Antidepressant-Like Potentials of Vernonia Amygdalina (Asteraceae) in Laboratory Mice and the Implication of the Monoaminergic Systems

Research Article

Ann Depress Anxiety. 2016; 3(1): 1075.

Antidepressant-Like Potentials of Vernonia Amygdalina (Asteraceae) in Laboratory Mice and the Implication of the Monoaminergic Systems

Onasanwo SA, Aitokhuehi NG and Faborode SO

Department of Physiology, University of Ibadan, Nigeria

Corresponding author: Onasanwo SA, Neurosciences and Oral Physiology Unit, Department of Physiology, Faculty of Basic Medical Sciences, College of Medicine, University of Ibadan, Nigeria

Received: April 05, 2016; Accepted: May 12, 2016; Published: May 17, 2016


Vernonia amygdalina commonly called bitter leaf, belongs to the family Astaraceae, and has been reported to be used locally in the treatment of psychiatric challenges. However, dearth work has been reported on anxiety and no work has been reported on depression. This study was therefore designed to investigate the antidepressant activities of Vernonia amygdalina and its probable mechanism of activities in mice.

The antidepressant-like potentials of VA (50-200mg/kg) was explored in Forced Swimming Test (FST), Tail Suspension Test (TST), reserpine-induced models and Open Field Test (OFT). Mice were pre-treated with graded doses VA (50-200 mg/kg) and imipramine (60mg/kg). And, also mice were pre-treated with monoamine receptor blockers: metergoline (5-HT2), prazosin (alpha-1- adrenoceptor) and sulpiride (D2) before VA (100mg/kg) was administered to elucidate the mechanisms involved in it antidepressant-like effects using the TST.

Vernonia amygdalina (100mg/kg and 200mg/kg) were found to be significantly increase mobility as when compared with control in FST and TST model. 100mg/kg and 200 mg/kg of VA reduced the ptosis in reserpine-induced depression and 200 mg/kg of VA was able to increase the temperature in mice in reserpine-induced depression. VA was seen to be mediated through alpha- 1-adrenergic receptor, dopamine D2 receptor and 5-HT2 receptor as there was significant increase immobility when compared to 100 mg/kg of VA.

This study showed that Vernonia maygdalina may possess antidepressantlike effects in FST, TST and reserpine-induced depression models which may be mediated through serotonergic, nor-adrenergic and dopaminergic system.

Keywords: Vernonia amygdalina; Depression; Forced swimming test; Tail suspension test; Monoamines


Depression is defined by the World Health organization [1] as a common mental disorder, presented by depressed mood, loss of interest or pleasure, feelings of guilt or low self worth, disturbed sleep or appetite, feelings of tiredness and poor concentration. At its worst, depression can lead to suicide. Almost one million lives are lost yearly due to suicide, which translates to 3,000 suicide deaths every day [1].

The widely accepted theory of depression is the decreased level of major neurotransmitters: serotonin, noradrenaline, and dopamine in the synapse. Antidepressants increase the level of these neurochemicals at the synaptic cleft. Conventional antidepressants have major setbacks which include slow onset of action, side effect. Hence, the interest in the use alternative medicine and to tap the untapped source of compound that might serve as a template for the development of antidepressant drugs is in the rise globally.

Vernonia Amygdalina (VA), a member of the Asteraceae family, is a small shrub that grows in the tropical Africa. V. amygdalina typically grows to a height of 2-5 m. The leaves are elliptical and up to 20 cm long. Its bark is rough [2]. V. amygdalina is commonly called bitter leaf in English because of its bitter taste. Locally, VA is called ewuro (Yoruba), onugbu (Igbo), chusar-doki (Hausa), oriwo (Edo) [3,4].

Vernonia Amygdalina has been shown to possess antioxidant properties and also contain chemical composition such as flavonoids, saponins, terpenes, phenolic acids and others [5]. VA has also been shown to possess anxiolytic property in elevated T-maze and holeboard apparatus [6]. This study therefore designed to study the effects of Vernonia amygdalina on depression in laboratory mice and also focusing on the roles of monoaminergic systems.

Materials and Methods

Plant material and extraction procedure

Fresh leaves of VA were collected within the University of Ibadan, Ibadan, and Oyo State, Nigeria. The identification and authentication of the plant was done at the herbarium section of the Forest Reserve Institute of Nigeria (FRIN) Ibadan, Oyo State, Nigeria by Mr. A, Adeyemo with the FHI No.: 110415.

Fresh leaves of V. amygdalina were collected, air-dried and pulverized. The pulverized V. amygdalina (1.2kg) was soaked in 4.5 liters of methanol for 72 hours. The mixture was filtered and the filtrate was concentrated using a rotary evaporator at a maximum temperature of 45°C to obtain the crude aqueous extract of the plant. Further drying of the extract was carried out using the freeze-dryer to obtain semi-solid extracts. The total dried methanol extract obtained from the leaf of V. amygdalina was 82.4g. The semi-solid paste of VA was further fractioned into n-hexane and ethyl acetate fraction, dried and kept in the desiccators for further use. The ethyl acetate fraction of VA was subsequently reconstituted in distill water at appropriate concentration. The extract was dissolved in distill water and was administered orally.

Experimental animals and treatment

Mice weighing 18–25g were used in this study and were obtained from the Laboratory Animal Centre of the College of Medicine, University of Ibadan, Nigeria. The animals were kept in a conducive laboratory environment with a 12-h cycle starting and fed with standard rodent pellet and water ad libitum. Animals were treated with any of saline (10ml/kg), methanol and ethyl acetate extract of Vernonia amygdalina (50mg/kg, 100mg/kg, or 200mg/kg), or standard drugs (imipramine, 60mg/kg) before subjecting them to their separate models.

The experimental procedures adopted in this study were in accordance with the United States National Institutes of Health Guidelines for Care and Use of Laboratory Animals in Biomedical Research [7].

Antidepressant activity

Forced swimming test: This experiment was done as described by Porsolt and co-workers [8]. The apparatus consisted of a clear Plexiglas cylinder (20 cm by 12 cm) filled to a 15 cm depth with water at 25±1oC. Experimental animals were pre-exposed to swimming environment for fifteen minutes each, 24 hours prior to the test. Each mouse was judged to be immobile when it ceases struggling and remained motionless in the water, making only those movements necessary to keep its head above the water. A decrease in the duration of immobility was an indication of anti-depressant-like effects [8].

Tail suspension test: The Tail Suspension Test (TST) was performed as described by Steru and co-workers [9]. Mice were individually suspended 60cm above the floor on a metal rod with an adhesive tape placed 1cm away from the tip of the tail. Animals were suspended for a total of 6 minutes and the duration of Immobility was recorded during the last 5 minutes of a 6-minute test using stop watch. Mice were considered immobile only when they hang passively and are completely motionless.

Reserpine-Induced depression: Five groups of mice received Reserpine (60mg/kg, i.p) 1 hour after the respective drugs/extract administration. Mice were observed for the presence of diarrhea and ptosis at 60, 90, 120, and 150 minutes, while for hypothermia at 1, 2, 3 & 4 hours after respective reserpine injection. Diarrhea was scored using 1, 2 and 3. (1= solid feces; 2= semi-solid feces; and 3= watery feces). Ptosis was scored using 1, 2 and 3. (1= eyes-open wide; 2= halfeye closure; and 3= Full-eyes closure). The temperature of mice was taken using a digital thermometer and was recorded.

Open field test: In order to eliminate any doubt of locomotive effect in the antidepressant-like activities of VA, mice were administered with same the various selected doses of drugs/extract, their locomotive activities (line crossing) was evaluated in open field apparatus. The test apparatus was made of wood 50cm in length, 50cm in width, and 25cm in height. The plain floor of the box was divided into 8cm, with 16 squares on it. A 20 W white bulb illuminated the apparatus. Mice were placed into the centre and allowed to explore the apparatus for 5 minutes. After the 5 minute test, the ambulation time was recorded and mice were returned to their home cages and the open field was cleaned with 10 % ethanol to remove any odour of the previous animal and permitted to dry between tests.

Statistical analysis

The results obtained were expressed as mean ± S.E.M. Variance was analyzed using One-way Analysis of Variance (ANOVA), followed by Newman– Keuls’ multiple comparisons test. P < 0.05 was considered to be statistically significant. All statistical analyses were done using (Graph-Pad Prism Software, San Diego, CA, USA).

Results and Discussion

Effect of methanol extract of Vernonia amygdalina on mice in Forced Swimming Test

Figure 1 shows that 50mg/kg of MEVA reduced immobility with no significance in comparison with control. However, treatment with 100mg/kg, 200mg/kg of MEVA and Imipramine 60mg/kg showed a significant reduction in immobility time (p<0.05) when compared to the control group.