Human absorption and metabolism of oleuropein and hydroxytyrosol ingested as olive (Olea europaeaL.) leaf extract

Abstract

Phenolic compounds derived from the olive plant (Olea europaea L.), particularly hydroxytyrosol and oleuropein, have many beneficial effects in vitro. Olive leaves are the richest source of olive phenolic compounds, and olive leaf extract (OLE) is now a popular nutraceutical taken either as liquid or capsules. To quantify the bioavailability and metabolism of oleuropein and hydroxytyrosol when taken as OLE, nine volunteers (five males) aged 42.8 ± 7.4 years were randomized to receive either capsulated or liquid OLE as a single lower (51.1 mg oleuropein, 9.7 mg hydroxytyrosol) or higher (76.6 mg oleuropein, 14.5 mg hydroxytyrosol) dose, and then the opposite strength (but same formulation) a week later. Plasma and urine samples were collected at fixed intervals for 24 h post-ingestion. Phenolic content was analyzed by LC-ESI-MS/MS. Conjugated metabolites of hydroxytyrosol were the primary metabolites recovered in plasma and urine after OLE ingestion. Peak oleuropein concentrations in plasma were greater following ingestion of liquid than capsule preparations (0.47 versus 2.74 ng/mL; p = 0.004), but no such effect was observed for peak concentrations of conjugated (sulfated and glucuronidated) hydroxytyrosol (p = 0.94). However, the latter peak was reached earlier with liquid preparation (93 versus 64 min; p = 0.031). There was a gender effect on the bioavailability of phenolic compounds, with males displaying greater plasma area under the curve for conjugated hydroxytyrosol (11,600 versus 2550 ng/mL; p = 0.048). All conjugated hydroxytyrosol metabolites were recovered in the urine within 8 h. There was wide inter-individual variation. OLE effectively delivers oleuropein and hydroxytrosol metabolites to plasma in humans.

Oxidative Status and Presence of Bioactive Compounds in Meat from Chickens Fed Polyphenols Extracted from Olive Oil Industry Waste

“…Figure 2b demonstrates the ability of the here-developed method to determine polyphenols at trace levels (1 µg/kg). The detection of polyphenol metabolites has been documented in the literature in human/animal biological fluids, as well as in rat tissues [39][40][41]. Therefore, in order to complete the analytical study, the possible presence of glucuronide and sulphate metabolites of hydroxytyrosol and tyrosol was investigated.…”

Bioavailability of wild blueberry (poly)phenols at different levels of intake

“…It is well known that the inter-individual variation in the absorption and metabolism of (poly)phenols is considerably high and it depends not only on age [35], gender [36], gut microbiota [37], but also on genetic polymorphisms of each individual [38], among other factors. However, the determination of this inter-individual variability is often underreported and most works present the data as average or mean and use the standard error of the mean as a dispersion parameter.…”

Oleuropein aglycone protects against pyroglutamylated-3 amyloid-ß toxicity: biochemical, epigenetic and functional correlates

“…3.7. Brain concentrations of OLE, HT, and HVA after an acute administration of OLE in wt mice It is known that intestinal OLE is rapidly adsorbed in the plasma of both rats and humans, distributed to various tissues, including brain, conjugated and metabolized in a number of compounds including HT, HVA and elenolic acid, and excreted in the urine (De Bock et al, 2013;Serra et al, 2012). We therefore sought to quantify by liquid chromatographyemass spectrometry/mass spectrometry (LC-MS/MS) the concentrations of OLE and its major metabolites HT and HVA in the brains of OLE-administered mice.…”