Sedative and CNS Depressant Effect of Nymphaea lotus
Authors: Salaudeen Maryam A. , Magaji M. G. , Mudashir F. I. , Chindo B. A. , Maiha B. B. 
Published: April 2020

Introduction

Nymphaea lotus is a medicinal plant used for management of insomnia, anxiety and other related disorders. This research investigated the effect of the methanol rhizome extract of water lily on sleep onset and duration as well as the effect on CNS depression.

Method

The sedative activity of the extract was evaluated using diazepam‐induced sleep (DIS) and beam‐walk assay (BWA) while the CNS effect was investigated using open field test (OFT) and light/dark box (LDB) test in mice.

In the DIS test, mice were divided into four (4) groups of six mice each. Mice in group I received normal saline (10ml/kg). Group II to IV mice received graded doses of the extract. All mice were administered diazepam 20 mg/kg after 30minutes treatment period. Mice were subsequently placed in cages individually and observed for onset and duration of sleep.

In BWA, mice were trained to walk from a start platform along a ruler (80cm long, 3cm wide) elevated 30cm above the bench by metal support to a goal box and successful mice were used for the study. Mice were divided into five (5) groups of 6 mice each. Group I and V received Normal Saline (10ml/kg, i.p) and diazepam (2 mg/kg, i.p) respectively, whereas mice in group II – IV received graded doses of the extract. 30 minutes post‐treatment, each mouse was placed at one end of the beam and allowed to walk to the goal box. Mice that fell were returned to the position they fell from, with a maximum time of 60s allowed on the beam. The number of foot slips and time taken to reach the goal box was recorded.

For OFT, a wooden box (7× 72 × 36 cm) with one of the side walls made of transparent Perspex glass and illuminated with a 60W bulb suspended 100 cm from above was used. Mice were randomly divided into five (5) groups of six mice each. Grouping and treatment are similar to those in BMA but with 0.5mg/kg dose of diazepam in group V. The mice were placed individually at the corner of the arena and the number of central squares and total number of squares crossed was observed for 5 min period.

In the LDB maze, a box of size 46 × 27 × 30 cm consisting of two compartments (1/3rd black compartment and 2/3rd white compartment illuminated with 40W light source and connected through a small open doorway) was used. Drug treatment is similar to that in the OFT. After 30 minutes treatment period, each mouse was placed individually in the center of the light compartment and observed for 5 minutes for the crossings between and time spent in the two compartments.

Male Swiss albino mice were employed for use in this research. Ethical approval for the use of lab animals was obtained from Ahmadu Bello University Committee on Animal Use and Care (ABUCAUC).

Results

In the DIS test, the extract at 100 and 200 mg/kg significantly (p ≤ 0.05) increased the mean duration of sleep but only significantly (p ≤ 0.05) hastened sleep onset at 200mg/kg (Fig.
1). In the BMA, the extract (50–200 mg/kg) significantly (p<0.001) increased the number of foot slips and the time taken to cross the beam (Fig.
2 and
3). In the OFT, the extract at 100 and 200 mg/kg significantly (p ≤ 0.05) decreased the number of squares crossed and the total number of central squares crossed (Table
1.0). In the LDB test, the extract at all doses significantly (p ≤ 0.05) increased time spent in dark area (Table 2.0).

Conclusion

Nymphaea lotus has sedative and CNS depressant activity and can be explored in the management of conditions where these are of benefit.

Effect of Aqueous Methanol Rhizome Extract of Nymphaea lotus on Diazepam‐ Induced Sleep in Mice. *=P < 0.05; ***=P<0.01; N=6.

Key: AMNL = Aqueous methanol rhizome extract of Nymphaea lotus; DZP = Diazepam; N/Saline = Normal Saline

Figure 1

Effect of Aqueous Methanol Rhizome Extract of Nymphaea Lotus on Motor Coordination in Mice using Beam Walking Assay.

* P ≤ 0.05; **P<0.01; Vs N/saline; N=6. AMNL: Aqueous methanol rhizome extract of Nymphaea lotus; DZP = Diazepam; N/Saline: Normal Saline

Figure 2

Effect of Aqueous Methanol Rhizome Extract of Nymphaea Lotus on Motor Coordination in Mice using Beam Walking Assay. *** P<0.001 Vs N/Saline; N=6. Key: AMNL = Aqueous methanol rhizome extract of Nymphaea lotus; DZP = Diazepam; N/Saline = Normal saline

Figure 3

Effect of Aqueous Methanol Rhizome Extract of Nymphaea lotus on Mice Behaviour in Open Field Test

Treatment

Dose (mg/kg)

No. of Squares Crossed

No. of Central Squares Crossed

N/Saline

10ml/kg

89.20 ± 5.60

1.00 ± 0.32

AMNL

50

54.33 ± 5.28

1.33 ± 0.62

AMNL

100

65.17 ± 2.60
*

1.17 ± 0.65

AMNL

200

44.67 ± 2.47
**

0.33 ± 0.21
*

DZP

0.5

102.33 ± 5.74
#

2.33 ± 0.56
*

Data for number of squares crossed and number of central square crossed are expressed mean ± S.E.M. Data are analysed using one‐way analysis of variance followed by Dunnett Post‐Hoc test with p value ≤ 0.05 considered to be statistically significant.

*p value <0.05,

**p value < 0.01,

#p value < 0.001 Vs N/Saline; N = 6.

Key: AMNL = Aqueous methanol rhizome extract of Nymphaea lotus; DZP = Diazepam; N/Saline = Normal Saline

Effect of Aqueous Methanol Rhizome Extract of Nymphaea lotus on Mice Behaviour in Light and dark box

Treatment

Dose (mg/kg)

TLC (Secs)

TDC (Secs)

NOC

N/Saline

10ml/kg

77.67 ± 4.87

222.33 ± 4.87

4.00 ± 0.52

AMNL

50

77.83 ± 5.07

222.17 ± 5.06

4.50 ± 0.43

AMNL

100

58.80 ± 5.51
*

241.20 ± 5.51
*

4.20 ± 0.37
*

AMNL

200

40.00 ± 2.71
*

260.00 ± 2.71
*

3.83 ±0.31
*

DZP

0.5

156.33 ± 7.60
*

143.67 ± 7.60
*

4.83 ± 0.48
*

Data for TLC, TDC and NOC are expressed mean ± S.E.M. Data are analysed using one‐way analysis of variance followed by Dunnett Post‐Hoc test with p value ≤ 0.05 considered to be statistically significant.

*p value <0.05 compared to N/Saline; N = 6.

Key: AMNL = Aqueous methanol rhizome extract of Nymphaea lotus; DZP = Diazepam; N/Saline = Normal Saline; TLC = time spent in Light Compartment; TDC = Time spent in Dark Compartment; NOC = Number of Crossings, Secs = Seconds.