Absorption, excretion, and distribution of dietary antioxidant betalains in LDLs: potential health effects of betalains in humans

ABSTRACTBackground: Betalains were recently identified as natural antioxidants.However, little is known about their bioavailability fromdietary sources.Objective: The objective was to evaluate the bioavailability ofbetalains from dietary sources.Design: The plasma kinetics and urinary excretion of betalains werestudied in healthy volunteers (n 8) after a single ingestion of 500 gcactus pear fruit pulp, which provided 28 and 16 mg indicaxanthinand betanin, respectively. The incorporation of betalains inLDLandthe resistance of the particles to ex vivo–induced oxidation was alsoresearched.Results: Betanin and indicaxanthin reached their maximum plasmaconcentrations 3 h after the fruit meal and declined according tofirst-order kinetics. The half-life of betanin (0.94 0.07 h) wasshorter than that of indicaxanthin (2.36 0.17 h). Both compoundshad disappeared from plasma by 12 h after intake. The urinaryexcretion of indicaxanthin and betanin over 12 h represented 76 3.0% and 3.7 0.2%, respectively, of the ingested compounds. LDLisolated 3 and 5 h after the fruit meal incorporated betalains at concentrationsof 100.5 11and50 7.2pmol/mgLDLprotein, respectively.In addition, the particles appeared more resistant to ex vivo–inducedoxidative injury than did the samples isolated before fruit ingestion (P 0.05)—the higher the amount of betalains incorporated, the higher theresistance. The concentrations of vitamin E and -carotene in LDL didnot change significantly after fruit ingestion.Conclusion: Our results show that cactus pear fruit is a source ofbioavailable betalains and suggest that indicaxanthin and betaninmay be involved in the observed protection of LDL against ex vivo–induced oxidative modifications.