apocarotenal and beta-apo-13-carotenone

β-Apocarotenoids are eccentric cleavage products of carotenoids formed by chemical and enzymatic oxidations. They occur in foods containing carotenoids and thus might be directly absorbed from the diet. However, there is limited information about their intestinal absorption. The present research examined the kinetics of uptake and metabolism of β-apocarotenoids. Caco-2 cells were grown on 6-well plastic plates until a differentiated cell monolayer was achieved. β-Apocarotenoids were prepared in Tween 40 micelles, delivered to differentiated cells in serum-free medium, and incubated at 37°C for up to 8 h. There was rapid uptake of β-apo-8'-carotenal into cells, and β-apo-8'-carotenal was largely converted to β-apo-8'-carotenoic acid and a minor metabolite that we identified as 5,6-epoxy-β-apo-8'-carotenol. There was also rapid uptake of β-apo-10'-carotenal into cells, and β-apo-10'-carotenal was converted into a major metabolite identified as 5,6-epoxy-β-apo-10'-carotenol and a minor metabolite that is likely a dihydro-β-apo-10'-carotenol. Finally, there was rapid cellular uptake of β-apo-13-carotenone, and this compound was extensively degraded. These results suggest that dietary β-apocarotenals are extensively metabolized in intestinal cells via pathways similar to the metabolism of retinal. Thus, they are likely not absorbed directly from the diet.

Topics: beta Carotene; Caco-2 Cells; Carotenoids; Chromatography, High Pressure Liquid; Humans; Kinetics; Mass Spectrometry; Vitamin A

Asymmetric β-apo-carotenoids (nonvitamin A-active metabolites) of provitamin A carotenoids have been observed in humans, but no study has investigated their formation during digestion.. The aim of this study was to follow the formation and absorption of asymmetric β-apo-carotenoids during digestion.. Healthy men were intragastrically and intraduodenally intubated, and randomly assigned to consume a lipid-rich control meal (n = 3) or a lipid-rich test meal containing 20 mg [13C-10]-β-carotene (n = 7). Digesta samples were collected over 5 h, and blood collected over 7 h. The triglyceride-rich lipoprotein (TRL) fractions of plasma were also isolated. Lipophilic extracts of digesta, plasma, and TRL were analyzed via a high-performance liquid chromatography-tandem mass spectrometry method developed to identify [13C]-labeled β-apo-carotenals/carotenone, [13C]-β-apo-carotenols, and [13C]-β-apo-carotenoic acids.. Relative to [13C]-β-carotene, [13C]-β-apo-carotenal levels remained ∼3 orders of magnitude lower throughout digestion (no [13C]-β-apo-carotenols, or [13C]-β-apo-carotenoic acids were observed). A mixed model determined relative influence of digesta type and time on digesta metabolite level. Increasing time significantly increased the model levels of digesta [13C]-β-apo-10',12',14',15-carotenal and [13C]-β-apo-13-carotenone (P < 0.05) and trended toward decreased [13C]-β-apo-8'-carotenal (P = 0.0876). Gastric digesta were associated with a significantly higher level of [13C]-β-apo-8'-carotenal (P = 0.0289), and lower levels of [13C]-β-apo-12',14',15-carotenal (P < 0.05), relative to duodenal digesta. Anticipated retinoids, but no asymmetric [13C]-β-apo-carotenals, [13C]-β-apo-carotenols, or [13C]-β-apo-carotenoic acids, were observed in the blood or TRL samples.. β-Carotene appears to be robust to digestion, with minor amounts of β-apo-carotenals/carotenone formed. Absence of asymmetric [13C]-β-apo-carotenals in plasma and TRL suggests lack of absorption, levels below the limit of detection, lack of stability, or further conversion during the digestive process to as-yet unidentified products. Lack of asymmetric [13C]-β-apo-carotenals in plasma also suggests a lack of postprandial intestinal BCO2 activity in healthy humans. This trial was registered at clinicaltrials.gov as NCT03492593.

Topics: Adolescent; Adult; beta Carotene; Carotenoids; Chromatography, High Pressure Liquid; Diet; Digestion; Gastrointestinal Tract; Humans; Lipoproteins; Male; Meals; Middle Aged; Nutritional Status; Oxidation-Reduction; Postprandial Period; Provitamins; Triglycerides; Young Adult

A putative carotenoid oxygenase from Novosphingobium aromaticivorans was purified with a specific activity of 0.8 U/mg by His-Trap affinity chromatography. The native enzyme was estimated to be a 52 kDa monomer. Enzyme activity for β-apo-8'-carotenal was maximal at pH 8.0 and 45 °C, with a half life of 15.3 h, K(m) of 21 μM, and k(cat) of 25 l/min. The enzyme exhibited cleavage activity only for carotenoids containing one β-ionone ring and its catalytic efficiency (k(cat)/K(m)) followed the order β-apo-8'-carotenal > β-apo-4'-carotenal > γ-carotene. The enzyme converted these carotenoids to β-apo-13-carotenones by cleaving their C(13)-C(14) double bonds. The oxygen atom of β-apo-13-carotenone originated not from water but from molecular oxygen. Thus, the enzyme was an apo-carotenoid 13,14-dioxygenase.

Topics: Carotenoids; Chromatography, Affinity; Electrophoresis, Polyacrylamide Gel; Escherichia coli; Hydrogen-Ion Concentration; Kinetics; Oxygenases; Recombinant Proteins; Sphingomonadaceae; Substrate Specificity; Temperature