| Abstract
| - The bioactivity of Israeli Jaffa blond (Shamouti) fresh orange and Israeli Jaffa red Star Ruby (Sunrise)grapefruit juices was investigated in vitro and in vivo. The contents of bioactive compounds of thesejuices were determined. The influence of bioactive compounds on plasma lipids and plasma antioxidantactivity in rats fed cholesterol-containing and cholesterol-free diets was assessed. Significantdifferences in the contents of dietary fibers were not found. The contents of total polyphenols,flavonoids, and anthocyanins in fresh orange and grapefruit juices were 962.1 ± 27.2 and 906.9 ±27.1; 50.1 ± 3.3 and 44.8 ± 3.2; and 69.9 ± 5.6 and 68.7 ± 5.5 μg/mL, respectively. The antioxidantpotential measured by the scavenging activity against nitric oxide, the β-carotene−linoleate modelsystem (β-carotene), and the 1,1-diphenyl-2-picrylhydrazyl and 2,2‘-azino-bis(3-ethyl-benzothiazoline-6-sulfonic acid) diamonium salt assays was higher in orange juice but not significantly. A high levelof correlation between contents of total polyphenols and flavonoids and antioxidant potential valuesof both juices was found. Diets supplemented with orange and to a lesser degree with grapefruitjuices improved plasma lipid metabolism only in rats fed added cholesterol. However, an increase inthe plasma antioxidant activity was observed in both groups. In conclusion, fresh orange and grapefruitjuices contain high quantities of bioactive compounds, which guarantee their high antioxidant potential,and the positive influence on plasma lipid metabolism and plasma antioxidant activity could makefresh orange and grapefruit juices a valuable supplement for disease-preventing diets. Keywords: Citrus juices; bioactive compounds; plasma lipids; plasma antioxidant activity; rats
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