**1. Introduction**

Several medicinal foods abound in traditional medicine with antioxidant activities. This could be of important for the managemen<sup>t</sup> of several diseases but has little or no scientific justification to substantiate their use. In the tropics, as in Asia and in sub-Saharan Africa, green leafy vegetables are used as one of the major components of local dishes.

*Solanum nigrum* L. (SN) belongs to the *Solanaceae* family to Europe, Asia, and North America and was introduced in South America, Australia, and Africa. It represents one of the largest and most variable species groups of the genus. SN, well known as "Black Nightshade" (the English name), is an herbal plant widely distributed throughout the world, extending from tropical regions to temperate regions [1].

In many developing countries, SN constitutes a minor food crop, with the shoots and berries not only used as vegetables and fruits but also for various medicinal and local uses [2]. SN serves mainly as vegetables for soup preparation in different parts of the world. Several studies have investigated the nutritive value of the 'vegetable black nightshade,' which put forward evidence that this species constitutes a nutritious vegetable [3]. This plant was chosen not only for being nutritive, but also for their folkloric reports of medicinal properties [4]. Studies document potential health benefits of different parts of this vegetable. SN leaves have been reportedly used in traditional medicine for the managemen<sup>t</sup> of several diseases including seizure and epilepsy, pain, ulcer, inflammation, diarrhea, some eye infections, and jaundice [5,6].

In folklore medicine, the leaves are used to treat oral ulcers in India where an interesting pharmacological investigation has been performed by using an aqueous extract of SN leaves [7].

More recently, many research studies have reported that SN showed anti-cancer activity for hepatocellular carcinoma cells [8], human ovarian carcinoma cells [9], human colorectal carcinoma cells [10], and human endometrial carcinoma cells [11]. The leaves can provide appreciable amounts of protein and amino acids, minerals including calcium, iron, and phosphorus, vitamins A and C, fats and fibers, and appreciable amounts of methionine, which is an amino acid scarce in other vegetables. Other chemical constituents reported in leaves are steroidal glycosides [12]. Very recently, from the unripe berries, a previously undescribed steroidal alkaloids [13] and steroidal glycosides [14] were isolated. Those compounds showed a potent inhibitory activity against the lipopolysaccharide (LPS)-induced nitric oxide (NO) production.

Because medicinal plants are gaining popularity for the production of reliable and safe medicines suitable for human, many studies investigated the composition of extracts, their biological activities, and optimization of extraction procedures [15,16].

The extracts of the SN contain many polyphenolic compounds. The leaves are rich in polyphenols, including phenolic acids and flavones [17]. Zaidi et al. demonstrated that treatment of rats with SN leaves extract was able to reduce oxidative stress, and, in particular, they showed the potential of this extract in preventing/alleviating stress-induced diseases, involving oxidative damage to cellular constituents especially the brain [18]. Antioxidant activity might be due to the presence of the above-mentioned polyphenolic compounds on SN stems and leaves [19]. Sun et al. demonstrated that oxidative stress has been associated with pathological conditions, including Central Nervous System (CNS) diseases and physiological brain aging processes [20].

A very interesting study has shown that dietary inclusions of Solanum leaf could protect against cognitive and neurochemical impairments induced by scopolamine, and, hence, this vegetable could be used as a source of functional foods and nutraceuticals for the prevention and managemen<sup>t</sup> of cognitive impairment-associated diseases such as Alzheimer's disease [21].

The formation and release of Radical Oxygen reactive Species (ROS) cause structural and functional alterations of cell membranes. Free radicals attack polyunsaturated fatty acids in bio-membranes and mitochondria begin the main source of ROS, when the mitochondrial respiratory chain is impaired. In these cases, a compound possessing antioxidant properties can be useful in stopping ROS production and limiting oxidative cell damages, which is particularly interesting if this activity is produced by a functional food [22]. Experimentally, ROS is well determined by using reduced glutathione (GSH), which is known as the most important scavengers of reactive species, and a reduced glutathione/oxidized glutathione ratio is used as a marker of oxidative stress [23].

At the central level, the oxidative stress may activate several calcium-dependent enzymes, causing mitochondria impairment, a decrease in adenosine triphosphate (ATP) levels, ROS production, and subsequent neuronal cell death [24]. A brief exposure to glutamate, which is a major excitatory neurotransmitter in the CNS, could determine several acute and chronic brain damages on differentiated astrocytes, which then causes cell swelling, whereas a prolonged incubation (excitotoxicity) induces cell damage [25,26]. This phenomenon causes alterations in glutamate transport, GSH depletion, and macromolecular synthesis [27].

Herein, we prepared two SN polar leaf extracts and assessed the total polyphenolic content and the concentration of phenolic acids and flavones compounds. Antioxidant activity in both an in vitro cellular free system and in vitro cellular system was evaluated. To verify whether SN1 and SN2 extracts were able to restore the oxidative status, which were modified by glutamate in primary cultures of astrocytes, GSH, ROS levels and the cytotoxicity of both extracts has been assessed.

#### **2. Materials and Methods**
