Obesity increases risks for hypertension and myocardial infarction (MI), which accounts for high rate of mortality globally. Therefore, agents targeting obesity and its cardiovascular complications are highly necessitated. Hibiscus sabdariffa Linn. (Roselle) is rich with antioxidants and we have recently shown that Roselle extract attenuate nicotine-induced cardiac injury1. Nevertheless, its effect on obese hearts after MI have not been shown. The aim of this study is to determine effect of Roselle extract on cardiac function in Langendorff-perfused obese rat heart after MI. Male Sprague-Dawley rats (300-350g) were fed with either standard diet (control) or obese fed with high-fat diet (HFD) (OB) for 12 weeks. Rats were given isoproterenol (ISO, 85 mg/kg s.c, 2 days, n=30) after 8 weeks of diet to induce MI. Roselle was given orally (100 mg/kg, n=12) after induction of MI for 4 weeks with continued diet. Control rats received either vehicle (n=12) or ACE inhibitor Enalapril (10 mg/kg, n=6). After 12 weeks, rats were sacrificed and their hearts were mounted on Langendorff apparatus in constant flow mode. Readings were taken after 20 minutes of steady-state perfusion. Values are expressed as mean ± SEM, analysis by one way ANOVA. In this study, 12 weeks of HFD significantly increased systolic blood pressure (SBP) and was further aggravated by ISO-induced MI. Rat hearts from obese rats had significantly lower LVDP (Table 1) as compared to the controls, suggesting impaired contractile function. ISO-induced MI similarly worsened LVDP level. Interestingly, Roselle was able to improve LVDP and its derivatives in obese rat hearts, however its effects were abolished in rats with MI. Conversely, administration of Enalapril was able to attenuate LVDP and its derivatives in obese rat hearts after MI. In addition, ISO-induced MI in obese rats also lowered coronary flow, suggesting diminished vasodilatory response, which was ameliorated by Roselle and Enalapril (Table 1). The conclusion of this study was supplementation of Roselle (100 mg/kg, 4 weeks) improves cardiac function in a rat model of HFD-induced obesity, however, its effects are abolished in presence of prior MI.