Effects of the crude extract of the fruit rind of rambutan (Nephelium lappaceum L.) on blood pressure, heart rate and respiratory rate in anaesthetized male rats

Abstract

The bark of rambutan (Nephelium lappaceum L.), which is normally discarded was found to contain extremely high antioxidant activity [1]. Since polyphenols found in plants are widely known to affect the cardiovascular system, there is no evidence suggesting how polyphenols found in the crude extract of the fruit rind of rambutan did. We, therefore, investigated acute effects of rambutan on cardiovascular and respiratory responses in male rats. The ethanolic rambutan bark extract with a total phenolic content of 18.69±0.2mg gallic acid/g dry sample extract were used in this experiment. Invasive arterial blood pressure, heart rate and respiratory rate were recorded in pentobarbital-anaesthetized male rats for 2 hours after single i.p. injected with vehicle (n=8) and 1g/kg rambutan bark extract (n=8). Intragroup comparison showed that rambutan rind extract markedly increased mean arterial blood pressure (MABP) and systolic blood pressure (p<0.05, compared to baseline). In comparison between groups, significant increases in MABP, systolic blood pressure, diastolic blood pressure and heart rate can be observed 60 minutes after rambutan bark extract (p<0.05, two way repeated measures ANOVA). Significant increases in those parameters were found over the rest period of investigation. However, there were no changes in respiratory rate In conclusion, this study provided the first evidence of prolonged cardiovascular response (increases in MABP, systolic blood pressure and heart rate) following acute rambutan rind extract in anesthetized male rats. The mechanism of which rambutan rind extract regulating blood pressure in normotensive, hypotensive and hypertensive conditions should be further investigated.