Tissue Distribution of Oleocanthal and Its Metabolites after Oral Ingestion in Rats

Claims for the potential health benefits of oleocanthal (OLC), a dietary phenolic compound found in olive oil, are based mainly on in vitro studies. Little is known about the tissue availability of OLC, which is rapidly metabolized after ingestion. In this study, the distribution of OLC and its metabolites in rat plasma and tissues (stomach, intestine, liver, kidney, spleen, lungs, heart, brain, thyroid and skin) at 1, 2 and 4.5 h after the acute intake of a refined olive oil containing 0.3 mg/mL of OLC was examined by LC-ESI-LTQ-Orbitrap-MS. OLC was only detected in the stomach and intestine samples. Moreover, at 2 and 4.5 h, the concentration in the stomach decreased by 36% and 74%, respectively, and in the intestine by 16% and 33%, respectively. Ten OLC metabolites arising from phase I and phase II reactions were identified. The metabolites were widely distributed in rat tissues, and the most important metabolizing organs were the small intestine and liver. The two main circulating metabolites were the conjugates OLC + OH + CH₃ and OLC + H₂O + glucuronic acid, which may significantly contribute to the beneficial health effects associated with the regular consumption of extra virgin olive oil. However, more studies are necessary to determine the concentrations and molecular structures of OLC metabolites in human plasma and tissues when consumed with the presence of other phenolic compunds present in EVOO.

In Vivo Anti-inflammatory and Antiallergic Activity of Pure Naringenin, Naringenin Chalcone, and Quercetin in Mice

Flavonoids, found in almost all fruits and vegetables, belong to a class of plant secondary metabolites with a polyphenolic structure and have properties with health-improving potential. However, few experimental studies on the effects of flavonoids have been carried out in vivo after external application and using pure compounds. Aiming to fill this gap, in this study we tested the topical anti-inflammatory and antiallergic activity of three flavonoids of high purity, naringenin, naringenin chalcone, and quercetin, in mouse models. The topical anti-inflammatory effects were assessed against arachidonic acid- (AA) and tetradecanoylphorbol-13-acetate- (TPA) induced ear edema. The anti-inflammatory effect of naringenin against ear edema was noticeable at a 1% dose in the AA model and at half this dose in the TPA model. Quercetin (1.3%) did not exert any topical anti-inflammatory activity in the AA model, but its inhibitory effect in the TPA model was similar to that of naringenin (2%); in contrast, naringenin chalcone was more active against the AA-induced than TPA-induced inflammation. The flavonoid effect on IgE-mediated passive cutaneous anaphylaxis was also studied in mice, both intravenously and topically. Naringenin, naringenin chalcone, and quercetin all showed strong antiallergic activity after intravenous dosing (0.02%) and when applied topically (2%). The results of this study suggest that the flavonoids naringenin, naringenin chalcone, and quercetin may be useful alternatives for the topical treatment of inflammatory and allergic skin disorders.