The plasma bioavailability of nitrate and betanin from Beta vulgaris rubra in humans.

PURPOSE: To evaluate the plasma bioavailability of betanin and nitric oxide (NOx) after consuming beetroot juice (BTJ) and whole beetroot (BF). BTJ and BF were also analysed for antioxidant capacity, polyphenol content (TPC) and betalain content. METHODS: Ten healthy males consumed either 250 ml of BTJ, 300 g of BF or a placebo drink, in a randomised, crossover design. Venous plasma samples were collected pre (baseline), 1, 2, 3, 5 and 8 h post-ingestion. Betanin content in BTJ, BF and plasma was analysed with reverse-phase high-performance liquid chromatography (HPLC) and mass spectrometry detection (LCMS). Antioxidant capacity was estimated using the Trolox equivalent antioxidant capacity (TEAC) and polyphenol content using Folin-Ciocalteu colorimetric methods [gallic acid equivalents (GAE)] and betalain content spectrophotometrically. RESULTS: TEAC was 11.4 ± 0.2 mmol/L for BTJ and 3.4 ± 0.4 µmol/g for BF. Both BTJ and BF contained a number of polyphenols (1606.9 ± 151 mg/GAE/L and 1.67 ± 0.1 mg/GAE/g, respectively), betacyanins (68.2 ± 0.4 mg/betanin equivalents/L and 19.6 ± 0.6 mg/betanin equivalents/100 g, respectively) and betaxanthins (41.7 ± 0.7 mg/indicaxanthin equivalents/L and 7.5 ± 0.2 mg/indicaxanthin equivalents/100 g, respectively). Despite high betanin contents in both BTJ (~194 mg) and BF (~66 mg), betanin could not be detected in the plasma at any time point post-ingestion. Plasma NOx was elevated above baseline for 8 h after consuming BTJ and 5 h after BF (P < 0.05). CONCLUSIONS: These data reveal that BTJ and BF are rich in phytonutrients and may provide a useful means of increasing plasma NOx bioavailability. However, betanin, the major betalain in beetroot, showed poor bioavailability in plasma.

Indicaxanthin from Opuntia ficus-indica Crosses the Blood-Brain Barrier and Modulates Neuronal Bioelectric Activity in Rat Hippocampus at Dietary-Consistent Amounts.

Indicaxanthin is a bioactive and bioavailable betalain pigment from the Opuntia ficus-indica fruits. In this in vivo study, kinetic measurements showed that indicaxanthin is revealed in the rat brain within 1 h from oral administration of 2 µmol/kg, an amount compatible with a dietary consumption of cactus pear fruits in humans. A peak (20 ± 2.4 ng of indicaxanthin per whole brain) was measured after 2.5 h; thereafter the molecule disappeared with first order kinetics within 4 h. The potential of indicaxanthin to affect neural activities was in vivo investigated by a microiontophoretic approach. Indicaxanthin, administered in a range between 0.085 ng and 0.34 ng per neuron, dose-dependently modulated the rate of discharge of spontaneously active neurons of the hippocampus, with reduction of the discharge and related changes of latency and duration of the effect. Indicaxanthin (0.34 ng/neuron) showed inhibitory effects on glutamate-induced excitation, indicating activity at the level of glutamatergic synapses. A molecular target of indicaxanthin is suggested by in silico molecular modeling of indicaxanthin with N-methyl-D-aspartate receptor (NMDAR), the most represented of the glutamate receptor family in hippocampus. Therefore, at nutritionally compatible amounts indicaxanthin (i) crosses the rat BBB and accumulates in brain; (ii) can affect the bioelectric activity of hippocampal neurons locally treated with amounts comparable with those measured in the brain; and (iii) modulates glutamate-induced neuronal excitation. The potential of dietary indicaxanthin as a natural neuromodulatory agent deserves further mechanistic and neurophysiologic investigation.

Dietary indicaxanthin from cactus pear (Opuntia ficus-indica L. Mill) fruit prevents eryptosis induced by oxysterols in a hypercholesterolaemia-relevant proportion and adhesion of human erythrocytes to endothelial cell layers.

Toxic oxysterols in a hypercholesterolaemia-relevant proportion cause suicidal death of human erythrocytes or eryptosis. This process proceeds through early production of reactive oxygen species (ROS), release of prostaglandin (PGE2) and opening of PGE2-dependent Ca channels, membrane phosphatidylserine (PS) externalisation, and cell shrinkage. The present study was the first to reveal that a bioavailable phytochemical, indicaxanthin (Ind) from cactus pear fruit, in a concentration range (1.0-5.0 µM) consistent with its plasma level after a fruit meal, prevents PS externalisation and cell shrinkage in a dose-dependent manner when incubated with isolated healthy human erythrocytes exposed to an oxysterol mixture for 48 h. Dietary Ind inhibited ROS production, glutathione (GSH) depletion, PGE2 release and Ca2+ entry. Ind alone did not modify the erythrocyte redox environment or affect other parameters. Ex vivo spiking of normal human blood with the oxysterol mixture for 48 h induced eryptosis, resulting in the production of ROS and decreased levels of GSH, which was prevented by concurrent exposure to 5 µm-Ind. The adherence of eryptotic erythrocytes to the endothelium causes vascular tissue injury. Erythrocytes isolated from blood incubated with the oxysterol mixture plus 5 µm-Ind did not adhere to endothelial cell monolayers. Eryptotic erythrocytes may contribute to thrombotic complications in hypercholesterolaemia. Our findings suggest the positive effects of diets containing Ind on erythrocytes in hypercholesterolaemic subjects.