Purpose: To evaluate the hypotensive, vasorelaxant and antihypertensive effects elicited by the
hydroalcohol extract from the fruits of
Syzygium cumini
(EHSCF) in non-anesthetized rats.
Methods: 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
spectrometry (ESI-MS).
Results: 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
relaxation (E
max = 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 (E
max = 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.
Conclusion: 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.
