Antioxidative Potency Of Fractions Isolated From Pomegranate Juice

Several fractions were isolated from pomegranate juice, including gallic acid, ellagic acid, tannins, total PJ anthocyanins, and specific anthocyanins such as cyanidin-3-0-P-glucopyranoside, cyanidin-3,5-di-0-P-glucopyranoside, delphinidin-3-0-P-glucopy-ranoside, and pelargonidin-3-0-P-glucopyranoside. The total anthocyanin and tannin fractions exhibited a dose-dependent antioxidative effect against copper ion-induced LDL oxidation. In the AAPH-induced LDL oxidation, both fractions exhibited weaker antioxidative properties in comparison to the copper ion-induced LDL oxidation. These results suggest that the anthocyanins and tannins also possess transition metal ion chelation properties in addition to their free-radical scavenging capabilities. The tannin fraction was more potent than the anthocyanin fraction in inhibiting LDL oxidation, and the IC50 of the tannins was half that of the anthocyanins. Both PJ ellagic and gallic acids and the anthocyanins delphinidin-3-0-P-glucopyranoside, pelargonidin-3-0-P-glucopyranoside, cyanidin-3-0-P-glucopyranodise, and cyanidin-3,5-di-0-P-glucopyranoside inhibited copper ion-induced LDL oxidation in a dose-dependent manner. Upon comparing the effects of ellagic acid to gallic acid, gallic acid was more potent (IC50 of 2.1 ^g/mL for gallic acid vs. 16 ^g/mL for ellagic acid). Similarly, the anthocyanins delphinidin-3-0-P-glucopyranoside and cyanidin-3-0-P-glucopyranodise were more potent than ellagic acid, with IC50 of 3.0, 2.0, and 16 ^g/mL, respectively. When comparing the antioxidative properties of the specific PJ anthocyanins, the anthocyanins pelargonidin-3-0-P-glucopyranoside and cyani-din-3,5-di-0-P-glucopyranoside were less potent than the other two (IC50 of 13 ^g/mL vs. 2 to 3 ^g/mL). A similar pattern was noted for the free-radical scavenging capabilities of the above PJ fractions. PJ administration to atherosclerotic patients and mice was shown to significantly increase PON1 activity.53-55 In order to analyze which of the PJ fractions is responsible for the effect on PON1, we incubated the PJ fractions (1 ^mol/L) with human serum. Cyanidin-3,5-di-0-P-glucopyranoside and pelargonidin-3-0-P-glucopyranoside significantly increased PON1 activity by 20%, whereas ellagic acid and delphinidin-3-0-P-glucopyranoside increased the activity by only 10%. Gallic acid and cyanidin-3-0-P-glucopyranodise did not affect PON1 activity.

The PJ hydrolyzable tannins are punicalin, pedunculagin, punicalagin, and gal-lagic and ellagic acidesters of glucose.65 We demonstrated that punicalagin inhibited copper ion-induced LDL oxidation and this effect could be related to its capability to scavenge free radicals. Punicalagin also reduced macrophage oxidative stress by up to 90%, and the ability of the cells to oxidize LDL by up to 40%.

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