Kajian antihiperglisemik, antioksidan, fitokimia dan ketoksikan daun gynura procumbens (lour.) merr.
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Date
2009
Authors
Rosidah
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Abstract
The dry powdered leaves of G. procumbens were extracted sequentially with
petroleum ether followed by methanol using the Soxhlet. Each of these extracts was
evaporated under reduced pressure. The potential of these extracts given orally in
reducing blood glucose levels were studied in normal rats, normal rats given glucose
loading intraperitoneally (IPGTT) and in streptozotocin induced diabetic rats. It was
found that in contrast to glibenclamide which reduces blood glucose of the rats lower
than normal level, petroleum ether and methanol extracts at 1.0 g/kg have no effect on
blood glucose of normal rats. Between these two extracts, only methanol extract was able
to inhibit the increase of blood glucose of the rats given glucose loading and to reduce
blood glucose levels of streptozotocin induced diabetic rats. Therefore, the methanol
extract was further fractionated into the chloroform, ethyl acetate, butanol and aqueous
fractions. Among these fractions, it was found that the ethyl acetate fraction was the most
potent in inhibiting the increase in blood glucose levels of rats given glucose loading and
in reducing blood glucose levels of streptozotocin induced diabetic rats. In vitro test
showed that ethyl acetate fraction was able to inhibit glucose absorption at rat jejunum
sac preparation similar to acarbose. The finding suggests that one of the antidiabetic
mechanisms of ethyl acetate is via the inhibition of glucose or carbohydrate absorption in
gastrointestinal tract. Ethyl acetate fraction was also found to be similar with metformin
and able to promote glucose absorption of in vitro isolated abdomen muscle preparation
of the rats. This suggests that the ethyl acetate fraction was able to reduce blood glucose
levels of diabetic rats by promoting the uptake of glucose by the muscle cells. In the
study of antioxidant activity, it was found that ethyl acetate fraction was able to scavenge
ABTS cation radical (2.69 %), bleach ~-carotene-linoleic acid (62.86 %) and inhibit
xanthine oxidase activity (82.20 %). The ethyl acetate fraction contains the highest
polyphenol compounds (23.43 %) and has the highest ability to scavenge free radicals
(99.50 %) using DPPH assay as compared to the other fractions. Thus, phytochemical
screening was carried out on ethyl acetate fraction using chromatography methods (TLC,
HPTLC, HPLC and LCMS) to determine the active chemical constituents of the ethyl
acetate fraction. Among the chemical constituents identified in the fraction were
chlorogenic acid, kaempferol 3-0-rutinoside (K30R) and astragalin. Acute toxicity study
on methanol extract of G. procumbens found that at an oral dose up to 5.00 g/kg, no
adverse effect was found in the rats until 14 days after ingestion. In sub-chronic toxicity
test at dose up to 500 mg/kg/day for 90 days, also no toxic effect in rats was found. The
treated rat's bodyweight increased every week similar to control rats and no physical or
behavioral changes were detected during daily observation. No significant change
detected in biochemical and haematology tests between control and treated animal
groups. The results indicate that methanol extract of G. procumbens given as an oral dose
up to 5 g/kg or repeated daily dose up to 500 mg/kg for 90 days was safe.
Description
Keywords
Antioksidan , Ketoksikan daun gynura , Procumbens (lour.)