F10 Fraction Of Terminalia Arjuna (TA) Bark Aqueous Extract Exerts A Positive Inotropic Effect On Adult Ventricular Myocytes

The bark of Terminalia arjuna (Roxb.) Wt. and Arn, (Combretaceae), a tropical evergreen tree, has been used for centuries in Ayurvedic medicine as a cardiotonic (naturoceutical) for treatment of cardiovascular disorders and recently became a popular over-the-counter dietary supplement for maintaining a healthy heart (a nutraceutical). Some active constituents of TA bark have been identified, including triterpene glycosides, triterpenes, tannins, flavonoids, polyphenols, gallic acid, ellagic acid, and oligomeric proanthocyanidins [1 – 3]. However, specific actions of these constituents and the mechanism of action remain undefined. We have previously shown that only the aqueous extract of TA bark (TA _AqE) enhances contractility of isolated adult rat ventricular myocytes (AVM) in contrast to organic extracts of TA bark [4]. The lyophilized TA _AqE was dissolved in ethanol, filtered and subjected to separation by a preparative high-performance liquid chromatography (HPLC) system using a reverse phase C18 column and a diode-array detector. Twelve peak-based fractions were collected, lyophilized and resuspended in ultrapure water (F1-F7) or in DMSO (F8-F12) to afford a stock solution of 5 mg/ml. After a 1000-fold dilution in normal Tyrode's experimental solution, the effect of each fraction (5 µg/ml) on contraction of AVM was evaluated in the same manner and compared with that of the parent TA _AqE. We found that only fraction 10 (F10) exerted a positive inotropic effect, comparable to that of the parent TA _AqE. This study will lead to further isolation and full characterization of active inotropic F10 of TA aqueous extract.

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