Bioavailability and antioxidant effects of orange juice components in humans

Abstract

Seven healthy females and six males consumed daily 256 mg of vitamin C, 271 mg of flavanones (mainly as glycosides), 6 mg of carotenoids (mainly xanthophylls and cryptoxanthins), and 0.16 mg of folate by incorporation of daily three times 236 mL of not from concentrate orange juice (OJ) into their habitual diet. At the end of 3 weeks, mean vitamin C, folate, carotenoid, and flavanone plasma concentrations increased significantly relative to baseline by 59% (p < 0.001), 46% (p = 0.018), and 22% (p < 0.001), and 8-fold (p = 0.045), respectively. Flavanones were excreted in urine 9-fold more at the end of the intervention (p = 0.01) but returned to baseline 2 days after study completion. After the 3 week intervention, plasma concentrations of vitamins A and E did not change. 8-Hydroxydeoxyguanosine in white blood cells declined by 16% (p = 0.38; n = 11), and in individuals with high baseline concentrations by 29% (p = 0.36; n = 7), respectively. Low-density lipoprotein (LDL)-/high-density lipoprotein (HDL)-cholesterol ratios decreased but cholesterol (HDL, LDL, total) and thiobarbituric acid reactive substance plasma concentrations did not change significantly. We conclude from this pilot study that OJ is an excellent food source to enhance circulating concentrations of valuable hydrophilic as well as lipophilic phytochemicals.

Figure 1

Mean plasma concentration change of individual and total carotenoids. t-LUT/ZEA=trans-lutein+trans-zeaxanthin; cis-LUT/ZEA=total cis-lutein+cis-zeaxanthin; a-CRX= alpha-cryptoxanthin; tr beta-CRX=trans beta-cryptoxanthin; cis beta-CRX=cis beta-cryptoxanthin; a-CAR= alpha-carotene; tr beta-CAR=trans beta-carotene. White bars = baseline, striped bars = after 1 week, black bars = after 3 weeks. Error bars indicate standard error. To convert into μmol/L see legend of table 2. ^* p<0.05 for paired t-test comparing to baseline.

Figure 2

Mean change in plasma concentrations of ascorbic acid, folic acid, and the flavonoids hesperetin and naringenin. Glucuronide and sulfate conjugates of flavonoids occurring in plasma were enzymatically hydrolyzed prior to extraction and LC/MS analysis. White bars = baseline, striped bars= after 1 week, black bars = after 3 weeks. Error bars indicate standard error. ^* p<0.05 for paired t-test comparing to baseline.

Figure 3

Mean change of the 8-hydroxy deoxyguanosine (8 -OHdG)/deoxyguanosine (dG) ratio in white blood cells and change in plasma concentrations of thiobarbituric acid reactive substances (TBARS) and homocysteine (HCy). The latter values are 10 times greater than displayed in graph. White bars = baseline, striped bars= after 1 week, black bars = after 3 weeks. Error bars indicate standard error. TBARS units are malondialdehyde (MDA) equivalents. HCy values were divided by 10 to fit scale of graph. ^* p<0.05 for paired t-test comparing to baseline.

Figure 4

Mean plasma concentration change of total, HDL and LDL cholesterol, and of triacylglycerols (TAG). White bars = baseline, striped bars= after 1 week, black bars = after 3 weeks. Error bars indicate standard error. To convert into μmol/L see legend of table 2. ^* p<0.05 for paired t-test comparing to baseline.