| Disease | 5 HEALTHY VOLUNTEERS, 3 MALES AND 2 FEMALES AGED BETWEEN 25 AND 39Y, INGESTED 225 G OF FRIED ONIONS AFTER AN OVERNIGHT FAST AND PERIPHERAL VENOUS BLOOD WAS COLLECTED 0.2,4,24 AND 48 H AFTER CONSUMPTION. QUERCETIN IN THE PLASMA, TOTAL ANTIOXIDANT
CAPACITY AND SUSCEPTIBILITY OF LOW DENSITY LIPOPROTEINS (LDL) TO OXIDATION WERE MEASURED. FOLLOWIG THE ONION MEAL, QUERCETIN LEVELS INCREASED FROM BASELINE VALUES (248.4+/- 103.9 NG/ML), DECREASING TO BASELINE AGAIN AFTER 24 H (P > 0.05). THIS
WAS ACCOMPAINED BY AN INCREASE IN THE TOTAL ANTIOXIDANT ACTIVITY OF THE PLASMA FROM BASELINE (1.70 +/- 0.04 MMOL/1 TROLOX EQUIVALENTS) TO 1.75 +/- 0.10 MMOL/1 TROLOX EQUIVALENTS AFTER 2 H AND 1.76 +/- 0.08 MMOL/1 TROLOX EQUIVALENTS AFTER 4 H.
THERE WAS NO SIGNIFICANT CHANGE IN THE SUSCEPTIBILITY OF THE PLASMA OR THE ISOLATED LDL TO OXIDATION OVER THE 48 H PERIOD AFTER CONSUMPTION OF THE FRIED ONIONS. IN VIEW OF THESE NEGATIVE FINDINGS, WE ISOLATED LDL AND OTHER LIPOPROTEINS FROM
PLASMA AT EACH TIME POINT. QUERCETIN WAS NOT DETECTED IN EITHER LDL OR VLDL, BUT WAS PRESENT IN THE HDL FRACTION, ALTHOUTH THIS FRACTION ALSO CONTAINS OTHER PROTEINS INCLUDING ALBUMIN. QUERCETIN CAN BE ABSORBED IN HUMANS FROM DIETARY SOURCES TO
HIGH ENOUGH CONCENTRATIONS TO INCREASE THE OVERALL ANTIOXIDANT ACTIVITY OF THE PLASMA. QUERCETIN, HOWEVER, HAS A STRONG AFFINITY FOR PROTEIN AND PROVIDES NO DIRECT PROTECTIVE EFFECT DURING LDL OXIDATION. |