Research Article
Evaluation of the in vivo antimalarial activity of ethanolic leaf
and stembark extracts of Anthocleista djalonensis
Antia S. Bassey, Jude E. Okokon1, Emmanuel I. Etim2, Francis U. Umoh3, Emmanuel Bassey1
Department of Chemistry,
Faculty of Science, 1Department
of Pharmacology and Toxicology,
Faculty of Pharmacy, 2Departments
of Pharmaceutical and Medicinal
Chemistry and 3Pharmacognosy and
Traditional Medicine, University of
Uyo, Uyo, Nigeria
Received: 01.11.2008
Revised: 23.01.2009
Accepted: 09.12.2009
DOI: 10.4103/0253-7613.59924
Correspondence to:
Dr. Jude E. Okokon
E-mail: judeefiom@yahoo.com
ABSTRACT
Objective: To evaluate the in vivo antimalarial activities of ethanolic leaf and stembark
extracts of Anthocleista djalonensis used traditionally as malarial remedy in Southern
Nigeria in mice infected with Plasmodium berghei berghei.
Methods: The ethanolic extracts of the A. djalonensis leaf (1000 – 3000 mg/kg/day) and
stembark (220 – 660 mg/kg/day) were screened for blood schizonticidal activity against
chloroquine-sensitive P. berghei in mice. The schizonticidal effect during early and
established infections was investigated.
Results: The A. djalonensis leaf extract (1000 – 3000 mg/kg/day) exhibited a significant
antiplasmodial activity both in the 4-day early infection test and in the established infection
with a considerable mean survival time, which was incomparable to that of the standard
drug, chloroquine (5 mg/kg/day). The stembark extract (220 – 660 mg/kg/day) also
demonstrated a promising blood schizontocidal activity in early and established infections.
Conclusion: These plant extracts possess considerable antiplasmodial activities, which
justify their use in ethnomedicine and can be exploited in malaria therapy.
KEY WORDS: Antimalarials, antiplasmodial, Anthocleista djalonensis, P. berghei berghei
Introduction
Malaria is still a major public health problem in Nigeria
and other tropical countries where transmission of the disease
is rarely controlled. Poor and inadequate drainage system
has encouraged breeding of mosquitoes, causing infection to
spread. Herbal preparations are patronised by most people in
urban areas for the treatment of malaria infections in spite of
the availability of conventional antimalarial drugs. Anthocleista
djalonensis A.Chev (Loganiaceae) is a medium-sized tree of
West tropical Africa, 30 – 45 feet-high, with blunt spines on the
unbranched, pale grey trunk and widespreading crown.[1] The
stem, rootbark and leaves of A. djalonensis are used to treat
malaria, jaundice, diabetes and abscesses.[1,2] The seeds, barks
and roots are used in Nigeria by the Igbos as antipyretic, laxative
and remedy for various stomach disorders.[3] It is used to cure
epilepsy in Ghana[2,4] and in southern Nigeria, the leaves and
stembark are used traditonally as malarial remedy.[4] Burkill[5]
reported that the plant is used as febrifuge, abortifacient and
pain killer. Okorie[6] isolated phthalide and xanthones from
A. djalonensis. Onocha et al.[7] isolated monoterpene diol,
djalonenol and iridoid glucoside djalonenoside (also sweroside).
They also isolated a dibenzo-alpha-pyrone-djalonensone from
this plant. Some of these compounds and their semisynthetic
derivatives were found to be cytotoxic against the brain tumortransformed fibroblasts.[8] Reports of antibacterial and wound
258 Indian J Pharmacol | Dec 2009 | Vol 41 | Issue 6 | 258-261
healing activity[3,9] as well as in vitro anthelmintic activity[10]
have been published. We have investigated the antiplasmodial
activity of the ethanolic extract of the leaves and stembark to
ascertain their ethnobotanical uses.
Materials and Methods
Plant material
The leaves and stembark of A. djalonensis (A.Chev)
(Loganiaceae) were collected in August, 2007, from the Nyan
forest in the Uruan area of Akwa Ibom State and authenticated
by Dr. Margaret Bassey, a taxonomist in the Department of
Botany, University of Uyo, Uyo, Nigeria. A voucher specimen of
the plant was deposited in the Faculty of Pharmacy Herbarium,
University of Uyo, Uyo. The plant materials were shade-dried
and then powdered.
Preparation of extracts
The dried and powdered leaves and stembark of A.
djalonensis (1 kg each) were separately and exhaustively
macerated in 70% ethanol for 72 h. The liquid extracts obtained
were concentrated in vacuo at 40°C. The corresponding yields
were 3.16 and 3.25%, respectively.
Phytochemical screening
Phytochemical screening of the extracts was carried out
employing standard procedures.[11,12]
Bassey, et al.: Antimalarial activity of Anthocleista djalonensis
Animals
Swiss albino mice (21-32 g) of both sexes were obtained
from the University of Uyo animal house, Uyo, Nigeria. The
animals were housed in standard cages and acclimatized for
a period of 10 days. The mice were maintained on standard
pelleted diet and water ad libitum. Approval for the study was
obtained from the Animal Ethics Committee, University of Uyo.
Acute toxicity
Acute toxicity study of the extracts was carried out
to determine the LD50 of the extracts using mice by the
intraperitoneal route using the method of Lorke.[13]
Parasite innoculation
The chloroquine-sensitive Plasmoduim berghei berghei
strain was obtained from the National Institute of Medical
Research (NIMR), Lagos, Nigeria, and was maintained in mice.
The inoculum consisted of 5 × 107 P. berghei berghei-parasitized
red blood cells per milliliters. This was done by determining
both the percentage of parasitaemia and the red blood cell
count of the donor mice using a hemocytometer and diluting
the blood with isotonic saline in the proportion indicated by
both determinations.
Drug administration
The drugs and the extract used in this study were orally
administered with the aid of a feeding cannula.
Evaluation of suppressive activity on early infection
A method described by Knight and Peters[14] was used. The
animals were divided into eight groups of five animals each
and administered with leaf extract of 1000, 2000 and 3000
mg/kg/day and stembark extract (220, 440 and 660 mg/kg)
and chloroquine (phosphate salt; Sigma, USA) (5 mg/kg) was
used as positive control and the negative control group received
distilled water. Each mouse was inoculated on the first day
(Do), intraperitoneally, with infected blood containing 1 x 107
P. berghei berghei-parasitized red blood cells. The mice were
treated daily from day 0 (immediately after infection) to day
3. On the fifth day of the test (day 4), a thin blood smear was
made from the tail blood sample of each mouse and stained with
Giemsa and the percentage of parasitaemia was determined
by counting the number of parasitized erythrocytes out of 200
erythrocytes in random fields of the microscope. The mean
chemosuppression was calculated as 100 [(A—B)/A], where
A is the mean percentage of parasitaemia in the negative
control group and B is the mean percentage of parasitaemia
in the test group.
Evaluation of curative activity on established infection (Rane
test)
A modified method similar to Ryley and Peters[15] was used.
On the first day (day 0), standard inoculum of 1 x 107 P. berghei
berghei-infected erythrocytes was injected intraperitoneally into
the mice. Seventy- two hours later, the mice were divided into
eight groups (A H) of five animals each. Groups A, B and C were
administered, respectively, with 1000, 2000 and 3000 mg/kg
of A. djalonensis leaf extract. A. djalonensis stembark extract
(220, 440 and 660 mg/kg) was administered to groups D, E
and F, respectively. Chloroquine (phosphate salt; Sigma) (5mg/
kg) was given to group G, which served as the positive control,
while the negative control, group H, was given distilled water.
The drug/extract was given once daily for 5 days. Thin smears
stained with Giemsa stain were prepared from the tail blood of
each mouse daily for 5 days to monitor the parasitaemia level.
The mean survival time for each group was determined in each
group over a period of 30 days (D0D29).
Statistical analysis
Data are reported as mean ± standard error of the mean
(SEM) and were analyzed statistically using one-way ANOVA
followed by the Tukey Kramer multiple comparison test and
values of P < 0.01 were considered significant.
Results
Phytochemical screening
The results of the phytochemical screening of the plant
extracts are summarized in Table 1.
Acute toxicity
The mice were treated intraperitoneally with a single
dose of 1, 2, 3, 4 and 5 g/kg of either A. djalonensis leaf or
stembark extract after being starved for 24 h. A. djalonensis leaf
extract (1–5 g/kg) produced physical signs of toxicity 1 h after
administration,which include writhing, decreased motor activity,
gasping and body/limb tone. All the animals treated with 5.0
g/kg of the extract survived and the LD50 was calculated to be
5.0 g/kg according to Lorke’s rule.
The stembark extract of A. djalonensis (1, 2, 3, 4 and 5
g/kg) produced physical signs of toxicity 30 min to1 h after
administration. The signs include writhing, gasping, palpitation,
ptosis, decreased respiratory rate and death. All the mice
treated with 2.5 g/kg and above doses of the extract died. The
LD50 was calculated according to Lorke’s rule to be 2.23 g/kg.
Suppressive test
Evaluation of the suppressive activity of A. djalonensis
leaf extract during early infection shows that the leaf extract
produced a dose-dependent chemosuppressive effect at the
various doses employed in this study (1000, 2000, 3000
mg/kg/day), with a chemosuppression of 17.05%, 26.82%
and 41.46%, respectively [Table 2]. Similarly, the ethanolic
stembark extract of A. djalonensis produced a dose -dependent
chemosuppressive effect at the different doses employed (220,
440 and 660 mg/kg), with a chemosuppression of 22.61%,
27.39% and 33.32%, respectively. The effects of these extracts
Table 1
The combined results of the phytochemical screening of the
extracts
Alkaloids
Cardiac Glycosides
De-oxy- sugars
Flavonoids
Phlobatanins
Saponins
Tannins
Terpenes
Anthraquinones
Source of extract
A. djalonensis leaf
extract
Stembark extract
+
+
+
+
+
+
+
-
+
+
+
+
+
+
-
Indian J Pharmacol | Dec 2009 | Vol 41 | Issue 6 | 258-261 259
Bassey, et al.: Antimalarial activity of Anthocleista djalonensis
were significant (P<0.05) when compared with the control.
The standard drug, chloroquine (5 mg/kg/day), caused 81.37%
suppression [Table 2].
Effect of extracts on established infection
Treatment of the P. berghei-infected mice with the
plant extracts caused a dose-dependent daily reduction in
parasitaemia in the extract-treated groups similar to that of
the chloroquine-treated group, while the control group showed
a daily increase in parasitaemia. In the groups treated with the
leaf extract of A. djalonensis 1000, 2000 and 3000 mg/kg/day,
the percentage of parasitaemia on day 7 was 14.3%, 12.0% and
10.4%, respectively, while the chloroquine-treated and control
groups, respectively, had percentage parasitaemia of 5.0 and
33.0% [Figure 1]. The stem bark extract-treated groups had
percentage parasitaemia of 15.3, 12.9 and 11.2%, respectively,
for the 220, 440 and 660 mg/kg doses of extract-treated groups
[Figure 2].
Data in Table 3 show that chloroquine (5 mg/kg/day) gave
Table 2
Suppressive activities of leaf and stembark extracts of
A. djalonensis during early P. berghei berghei infection in mice
(4- day test)
Drug/ extract
Dose
Average %
Average %
(mg/kg/
day)
parasitaemia
suppression
1000
22.67 ± 0.40*
17.05
2000
3000
220
440
20.00 ± 0.63*
16.00 ± 0.63*
21.67 ± 0.08*
20.32 ± 0.53*
26.82
41.46
21.61
27.39
660
18.67 ± 0.70*
33.32
5
0.2ml
4.67 ± 0.53*
28.06 + 0.07
81.37
-
A.djalonensis leaf
extract
Stembark extract
Chloroquine Distilled
water (control)
a mean survival time of 30.0 + 0.00 (mean + SEM) days
compared to 17.67 + 1.70, 20.33 + 0.47 and 21.67 + 3.86
days, respectively, observed for the groups treated with 1000,
2000 and 3000 mg/kg of ethanolic leaf extract of A. djalonensis.
Animals treated with 220, 440 and 660 mg/kg of A. djalonensis
stembark extract had a mean survival time value of 16.33 +
2.08, 18.38 + 1.15 and 21.33 + 0.58 days, respectively. The
mice in the control group survived for 14 days only.
Discussion
The results show that A. djalonensis leaf and stembark
extracts have moderate to negligible toxicity, as shown in
their LD50 values of 5.0 g/kg and 2.23 g/kg for the leaf and
stembark extract, respectively.[16] The results also show that
the plant extracts possess significant antiplasmodial activity,
as evident from the chemosuppressions obtained during the
4- day early-infection test. The leaf and stembark extracts
also exhibited a significant curative effect during established
infection less than to the standard drug, chloroquine (5 mg/kg/
day), as demonstrated in the mean survival time of the mice
in the extract- and chloroquine-treated groups. Although the
antimalarial activities demonstrated by the leaf and stembark
extract of A. djalonensis are low, these may have resulted from
the crude nature of these extract and could be enhanced by
further purification of these extracts. A. djalonensis leaf has
been reported above to contain some phytochemical compounds
like alkaloids, terpenes (monoterpenes) and flavonoids.
Figure 1: Antiplasmodial activity of the ethanolic leaf extract of
Anthocleista djalonensis during early infection
Data are expressed as mean ± SEM for five animals per group.*P < 0.05 when
compared with control
Table 3
Mean survival time of mice receiving the various doses of
ethanolic extracts of leaf and stembark extracts of A. djalonensis
during an established P. berghei infection in mice
Drug/extract
A.djalonensis Leaf extract
Stembark extract
Chloroquine Distilled
water (control)
Dose (mg/kg/
day)
Mean survival time
(days)
1000
2000
3000
220
440
660
5
0.2 ml
17.67 ± 0.70*
20.33 ± 0.47*
21.67 ± 0.86*
12.33 ± 0.15*
16.33 ± 0.18*
21.33 ± 0.58*
30.0 ± 0.00*
13.67 ± 0.47
Data are expressed as mean ± SEM for five animals per group.*P<0.05 when
compared to control
260 Indian J Pharmacol | Dec 2009 | Vol 41 | Issue 6 | 258-261
Figure 2: Antiplasmodial activity of the ethanolic stembark extract of
Anthocleista djalonensis during early infection
Bassey, et al.: Antimalarial activity of Anthocleista djalonensis
Antiplasmodial screening of plants has implicated alkaloids,
terpenes and flavonoids in this activity.[17,18] Sesquiterpenes
and monoterpenes such as limonene have been implicated
in endoperoxidation, leading to plasmodicidal activity.[19] The
antiplasmodial activity observed with this plant could have
resulted from its phytochemical constituents. Although the
mechanism of action of these extracts has not been elucidated,
some plants are known to exert antiplasmodial activity either
by causing red blood cell oxidation[20] or by inhibiting protein
synthesis,[21] depending on their phytochemical constituents.
The extract could have exerted its action through either of the
two mechanisms mentioned above or by some other unknown
mechanism. These compounds may be acting singly or in synergy
with one another to exert the antiplasmodial activity observed
in this study. Thus, the active principle needs to be identified.
The results of the present study indicate that the extracts of
the leaf and stembark extracts of the plant possess antimalarial
activity. This confirms their use in ethnomedicine in the
treatment of malaria. Therefore, it would be interesting if the
active principles are isolated and characterized.
Acknowledgement
The authors are grateful to Mr. Nsikan Malachy of the
Department of Pharmacology and Toxicology, University of Uyo,
Uyo, for his technical assistance.
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