Effects of Laurus extract against cadmium-induced neurotoxicity in rats

1 Introduction

Cadmium is a heavy metal that the body does not need and is known to be toxic to humans (Genchi et al., 2020). It is currently considered the seventh most hazardous chemical for human health, based on its toxicity and the frequency of human exposure (ATSDR, 2022). In addition to workplace exposure, people can come into contact with cadmium through food, cigarette smoke, and polluted air. Cadmium accumulates in the human body, particularly in the kidneys and liver, and has a half-life of 25–30 years because it is not easily excreted. This metal can enter cells by mimicking zinc, utilizing zinc transporters and calcium channels in a process referred to as the “Trojan horse” mechanism (Thévenod et al., 2019; MGenchi et al., 2020). Once inside, cadmium can replace zinc, iron, and copper in many proteins, causing oxidative stress, DNA damage, endoplasmic reticulum (ER) stress, mitochondrial dysfunction, and autophagy (Ma et al., 2022).

Cadmium has been identified as neurotoxic, as reported by Wang and Matsushita (2021) and Ruczaj and Brzóska (2023). This heavy metal has been found to accumulate in different brain regions, particularly in the locus ceruleus neurons of individuals with various clinicopathological conditions and causes of death (Pamphlett et al., 2018). Environmental exposure to cadmium is suggested to damage the nervous system and contribute to neurodegenerative diseases like Alzheimer's, Parkinson's, and amyotrophic lateral sclerosis (Ruczaj and Brzóska, 2023). Studies have also shown that cadmium can induce apoptosis in motor neurons from human embryonic spinal cord explants (Sarchielli et al., 2012) and in the olfactory bulbs of animals exposed through diet or inhalation (Sunderman, 2001). Also, Recent studies reveal that cadmium exposure can impair cognitive function (Sasaki and Carpenter, 2022; Deng et al., 2023).

Medicinal plants and commercially produced natural products have a significant and extensive impact in mitigating the adverse consequences resulting from exposure to environmental contaminants, medicinal plants like Laurus have gained attention for their therapeutic potential (Almeer et al., 2019). Known for its antioxidant properties (Vardapetyan et al., 2013), Laurus has been extensively studied for its ability to alleviate oxidative disorders related to stress, attributed to its rich phenolic and flavonoid content (Hassan et al., 2019). Laurus nobilis L., commonly referred to as laurel, is not only a popular culinary herb for its flavor and aroma but is also recognized for its medicinal benefits, including its effectiveness in treating diseases, nerve pain, and intestinal spasms (Chaudhry and Tariq, 2006). Laurel leaf extract has also shown potential in preventing neurotoxicity induced by lead exposure (Gazwi et al., 2020).

This study aimed to explore the therapeutic efficacy of Laurus in counteracting adverse brain effects induced by Cd.

2 Materials and methods

3 Results

3.2

3.2 GC–MS analysis

The GC–MS analysis of the Laurus ethanol extract revealed various compounds, as detailed in Table 2 and Fig. 1. Notable among these compounds is Hexadecanoic acid, methyl ester (methyl palmitate), an organic compound. Additionally, (Z)-13-Docosenamide was found which a long-chain fatty acid amide found in plants, insects, and mammals, Also other significant compounds found in the Laurus extract include Santamarine and Reynosin, sesquiterpene lactones.

Table 2 The major phytocomponents present of ethanolic leaves extract of Laurus using GC–MS analysis.

NO	RT	Compound Name	MF	MW	Area %
1	48.30	Hexadecanoic acid, methyl ester	C17H34O2	270	11.8
2	48.89	Azuleno(4,5-b)furan-2(3H)-one decahydro-3,6,9-tris(methylene)-, (3aS-(3aà,6aà,9aà,9bá))-	C15H18O2	230	3.68
3	54.31	Santamarine	C15H20O3	248	2.83
4	54.68	Octadecanoic acid, methyl ester	C19H38O2	298	9.93
5	55.21	Reynosin	C15H20O3	248	4.12
6	58.84	2-(3-Hydroxy-2-nitro-1-phenyl butyl)cyclohexanone	C14H17NO3	247	1.27
7	73.37	13-Docosenamide, (Z)-	C22H43NO	337	10.71
8	74.64	Tris(2,4-di-tert-butylphenyl)Phosphate	C42H63O4P	663	1.19
9	75.45	silane, trimethyl(((3á)-stigma st-5-en-3-yl)oxy)-	C32H58OSi	487	1.10
10	77.63	9,12-octadecadienoic acid (z,z)-,2,3-bis((trimethylsilyl) oxy)propyl ester	C27H54O4Si2	499	1.01
11	81.45	Vitamin E	C29H50O2	431	1.42

RT: Retention Time MF: Molecular Formula MW: Molecule Weight.

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Fig. 1

GC–MS chromatogram of compounds identified in Laurus extract.

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3.3

3.3 HPLC analysis

The analysis of the sample revealed the presence of various phenolic compounds, emphasizing their potential as bioactive agents with significant pharmaceutical and therapeutic applications. Fig. 2 and Table 3 shows the High-Performance Liquid Chromatography (HPLC) chromatogram, which highlights the detection of several phenolic compounds in the sample. The analysis indicated that phenantherine was the most abundant, with a concentration of 18.2 µg/g. Other identified phenolic compounds include Coumaric (4.4 µg/g), ellagic acid (3.0 µg/g), resorcinol (1.5 µg/g), chlorogenic acid (0.6 µg/g), Cinnamic (0.5 µg/g), vanillic acid (0.3 µg/g), ferulic acid (0.1 µg/g), and Pyrochatechol (0.1 µg/g), as illustrated in Fig. 2 and Table 3.

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Fig. 2

HPLC chromatogram of phenolic compounds identified in ethanol extract of Laurus.

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Table 3 Chemical composition analysis of phenolic and flavonoid compounds of ethanol extract from Laurus by HPLC.

Components	RT (min)	Conc (µg/g)
Phenolic Compounds
Ellagic	3.253	3
Cinnamic	3.483	0.5
Chlorogenic	4.310	0.6
Resorcinol	5.407	1.5
Pyrochatechol	8.407	0.1
Vanillic	10.820	0.3
Ferulic	11.197	0.1
Phenantherine	14.500	18.2
Coumaric	16.207	4.4
Flavonoids Compounds
Apiginin	4.6	0.1274
Rutin	5.2	58.6617
Hesperidin	8.1	15.5859
Kaempferol	9.0	135.8448
Quercetin	10.0	38.0600

The flavonoid profile of the sample was comprehensively analyzed, revealing the presence of several key flavonoid compounds. The analysis identified kaempferol as the most abundant flavonoid, with a concentration of 135.84 µg/g. Other detected flavonoids include rutin (58.66 µg/g), quercetin (38.06 µg/g), hesperidin (15.58 µg/g), and apigenin (0.1274 µg/g), as detailed in Table 3 and Fig. 3. These flavonoids are known for their antioxidant properties and contribute significantly to the therapeutic potential of the sample, supporting its use in various health-related applications.

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Fig. 3

HPLC chromatogram of flavonoid compounds identified in Laurus extract.

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3.9

3.9 Histopathological examination of brain

Microscopically, the control group rats showed a typical histological structure (cerebral cortex). Also, the Laurus group's rat brain did not show any histopathological changes Conversely, tissue sections from the Cd-exposed group exhibited neuronal necrosis (arrow), focal gliosis, and neuronophagia. Pre-treatment with Laurus significantly ameliorated the cortical abnormalities induced by Cd exposure (arrow) (Fig. 4 and Table 9).

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Fig. 4

Brain photomicrograph (cerebral cortex) for Control and treated groups (H & EX 400, Scale bar 50 µm).

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Table 9 The severity of histological changes in brain (cerebral cortex).

Histopathological lesion	Control	Laurus	Cadmium	Cadmium + Laurus
Necrosis of neurons	−	−	+++	+
Neuronophagia	−	−	++	+
Focal gliosis	−	−	++	−

(−) no change (+) mild change (++) moderate change (+++) severe change.

3.10

3.10 Insilco analysis

3.10.1

3.10.1 SOD model analysis and Validation

SOD shows a strong molecular structure with a resolution of 2.05 Å, SOD was selected for further analysis by X-ray diffraction. The high resolution allows for accurate identification of the molecular structure by allowing an exhaustive and precise analysis of its many complexities. The strong correlation of the improved model (R values) with the experimental data provides additional evidence of the accuracy of the structure. The results demonstrate a high level of precision and reliability, as shown by the R values for work (0.192), free (0.236), and observed (0.194). Once the molecular composition is identified, it provides a solid foundation for future research. The selected SOD model, which had a C-score of 0.30, was uploaded to the iMod server and displayed in four unique modes, as seen in Fig. 5. The selected model has a high degree of structural stability, as shown favorable C-score and normal Z-score. Secondary structure representation often shows a helical appearance, highlighting possible binding locations and functional regions.

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Fig. 5

SOD model different modes for rotation about verification of high degree of structural stability.

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3.10.2

3.10.2 Docking study

Binding affinities with good binding energies were obtained after coupling the ligands kaempferol and rutin to superoxide dismutase a2 (SOD) with the energies being − 8.1 kcal/mol and − 8.7 kcal/mol, respectively. Illustrations of the interactions observed after modeling kaempferol in the binding site of SOD, as seen in Fig. 6(A) shows that the key residues involved in this interaction are VAL5, CYS6, VAL7, LEU8, LYS9, GLY10, ASP11, ASN53, GLY56, CYS57, CYS146, GLY147, VAL148 and ILE149. In Fig. 5(B) and Fig. 5(C), the key residues interacting with rutin are CYS6, VAL7, LEU8, LYS9, GLY10, ASP11, GLY12, PRO13, VAL14, GLN15, ASN53, THR54, ALA55, GLY56, CYS57, ALA145, CYS146, GLY147 and VAL148. Fig. 6(B) also shows the key residues interacting with F chain residues in SOD indicated as CYS6, VAL7, LEU8, LYS9, GLY10, ASP11, GLY12, and GLN15. These interactions reveal a promising prospective therapy to be gained from utilizing rutin, kaempferol, and drugs containing any or both of these bioactive agents.

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Fig. 6

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A docking study proves that rutin possesses the most negative interaction energy with superoxide dismutase (SOD) among the three chemicals. Rutin’s binding energy is 8.7 kcal/mol, whereas kaempferol’s binding energy is only –8.1 kcal/mol per mole. There is more interaction between rutin and the active site of SOD than between kaempferol and its active site. Exchangeable Hydrogens on SOD are more involved with rutin. More residues are interacting with rutin, and act in additional interaction with residues on the F chain. In-silico studies provide evidence that rutin is a superior chemical compared to both kaempferol and ascorbic acid in terms of its ability to modify SOD’s activity (overall negative binding energy). Nevertheless, some of these findings have yet to be investigated in the laboratory, or taken up to the in vivo level for convincing and persuasion.

3.10.3

3.10.3 PyLip interactions

PyLip Interactions within a protein structure, including metal complexes, hydrogen bonds, and water bridges. several observations were made regarding the interactions of kaempferol, rutin, or their interactions with Superoxide Dismutase A2 (SOD) within the protein structure, particularly focusing on metal complexes, hydrogen bonds, and water bridges as mentioned in the Supplementary File (S1). The results detail provided encompasses analyses of metal complexes, hydrogen bonds, and water bridges within a protein structure as shown in Fig. 7. In the metal complexes section, two distinct complexes are examined: one involving copper (Cu) in a trigonal planar coordination environment, and the other involving zinc (Zn) in a trigonal bipyramidal coordination geometry. For the Cu complex, residues HIS 46A, HIS 48A, and HIS 120A are coordinated with distances of approximately 1.99 to 2.02 Å from the metal ion. Similarly, for the Zn complex, residues HIS 63A, HIS 71A, HIS 80A, ASP 83A (twice), and ASP 83A (again, twice) coordinate with distances ranging from approximately 1.92 to 2.85 Å.

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Fig. 7

Interaction of SOD with Kaempferol and Rutin.

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Hydrogen bonds, and interactions are noted between various residues and surrounding atoms. For example, THR 137A forms a hydrogen bond with a distance of approximately 2.50 Å to the donor atom and 2.87 Å to the acceptor atom, with a donor angle of around 102.56 degrees. Similar interactions are observed for GLY 141A, THR 58A, and ARG 143A. Lastly, water bridges are identified, indicating interactions between protein residues and water molecules. These bridges involve residues like THR 58A, ARG 143A, ASN 139F, GLY 141F, and SER 142F, with distances ranging from approximately 2.71 to 4.09 Å between the donor and water, and donor angles varying from around 101.61 to 158.84 degrees. These findings collectively provide insight into the structural features and interactions within the protein system under investigation

3.10.4

3.10.4 Comparative analysis of Solubility, Lipophilicity, and drug Likeness of Kaempferol and rutin

Solubility curves, lipophilicity parameters and chemical similarity analyzes of kaempferol and rutin show significant differences in their physicochemical and pharmacokinetic properties. The solubility curve according to Table 10 (A) shows that the Log S (ESOL) value of kaempferol is −3.31, indicating a solubility of 1.40e-01 mg/ml (4.90e-04 mol/l), which is classified as as: easily soluble. In contrast, rutin has a similar Log S value (ESOL) of −3.30 and a solubility of 3.08e-01 mg/ml (5.05e-04 mol/l), also classified as soluble. However, other solubility tests such as Log S (Ali) and Log S (SILICOS-IT) show that routine is slightly more soluble than Log S (SILICOS-IT). High resolution varies depending on the method used.:1.70, XLOGP3: 1.90, WLOGP: 2.28, MLOGP: −0.03, SILICOS-IT: 2.03), resulting in a consistent log Po/w of 1.58. This shows that the lipophilic environment is suitable for drug-like products. On the other hand, the negative log Po/w for the routine is −1.29, and all values vary significantly (iLOGP: 1.58, XLOGP3: −0.33, WLOGP: −1.69, MLOGP: −3.89, SILICOS- IT: − 2.11) will affect its permeability and absorption, reflecting its low lipophilicity.

Table 10 Solubility Profile, Lipophilicity Parameters Analysis, and Drug Likeness Assessment of Kaempferol.

Table 2 (A)	Solubility profile
Compounds	Kaempferol	Rutin
Log S (ESOL)	−3.31	−3.30
Solubility	1.40e-01 mg/ml; 4.90e-04 mol/l	3.08e-01 mg/ml; 5.05e-04 mol/l
Class	Soluble	Soluble
Log S (Ali)	−3.86	−4.87
Solubility	3.98e-02 mg/ml; 1.39e-04 mol/l	8.30e-03 mg/ml; 1.36e-05 mol/l
Class	Soluble	Moderately soluble
Log S (SILICOS-IT)	−3.82	−0.29
Solubility	4.29e-02 mg/ml; 1.50e-04 mol/l	3.15e + 02 mg/ml; 5.15e-01 mol/l
Class	Soluble	Soluble
Log S (ESOL)	−3.31	−3.30
Table 2(B)	Lipophilicity Parameters Analysis
Compounds	Kaempferol	Rutin
Log Po/w (iLOGP)	1.70	1.58
Log Po/w (XLOGP3)	1.90	−0.33
Log Po/w (WLOGP)	2.28	−1.69
Log Po/w (MLOGP)	−0.03	−3.89
Log Po/w (SILICOS-IT)	2.03	−2.11
Consensus Log Po/w	1.58	−1.29
Log Po/w (iLOGP)	1.70	1.58
Table 2(C)	Drug Likeness Assessment
Compounds	Kaempferol	Rutin
Lipinski	Yes; 0 violation	No; 3 violations: MW > 500, NorO > 10, NHorOH > 5
Ghose	Yes	No; 4 violations: MW > 480, WLOGP < -0.4, MR > 130, #atoms > 70
Veber	Yes	No; 1 violation: TPSA > 140
Egan	Yes	No; 1 violation: TPSA > 131.6
Muegge	Yes	No; 4 violations: MW > 600, TPSA > 150, H-acc > 10, H-don > 5
Bioavailability Score	0.55	0.17
PAINS	0 alert	1 alert: catechol_A
Brenk	0 alert	1 alert: catechol
Leadlikeness	Yes	No; 1 violation: MW > 350
Synthetic accessibility	3.14	6.52

Muegge law, no violation, bioavailability score 0.55. It also showed no warnings in the PAINS or Brenk test and was considered a leader with a combined range of 3.14. In contrast, rutin is incompatible with many similar chemicals, including Lipinski (three violations: molecular weight > 500, number of oxygen or nitrogen atoms > 10, number of hydrogen allocations > 5), Ghose (four violations: molecular weight > 480).), WLOGP < -0.4, molar refractive index > 130, atomic number > 70), Veber (one violation: topological polar surface > 140), Egan (one violation: TPSA > 131.6), and Muegge (four violations: Molecular weight) > 600, TPSA > 150, hydrogen bond acceptor > 10, hydrogen bond donor > 5). Rutin has a lower bioavailability score of 0.17; this stimulates all PAINS and Brenk tests due to its molecular weight of > 350, unlike lead, and a higher rating of 6.52 from electronic products, indicating that it is more difficult to synthesize. Although Rutin has a high solubility in some substances, it faces significant problems due to its poor lipophilicity, interference with many similar drugs, and lack of bioavailability, which may limit its ability as a drug candidate.

3.10.5

3.10.5 Simulation analysis

The selected model allows a comprehensive examination of the molecular structure. The deformability values of the residues tend to increase with higher atomic numbers, as shown by the positive correlation observed in the plot of deformability and atomic index (Fig. 8A). The protein structure exhibits a remarkable level of flexibility, as evidenced by the range of deformability values, which range between 0.2 and 0.5. The self-analysis findings reveal that the protein structure exhibits a significant degree of flexibility, as demonstrated by the relatively high deformability scores. A closer analysis of the protein sequence reveals that areas exhibiting substantial sequence variability align with regions characterized by high deformability. This suggests that the protein could be undergoing conformational alterations to adapt to different binding partners. Residues with higher atomic numbers often exhibit higher B-factor values, as seen by the positive correlation observed between these two parameters in the plot of B-factor and atomic index (Fig. 8B).

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Fig. 8

A represents the model detail of Eigenvalues, B Variance, C Covariance Map and D shows Elastic Network.

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The B factor values, ranging from 0 to 1, represent the level of thermal mobility or flexibility of the protein structure. The range of the MNA B factor, illustrated above, spans from 0.6 to 1, indicating a notable level of flexibility in this specific region. The PDB B factor ranges from 0.2 to 0.6, indicating a notable degree of flexibility in this region. According to a self-analysis, The protein structure reveals that areas with high crystallographic temperature factors correspond to regions with high B factors. This suggests that the protein may be undergoing thermal motion to facilitate binding or catalysis. Fig. 8 (C) shows the eigenvalues of −2.492433e-04, which represent the energy required to modify the level of stiffness and structure.

A lower eigenvalue means a lower degree of complex deformation. Deformation requires a specific amount of energy expenditure because the stiffness constant of the structure is 0.024. Fig. 8(D) shows the variance associated with each normal mode, ranging from 0.01 to 0.1. Individual (red) and cumulative (green) fluctuations combine to form a total variance of 0.5, indicating the level of adaptability and diversity of the structure. Fig. 8 (E) presents a covariance map with a correlation coefficient of 0.7. The map represents the correlation between pairs of residuals, with values ranging between −0.5 and 0.5. The data displayed exhibits a positive correlation (red), no correlation (white), or a negative correlation (blue). Fig. 8 (F) shows the elastic network paradigm, which defines the relationships between atoms using springs. The model provides a deep understanding of structural dynamics, stiffness, flexibility, and their relationships, with an average spring constant of 0.5. The stiffness of the points determines their tone. Points with higher grayscale values have stiffness values ranging from 0.1 to 1, while points with lighter grayscale values have stiffness values ranging from 0.01 to 0.1.

4 Discussion

The results of this study highlight the Laurus extract's strong capability to neutralize ABTS radicals, pointing to its potential in treating diseases related to free radicals. This aligns with the findings of Guenane et al. (2016), who also reported significant antioxidant activity of Laurus assessed by ABTS. Also the FRAP assay, assessing antioxidant reduction capacity, involves the interaction with ferric tripyridyltriazine (Fe3 −TPTZ) forming ferrous tripyridyltriazine (Fe2 −TPTZ) (Benzie and Strain 1996). The reduction properties are typically associated with hydrogen atom donors, disrupting free radical chains (Duh et al., 1999). These findings suggest that Laurus leaf extract's antioxidant properties could be effective in preventing diseases caused by free radicals, like those induced by cadmium toxicity in tissues such as the brain.

In this study The GC–MS analysis of the Laurus ethanol extract revealed various compounds, among these compounds is Hexadecanoic acid, methyl ester (methyl palmitate), an organic compound known for its antimicrobial, anticancer, anti-inflammatory, and insecticidal activities (Mohamed et al., 2021). Additionally, (Z)-13-Docosenamide, a long-chain fatty acid amide found in plants, insects, and mammals, has been researched for its biological activities and potential applications (Banc et al., 2023). This compound is noted for its anti-inflammatory properties, inhibiting pro-inflammatory molecules production, and has been suggested to have neuroprotective effects, potentially protecting neurons from damage due to oxidative stress and inflammation (Yang et al., 2021). Several studies have proposed potential neuroprotective effects of (Z)-13-Docosenamide. It is believed to shield neurons from damage induced by oxidative stress, inflammation, and other harmful factors, thereby potentially safeguarding neuronal health (Lee et al., 2020). Other compounds in the Laurus extract include Santamarine and Reynosin, sesquiterpene lactones with biological activities like anti-allergenic, anti-inflammatory, antispasmodic, and cytotoxic properties (Tucker and Debaggio, 2000; Harborne and H. Baxter et al., 1983; Duke,1992).

Several studies have highlighted the substantial influence of various flavonoids and other phenolic compounds on immune system function and inflammatory processes (Middleton and Kandaswami, 1992; Locatelli et al., 2018). The flavonoids quercetin, apigenin, and hesperidin have been identified as having possible anti-inflammatory properties (Pham-Huy et al., 2008). Quercetin, a member of the flavonol class, has been documented as a noteworthy substance with potential anticancer properties, particularly in relation to prostate and breast cancers (Pham-Huy et al., 2008; Brusselmans et al., 2005).

These findings highlight the crucial role that Laurus leaf extract, with its rich content of phenolic and flavonoid compounds, may play in health and disease management. The anti-inflammatory and potential anticancer properties of these compounds could be particularly beneficial in combating diseases associated with oxidative stress and inflammation, such as those induced by cadmium exposure.

In biological experiment results reported that Cd exposure led to a notable reduction in body weight gain and brain weight (p < 0.05) compared to the control group. This finding aligns with previous research on body weight and organ weights (Nnaa et al., 2017). Rahman et al. (1998) reported a direct association between long-term Cd exposure and an increased risk of type 2 diabetes, leading to weight loss in rats. Also, heavy metal exposure deteriorates the glucocorticoid system, correlated with weight gain/loss (Kaltreider et al. 2001). Most recent phytochemical studies reported phenolics, flavonoids, alkaloids, and numerous other biological activities in Laurus (Gazwi et al., 2020). These components support Laurus as natural antioxidant therapy of diseases caused by oxidative stress. The nutritional and calorific properties of Laurus may result in this improvement in weight (Shaba et al. 2015).

Donmez et al. (2019) and El-Boshy et al. (2015), who reported similar decreases in hematological parameters due to Cd toxicity. Cd exposure can lead to anemia by accumulating toxic metals in the kidney, spleen, and liver, causing peripheral RBC deformities and hemolysis (Kunimoto et al., 1985). Cd also adversely affects intestinal iron absorption, contributing to anemia.

This immune response alteration could result from diminished antioxidant activity and increased free radicals due to Cd exposure, as well as suppression of non-specific and systemic inflammation (Fahim et al. 2012).

On the other hand, Laurus treatment ameliorated these hematological alterations, showing protective effects against RBC degradation caused by Cd (Nazima et al. 2016). Laurus seems to exert a protective influence on the hematopoietic system, as evidenced by improvements in some hematological parameters and lymphocyte concentrations compared to the Cd group.

These results demonstrate the adverse effects of Cd on body weight, brain weight, and hematological parameters, while also highlighting the potential protective role of Laurus extract in mitigating these effects. This suggests the efficacy of Laurus as a therapeutic agent in conditions involving oxidative stress and toxicity. The results in this study are consistent with findings by Abu Al-Dhahab et al. (2019) and Prabu et al. (2012), who observed similar increases in ALT, AST, bilirubin, and ALP in Cd-treated mice. Altered renal enzyme levels reflect Cd-induced renal damage as noted by Bekheet et al. (2011). In another hand In contrast, Laurus extract was administered alongside cadmium, showed noticeable reductions or mitigations in these biomarker levels. This suggests a protective effect against oxidative stress and potential hepatorenal toxicity induced by cadmium exposure. These results highlight the potential therapeutic role of Laurus extract in ameliorating cadmium-induced oxidative stress in biological systems.

Antioxidants, known for their scavenging activity and ability to modulate antioxidant enzyme systems, are proposed to mitigate Cd-induced oxidative damage. Cd-induced reactive oxygen species (ROS) overproduction depletes both enzymatic (SOD and CAT) and non-enzymatic (GSH) antioxidants, disrupting antioxidant defenses (Li et al., 2017; Al Olayan et al., 2020; Al-Quraishy, 2020). Antioxidants protect against oxidative damage, but Cd exposure disrupts their activities, leading to immune imbalance (Seif et al., 2019 and Ishtiaq et al., 2022).

Notably, Laurus ameliorated oxidative damage caused by Cd in brain tissue, as evidenced by reduced MDA levels and increased antioxidant proteins. These findings align with Gazwi et al. (2020), who reported the efficacy of Laurus as an antioxidant in rats exposed to heavy metals. Phytochemical analysis via GC–MS identified 13-Docosenamide (Z)-, also known as erucamide, as a major component in the extract. Erucamide is a long-chain unsaturated fatty acid amide known for its antinociceptive and anti-inflammatory properties [Shareef et al., 2016]. Additionally, hexadecanoic acid, methyl ester, another significant component of the extract, has been shown to possess neuroprotective qualities in rats by modulating cerebral blood flow [Lee et al., 2019]. Thus, the observed biological effects can be attributed to these key phytochemicals, which contribute to the antioxidant and neuroprotective properties of Laurus extract.

The reduction in AChE activity observed in our study is indicative of brain dysfunction, This finding aligns with the results of Al Olayan et al. (2020). Under oxidative stress, AChE activity diminishes, leading to the accumulation of ACh in the central nervous system (CNS). This buildup can result in increased neuronal excitability, manifesting as cholinergic hyperactivity, and potentially leading to epilepsy-like behavior and seizures (Tsakiris et al., 2000).Previous studies, such as those by Al Omairi et al. (2018), have demonstrated that Cd-induced changes in neurochemical transmission can lead to impaired brain function. as AChE plays a critical role in breaking down acetylcholine (ACh) in synapses into acetic acid and choline. This suggests that Laurus extract mitigates the toxic effects of Cd on AChE activity. Supporting this, Gazwi et al. (2020) found that polyphenols, known for their antioxidant properties, exhibit strong anti-AChE inhibitory activity (Dizdar et al., 2018). Histopathology examination of brain in this study are consistent with the observations of Al Olayan et al. (2020). Kaoud and Mekawy (2011) which appeared that there was necrosis of neurons in the Microphotograph of the brain in the cadmium group. The dangerous changes in the nerve cells are due to ROS's presence (Kuhad and Chopra, 2007). The protective effects of the Laurus extract are likely due to its antioxidant compounds that inhibit free radical formation and reduce their detrimental impact on neural tissue (Gazwi et al., 2020). Al Olayan et al. (2020) have suggested that antioxidants targeting neurotrophic factors could play a crucial role in safeguarding nervous tissue against Cd toxicity.

5 Conclusion

In conclusion, this study elucidates the detrimental effects of Cd exposure on neurological health and underscores the therapeutic efficacy of Laurus nobilis L. in mitigating Cd-induced neurotoxicity. The neuroprotective effects of Laurus extract are attributed to its antioxidant constituents, which scavenge free radicals, inhibit oxidative stress, and preserve neuronal integrity. The findings provide valuable insights into the use of Laurus as a potential therapeutic agent against heavy metal toxicity-induced neurodegenerative disorders. In-slico analysis shows that High resolution 2.05x structural analysis and identification of superoxide dismutase (SOD) were shown to be supported by positive R values (active: 0.192, free: 0.236, apparent: 0.194) and a C value of the molecular structure final 0.30. Docking studies showed that kaempferol (−8.1 kcal/mol) and rutin (−8.7 kcal/mol) have a strong affinity for SOD and key residues such as VAL5, CYS6, and ASP11 are involved in the interaction. Comparative analysis shows that kaempferol has a solubility of 1.40e-01 mg/ml, high lipophilicity (Log Po/w 1.58), and has no violations in drug-like tests and its bioavailability is better than routine when the routine faces many violations. Low simulation analysis showed protein variation indicated by strain values (0.2–0.5) B factor ranges (0–1) and eigenvalues (−2.492433e-04), indicating the adaptability of the protein and the potential for future research. This comprehensive review confirms the reliability and therapeutic potential of SOD, especially kaempferol, as a promising drug candidate. Further research is warranted to elucidate the underlying mechanisms and optimize dosage regimens for clinical applications.

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Not applicable.

Authors contribution

Hanaa M. Hassan, Hanaa S.S Gazwi , and Eman E. Yassien conceived the project. Hanaa M. Hassan, Hanaa S.S Gazwi, Asmaa Hussein Zaki, and Eman E. Yassien designed and per-formed the experiments. Hanaa M. Hassan, Hanaa S.S Gazwi , Asmaa Hussein Zaki, and Eman E. Yassien analyzed the data. Hanaa S.S Gazwi , Hanaa M. Hassan, Asmaa Hussein Zaki, Marija Milošević, Salim S. Al-Rejaie, Mohamed Mohany and Eman E. Yassien wrote the manuscript. Hanaa S.S Gazwi, Hanaa M. Hassan, Asmaa Hussein Zaki, Marija Milošević, Salim S. Al-Rejaie, Mohamed Mohany , and Eman E. Yassien provided critical discussion, editing, and final approval of the manuscript. All authors contributed to the preparation of the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

This work was funded by the Researchers Supporting Project (RSPD2024R758), King Saud University, Riyadh, Saudi Arabia.

CRediT authorship contribution statement

Hanaa M. Hassan: Writing – review & editing, Writing – original draft, Supervision, Resources, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization. Hanaa S.S. Gazwi: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Software, Resources, Project administration, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. Inas Hussein Refaat: Writing – review & editing, Writing – original draft, Project administration, Methodology. Asmaa Hussein Zaki: . Marija Milošević: Writing – review & editing, Writing – original draft, Visualization, Project administration, Methodology, Investigation, Data curation. Salim S. Al-Rejaie: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Resources, Project administration, Investigation, Funding acquisition, Formal analysis, Data curation. Mohamed Mohany: Writing – review & editing, Writing – original draft, Software, Methodology, Investigation, Data curation. Eman E. Yassien: Writing – review & editing, Writing – original draft, Formal analysis, Data curation, Conceptualization.