Pharmacological Evaluation of Anxiolytic Activity of Ursolic Acid Stearoyl Glucoside Isolated from Lantana camara
Anxiety disorders are the most common psychiatric disorders 1. Present epidemiological data suggest half of the population suffers from this disorder 2. Many secondary plant metabolites are used in traditional medicine practice, either directly or indirectly affecting the central nervous system and altering gamma-amino butyric acid (GABA), serotonin noradrenalin, benzodiazepine (BDZ) neurotransmitter activities 3. Dried powder of Lantana camara leaves (4 kg) was extracted with methanol (12 L) at 50°C for 1 day. The slurry was dissolved in methanol and was adsorbed on silica gel column (60–120 mesh).Using CHCl3/MeOH (49:1; 2.0 L) gradient system in the column leads to the elution of colorless crystals of UASG (yield, 11.2 g; 0.28%) 4. Isolated UASG crystals were examined for anxiolytic potential.
The animals were divided into four groups with six mice each: Group I, solvent control (received 0.9% [w/v] of saline); Group II, a positive control (diazepam, 1 mg/kg); and Groups III and IV received 25 and 50 mg/kg of UASG suspended in 1% Tween 80 (v/v). All the animals were administered the aforementioned drugs/solvent intraperitoneally 30 min prior to start of the experiment.
Elevated plus-maze test (EPM): Vehicle, diazepam (1 mg/kg), and UASG (25 and 50 mg/kg) were intraperitoneally administered 30 min prior to the test. Each animal was placed on the central platform. The movement and duration of entries into the closed and open arms were observed for 5 min. The percentage of time spent in the open arms and percentage of the number of open arm entries were calculated for each mouse 5.
Open-field test: Treatment was initiated with vehicle, diazepam (1 mg/kg), and UASG (25 and 50 mg/kg), by placing the animals in corner squares, and the number of rearing, assisted rearing, and number of squares crossed were observed for 5 min 6.
Light and dark test: Each animal was placed in center of the light box and was observed for 5 min 7.
The animals were more stable in the open arm when treated with diazepam (1 mg/kg) and UASG (25 and 50 mg/kg), with significant P-values (P < 0.05 and P < 0.001), whereas significant (P < 0.01 and P < 0.001) reduction was observed in the number of entries and the time spent in the closed arm. UASG (25 and 50 mg/kg) and diazepam significantly (P < 0.001) increased the percentage of the time spent and entries in open arm (Table 1).
| Treatment (mg/kg, i.p.) | No. of entries | Time spent (second) | % OAE | TSOA (second) | ||
|---|---|---|---|---|---|---|
| Open arm | Closed arm | Open arm | Closed arm | |||
| Vehicle | 4.86 ± 0.28 | 33.8 ± 0.74 | 53.3 ± 1.52 | 135.4 ± 1.62 | 23.8 ± 0.74 | 35.9 ± 0.78 |
| Diazepam (1) | 9.88 ± 0.63*** | 23.9 ± 0.47*** | 74.6 ± 1.41*** | 85.5 ± 1.73*** | 49.6 ± 1.79*** | 56.2 ± 1.00*** |
| UASG (25) | 6.10 ± 0.45* | 17.6 ± 0.24** | 57.9 ± 1.20 | 110.6 ± 1.93*** | 52.4 ± 2.05*** | 42.3 ± 0.58** |
| UASG (50) | 8.36 ± 0.52*** | 20.0 ± 0.38*** | 74.5 ± 1.19*** | 86.8 ± 1.71*** | 52.2 ± 2.20*** | 54.9 ± 1.16*** |
- Values are the mean SEM of six mice/treatment. Significant *P < 0.05, **P < 0.01 and ***P < 0.001 compared with control.
Diazepam and UASG (25 and 50 mg/kg) displayed significant effect (P < 0.05 and P < 0.001) on the number of squares crossed. The self-rearing and assisted rearing were increased by UASG (25 and 50 mg/kg) (P < 0.05 and P < 0.001) (Table 2). Diazepam (1 mg/kg) and UASG (25 and 50 mg/kg) showed marked change (P < 0.05, P < 0.001, and P < 0.001) in time spent, which was increased in lighted box and decreased in the dark box. UASG (25 mg/kg) failed to have any effect on the number of crossing and duration of immobility, whereas diazepam (1 mg/kg) and UASG (50 mg/kg) showed significant (P < 0.05 and P < 0.01, respectively) increase in the number of crossing and decrease in the duration of immobility (Table 2).
| Treatment(mg/kg, i.p.) | Open field test | Light and dark model | |||||
|---|---|---|---|---|---|---|---|
| No. of rearing | No. of assistedrearing | No. of squarescrossed | Time spent in lightedbox (second) | Time spent in darkbox (second) | No. of crossing | Duration ofimmobility(second) | |
| Vehicle | 17.4 ± 0.44 | 18.9 ± 0.88 | 84.8 ± 1.58 | 86.4 ± 1.51 | 201.1 ± 2.01 | 24.1 ± 1.98 | 37.8 ± 2.92 |
| Diazepam (1) | 31.7 ± 1.46*** | 33.3 ± 0.95*** | 172.8 ± 1.36*** | 175.0 ± 1.82*** | 121.4 ± 2.62*** | 32.5 ± 1.63* | 28.2 ± 2.31* |
| UASG (25) | 28.0 ± 0.40*** | 26.0 ± 0.97** | 105.4 ± 1.10* | 106.2 ± 1.50* | 177.2 ± 2.56** | 26.0 ± 1.35 | 34.2 ± 2.23 |
| UASG (50) | 28.9 ± 1.64*** | 29.8 ± 0.74*** | 147.9 ± 1.34*** | 156.6 ± 1.69*** | 125.3 ± 2.39*** | 31.9 ± 1.93* | 25.6 ± 1.65** |
- Values are the mean SEM of six mice/treatment. Significant *P < 0.05, **P < 0.01 and ***P < 0.001 compared with control.
The time spent on the central platform appears to be related to decision making and/or risk assessment, and total arm entries is a contaminated measure reflecting changes in anxiety or general activity 8. UASG, in a dose-dependent manner, induces significant increases both in the number of entries and in time spent in the open arms, and vice versa in the closed arm, proving its anxiolytic nature. The open-field model evaluates anxiety-related activities such as location, fear characterized to an open and bright area 9. UASG significantly changes anxiety parameters, which results in the increase in the number of self-rearing, number of assisted rearing, and number of squares crossed, exhibiting its anxiolytic effect. The light and dark box method is a natural test used for rodents to avoid bright places. UASG reduces the fear of animal, which may be due to the agonistic effect on GABA/BDZ receptor complex. UASG, a derivative of ursolic acid, may be responsible for anxiolytic activity. In a nutshell, UASG from the above experiment and results demonstrates marked anxiolytic activity. Exact mechanism of action needs is under study.
