Depression stands for low behavioral & disinclination to the particular action that can have negative impact on ones thinking, motivation, perception, behavior, and other positive senses. It can either be short term or long term (De Zwart et al., 2018). Depression is included in a usual and familiar risky condition for life (Uddin et al., 2017). Patients suffering from depression normally show a reduction in the neurotransmitters like - serotonin, nor epinephrine and dopamine (Brown et al., 1997). Synthetic drugs of neurological disorders have more side effects (such as insomnia, sedation, muscle relaxation, anxiety, weight gain etc.) than their efficacious (Barua et al., 2009; Shazeed-Ul-Karim, 2019). The efficacy of natural (herbal) drugs is better than synthetic drugs as herbal drug is generally considered to be safe for human health (Zhang, 2004). 

B. monnieri is a small, aquatic herb having several branches, light purple flowers, and tiny oblong leaves. It is commonly known as Brahmi. The plant is spread all along the warm and wet lands zones of our planet and especially in Bangladesh. Traditionally, it is utilize as a brain tonic to alleviate anxiety or epileptic disorders in patients and to improve intellectual development (Chopra, 1958). Different medicinal plants (including B. monnieri) could be considered as alternative medicine source to treat neurological disorders (Galdino et al., 2009).

In Bangladesh, Brahmi is used to prevent miscarriage and to treat rheumatism (Sudharani et al., 2011). It possesses a wide range of traditional medicine values as a neurological tonic to treat toothache, respiratory, cardiac and digestive disorders and purifies blood (Valko et al., 2007; Kumar et al., 2009). 

Brahmi also possesses analgesic, sedative, antipyretic, antiulcero-genic, anti-inflammatory, antioxidant, antimicrobial, antidiarrhoeal anti-lipid peroxidative and free radical scavenging activities (Sairam et al., 2001; Kishore and Singh, 2005; Afjalus et al., 2013). 

B. monnieri contains different phytochemicals such as alkaloid brahmine, nicotinine, herpestine, β-sitosterol, D-mannitol, stigmastanol, stigmasterol and betulinic acid (Chopra et al., 1956; Sastri et al., 1959; Avanigadda and Vangalapati, 2011). The present research was undertaken to examine the neuropharmacological activities of methanolic isolate of B. monnieri in mice models.

Collection of plant material - Whole plant of B. monnieri was collected from the Mongla of Bagerhat district during the first week of December, 2017. The collected plant samples were recognized by Bangladesh National Herbarium, Mirpur, Dhaka, Bangladesh.

Preparation of B. monnieri Methanolic Extract (BMME) - Extraneous materials were removed from the fresh plants by washing. Then the washed plants were dried under a shade and then powdered by grinder, weighed with analytical balance and stored properly in air tight jar. About 300 g of powder was taken in beaker and then soaked in 1200 ml methanol for 7days. The mixture was stirred at an interval of 18 hours. The solution was elapse through Whatman filter paper no.1 for three times. Next, the solvent was expelled by rotary evaporator at pressure at the temperatures below 45° C leaving a residue, deep brown in color. The residue was stored in air tight jar at 40° C.

Collection and maintenance of animals - Swiss-albino mice were selected for the animal trial. The mice were aged between 4 to 5 weeks and the weighted between 20 to 25 g. The mice were calmed from the Animal Research centre of the Jahangirnagar University, Savar, Dhaka, Bangladesh. 

The experi-mental mice were kept in favorable environment (temperature: 25°C, relative humidity: 58-62% and 12 h light/12 h dark cycle) for 2 weeks so that they can get adjusted with the environment. The mice were fed rodent food (commercial formulation) and pure drinking water (Hossain et al., 2009). Here, the animal trial was permitted and accepted by the Institutional Ethical Committee.

Preparation of sample - The sample was prepared by dissolving B. monnieri Methanolic Extract (BMME) in deionized water at two doses (100 mg/kg body weight, 200 mg/kg body weight).

Evaluation of Neuropharmacological activity - Neuropharmacological (antidepressant) pursuit was determined by forced swimming test, TST as well as elevated plus maze test. Drugs and chemicals of neuropharmacological pursuit were representing in Table 1.

Table 1: Drugs and chemicals of neuropharmacological activity.

Forced swimming test (FST) - The forced swimming test was conducted according to the protocol of Porsolt et al. (1977) with minor changes. All the mice were kept in a room having controlled environmental condition (temperature: 25°C; humidity: 48-54%; 12h/12h light–dark cycle). Chow and pure drinking water were provided. Mice were exposing to random division for control, standard and two treatment groups (Group-3 and Group-4). Each group was consisted of 5 mice. In standard group, imipramine HCl (30 mg/kg body weight) was administered orally. 

Two treatment groups received the extract of B. monnieri (100, and 200 mg/kg body weight, respectively), and the control group received deionized water only. Mice were kept in an acrylic cylinder (height 46 cm and diameter 20 cm) which was loaded with water at 25°C of 16 cm depth for 2 minutes. Next to the pre-test session, the mice were exposing to the identical conditions for 4 minutes. A mouse was considered secure when it remained floating in the water, except for negligible movements (Sakakibara et al., 2006).

Tail suspension test (TST) - The TST was carried out according to Steru et al. (1985) with minor modi-fications. All the mice were kept in a room having controlled environmental condition (temperature: 25°C; humidity: 48-54%; 12h/12h light–dark cycle). Chow and pure drinking water were provided. Mice were exposing to random division for control, standard and two treatment groups (Group-3 and Group-4). Each group was consisted of 5 mice. In standard group, Diazepam (1 mg/kg body weight) was administered orally. Two treatment groups received the extract of B. monnieri (100, and 200 mg/kg body weight, respectively) and the control group received deionized water only. Two stands, each having a clamp situated about 24 cm from the ground surface and they were kept apart at 25 cm intervals. A mouse was hung 6 cm from the tails end on a stand, and the value was recorded for 6 minutes (Sakakibara et al., 2006).

Elevated plus maze test - The materials utilized for the elevated plus maze test was in the configuration of a+ and composed of 2 unlocked arms (25×5×0.5 cm) across each other and perpendicular to 2 closed arms (25×5×15 cm) with a centered platform (5×5×0.5 cm). The expose arms had a tiny (0.5 cm) wall to reduce the number of falls, whereas the closed arms had a high (15 cm) wall to enclose the arm. The entire system was 50 cm above the floor. The apparatus was build of wood. The platform is white and the walls are hard board. The reason of such variation in materials and color is to ease the measurement of elevated plus maze. The mice were kept in the center and allowed to move through the maze freely. The behavior was noted for 5 min to ensure the chance for phenotypic detection. The unlocked and closed elevated arms caused an exploration conflict. The values of the elevated plus maze test are taken by skilled person (Komada et al., 2008).

Statistical analysis - The data obtained from the experiment was evaluated by SPSS windows version 16.0 using one way investigate of variance (ANOVA) followed by Dennetts post-Hoc analysis. All the results obtained from the experiment were expressed as mean± SEM and level of significance was set at p<0.05.

Forced swimming test - The forced swimming test (FST) was one of the better widely used animal models for determining antidepressant effect in mice. The findings were shown in (Table 2 and Fig 1). In forced swimming test, control group of mice showed immobility time of (2.96±0.12) min whereas immobility time of standard drug (imipramine HCl) group mice was (0.14±0.04) min. Test drug BMME at dose of 100 mg/kg showed immobility time of (1.42±0.05) and higher dose of BMME showed immobility time of (0.57±0.07). When test drugs and standard drug collate to control group of animals, a significant difference was observed in immobility period of both the groups collate to control. Alcoholic extract of BMME at 2 doses of (100, 200 mg/kg) and standard drug imipramine HCl significantly (P<0.01) reduce in immobility time was seen as collate to the control group. In both doses of BMME (100, 200 mg/kg) contributed a greater decrease in immobility time as collate to the control group.

Table 2: The effect of B. monnieri Methanolic Extract (BMME) of in forced swimming test; Values of immobility time were represented in mean ± SEM.

Fig 1: Graphical representation of effect of plant of B. monnieri on force swimming test on immobility time in mice. Control=Deionized water, 10 ml/mice, Imipramine HCl= 30 mg/kg, Group 3=BMME 100 mg/kg, Group 4= BMME 200 mg/kg, body weight. * p < 0.05 collate with the control group (Dunnett‘s test). 

Tail suspension Test - The TST has become one of the most widely used animal models for assessing antidepressant–like pursuit in mice. The results were summarized in (Table 3, and Fig 2). In TST, control group of mice showed immobility time of (2.95±0.09) min, whereas immobility duration of standard drug (Diazepam) group animal was (3.33±0.09) min. Test drug BMME at dose of 100 mg/kg showed immobility time of (2.29±0.08) min and higher dose (200 mg/kg) of BMME showed immobility time was (1.37±0.18) min. 

When test drugs and standard drug collate to control group of animals, there was a notably difference in immobility duration of both the groups collate to control. Alcoholic extract of BMME at 2 doses of (100, 200 mg/kg) significantly (P<0.01) decrease in the immobility time was seen as collate to the control group. In both doses of BMME (100, 200 mg/kg) contributed a greater decrease in immobility time as collate to the control group.

Elevated plus maze test - In elevated plus maze test, Group 3=BMME 100 mg/kg, Group 4= BMME 200 mg/kg body weight, significantly enlarged the number of complete of mice into the unlocked arms and the time depleted in the unlocked arms of the elevated plus maze. However, the effects of treatment of mice with all doses on unlocked arm entries and time depleted in unlocked arms were near to each other test animals statistically significant. It indicated that the experiment was positive. The results were shown in Table 4.

Table 3: The effect of B. monnieri Methanolic Extract (BMME) in TST; Values of immobility time are represented in mean ± SEM.

Fig 2: Graphical representation of effect of plant of B. monnieri on TST on immobility time in mice. Control=Deionized water, 10 ml/mice, Diazepam= 10 mg/kg, Group 3=BMME 100 mg/kg, Group 4=BMME 200 mg/kg, body weight. *p < 0.05 collate with the control group (Dunnett‘s test).

Table 4: The effect of B. monnieri Methanolic Extract (BMME) in elevated plus maze test.

In the current research FST and TST ensured that B. monnieri has an effective antidepressant pursuit in the mice model. The methanol extracts and numerous fractions of B. monnieri were investigated for their antidepressant pursuit in the TST and forced swimming test (FST) in mice. Researchers can further investigate the presence of antioxidants in B. monnieri that will be helpful in pharmaceutical industries and food industries for the discovery of drugs and food products to maintain human and animal health.

The author is thankful to his co-authors who were encouraged and supported to the successful work.

The authors declare that there is no conflict of interest about the publication of the article.