Phytochemicals from mulberry extract ( Morus sp . ) : Antioxidant and neuroprotective potentials

Article history: Received on: 23/08/2016 Revised on: 15/09/2016 Accepted on: 04/10/2016 Available online: 31/01/2017 ROS are involved in aging, progressive neuronal death, and age related disorders. During the last decade, there is increasing evidence indicating the beneficial role plant rich phytochemicals for the treatment of oxidative stress-induced disorders in the brain due to their antioxidant activity. Mulberry extract has been reported to have antioxidant activity which attenuates deleterious effects of oxidative stress. Their neuroprotective effects in vitro and in vivo models of neurodegenerative disorders have been documented. In this paper, mechanisms of action of polyphenols mulberry extracts and related compounds as neuroprotectors in brain damage and aging will be reviewer.


INTRODUCTION
Generally, phytochemicals and bioactive compounds derived from medicinal plants have the ability of preventing or curing some diseases.Neurodegenerative diseases are characterized by progressive nervous system dysfunction and affected central or peripheral structures of the nervous system.Oxidative stress may play a crucial role in neuronal death and physiopathology of neurodegenerative disorders.Among active phytochemicals are phenolic compounds, or polyphenols, products of the secondary metabolism constitute one of the most numerous and widely-distributed groups of substances in the plant.Polyphenols exhibit a wide range of biological effects as a consequence of their antioxidant properties.they are known to have the ability to scavenge a wide range of reactive species, including hydroxyl radicals, peroxyl radicals hypochlorous acid and superoxide radical, O 2.
Mulberry or Morus (L.,Moraceae) is a genus of 10-16 species that are distributed Worldwide (Iqbal et al., 2012).Mulberry is found from temperate to subtropical regions of the Northern hemisphere to the tropics of the Southern hemisphere and they can grow in a wide range of climatic, topographical and soil conditions.
Mulberry is known in some traditional and folk Chinese medicinal formulas and several studies indicating that it may provide certain health benefits.Mulberry extracts are rich in many phytochemicals and bioactive compounds leading to several pharmacological and biological properties.Apart from antibacterial, antiviral (Wang et al., 2008), antitussive, hypoglycemic (Nickavar et al., 2009;Naowaboot et al.,2009), hypotensive (Chirino et al.,2009), antiatherogenic, antihyperlipidemia (Nickavar et al.,2009, Varposhti et al.,2007), diuretic, astringent, antioxidant (Yang et al.,2010, Kobayashi et al.,2010) and α-amylase inhibitory effects (Nickavar et al.,2009)In recent years, numerous data in the literature indicate that phytochemicals rich-mulberry extract related exhibit wide range of protective and therapeutics role in the pathogenesis of brain disease.This protective effect is most likely due to the presence of phenolic compounds in mulberry.Besides, numerous pharmacological activities of mulberries were correlated to phenolic qualitative and quantitative contents, particularly the flavonoïds and anthocyanin they contain and a well correlation between antioxidant activity and phenolic constituent (Chen et al., 2006).Various studies have illustrated that mulberry extracts may be a potential agent in neuroprotection and brain insults.Their neuroprotective activity has been documented.In this review we focus on neuroprotective abilities and mechanism of action of mulberry extract against neurodegenerative diseases.Mulberry extract and its related phenolic compounds have the ability to remedy the symptoms of degenerative diseases particularly Alzheimer's disease (AD) and Parkinson's disease (PD), and there to prevent age-related neurodegeneration.Mulberry extract exerts strong antioxidative and anti-inflammatory activities and also exhibits anti-convulsive, antidepressant, and improvement of memory deterioration in ageing and on the promotion of cognition in senescence-accelerated.

Antioxidant potential
Prior studies has been investigated the antioxidant activity of Mulberries extracts and it has been reported to have potent antioxidant Activity (Zhang et al., 2008).Generally, extracts from different parts of Tut plant parts: the stems, roots, bark, leaves, fruits, and seeds had strong hydroxyl and DPPH radical scavenging activities (Khan et al., 2013).Fur there, it have been have reported that mulberry leaf extract has antioxidant activity (Katsube et al., 2009;Lim et al., 2013).Since structural features of phenolic compounds are responsible for the antioxidant activity, the antioxidant activities of the tested mulberry leaves may be related to their total phenol content and the underlying mechanism suggested as explaining the neuroprotective effect of mulberries polyphenolic compounds can be principally summarized as scavenging intracellular ROS and inhibition of LDL oxidation.Doi, Kojima, and Fujimoto (2000) reported that 1butanol extract of mulberry leaves scavenged the DPPH radical and inhibited the oxidative modification of rabbit and human LDL.
The dominant phenolic acid in mulberry extracts is chlorogenic acid and its isomers.Chlorogenic acid exhibited the largest contribution to DPPH radical scavenging activity, to the total amount of activities.Flavonoids are known to have antioxidant activities in vitro, being able to scavenge a wide range of reactive species, including hydroxyl radicals, peroxyl radicals hypochlorous acid and superoxide radical, O 2 (Rice-Evans et al.,2000).There are four main groups of flavonoids, including flavones, flavanones, catechins, and anthocyanins.Katsube (2009) reported that the most abundant flavonol glycoside was quercetin, the greatest contributor to antioxidant activity in mulberry leaves.In contrast, kaempferol glycosides as an aglycon exhibited only a slight contribution to DPPH radical scavenging activity due to their weak scavenging abilities and the presence of a 3', 4'catechol moiety in the B ring correlated with high activity (Wang et al., 2006).Therefore the 3',4'-catechol moiety of flavonol glycosides may affect antioxidant activity to a greater degree than those of their aglycons.Furtherer, flavonoids chelate transition metal ions such as iron and copper, decreasing their ability to promote reactive species formation (Mira et al., 2002) Mulberry fruits have recently been received much attention as potential sources of anthocyanins and their biological effects on human health.Bae, S. H et al (2007) confirms that extract of mulberry fruits represents a significant source of anthocyanic antioxidants.Therefore anthocyanins are considered as secondary metabolites with potential nutritional value and antioxidant capacity.The antioxidant activity of anthocyanins is attributed to their peculiar structure, namely the oxonium ion in the C ring (Van Acker et al., 1996).Anthocyanis antioxidant have been attributed to aglycone moiety, the number of sugar residues at the 3-position, the oxidation state of the C ring (Wang et al., 1999).Lee and Wicker (1991) reported that the two major anthocyanin contents of several mulberries cultivar are cyanidin-3-glucoside and cyanidin-3-rutinoside.

Neuroprotective activity
Numerous studies indicate the beneficial role of mulberry extracts for the treatment of oxidative stress-induced disorders in the brain.Mulberry leaf extract (MLE) reduces oxygen glucose deprivation-induced cerebral ischemic condition and GABA depletion in the brain .Cyanidin-3-glycoside the most notorious and investigated among cyanidin-glycosides.Kang et al, (2006) investigated of neuroprotective effects of the cyanidin-3-O-beta-Dglucopyranoside C3 G isolated from the fruits of M. alba against neuronal cell damage and cerebral ischemia.Flavonoids isolated from the fruits of Morus alba L; artoindonesianin O, isobavachalcone, morachalcone A, quercetin , astragalin , isoquercetin , and rutin have neuroprotection effects on glutamateinduced oxidative injury in HT22 hippocampal cells ( Seo et al.,2014).Mulberroside A is a natural polyhydroxylated stilbene compound present at relatively high abundance in the roots and twigs of Morus alba L. Wang et al ( 2014), show that mulberroside A have neuroprotective effects that can be used in the treatment of brain ischemic injury using primary culture of rat cortical neurons in vitro model .Mulberroside A has the ability to counteract the hypoxia-ischemia impairment and exhibiting anti-inflammatory and antiapoptotic effects.Another component, Oxyresveratrol is a potent antioxidant and free-radical scavenger found in mulberry wood (Morus alba L.) that demonstrated protective effects against cerebral ischemia (Weber et al., 2012).Oxyresveratrol exert differential neuroprotective ability against two pathologies of high glutamate exposure and trauma.

Mulberry extracts and improvement of memory
Lead (Pb) a highly neurotoxic agent that affects the developing central nervous system is ubiquitous in the environment, and low-level Pb exposure can cause neurotoxicity and irreversible damage to children's cognition, learning and memory ability.Mulberry extract (ME) exhibited neuroprotective effects of against Pb-induced learning and memory deficits in mice, and restore NO production and anti-oxidant enzymes.MLE inhibits Pb-induced neurotoxicity by reversing Pb-induced alterations in the aspect of neurotoxic effects and improving learning and memory.Furthermore, anthocyanin-rich fruits have been described that show memory improvement efficacy in animal models (Andres-Lacueva et al., 2005).The protective effect of mulberry fruit extract on memory impairment and brain damage in animal model of vascular dementia has been also regarded by Kaewkaen et al (2012).Mulberry fruit extract improved oxidative status and increase Bcl-2 resulting in the increased densities of neurons and cholinergic neurons in hippocampus especially in CA3 that contribute the important role in associative memory function.Morus Atropurpurea supplementation, rich in phenolics and anthocyanins have been shown to have beneficial effects on prevention of Alzheimer disease and to be advantageous to the induction of an antioxidant defense system and for the improvement of memory deterioration in ageing and on the promotion of cognition in senescence-accelerated mice (Shih et al., 2010).

Mulberry extract and depression
Depression is one of the most common mental disorders, affecting nearly 21% of the world's population (Schechter et al., 2005).Depression is a pathophysiological process may be triggered by excessive and prolonged secretion of adrenal glucocorticoids.The antidepressant-like effects of the alcohol extract Cortex Mori Radicis (CMR) have been demonstrated by Lee et al., 2013.Mulberry extract produced antidepressant-like effect through producing a downregulation of serine/threonine protein phosphatase 5 levels, leading to a strong negative relationship with pGR (S232).
Lim et al (2014) demonstrated that M. alba EtOAc fraction have beneficial effects on depressive behavior.Ethyl acetate fraction of M.alba decreased the immobility time in rats exposed to the Fprced Swim Test and decreased the hypothalamic -Pituitary -adrenal HPA response to the stress ,as indicated by an attenuated corticosterone response and decreased c-fos immunoreactivity in the hippocampal and hypothalamic paraventricular nucleus (PVN) region.

Anti-aging effect
ROS are involved in aging, progressive neuronal death, and age related disorders (Sohal and Orr 2012).Polyphenols has the abilities to reduce inflammation and modulating the activity of intracellular signal transduction molecules in the brain (Choi et al., 2012).The anti-aging effect of mulberry leaves extracts on the aging of model animals have been investigated by Zheng et al (2014) which indicated that MLE extended the mean life span of C. elegans , improved oxidative stress resistance and regulate transcription factors and gene expression downstream of the germline signaling pathway in Caenorhabditis elegans in vivo model .

Anticonvulsant activity
Morus alba leaves methanolic extract showed protection against PTZ-induced convulsions.PTZ is a GABA-A receptor complex antagonist and produces seizures by the GABA pathway inhibition in the central nervous system due to the imbalance in ionic concentrations of the membrane.A finding supported by Gupta et al., 2014 reveals that MLE exhibits potential antiepileptic activity via facilitation of GABA transmission Chronic treatment with typical antipsychotics leads to the development of abnormal hyperkinetic orofacial movements (vacuous chewing movements, tongue protrusions and facial jerking) in rats and is widely accepted as the animal model for tardive dyskinesia.
Haloperidol is a typical neuroleptic that long -treatment plays an important role in the development of orofacial dyskinesia.A protective effect of Morus alba extract against haloperidolinduced orofacial dyskinesia and oxidative stress was assessed.Methanol extract of Morus alba Linn.Leaves on an animal model of tardive dyskinesia showed a marked effect on behavioral parameters altered by haloperidol treatment.Extract attenuated the increase in vacuous chewing movements and tongue protrusions induced by haloperidol (Nade et al., 2010).Even further, these last Nade et al., 2010 has been shown anti-stress effects of Morus alba in chronic restraint stress (RS)-induced perturbations in behavioral, biochemical and brain oxidative stress status.Restraint stress is a well-known method to induce chronic stress which leads to alterations in various behavioral and biochemical parameters.

Mulberry extarct and Parkinson diseases (PD)
Parkinson's disease (PD) is characterised by the loss of dopaminergic neurons in the substantia nigra pars compacta to the striatum.Epidemiological findings suggest that the consumption fruits particularly of berries rich in anthocyanins and proanthocyanidins may reduce PD risk.Mulberry fruit from Morus alba L contains well-known antioxidant agents such as anthocyanins protects dopaminergic neurons in toxin-induced Parkinson's disease models (Kim et al., 2010).Extract of mulberry fruit exhibited a protective effect against neurotoxicity in in vitro and in vivo PD .models.Mulberry extract protect SH-SY5Y cells stressed with 6-hydroxydopamine (6-OHDA) and this neuroprotective of ME was mediated by its antioxidant and antiapoptotic effects, regulating reactive oxygen species and NO generation, Bcl-2 and Bax proteins, mitochondrial membrane depolarisation and caspase-3 activation.In the sub-acute mouse PD model induced by 1-methyl-4-phenyl-1, 2, 3, 6tetrahydropyridine (MPTP), mulberry extract (ME) showed a preventative effect against PD-like symptoms (bradykinesia) in the behavioural test and prevented MPTP-induced dopaminergic neuronal damage in an immunocytochemical analysis of the substantia nigra pars compacta to the striatum.
Recent finding suggest that PD risk increases as a result of chronic exposure to environmental pollutants.Administration of rotenone, a potent rotenoid used in insecticides, has been used as a model of Parkinson's disease; it has been shown to result in the systemic inhibition of mitochondrial complex I activity, which leads to the degeneration of dopaminergic neurons within the substantia nigra and striatum (Yang et al., 2006).Chinese mulberry (Morus alba) extract rich in anthocyanins and proanthocyanidins is able to alleviate neurodegeneration in PD via enhancement of mitochondrial function (Strathearn et al., 2014).Other study revealed that an oxyresveratrol (oxy) a polyhydroxylated stilbene -rich mulberry extract alleviated rotenone neurotoxicity in primary midbrain cultures and attenuated neuronal cell death triggered by PD-related insults in cellular or animal models (Khan et al., 2010).Even further, due to its antioxidant activity and blood-brain barrier permeability, oxyresveratrol show to exert neuroprotective effects against parkinsonian mimetic 6-hydroxydopamine (6-OHDA) neurotoxicity via phosphorylation of JNK and c-Jun and increasing the basal levels of SIRT1 ( Chao et al.,2008).
Previous studies have shown that monomeric proanthocyanidin such as catechin and epigallocatechin-3-gallate and extract rich in these polyphenols, are neuroprotective in cellular and rodent models of PD (Choi et al., 2002;Guo et al., 2007;Levites et al., 2002).Catechin may protect brain against Peroxynitrite induced formation of the neurotoxins 5-S-cysteinyl-dopamine, an endogenous neurotoxins involved in the onset of Parkinson's disease (Vauzour et al., 2008).
In addition, other studies indicate that catechin derivatives may delay the onset of neurodegenerative disorders through a numerous different mechanisms such as iron chelators, radical scavengers, and modulators of prosurvival genes.Ishige et al. (2001) found that flavonoid protection against glutamate toxicity was dependent on the degree to which the substance is able to enter the cell.These findings were in accordance with those supported by Pavlica et al (2010) who suggested that the presence of catechol group inflavonoid metabolites was sufficient to exert antioxidative and scavenging activities.Neuroprotective effects of the parent flavonoid were mimicked to a greater degree by thelipophilic metabolite, emphasizing lipophility as a determinant in the overall degree of flavonoid protection to neuronal cells.

Mulberry extract and Alzheimer disease
Alzheimer's disease (AD) is the most common neurodegenerative disorder, affecting millions of people worldwide.It is known that, mulberry leaves exert antiamyloidogenic action and neuroprotective effects against Aβ peptides.Morus nigra mulberry fruits completely reverse Aβ 25-35induced neuronal injury, counteract ROS formation, and inhibit apoptosis.Mulberries extract downregulated mRNA levels of Apoptotic protease-activating factor (Apaf1) and the changes of transcription level of which may associate with the development of AD.ME also inhibit Aβ 25-35 -induced upregulation of Bace2 mRNA expression which exhibits β-secretase-like activity, a key enzyme in the production of the amyloid-β peptide (Aβ) and is thought to be involved in Alzheimer's disease (AD) pathogenesis.These finding proved that the bioactive components in ME can inhibit cell apoptosis, Aβ formation, or membrane damageassociated gene expression (Song et al., 2014).
It has been reported that quercetin is the most abundant flavonol glycoside and the greatest contributor to antioxidant activity in mulberry leaves (Katsube et al., 2009).Pretreatment of primary hippocampal cultures with quercetin significantly attenuates Aβ-induced toxicity, lipid peroxidation, protein oxidation and apoptosis (Ansari et al., 2009) In addition, numerous studies indicate that catechin derivatives may delay the onset of neurodegenerative disorders such as Alzheimer's disease through a numerous different mechanisms such as iron chelators, radical scavengers, and modulators of pro-survival genes.A novel Phenolic compound from mulberry, artoindonesianin O (AIO) exert neuro-protection by blocking ologomer Aβ 42 -or NMDA -induced neurotoxicity and pkadaic acid induced tau protein hyperphosphorylation through inhibiting the expression of kianse p-ERK1/2.AIO is suitable and possible candidature for the development of general food type neuroprotection on AD by protecting against brain damage and memory impairment and synaptic plasticity (Qiao et al., 2015).

Hypercholesterolemia
and altered cholesterol metabolism are associated with increased oxidative stress and the development of neurotoxicity and Alzheimer's disease.Cholesterol is a major constituent, derived by de novo synthesis and the bloodbrain barrier.Cholesterol is tightly regulated between neurons and glia-that is, astrocytes, microglia, and oligodendrocytes and is essential for normal brain development.Enzymatic production of the beta amyloid peptide, the peptide thought to play a major role in AD pathogenesis, is affected by membrane cholesterol levels.El-Sayyad HI (2015) has been found that Morus alba leaves, fruit, and bark improved brain function and reduce low-densitylipoprotein cholesterol level and can act as antilipidimic drugs and prevent cholesterol neurotoxicity

Mulberry rich-polyphenols and brain infection
Bauomy (2014) investigate the potential role of mulberry extract on the brain on mice infected with Schistosoma mansoni.Schistosomiasis is a tropical disease which is associated with neuropsychiatric and neuropathological disorders.Schistosomiasis induced brain oxidative stress as evidenced by the decrease of glutathione level, total antioxidant capacity and the activity of catalase significantly, while a significant elevation in the levels of nitrite/nitrate and malondialdhyde.Besides, this disease infection is resulted in neurochemical disturbances and characterized by; the decreased level of inhibitory amino acid, γaminobutyric whereas the level of chloride ions and acetylcholine esterase activity were significantly increased.Impairments in the brain are also detected.In this case, the treatment with mulberry extract ameliorated the induced disturbances in schistosome-infected mice where the levels of non-enzymatic and enzymatic antioxidants were elevated.ME reduce the levels of nitrite/nitrate and malondialdhyde, improved the altered levels of γaminobutyric acid level and chloride ion and improved the recorded impairments of the histopathological section in the brain of schistosome infected mice (Bauomy et al., 2014)

CONCLUSION
There is growing evidence that dietary polyphenols may play an important role to suppress oxidative stress and preventing neurodegenerative disorders.Mulberry rich polyphenols appear to be a good candidate for neuroprotection and treatment of oxidative stress-induced disorders in the brain and there to prevent agerelated neurodegeneration.
Bioactive components in mulberry extract exert strong antioxidative potential protecting against brain damage.The effects of the mulberry extract in animals model and patients with brain disorders such as AD, PD will be investigated and underline the evidence for a neuroprotective effect of antioxidants in the treatment of neurodegenerative disorders in humans.
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