Abstract: Extract of the plant Piper longum Linn (Family: Piperaceae) is used as folk medicine in India and China. Roots of the plant Piper longum are reported for the treatment of heart diseases in ancient literature of East Asia. However, no data is available on exact role of fractions of plant in heart diseases. In the present study we have isolated four major fractions namely F, G, H and I and the activity of the fractions was studied on isolated frog heart. Fraction F has produced negative inotropic and negative chronotropic effect on isolated frog heart at 200 μg mL-1. Fraction F shows maximum antagonistic activity on beta-receptors by decreasing heart rate and force of contraction. Actions of Adrenaline are blocked by fraction F and in the presence of propanolol, it shows continuous decrease in heart rate and force of contraction. In the present study, it was observed that fraction F shows antagonistic activity on beta adreno-receptors.