Pemencilan berpandukan aktiviti kardiovaskular in vitro ke atas tinospora crispa, miers dan aktiviti antihiperglisemiknya

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Date
2005
Authors
Bakhari, Noraziyah
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Abstract
The present study was carried out to examine the effect of Tinospora crispa extracts on the cardiovascular system and their ability to reduce the blood glucose level. The group of compounds or pure compounds responsible for the cardiovascular activity were then isolated and identified through activity guided isolation procedure. The dried powdered stems of T. crispa were serially extracted with petroleum ether, followed by chloroform, methanol and water. The effect of these extracts on the contraction of left and right atria, and also the aortic strips of adult Sprague-Dawley rats in vitro were studied. Screening results showed that the chloroform extract exhibited the strongest inhibition (82. 7 .:t._3.1% (p<0.001) of maximum response at 1.0 mg/mL) on the inotropic effect of isoprenaline (ISP) to the left atria. The inhibition was non-competitive, since the maximum of the log dose-response curve of the atria to ISP was reduced. However, none of the extracts (0.2 - 1.0 mg/mL) significantly influence the inotropic activity of the right atria to ISP. The chloroform extract was found to be most potent in inhibiting the inherent spontaneous contraction of the right atria. All of the extracts studied also noncompetitively inhibited the noradrenaline (NA)-induced contraction of rat aortic strips. Chloroform extract which was again found to be most potent with 87.2_:!:2.9% (p,0.001) inhibition at 1.0 mg/mL was separated into four fractions, Cf1, Cf2, Cf3 and Cf4 using dry-column flash chromatography with various combinations of n-hexane, chloroform and methanol as eluents. Screening of the chloroform fractions on cardiovascular activities, using the same isolated tissue preparations showed that Cf3 fraction is most potent in inhibiting the inotropic effect of ISP in left atria preparation, with 98.7 ± 1.1% (p<0.001) inhibition at 1.0 mg/mL. Results also showed that Cf3 fraction is the most active chloroform fraction in inhibiting noradrenaline-induced contraction of the isolated aortic strips, where 1.0 mg/mL of the fraction inhibited 98.6 :!: 0. 7% (p<0.001) of contraction. The isolation of the constituents in the most active fraction (Cf3) using various chromatography techniques such as thin layer chromatography, column chromatography and high perfomance liquid chromatography revealed the presence of the N-acylaporphlne alkaloids namely N-formylnornuciferine and N-acetylnornuciferine as the major compounds. A small amount of an oxoaporpine alkaloid, lysicamine was also isolated. Other compounds that have been isolated include a long chain aliphatic alcohol and n-tetracosyl trans-ferulate. Structural identification of the compounds is based on spectral analysis such as NMR, UV, IR and GC-MS. The hypoglycaemic effect of all T. crispa extracts i.e petroleum ether, chloroform, methanol and aqueous extracts on normal and diabetic adult Spraque-Dawley rats were also studied. However, none the extracts significantly reduced the blood glucose level in both normal and diabetic rats. All the extracts did not significantly influence the glucose tolerance in normal rats as shown by the glucose tolerance test.
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Keywords
Kardiovascular , Tinospora crispa , Antihiperglisemiknya
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