Abstract: This study was conducted to evaluate phytochemical component and anti-stress potential of aqueous root extract of Alchornea cordifolia in mice. The phytochemical tests showed the presence of flavonoids, tannins, carbohydrates, glycosides, saponins and alkaloids. The antistress activity was evaluated using the forced swimming endurance and anoxic tolerance test. These activities were tested at oral doses of 100-400 mg kg-1 of the extract  using Panax ginseng as experimental control. In the forced swimming test, A. cordifolia (100-400 mg kg-1, p.o) significantly prolonged the swimming time in a dose dependent manner. The swimming time (sec) was increased from 313.8±18.24 in the control group to 434.2±20.50 and 531.0±16.58 in groups pre-treated with 200 and 400 mg kg-1 of the extract respectively. In the same vein, the extract dose dependently prolonged the mean time (min) to onset of clonic convulsion, the onset of clonic convulsion was increased from 23.6±0.51 in control group to 39.4±1.84 and 52.0±1.30 in groups pretreated with 200 and 400 mg kg-1 of the extract, respectively. This ability of A. cordifolia to prolong both the swimming time and onset of clonic convulsion, therefore suggest an antistress property.
INTRODUCTION
Stress is a biological response to aversive conditions such as injury, emotional disturbances. This response consists of reactions that tend to threaten or perturbs the homeostasis of the organisms (Bhattacharya and Ghosal, 2000).
The notion that aversive events may provoke or exacerbate clinical depression in humans is well reported in literature (Weiss et al., 1981; Anisman and Zacharko, 1991; Subarnas et al., 1993).
We explored the anti-stress potential of Alchornea cordifolia and compared it with that of Panax ginseng using the forced swimming and anoxic tolerance test as models of stress. The forced swimming test is based on the observation that rats or mice forced to swim in water eventually assumed a characteristic immobile posture devoid of any activity (Weiss et al., 1981; Subarnas et al., 1993). The appearance of immobility therefore reflects a state of tiredness, fatigue or reduced stamina, a lowered mood (hopelessness). These signs represent some of the core symptoms seen in depressed patient or individual under intense stress (Baldessarini and Tarazi, 2001; Subarnas et al., 1993).
The growing popularity of herbal medicine is based on the facts that many people believe that they are safer, ‘more natural than synthetic drugs’. Moreover, they are also affordable and more accessible to people (Vandebroek et al., 2004).
Furthermore, the belief and cultural ways of life of the people are closely linked with herbal remedial practices (Ashorobi and Umukoro, 1999).
Medical plants have been found to posses several phytochemical active compounds. These active compounds possess a wide range of biological activities, which are responsible for the observed curative effects of herbal medicines (Baladrin et al., 1993; Cragg and Newman, 2001).
The zeal for continuing to study the traditional sources of medicine has therefore prompted research into the investigation of antistress property of Alchornea cordifolia.
Alchornea cordifolia Mull.Arg (Euphorbiaceae) is a widely distributed plant in Africa. It is used in traditional medicine of many African countries for the treatment of bacterial, fungi, parasitic and inflammatory disorder.
Moreover, it has been indicated in wounds, cicatrisation, ulcers (Bouquet and Debray, 1974; Kerhoro and Adam, 1974; Kambu, 1990; Neuwinger, 2000). However, a number of plants such as; Asparagus racemosu, Ocimum sanctum, Panax ginseng, Hypericum perforatum etc. have been shown to possess anti-stress properties (Ellis and Reddy, 2002; Bhattacharya and Ghosal, 2000).
No studies have shown anti-stress or endurance promoting activity of Alchornea cordifolia. This study therefore, reports on the phytochemical constituents and anti-stress potential of aqueous root extract of Alchornea cordifolia in mice.
MATERIALS AND METHODS
Animals
Swiss albino mice (18-25 g) of either sex used in the study were purchased
from the Laboratory Animal Centre, College of Medicine, University of
Lagos. Lagos, Nigeria. This research work was carried out in 2006. Animals
were kept in a well-ventilated environment with free access to food and
water ad libitum. the ethical guidelines for the handling of experimental
animals were followed in the study.
Drugs
Korea Panax ginseng (Masons Vitamins Inc., Miami Lakes, Fl 33014,
USA) was used as reference drug in this study.
Plant Material
The dried roots of Alchornea cordifolia were purchased from Mushin
Market, Lagos, Nigeria. Identified and authenticated by Prof. J.A. Olowokudejo
of the Department of Botany and Microbiology, University of Lagos, Lagos,
Nigeria.
Extraction Procedure
The dried roots of Alchornea cordifolia were ground into fine powder.
Four hundred grams of the powdered roots were soaked in 650 mL of distilled
water for 48 h and the filtrate was evaporated to sticky residues at 38°C.
The yield of the extract was 14.5 g with reference to the powdered roots.
Four hundred milligram of the residue was dissolved in 10 mL of distilled
water for the study.
Experimental Procedure
Forced Swimming Endurance Test
Mice (six per group) were treated with the extract (100-400 mg kg-1,
p.o), ginseng (50 mg kg-1, p.o) and distilled water (5 mL kg-1).
One hour after pre-treatment, the animals were allowed to swim till exhausted
in a propylene tank of dimension (37x37x30 cm), filled with water to a
height of 25 cm. The end point was taken when the animals drowned and
Swimming time for each animal was noted. The mean swimming time for each
group was calculated and the data was statistically analysed (Kumar et
al., 1999).
Anoxic Tolerance
The method described by Subarnas et al. (1993) was used in this
study. Mice (six per group) were treated with extract (100-400 mg kg-1,
p.o), Ginseng (50 mg kg-1, p.o) and distilled water (5 mL kg-1)
one hour before mice were subjected to anoxic stress by keeping them in
a confined airtight 250 mL glass jar. The time taken for the mice to exhibit
clonic convulsion was taken as the end point. The mice, were thereafter,
removed from the glass jar for recovery.
Statistical Analysis
Data obtained from the study were expressed as mean±SEM statistical
analysis was performed using ANOVA. p-values less than 0.05 were considered
statistically significant.
RESULTS AND DISCUSSION
The extract (200-400 mg kg-1, p.o) produced a significant (p<0.05) increase in the duration of swimming in mice.
Similar effects were observed in animals pretreated with Panax ginseng (Table 1) in the forced swim test.
In the anoxic tolerance test (Table 2), the extract (200-400 mg kg-1) statistically produced a significant (p<0.05) increase in mean time to convulsion in mice subjected to anoxic stress. The phytochemical screening revealed the presence of alkaloids, flavonoids, tannins, carbohydrates, saponins and glycosides.
The results of the study revealed that the extract possess antistress property as it significantly increased swimming time as well as prolongation of the onset of clonic convulsion in animals exposed to anoxic stress.
The forced swimming is the most widely used method for assessing the anti-stress property of a novel compound (Subarnas et al., 1993; Anisman and Zacharko, 1991). This paradigm is based on the observation that animals forced to swim in water eventually assumed a characteristic immobile posture, devoid of any activity (Weiss et al., 1981).
The appearance of immobility therefore, reflects a state of tiredness, fatigue, reduced stamina with the end point being the moment when the mouse could not swim further and started drowning.
However, increased swimming time has been reported in mice pre-treated with antistress and adaptogenic agents (Bargava and Singh, 1981). This ability of the extract to prolonged swimming time in mice, therefore, suggests an antistress property.
| Table 1: | Effect of aqueous root extract of Alchornea cordifolia in forced swimming endurance test in mice |
| Each value represents the mean±SEM for six animals per group. *: p<0.05 when compared with distilled water treated group (ANOVA) | |
| Table 2: | Effects of aqueous root extract of Alchornea cordifolia in anoxic tolerance in mice |
| Each value represents the mean±SEM for six animals per group. *: p<0.05 when compared with distilled water treated group (ANOVA) | |
This study has shown that the extract prolonged mean time to convulsion, which therefore demonstrate antistress property. The prolongation of mean time to convulsion could be attributed to its powerful anti-oxidant and free radical scavenging activities (Oke and Hamburger, 2001).
This ability of Alchornea cordifolia to prolonged swimming time and mean time to convulsion suggests that the extract contained phytochemically active constituents i.e., flavonoid and glycoside, which could have increased the level of central neurotransmitter.
The phytochemical screening revealed the presence of alkaloid flavonoid, tannins, saponin, carbohydrate and glucoside. The antistress potential of Alchornea cordifolia can be attributed to its flavonoid, carbohydrate, saponins and glycoside contents, they have all been shown to offered protection of cellular component (Rastrelli et al., 1998).
The presence of these phytoactive agents may perhaps account for the pharmacological effects demonstrated by Alchornea cordifolia.
In conclusion, the results of this study showed that the root extract of Alchornea cordifolia possess antistress property.