To evaluate the hypotensive, vasorelaxant and antihypertensive effects elicited by the
hydroalcohol extract from the fruits of Syzygium cumini
(EHSCF) in non-anesthetized rats.
The rats were anesthetized and polyethylene catheters were inserted into the lower
abdominal aorta and into the inferior vena cava for blood pressure measurements and administration of
drugs. After a recovery period of 24 h, EHSCF (0.5; 1; 5; 10; 20 and 30 mg/kg, i.v.) was administered in
non-anesthetized rats. The mean arterial pressure and the heart rate were recorded. To investigate the
effects of extract, doses EHSCF were administered after pretreatment with L-NAME, atropine,
indomethacin, and hexamethonium. For measurement of isometric tension, a concentration-response
curve was obtained after Phenylephrine and KCl (80 mM) pre-contractions. The bioactive extract was
analyzed via mass spectrometry (MS) fingerprinting using direct electrospray ionization mass
EHSCF (0.5; 1; 5; 10; 20 and 30 mg/kg) induced hypotension (-15 ± 1, -14 ± 1, -15 ± 1, -13 ±
1, -11 ± 1 and -13 ± 2 %) and bradycardia (-6 ± 1, -5 ± 1, -6 ± 1, -14 ± 1, -8 ± 1 and -10 ± 2 %) in
normotensive rats. These responses were attenuated by pre-treatment with L-NAME, indomethacin,
hexamethonium or atropine. In phenylephrine, pre-contracted mesenteric rings, EHSCF-induced
= 54.6 ± 4.5 % and pD2 = 2.7 ± 0.1) that were affected by endothelium removal.
EHSCF caused relaxant effect of KCl (80 mM) pre-contracted rings (Emax
= 100 ± 0.2 % and pD2 = 2.2 ±
0.1). This effect was not changed in denuded rings. A single oral administration of the extract reduced
significant mean arterial pressure in spontaneously hypertensive rats. ESI-MS/MS analyses of EHSCF
demonstrated that the major constituents of the analyzed samples coincided with the mass of the malic,
gallic, caffeic and ferulic acids.
The results suggest that EHSCF induces hypotension probably due to a decrease in
peripheral resistance, mediated by the endothelium. Bradycardia may be due to indirect cardiac
muscarinic activation. The extract also causes an antihypertensive effect.