The present study investigated the effects of different
extracts and fractions from leaves of Gynura procumbens Merr. on rat atrial contraction
in vitro. Isolated left and right atria, mounted in a 20-ml organ bath, were allowed to equilibrate
for 15 min before the application of the extracts or fractions. The extracts (petroleum-
ether extract (PE) and methanol extract (ME)) and the fractions (chloroform fraction
(CHL), ethyl-acetate fraction (EA), n-butanol fraction (NB) and water fraction (WA) of
the methanol extract) were tested at three concentrations (0.25, 0.5 and 1.0 mg/ml), with
a b-adrenergic agonist (isoprenaline) as a control. All data on contraction responses were
log-transformed and analyzed. When exposed to the different extracts, both atria tended
to exhibit greater contractive responses with the NB whereas cardiac contractions had
a tendency to be reduced with most other extracts. For a given extract, the contraction responses
were particularly greater at 0.5 mg/ml for the right atrium and at 1 mg/ml for the
left atrium. Further analysis focusing on the NB fraction revealed that positive inotropism
was greater in left atria exposed to highly-concentrated F2 and F3 sub-fractions. Taken together,
our results suggest that NB extracts and fractions from the G. procumbens-leaf
methanol extract have positive inotropic activities and