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Fruit and vegetable consumption reduces the risk for cardiovascular disease development. The postprandial state is an important contributor to chronic disease development. Orange flavonoids may reduce postprandial oxidation. It was hypothesized that a mixture of orange flavonoids would reduce postprandial oxidation better than a single orange flavonoid or orange sugar and ascorbic acid, but not as well as orange juice, when consumed with a typical breakfast. A placebo-controlled crossover trial (16 male and female participants, 4 treatments, 4 visits) was carried out. Treatments were placebo (ascorbic acid and sugar equivalent to orange juice); placebo plus hesperidin; placebo plus hesperidin, luteolin, and naringenin (mixture; found to have synergistic antioxidant properties in vitro in previous work); and orange juice (positive control). Serum oxygen radical absorbance capacity (ORAC), total plasma phenolics (TP), and serum lipoprotein oxidation (LO) were measured after a 12-hour baseline fast and at 1, 2, and 3 hours after sample consumption. The placebo plus mixture and orange juice groups were significantly increased in ORAC and LO lag time. Data for TP were inconsistent with ORAC and LO. Contrary to previous studies attributing the protective postprandial effect to fructose and ascorbate in other fruit trials, orange phenolic compounds contribute directly to the postprandial oxidative protection of serum, despite an inconsistent change in serum TP.

The interactive antioxidant capacity of phenolic compounds from specific foods has not been well explored. The antioxidant capacity of a whole fruit exceeds the sum of the antioxidant capacities of individual antioxidants within that fruit, suggesting synergism among compounds. The interactions of seven phenolic compounds (p-coumaric acid, cyanidin, catechin, quercetin-3-glucoside, kaempferol, pelargonidin and ellagic acid) at relative concentrations found in strawberries were tested using the oxygen radical absorbance capacity assay. Statistically significant synergism was found for three combinations of two phenolic compounds, and among five combinations of three phenolic compounds. Statistically significant antagonism was observed among two combinations of two phenolic compounds and among one combination of three compounds. A chemical/structural model that best explained the results included reduction potentials, relative concentration, and the presence or absence of catechol (o-dihydroxy benzene) groups. This work demonstrates unique interactions that occur in a complex environment within the framework of strawberries. The synergism discovered at food-based antioxidant ratios could be applied to food preservation.