Viola tricolor Linn. is used as cardio-protective and anti-hypertensive agent in traditional medicine. Current study objective was to evaluate cardio-protective and hypotensive effects of Viola tricolor L. in vitro and in vivo studies. Viola tricolor L. crude extract (Vt.Cr) and its fractions (Aqueous and organic) were tested at rabbit atria and aorta coupled to Power Lab Data Acquisition System for cardio depressant and vasorelaxant effects in vitro whereas in vivo Blood Pressure was checked by invasive method in normotensive ketamine-diazepam anesthetized rats. Isoproterenol was employed for acute myocardial infarction (AMI) and left ventricular hypertrophy (LVH) development and cardioprotective effects of Vt.Cr were evaluated hemodynamically and histopathologically. Vt.Cr and its fractions decreased heart rate and contractile force in paired atria and relaxed Phenylephrine (1 µM) and K⁺ (80 mM) stimulated contractions in aorta possibly mediated through Voltage dependent L-type calcium channels blockage supported by in vivo hypotensive action. In LVH, Vt.Cr lowered Angiotensin Converting Enzymes and renin, increased cyclic Guanosine Monophosphate and nitric oxide levels, decreased cardiomyocytes size and fibrosis attributed to Gallic acid as detected by High Performance Liquid Chromatography. Partial positive results were seen hemodynamically and histologically in AMI Viola tricolor L. showed vasorelaxant, cardio-relaxant, hypotensive, and cardio protective effect validating traditional practice in cardiovascular disorders.

Keywords: VDLCs; Vasodilator; calcium channel blocker; cardiac depressant; histopathology; in vitro/in vivo; invasive blood pressure.