Antihypertensive effects of Ocimum gratissimum extract: Angiotensin-converting enzyme inhibitor in vitro and in vivo investigation

•Ocimum gratissimum extract has a significant blood pressure lowering effect in spontaneous hypertension rats (SHR).•Ocimum gratissimum extract exhibited an Angiotensin-converting enzyme (ACE) inhibitory activity in vitro.•Ocimum gratissimum extract showed significant decreases in lung ACE levels in SHRs.•Rutin was the main polyphenol of Ocimum gratissimum extract. This study aimed to examine whether Ocimum gratissimum (OG) has the Angiotensin-converting enzyme (ACE) inhibitory activity in vitro and in spontaneously hypertensive rats (SHRs). OG water extract exhibited an in vitro ACE-inhibition activity, with the 50% inhibition concentration (IC50) value being 56.3μg/mL, which is higher than rutin’s 43.08μg/mL. The main phenolic compound found in OG extract was rutin, according to the HPLC fractionation profile. The anti-hypertension effect in vivo was tested with SHRs. SHRs were fed orally with a distilled water, 100 or 500mg/kg BW OG extract for 8weeks. Systolic blood pressure, ACE levels in plasma and lung, and plasma endothelin-1 were significantly lower in the 500mg/kg OG group compared with the SHRs group. These results suggested that OG extract has the ACE inhibition activity in vitro and also in SHRs, which may be due to its main component of phenolic compound, rutin.