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.
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Antioksidan , Ketoksikan daun gynura , Procumbens (lour.)
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