Hypocholesterolemic properties of grapefruit (Citrus paradisii) and shaddock (Citrus maxima) juices and inhibition of angiotensin-1-converting enzyme activity

Grapefruit (Citrus paradisii) and shaddock (Citrus maxima) juices are used in folk medicine for the management of hypertension and other cardiovascular diseases, but the mechanism of action by which they exert their therapeutic action is unclear. The aim of this study was to investigate the effect of grapefruit and shaddock juices on angiotensin-1-converting enzyme (ACE) activity in vitro and the hypocholesterolemic properties of the juices in rats fed a high-cholesterol diet. Grapefruit juice had higher total phenol and flavonoid contents than shaddock juice, while both juices inhibited ACE activity in a dose-dependent manner. Furthermore, administration of the juices to rats fed a high-cholesterol diet caused a significant reduction in plasma total cholesterol, triglyceride, and low-density lipoprotein–cholesterol levels and an increase in high-density lipoprotein–cholesterol levels. The inhibition of ACE activity in vitro and in vivo hypocholesterolemic effect of the juices could explain the use of the juices in the management of cardiovascular diseases.