HYPOCHOLESTEROLEMIC EFFECT OF SOME CITRUS FRUIT JUICES AND THEIR INHIBITION OF ANGIOTENSIN-I CONVERTING ENZYME

Abstract

This study sought to investigate the effect of four Nigerian citrus fruit juices [lemon (Citrus limon), lime (Citrus aurantifolia), grapefruit (Citrus paradisii) and shaddock (Citrus maxima)] on angiotensin-1 converting enzyme (key enzyme linked to hypertension) activity in vitro and investigate the hypocholesterolemic properties of the juices in vivo. The juices of the citrus species were obtained by manual squeezing and a dilution(1:100) of the juices was prepared. Grapefruit juice had the highest total phenol content (134mg/L) and flavonoid content (35mg/L) of the juices tested while lime juice (52.0mg/L) had the least phenol content and lemon juice (24mg/L) had the lowest total flavonoid content (29.5mg/L) of the four juices tested. The citrus fruit juices all inhibited ACE activity in a dose-dependent manner with lime juice (EC50 = 1.67mL/L) having the highest ACE inhibiting activity while grapefruit juice (EC50 = 2.51 mL/L) had the least ACE inhibiting ability. The juices also exhibited antioxidant activities as typified by their reducing power (Grapefruit juice highest with 22.96 mg AAE/L while lemon juice was least with 11.85 mg AAE/L), and various radicals (DPPH*, ABTS* and OH*) scavenging abilities. The juices were also able to inhibit Fe2+-induced lipid peroxidation [lemon juice had highest inhibitory ability (EC50 = 4.71mL/L) while grapefruit juice had the lowest inhibitory ability (EC50 = 5.93 mL/L)] and sodium nitroprusside-induced lipid peroxidation [lime juice had highest inhibitory ability (EC50 = 4.93 mL/L) while shaddock juice had the lowest inhibitory ability (EC50 = 7.48 mL/L) in rat’s liver - in vitro Furthermore, administration of the citrus fruit juices in high cholesterol diet fed to rats caused a significant reduction in serum total cholesterol, triglyceride and LDL cholesterol levels and an increase in serum HDL-cholesterol levels (these are all essential for restoration of the rat to pre-hypercholesterolemia induced state) correlated with increased administration of the juices to the high cholesterol fed rats. In conclusion, the inhibition of ACE activity in vitro and in vivo hypocholesterolemic effect of the juices could lead to the use of the juices in the management of cardiovascular diseases.