, time spent in maze arms, and number of entries, allowing evaluation of the extract’s impact on cognitive functions.
Y-maze test
The spontaneous alternation test in a Y-maze started on treatment day 14 and comprised two phases: habituation and retention.19
During habituation (day 14), animals were individually placed at the starting compartment end and allowed to explore the maze freely for 5 m. Mice spontaneously explored the less recently visited arm, demonstrating their ability to alternate visits across the three arms.
The retention phase (day 15) began 24 h later. The parameter recorded was the number of successive entries into the three different arms of the Y-maze.
An animal was considered to have entered an arm only if all four paws were inside. After each animal, the maze was cleaned with 70% ethanol. Spontaneous alternation was defined as three successive entries into different arms (e.g., ABC, CAB, or BCA). The percentage of spontaneous alternation (% AS) and the alternation index were used as indices of working memory performance:
% AS=Number of alternations performedTotal number of arms visited−2*100
The number of possible alternations corresponds to the total number of arms visited minus 2.
Alternation index=Number of alternations performedNumber of arms visited*100
Evaluation of the antioxidant capacity of the extract in vivo
Brain sampling and homogenate preparation
Immediately after behavioral tests, animals were sacrificed by cervical decapitation. Brains were removed, rinsed in 0.9% NaCl solution, blotted dry, weighed, and placed in a ceramic mortar. 500 µL of phosphate-buffered saline (PBS) was added, and the tissue was homogenized. The homogenate was centrifuged at 10,000 rpm for 15 m. The supernatant was collected and stored in labeled tubes for oxidative stress parameter assays.
Determination of oxidative stress markers
Malondialdehyde (MDA) assay
MDA presence leads, under hot acidic conditions (100°C), to the formation of aldehydes that react with thiobarbituric acid to form a pink complex. Absorbance was read at 530 nm against a blank following the protocol by Wilbur et al.20 Briefly, 0.5 mL homogenate was mixed with 0.25 mL Tris-HCl buffer (blank tube) or test tubes; then 0.25 mL 20% trichloroacetic acid and 0.5 mL 0.67% thiobarbituric acid were added. Tubes were sealed with glass beads and incubated at 90°C for 10 m, cooled, then centrifuged at 3,000 rpm for 15 m at room temperature. Absorbance of the supernatant was measured at 530 nm. MDA concentration was calculated as:
[MDA] (mol/g tissue)=DO×Vtε×L×Vi×m
where: OD: optical density; Vt: total volume in tube (mL) = 1.25 mL; Vi: volume of supernatant used for assay (mL) = 0.5 mL; m: mass of tissue used (g) = 0.4 g; L: length of cell = 1 cm; ε: molar extinction coefficient = 1.56×105 mol−1.cm−1.Determination of catalase activity
Catalase activity was determined by the method of Beers and Sizer in 1952.21 Two hundred and fifty microliters of distilled water and 250 µL of seahorse homogenate were added to cuvettes, followed by 250 µL phosphate buffer (0.1 M, pH 7.2) and 1,000 µL 30 mM H2O2. After rapid mixing at room temperature, absorbance was read at 240 nm after 30 s and 90 s. Catalase activity was calculated using Beer-Lambert law.
Catalase activity=Am×103×Vt1×ε×m×Ve
where: Am = mean absorbance at 240 nm; ε = molar extinction coefficient = 40 M−1; cm−1; Vt is the total volume of the reaction medium; Ve is the volume of the homogenate; t is the reaction time (m); l is the optical path of the cell.
Reduced glutathione assay
Reduced glutathione was quantified using Ellman’s method (1959).22 2,2-dithio-5,5′-dinitrobenzoic acid reacts with –SH groups to form a yellow complex, measured at 412 nm. Three milliliters of reagent were mixed with 200 µL of homogenate (test) or Tris-HCl buffer (control). After vortexing and 1-h incubation at room temperature, absorbance was read. Glutathione concentration was calculated as:
[Reduced glutathione] (mol/g tissue)=DO×Vtε×L×Vi×m
where: OD: optical density; Vt: total tube volume = 3.2 mL; Vi: volume of supernatant used for assay = 0.2 mL; m: mass of tissue used = 0.4 g; L: length of cell = 1 cm; ε: molar extinction coefficient = 13,600 mol−1.cm−1.Superoxide dismutase activity (SOD)
SOD activity was measured by its inhibition of adrenaline oxidation to adrenochrome, monitored by absorbance increase at 480 nm between 20 and 80 s. The Misra and Fridovich method (1972) was used to calculate SOD units per mg protein,23 where one unit corresponds to 50% inhibition.
Activité SOD=Umgdeprotéine =Nombred d'unités de SODaLmg de protéine *Facteur de dilution
SOD unit = (100 - ((Δ DOessay x 100)) / ΔDOwhite = % inhibition; 50% inhibition corresponds to 1 SOD unit; OD variation: ΔDOm = DO20s - DO80s.Determination of the cholinergic transmission system
Acetylcholinesterase (AchE) activity
AChE activity, which degrades acetylcholine, was determined by Ellman’s method.22 Absorbance at 412 nm was recorded over 2 m to calculate enzyme activity expressed in units per minute per mg protein. One unit corresponds to the enzyme amount hydrolyzing 1 µmol acetylthiocholine iodide per minute.
AchE=Am×Vtε×b×Vs
where: A/m is absorbance variation per minute; ε is 1.361 X 104 M−1; cm−1; b is the length of the cell (1 cm); Vt is the total volume (3.2 mL); Vs is the sample volume (0.4 mL). Enzyme activity is expressed in U/m/mg protein in brain tissue (1 U/m/mg AchE was defined as the amount of enzyme that as the amount of enzyme hydrolyzing 1 µmol acetylthiocholine iodide).Statistical analysis
Data were analyzed using descriptive statistics with Microsoft Excel 2016 to determine mean ± standard error of the mean. Analysis of variance followed by Tukey’s multiple comparison test was performed using GraphPad Prism version 8.3.1. Differences were considered significant at P ≤ 0.05.
Results
Qualitative phytochemical screening of S. birrea extract
Phytochemical characterization tests of S. birrea extract revealed the presence of the following major chemical families: polyphenols, tannins, anthraquinones, alkaloids, saponins, and triterpenes. These results are summarized in Table 1 below.
Table 1Main chemical families in Sclerocarya birrea extract
| Chemical compound families | Existence (scale 1–3) |
|---|
| Alkaloids | 2 |
| Flavonoids | 1 |
| Saponins | 1 |
| Tannins | 3 |
| Triterpenes | 3 |
| Anthraquinones | 2 |
| Steroids | 2 |
| Polyphenols | 3 |
Content of bioactive compounds in S. birrea extract
The bioactive compound assay showed a high polyphenol content of 194.75 ± 0.05 mg EAG/g (gallic acid equivalent per gram) extract, followed by tannins at 6.65 ± 0.30 mg EqCat/g extract. The triterpene content was relatively low, at 1.60 ± 0.29 mg EqLu/g extract.
Anti-free radical activity of S. birrea extract Iron reducing power
The reducing power of the extract increased proportionally with concentration and is expressed in milligrams of ascorbic acid equivalent per gram of dry extract Equivalent antioxidant activity per gram (mg EAA/g dry extract). The results are presented in Table 2.
Table 2Reducing power of extracts
| Extract concentrations (mg/mL) | Reducing power of Vit C (mg AAE/g dry extract) | Reducing power of decoctate (mg AAE/g dry extract) |
|---|
| 0.5 mg/mL | 85,63 ± 0,07 | 69,09 ± 0,17 |
| 0.4 mg/mL | 81,81 ± 0,10 | 54,54 ± 0,25 |
| 0.3 mg/mL | 66,27 ± 0,18 | 44,54 ± 0,30 |
| 0.2 mg/mL | 56,90 ± 0,23 | 40,54 ± 0,32 |
| 0.1 mg/mL | 47,90 ± 0,28 | 34,54 ± 0,36 |
Effects of S. birrea on MSG-induced memory loss in the T-maze test
Effects on latency to enter the first arm
A significant increase (P < 0.001) in latency to enter the first arm (Fig. 1) was observed during all three phases of the T-maze (habituation, acquisition, retention), increasing from 9.4 ± 0.84 s in normal controls to 19 ± 0.74 s in negative controls. S. birrea extract antagonized the effects of MSG, significantly (P < 0.001) reducing latency to 2.8 ± 0.88 s and 4 ± 0.83 s in animals treated with 410 mg/kg and vitamin C, respectively, compared with the negative control during habituation.
During acquisition, latency increased from 7.8 ± 0.72 s (normal controls) to 16 ± 0.72 s (negative controls). Treatment with S. birrea at 410 mg/kg and vitamin C significantly (P < 0.001) decreased this to 2.4 ± 0.88 s and 3.2 ± 0.42 s, respectively.
During retention, latency rose from 5.4 ± 0.88 s (normal controls) to 12.4 ± 0.50 s (negative controls). S. birrea at 205 mg/kg and vitamin C significantly (P < 0.001) reduced latency to 1.8 ± 0.66 s and 2.6 ± 0.44 s, respectively.
Effects on the number of returns to the baseline arm
Daily administration of MSG induced a significant increase (P < 0.001) in the number of returns to the starting arm (Fig. 2), rising from 7.4 ± 0.88 in normal controls to 8.8 ± 0.64 in negative controls. Treatment with S. birrea significantly (P < 0.001) reduced this number to 3.4 ± 0.88 and 4.4 ± 0.88 at 410 mg/kg and with vitamin C, respectively, during habituation.
During acquisition, the number of returns increased from 5.6 ± 0.88 (normal controls) to 9.8 ± 0.64 (negative controls). Treatment with S. birrea (410 mg/kg) and vitamin C significantly (P < 0.001) decreased this to 2.6 ± 0.88 and 3.4 ± 0.88, respectively.
During retention, returns rose from 4.6 ± 0.48 (normal controls) to 10.4 ± 0.48 (negative controls). S. birrea and vitamin C significantly (P < 0.001) lowered returns to 1.8 ± 0.32 and 2.4 ± 0.48, respectively.
Effects on time spent in the preferred arm
Daily MSG administration significantly (P < 0.001) decreased time spent in the preferred arm (Fig. 3), from 117.4 ± 0.64 s in normal controls to 88.2 ± 0.84 s in negative controls. Treatment with S. birrea significantly (P < 0.001) increased this time to 172 ± 0.55 s and 150.4 ± 0.66 s at 410 mg/kg and with vitamin C, respectively, during habituation.
During acquisition, time spent decreased from 78.6 ± 0.72 s (normal controls) to 69 ± 0.32 s (negative controls). S. birrea treatment significantly (P < 0.001) increased this time to 195.4 ± 0.66 s and 159 ± 0.66 s at 410 mg/kg and with vitamin C, respectively.
During retention, time spent decreased from 57.8 ± 0.64 s (normal controls) to 49 ± 0.66 s (negative controls). S. birrea reversed these effects, significantly (P < 0.001) increasing time to 203.6 ± 0.44 s and 186 ± 0.83 s at 410 mg/kg and with vitamin C, respectively.
Effects of S. birrea on MSG-induced neurotoxicity in the Y-labyrinth test
Effects on the number of spontaneous alternations
After 15 days of treatment, Figure 4 shows that MSG significantly (P < 0.001) reduced the number of alternations in the Y-maze from 4.2 ± 0.83 in normal controls to 1.4 ± 0.44 in negative controls. S. birrea extract antagonized this effect by significantly (P < 0.001) increasing the number of alternations at all doses, with optimal values of 7 ± 0.55 and 5.2 ± 0.27 in mice treated with 102.5 mg/kg and vitamin C, respectively, compared to the negative control.
Effects on the percentage of spontaneous alternation
Figure 5 shows the effect of S. birrea extract on the percentage of spontaneous alternation in MSG-treated animals. MSG caused a significant decrease (P < 0.001) in spontaneous alternation percentage, from 12.6 ± 0.66% in normal controls to 4.8 ± 0.27% in negative controls. S. birrea extract significantly (P < 0.001) increased this percentage to peak values of 23.2 ± 0.55% and 13.8 ± 0.27% in animals treated with 410 mg/kg and vitamin C, respectively, compared to the negative control.
Effects on the spontaneous alternation index
Figure 6 shows that daily administration of MSG significantly (P < 0.001) decreased the alternation index from 11.4 ± 0.77 in normal controls to 7.4 ± 0.44 in negative controls. S. birrea extract antagonized this effect by significantly (P < 0.001) increasing the index at all doses, with maximum values of 19.8 ± 0.55 and 12.8 ± 0.55 in animals treated with 410 mg/kg and vitamin C, respectively, compared to the negative control.
Effects on MDA concentration
Table 3 shows that MSG caused a significant increase (P < 0.001) in MDA levels, from 4.65 ± 0.51 µmol/g tissue in normal controls to 10.39 ± 0.21 µmol/g tissue in negative controls. S. birrea extract significantly (P < 0.001) inhibited this increase, reducing MDA concentration to 8.60 ± 0.19 µmol/g tissue at 102.5 mg/kg and 4.97 ± 0.29 µmol/g tissue in the vitamin C-treated group, compared to negative controls.
Table 3Effects of Sclerocarya birrea on oxidative stress markers
| Treatments (mg/kg) |
|---|
| DW + DW | DW + MSG | 102,5 + MSG | 205 + MSG | 410 + MSG | Vit C+ MSG |
|---|
| MDA (mol/g) | 4,65 ± 0,51*** | 10,39 ± 0,21 | 8,60 ± 0,19* | 9,88 ± 0,24* | 10,80 ± 0,17 | 4,97 ± 0,29*** |
| CAT (mol/g) | 13,88 ± 0,34*** | 10,61 ± 0,45 | 14,44 ± 0,92*** | 12,14 ± 0,71** | 11,57 ± 0,50* | 14,52 ± 1,30*** |
| Reduced GSH (mol/g) | 0,06 ± 0,00*** | 0,04 ± 0,00 | 0,05 ± 0,00** | 0,06 ± 0,00*** | 0,03 ± 0,00 | 0,07 ± 0,00*** |
| SOD (SOD/mg) | 5,02 ± 0,69*** | 4,07 ± 0,61 | 5,08 ± 0,34*** | 5,09 ± 0,22*** | 4,86 ± 0,32 | 5,13 ± 0,11*** |
Effects on catalase concentration
Table 3 also shows that MSG significantly (P < 0.001) decreased catalase levels from 13.88 ± 0.34 µmol/g tissue in normal controls to 10.61 ± 0.45 µmol/g tissue in negative controls. Treatment with S. birrea extract significantly (P < 0.001) increased catalase concentration at all doses, with optimal values of 14.44 ± 0.92 and 14.52 ± 1.30 µmol/g tissue in mice treated with 102.5 mg/kg and vitamin C, respectively, compared to negative controls.
Effects on reduced glutathione concentration
MSG significantly (P < 0.001) reduced glutathione levels from 0.06 ± 0.00 µmol/g tissue in normal controls to 0.04 ± 0.00 µmol/g tissue in negative controls. S. birrea extract treatment significantly (P < 0.001) reversed this decrease, raising glutathione concentrations to 0.06 ± 0.00 and 0.07 ± 0.00 µmol/g tissue in animals treated with 205 mg/kg and vitamin C, respectively, compared to negative controls.
Effects on SOD concentration
MSG caused a significant (P < 0.001) reduction in SOD activity, decreasing from 5.02 ± 0.69 U/mg protein in normal controls to 4.07 ± 0.61 U/mg protein in negative controls. Treatment with S. birrea extract significantly (P < 0.001) mitigated this decline at all doses, with peak activities of 5.09 ± 0.22 and 5.13 ± 0.11 U/mg protein in mice treated with 205 mg/kg and vitamin C, respectively, compared to negative controls.
Effects of S. birrea on parameters of the MSG-induced cholinergic transmission system; Effects on AchE concentration
Figure 7 illustrates that MSG caused a significant (P < 0.001) increase in AchE activity, from 0.05 ± 0.03 µM/mg/m in normal controls to 0.11 ± 0.07 µM/mg/m in negative controls. S. birrea extract significantly (P < 0.001) reduced AchE activity, reaching minimum values of 0.06 ± 0.05 and 0.06 ± 0.03 µM/mg/m in animals treated with 410 mg/kg and vitamin C, respectively, compared to negative controls.
Discussion
S. birrea is extensively used in traditional medicine due to its numerous therapeutic properties,24 largely attributed to its rich content of phytochemicals and antioxidants such as alkaloids, flavonoids, tannins, terpenoids, saponins, and phenolic compounds.25 The objective of this study was to evaluate the neuroprotective and antioxidant effects of oral administration of aqueous extracts from S. birrea root bark in a mouse model of oxidative stress and memory impairment induced by MSG.
Our findings confirm that the S. birrea extract contains a substantial amount of phenolic compounds, including polyphenols, tannins, and triterpenes,26 secondary metabolites well recognized for their diverse beneficial effects,26 particularly their antioxidant and neuroprotective properties.27 These compounds are responsible for the radical scavenging activity observed in the FRAP assay, demonstrating the extract’s ability to neutralize free radicals and enhance the enzymatic antioxidant defense system.28
Behaviorally, administration of the extract significantly reversed MSG-induced impairments.29 In the T-maze test, the extract reduced latency and increased the time spent in the preferred arm, indicating improved memory performance along with reduced stress and anxiety,30 which facilitated exploratory behavior. These results align with those reported by Boix et al.,31 who observed similar neuroprotective effects of fisetin on neurodegeneration and memory deficits induced by lipopolysaccharides. Furthermore, in the spontaneous alternation test using the Y-maze, the extract enhanced the number, percentage, and index of alternation, reflecting a significant improvement in short-term memory consistent with the protective effects of wogonin reported by Huang et al.32 in Alzheimer’s disease models. Biochemical analyses revealed that treatment with S. birrea extract mitigated glutamate-induced cerebral oxidative stress, as evidenced by decreased MDA levels and increased concentrations of reduced glutathione, SOD, and catalase. These findings corroborate the work of Lobo et al.,33 highlighting the critical role of antioxidants in protecting against oxidative damage. Given that oxidative stress is a key contributor to Alzheimer’s disease pathogenesis,34 these data suggest a promising neuroprotective potential of S. birrea extract in preventing brain degeneration.35
Additionally, we observed a significant increase in AchE in the brains of glutamate-exposed mice, indicative of cholinergic system dysfunction associated with oxidative stress and cholesterol degradation.36 Treatment with the extract significantly reduced this enzymatic activity, suggesting restoration of cholinergic function and neuroprotection. In summary, S. birrea extract acts as a potent antioxidant and neuroprotective agent capable of attenuating cognitive deficits and oxidative stress induced by glutamate. These results support its traditional use and open avenues for its development as a complementary therapy for neurodegenerative disorders.37
However, despite these promising findings, several limitations must be acknowledged for a rigorous interpretation of the extract’s effects. The MSG-induced neurotoxicity model only partially replicates the complex mechanisms underlying human neurodegenerative diseases.38 The behavioral tests employed (T-maze and Y-maze) primarily assess spatial memory and exploratory behavior but do not encompass the full spectrum of cognitive or emotional functions. The biochemical markers measured (MDA, glutathione, SOD, catalase, AchE) provide insight into oxidative stress and neuroprotection but do not address other relevant mechanisms such as inflammation, apoptosis, or neurotransmission. Furthermore, variability in administered doses of both neurotoxic agents and therapeutic compounds may compromise the reproducibility and stability of the results obtained in vivo. In addition, the precise molecular mechanisms underlying the observed effects remain only partially elucidated, requiring further research, particularly through the use of transgenic animal models dedicated to neurodegenerative diseases. Finally, the study compares S. birrea extract only to vitamin C as a positive control; the absence of comparison with other established neuroprotective agents or reference drugs limits the relative assessment of its efficacy.39,40 In summary, although S. birrea extract demonstrates noteworthy antioxidant and neuroprotective potential in this animal model, further studies are warranted to confirm these effects, elucidate underlying mechanisms, evaluate long-term safety, and explore clinical applicability in humans.
Future directions
Regarding future avenues, it would be relevant to further utilize transgenic animal models to deepen our understanding of the molecular pathways involved and better target the pharmacological potential of S. birrea in various neurodegenerative diseases. Furthermore, it is important to analyze the stability, consistency, and reproducibility of the observed effects in order to standardize its therapeutic use. Finally, confirming clinical efficacy, clarifying mechanisms of action, and exploring the integration of this extract into innovative therapeutic strategies represent key steps before any practical medical application.
Conclusions
This study highlights the significant potential of S. aqueous extract as a neuroprotective and antioxidant agent. Its effects effectively counteract neurotoxicity, oxidative stress, and behavioral alterations induced by MSG. These results provide a scientific basis for the traditional use of S. birrea in the prevention and treatment of cognitive deficits, thus confirming its promising therapeutic value.
Declarations
Acknowledgement
We express our deep gratitude to all the individuals and institutions who contributed to this study. We particularly thank the Ethics Committee of the University of Ngaoundere for its supervision, as well as the departments and colleagues for their technical and scientific support. We also extend our sincere thanks to the organizations and professionals for their valuable resources and advice.
Ethical statement
The in vivo experimental protocols were fully reviewed and approved by the Animal Experimentation Ethics Committee of the University of Ngaoundéré. All animal experimental procedures strictly adhere to current national and international recommendations, including guidelines issued by the Ministry of Research, to ensure the protection, welfare, and dignity of animals used for scientific purposes. We implement rigorous measures to minimize pain, suffering, and stress in animals, fully applying the 3Rs (Replacement, Reduction, Refinement) to minimize the number of animals used while optimizing the quality of care provided.
Data sharing statement
The data supporting the findings of this study are available from the corresponding author upon reasonable request.
Funding
This work did not receive any funding.
Conflict of interest
The authors declare no conflict of interest.
Authors’ contributions
Study design (RN, AHM), manuscript drafting, data analysis, and interpretation (RN, AHM, ENB), and supervision and guidance to ensure that the manuscript met quality standards (ENB). All authors listed made valuable contributions to the manuscript design, data collection, analysis, and interpretation. All authors reviewed the final version of the manuscript and approved it for publication. Each author was sufficiently involved in the work to assume overall responsibility for appropriate portions of its content.