Hesperidin is the predominant polyphenol consumed from citrus fruits and juices. However, hesperidin is proposed to have limited bioavailability due to the rutinoside moiety attached to the flavonoid. The aim of this study was to demonstrate in human subjects that the removal of the rhamnose group to yield the corresponding flavonoid glucoside (i.e., hesperetin-7-glucoside) will improve the bioavailability of the aglycone hesperetin. Healthy volunteers (n=16) completed the double-blind, randomized, crossover study. Subjects randomly consumed hesperetin equivalents supplied as orange juice with natural hesperidin ("low dose"), orange juice treated with hesperidinase enzyme to yield hesperetin-7-glucoside, and orange juice fortified to obtain 3 times more hesperidin than naturally present ("high dose"). The area under the curve (AUC) for total plasma hesperetin of subjects consuming hesperetin-7-glucoside juice was 2-fold higher than that of subjects consuming the "low" dose hesperidin juice [3.45+/-1.27 vs. 1.16+/-0.52 mmol/(L.h), respectively, P>0.0001]. The AUC for hesperetin after consuming the hesperetin-7-glucoside juice was improved to the level of the "high" dose hesperidin juice [4.16+/-1.50 mmol/(L.h)]. The peak plasma concentrations (C(max)) of hesperetin were 4-fold higher (2.60+/-1.07 mmol/L, P<0.0001) after subjects consumed hesperetin-7-glucoside juice compared with those consuming "low" dose hesperidin juice (0.48 +/- 0.27 mmol/L), and 1.5-fold higher than those consuming "high" dose hesperidin juice (1.05+/-0.25 mmol/L). The corresponding T(max) was much faster (0.6+/-0.1 h, P<0.0001) after subjects consumed hesperetin-7-glucoside juice compared with "low" dose (7.0+/-3.0 h) and "high" dose (7.4+/-2.0 h) hesperidin juices. The results of this study demonstrated that the bioavailability of hesperidin was modulated by enzymatic conversion to hesperetin-7-glucoside, thus changing the absorption site from the colon to the small intestine. This may affect future interventions concerning the health benefits of citrus flavonoids.

The French have one of the lowest incidences of coronary heart disease in the Western world despite a diet with a relatively high fat content. This phenomenon that has puzzled researchers worldwide for more than a decade is known as the 'French paradox' and has been linked to the high consumption of red wine in France. Red wine is rich in the complex polyphenols, the proanthocyanidins, and these compounds have recently attracted attention as potential cardiac-protective compounds. The present review summarizes the literature on proanthocyanidins with focus on their chemical structure, the occurrence, the daily intake from foods, the bioavailability and metabolism, and the evidence for a protective effect against cardiovascular diseases.

Fruit and vegetables increase erythrocyte glutathione peroxidase activity and resistance of plasma lipoproteins to oxidation more efficiently than do the vitamins and minerals that fruit and vegetables are known to contain. Plasma protein carbonyl formation at lysine residues increases because of the vitamins and minerals in fruit and vegetables.