ABSTRACT
BACKGROUND: Currently, olive leaves are considered waste, although their high phenolic content makes them a source of antioxidants that could be used directly. The aim of this work was to study the behavior of phenolic compounds contained in olive leaf from the olive mill production chain during their gastrointestinal digestion. RESULTS: Phenolic compounds in the gastric digestion analyzed by high-performance liquid chromatography-diode array detection-mass spectrometry increased by 58% to 314.5% compared to the meal, while in the intestinal stage they ranged from 1.87 to 9.04 times higher. An increase of between 187% and 903% in bioaccessibility of phenolic compounds in the intestinal phase was observed, except for verbascoside. Furthermore, such compounds were fully bioavailable, except for apigenin-7-O-glucoside, which showed a bioavailability of 56%. CONCLUSION: The current study showed that the concentration of oleuropein, apigegin-7-O-glucoside, hydroxytyrosol hexoside and hydroxytyrosol contained in olive leaf continued to be extracted during the gastrointestinal digestion process. Furthermore, the results obtained with respect to their bioaccessibility and bioavailability suggest a good disposition to pass into the bloodstream where they could exert beneficial effects. Therefore, these results are promising for olive leaf becoming a consumable by-product that could be directly ingested through a simple infusion. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
ABSTRACT
Although olives leaves are currently considered a waste material from oil mills, they have great potential to be transformed into by-products due to their high oleuropein content. Oleuropein is a glycoside precursor of hydroxytyrosol, which is the phenolic compound with the highest antioxidant capacity in nature and which is associated with multiple health benefits. For this reason, the demand for oleuropein is growing in the pharmaceutical, cosmetic and food sectors. The objective of this study is to determine the stability of oleuropein in olive leaves from oil mills in solid and aqueous forms under different conditions of temperature, relative humidity and lighting. The results indicate that the degradation of oleuropein conforms well to first-order kinetics. The rate constants at the temperatures tested in the aqueous extracts indicate activation energies from RTl to 80 °C and from 7 °C to 14 °C, as the degradation reactions were different in these ranges. Furthermore, olive leaf powder stored at any temperature with an RH ≥ 57% showed greater stability after six months, which is an encouraging result for the storage and transformation of this waste in oil mills.
