Elsevier

Journal of Ethnopharmacology

Volume 137, Issue 1, 1 September 2011, Pages 585-591
Journal of Ethnopharmacology

Neuroprotective effect of the methanolic extract of Hibiscus asper leaves in 6-hydroxydopamine-lesioned rat model of Parkinson's disease

https://doi.org/10.1016/j.jep.2011.06.008Get rights and content

Abstract

Ethnopharmacological relevance

While the Hibiscus asper Hook.f. (Malvaceae) is a traditional herb largely used in tropical region of the Africa as vegetable, potent sedative, tonic and restorative, anti-inflammatory and antidepressive drug, there is very little scientific data concerning the efficacy of this.

Materials and methods

The antioxidant and antiapoptotic activities of the methanolic extract of Hibiscus asper leaves (50 and 100 mg/kg) were assessed using superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT) specific activities, total glutathione (GSH) content, malondialdehyde (MDA) level (lipid peroxidation) and DNA fragmentation assays in male Wistar rats subjected to unilateral 6-hydroxydopamine (6-OHDA)-lesion.

Results

In 6-OHDA-lesioned rats, methanolic extract of Hibiscus asper leaves showed potent antioxidant and antiapoptotic activities. Chronic administration of the methanolic extract (50 and 100 mg/kg, i.p., daily, for 7 days) significantly increased antioxidant enzyme activities (SOD, GPX and CAT), total GSH content and reduced lipid peroxidation (MDA level) in rat temporal lobe homogenates, suggesting antioxidant activity. Also, DNA cleavage patterns were absent in the 6-OHDA-lesioned rats treated with methanolic extract of Hibiscus asper leaves, suggesting antiapoptotic activity.

Conclusions

Taken together, our results suggest that the methanolic extract of Hibiscus asper leaves possesses neuroprotective activity against 6-OHDA-induced toxicity through antioxidant and antiapoptotic activities in Parkinson's disease model.

Graphical abstract

The methanolic extract of Hibiscus asper leaves showed significant antioxidant and antiapoptotic activities at the doses of 50 mg/kg and 100 mg/kg in 6-OHDA-lesion rat model of Parkinson's disease.

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Introduction

Parkinson's disease (PD) is a progressive neurodegenerative disorder with unknown etiology. Its neuropathology includes the degeneration of dopaminergic nigrostriatal pathway, which is a cumulative effect of glutathione depletion, iron deposition, increased lipid peroxidation, oxidative DNA damage, mitochondrial dysfunction, excitotoxicity and alterations in antioxidant enzymes activities (Gerlach et al., 2003, Chaturvedi et al., 2006, Hritcu et al., 2008, Zhou et al., 2008, Ciobica et al., 2009).

Although the etiology of the neurodegenerative processes found in PD is not completely understood, it is suggested that a state of oxidative imbalance is triggered by one or more factors, among which are brain aging, genetic predisposition, mitochondrial dysfunction, free radical production and environmental toxins (Fukae et al., 2007, Henchcliffe and Beal, 2008, Zhou et al., 2008, Moreira et al., 2010). Recent reports revealed that, neurodegeneration in PD has also been linked to dietary habits, where deficiency of antioxidant components such as folic acid (Zhu, 2004), vitamins (A, C, E and niacin) and selenium in body has been shown to increase the risk of PD (Paraskevas et al., 2003, Chaturvedi et al., 2006). Deficiency of these compounds leads to increase in the level of reactive oxygen species (ROS) and it has been speculated that oxidative stress (OS) possibly plays a role not only in onset of the PD but also in progression of the disease (Zhu, 2004, Hritcu et al., 2008). OS contributes to the damage to lipids, proteins, and DNA, and the cascade of events leads to the dopamine (DA) cell degeneration in PD. In addition to this, OS has also been shown to pose a major limitation in l-DOPA therapy, as l-DOPA and endogenous DA gets autooxidized forming quinone and ROS and these may further accelerate the progression of the disease (Fahn and Sulzer, 2004, Foster and Hoffer, 2004).

To overcome free radical mediated consequences of disease processes and drug therapies, various antioxidant supplements have been proposed and have been shown to play an important role in neuroprotection (Chaturvedi et al., 2006, Datla et al., 2007, Moreira et al., 2010, Hwang et al., 2011). Reports indicate that administration of antioxidants with l-DOPA therapy protects against ROS-induced damage both in vivo and in vitro (Chalimoniuk et al., 2004).

6-Hydroxydopamine (6-OHDA) is a selective catecholaminergic neurotoxin that has been widely used to produce PD models in vitro and in vivo because it induces apoptotic activity through OS (Hritcu et al., 2008, Shim et al., 2009). Our previous reports demonstrated that rats treated with 6-OHDA suffered impairments in memory processes, which are associated with alterations in the brain antioxidant status and lipid peroxidation (Hritcu et al., 2008, Ciobica et al., 2009). Consequently, several reports suggested that many plant extracts have neuroprotective activity against 6-OHDA-induced toxicity through antioxidative and antiapoptotic activities in PD models (RajaSankar et al., 2009, Shim et al., 2009, Moreira et al., 2010, Hwang et al., 2011).

Hibiscus asper Hook.f. (Malvaceae) is an important medicinal plant widely distributed throughout tropical Africa and in Madagascar. This species belongs to the genus Hibiscus represented by 250 species and characterizes by the presence of biologically active compounds like flavonoids, phenolic acids, and polysaccharides (Vasudeva and Sharma, 2008). In the western region of the Africa, this plant is widely used by the traditional practitioners for the treatment of inflammation, anemia, jaundice, leucorrhoea, poison antidote, depression and dysmenorrhea (Schippers and Bosch, 2004). In the Western Region of Cameroon the leaves are used as a potent sedative, tonic and restorative. It is also used to treat male infertility and skin infection (Burkill, 1985). Furthermore, recently, we demonstrated that the methanolic extract of Hibiscus asper leaves possesses a wide spectrum of biological activities, including in vitro antioxidant activity, anxiolytic and antidepressant actions, as well as positive effects on spatial memory formation (Foyet et al., 2011). Moreover, we suggested that the effects of the methanolic extract of Hibiscus asper leaves could be attributed to the presence of various phytoconstituents in the plant extract, including flavonoids, polyphenols and saponines. Therefore, the aim of the present study was to investigate the relationship between the antioxidant and antiapoptotic actions of the methanolic extract of Hibiscus asper leaves and its neuroprotective properties in 6-OHDA-lesioned rat model of PD.

Section snippets

Plant material and plant extract

Hibiscus asper leaves were collected in Fotouni (Western Region, Cameroon) in May 2010 and identified by Dr. Focho Derreck, Department of Plant Biology (University of Dschang, Cameroon). Voucher specimen was deposited in the Cameroon National Herbarium, Yaoundé, under the number Lucha034. Basically, the preparation of plant extracts was the same as previously described by Foyet et al. (2008), but with modification. The leaves of Hibiscus asper were dried under shade and pulverized. 100 g of the

Apoptosis

Total DNA was isolated from the temporal cortex samples using the phenol/chloroform method described by Ausubel et al. (2002). 50 mg brain tissue sample was digested overnight at 37 °C in 0.6 mL digestion buffer (100 mM NaCl, 10 mM Tris/HCl, 25 mM EDTA pH 8.00, 0.5% SDS) containing 0.1 mg/mL proteinase K (Boehringer Mannheim, Germany). The digest was extracted with equal volumes of Tris-saturated phenol (pH 8.0) (Roti-phenol, Roth, Germany) by shaking gently to completely mix the two phases. The

Histological control

After the temporal cortexes were removed for oxidative stress assays, the brains were placed in a 30% sucrose/formalin solution, then frozen and cut into coronal sections (50 μm) using a freezing microtome and stained with Cresyl violet for the verification of the point of the syringe needle. Only experimental data from lesions correctly located in the SN were used for statistical analysis.

Statistical analysis

All results are expressed as mean ± S.E.M. Statistical analyses were performed using one-way analysis of variance (ANOVA). Significant differences were determined by Tukey's post hoc test. F values for which p < 0.05 were regarded as statistically significant. Pearson's correlation coefficient and regression analysis were used to evaluate the connection between the antioxidant defence and lipid peroxidation.

Histological verification

After 6-OHDA-lesions the rats recovered quickly and gained weight by 1 week. In the majority of SN-lesioned rats (8/10) the point of the syringe needle was positioned in the central part of the SN and the lesions extended to a part of adjacent structures including substantia nigra pars reticulata, without any significant damage.

Effect of Hibiscus asper extract on SOD, GPX and CAT activities

Biochemical analyses showed a significant increase of the main enzymatic antioxidant defences (SOD, GPX and CAT) estimated in the temporal lobe homogenates of the

Discussion

Therapeutic strategies that slow or stop the neurodegenerative processes of PD are expected to have a major impact on the treatment of PD (Meissner et al., 2004). The current hypothesis about the mechanisms by which neurons come into necrotic or apoptotic processes has led to believe that the therapeutic use of antioxidants may be beneficial in aging and neurodegenerative disorders (Di Matteo and Esposito, 2003, Zhou et al., 2008). Following this line of evidence, the number of studies with

Conclusions

In summary, the present study demonstrated that the methanolic extract of Hibiscus asper leaves acts as antioxidant agent and may confer neuroprotection against the underlying dopaminergic neuron degeneration in the 6-OHDA-lesion rodent model of Parkinson's disease.

Acknowledgments

Harquin Simplice Foyet was supported by Postdoctoral scholarships Eugen Ionescu (2009/2010), Alexandru Ioan Cuza University, Iasi, Romania. Hritcu Lucian, Stefan Marius and Mihasan Marius were supported by CNCSIS-UEFISCSU, Impact of bacterial superantigens on the animal organism physiological status project number 1073/2009, PNII – IDEI code 85/2008, Romania.

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