Pharmacognosy Magazftie The effect of the aqueous stem bark extract of Kokoona zeylamca Thw. on the blood glucose level of mice

Abstract

This study examined the blood glucose lowering potential of the aqueous stem bark extract (ABE) of Sri Lankan endemic plant-Kokoona zeylanica (Family: Celestraceae). This was tested in normoglycaemic mice using three oral doses (1800, 2500 and 3000 mg/kg of body weight). The results show a moderate but dose dependant acute hypoglycaemic activity with a fairly rapid onset (4 h). However, It did not have a hypoglycaemic effect in non fasted mice or in fasted mice (treated consecutively for 30 days). ABE did not improve the glucose tolerance test indicating the Lack of antihyperglycaemic activity. However, ABE improved the sucrose tolerance test indicating the a-glucosidase inhibitory activity, which appears to be the main mechanism of hypoglycaemic activity. ABE was well tolerated {in terms of overt clinical signs of toxicity, hepatotoxicity and renotoxicity), and it did not provoke a change in the lipid profile. It is concluded that the ABE of K. zeylanica has a safe, moderate and acute hypoglycaemic activity

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Pharmacognosy
Magazftie
ISSN:
0973-1296
PHCOG MAG.
An
official
Pubiication of Phcog.Net;
PHCOG
MAG.:
Research
Article
The
effect
of the
aqueous
stem
bark
extract
of
Kokoona
zeylamca
Thw. on the
blood
glucose
level
of
mice
P.D.
Dayananda,
W.B.
Yapa
and W.D.
Ratnasooriya
Department
of
Zoology,
University
of
Colombo.
Colombo
03, Sri
Lanka
Address
correspondence:
wdr@zoology.cmb.ac.lk
ABSTRACT
This study examined the blood glucose lowering potential of the aqueous stem bark extract (ABE) of Sri Lankan
endemic plant -
Kokoona
zeylanica (Family: Celestraceae). This was tested in normoglycaemic mice using three
oral
doses
(1800,
2500
and
3000
mg/kg
of body weight). The results show a moderate but dose dependant acute
hypoglycaemic activity with a fairly rapid onset (4 h). However, It did not have a hypoglycaemic effect in non
fasted
mice or in fasted mice (treated consecutively for 30 days). ABE did not improve the glucose tolerance test
indicating
the Lack of antihyperglycaemic activity. However, ABE improved the sucrose tolerance test indicating
the
a-glucosidase inhibitory activity, which appears to be the main mechanism of hypoglycaemic activity. ABE was
well
tolerated {in terms of overt
clinical
signs
of toxicity, hepatotoxicity and renotoxicity), and it did not provoke
a change in the
lipid
profile. It is concluded that the ABE of K. zeylanica has a safe, moderate and acute
hypoglycaemic activity
KEY
WORDS:
Kokoona
zeylanica, Hypoglycaemia," Diabetes, Toxicity
INTRODUCTION
Kokoona
zeylanica Thw. (Family: Celestraceae) is a
large tree (20 - 35 m high) branched towards the top
with
a rough outer bark which is corky and grey in
colour
and an inner bark which is bright yellow or dark
orange in colour. Leaves are obovate, cuneate at base,
rounded or letuse at apex with serrated margins
entirely
or faintly. Flowers are in axillary panicles,
bisexual and duU yellowish brown in colour, (1).
Kokoona
species occur in the Annamallay hills in India
and in Sri Lanka.
Kokoona
zeylanica is endemic to Sri
Lanka, which is rather rare in the country and found in
forests (Pelawatte, Pasdun Korale, Ratnapura,
Ambagamuwa, Udugama and Hiniduma) in moist
regions between 1000 -
4000
feet altitude (2, 3).
According to phytochemical studies, the water extract
has revealed the presence of alkaloids, saponins,
terpenes and tannins in the inner stem bark of K.
zeylanica (4). Twelve D:A-friedo-oleanane triterpenes
have been isolated from the hot benzene extract of
the
inner stem bark of K. zeylanica (5). Zeylasterone,
pristimerin
(6), minor triterpene and celastranhydride
(7) are also recorded from the outer stem bark of K.
zeylanica from the light petroleum extract.
In the traditional medicine, the inner bark is used as a
treatment
for snakebites, swollen Joints, eye diseases,
framboesia pimples and skin diseases. The inner bark
may also be used to lighten the colour of the skin and
for
removing marks from the face. It is often used as a
snuff for severe headaches and the oil from the seed is
used as a leech repellent (2). K. zeylanica is also
claimed
to be useful as a treatment for diabetes
mellitus
(2, 8, 9). Several of the multiplant decoctions
for
diabetes mellitus also contain the inner stem bark
of K. zeylanica as one of the components (8). However,
so far its effect on blood glucose
level
has not been
scientifically
investigated. The aim of this study was to
examine the hypoglycemic potential, and the toxic
effects
of the aqueous stem bark extract of K.
zeylanica.
MATERIALS
AND
METHODS
Plant
collection authentication
The stem bark of K. zeylanica was purchased from D.
Peris a
Sons
Ltd.
Drug
Merchants, Gabo's Lane,
Pettah,
Colornbo and was identified and authenticated
by Dr. M. Chandrasena of the Institute of
Indigenous
Medicine,
University of Colombo. A voucher specimen
of the leaves and bark
(WDR/kokun)
was deposited at
the
museum of the Department of Zoology.
Preparation
of the ABE of K.zeylanica
The outer gray bark of the K. zeylanica was removed
and the pieces of inner bark were dried in the shade
for
two
days
and powdered using a mechanical grinder
(Sumeet Master No: 864, Sumeet machines Ltd, Nasik,
India). The powder (750 g) was mixed with tap water
and then refluxed with 4 I of tap water for two
days
in
a round bottom flask
fitted
to a Leibig's condenser.
308