New possibilities for the valorization of olive oil by-products

Abstract

In this contribution, the capabilities of pressurized liquid extraction (PLE) using food-grade solvents, such as water and ethanol, to obtain antioxidant extracts rich on polyphenolic compounds from olive leaves are studied. Different extraction conditions were tested, and the PLE obtained extracts were characterized in vitro according to their antioxidant capacity (using the DPPH radical scavenging and the TEAC assays) and total phenols amounts. The most active extracts were obtained with hot pressurized water at 200 °C (EC(50) 18.6 μg/mL) and liquid ethanol at 150 °C (EC(50) 27.4 μg/mL), attaining at these conditions high extraction yields, around 40 and 30%, respectively. The particular phenolic composition of the obtained extracts was characterized by LC-ESI-MS. Using this method, 25 different phenolic compounds could be tentatively identified, including phenolic acids, secoiridoids, hydroxycinnamic acid derivatives, flavonols and flavones. Among them, hydroxytyrosol, oleuropein and luteolin-glucoside were the main phenolic antioxidants and were quantified on the extracts together with other minor constituents, by means of a UPLC-MS/MS method. Results showed that using water as extracting agent, the amount of phenolic compounds increased with the extraction temperature, being hydroxytyrosol the main phenolic component on the water PLE olive leaves extracts, reaching up to 8.542 mg/g dried extract. On the other hand, oleuropein was the main component on the extracts obtained with ethanol (6.156-2.819 mg/g extract). Results described in this work demonstrate the good possibilities of using PLE as a useful technique for the valorization of by-products from the olive oil industry, such as olive leaves.

Compressed fluids for the extraction of bioactive compounds

“…Table 4 shows a selection of some of the most remarkable SWE applications to obtain bioactive compounds from natural sources published during the period 2008-2012. As can be seen, a quite large number of recent works described in the literature have been applied to the extraction of antioxidants from rosemary [12], grape pomace [145], grape skin [146], seabuckthorn leaves [147], pomegranate seed [148], rice bran [149], olive leaves [108], Citrus unshiu peel [150], bitter melon [151] or onion skin [152], among others. Not only antioxidant compounds have been extracted by SWE but also other bioactive compounds possessing different activities.…”

Olive Leaf Extract Elevates Hepatic PPARαmRNA Expression and Improves Serum Lipid Profiles in Ovariectomized Rats

“…Ground olive leaf (50 g) was refluxed with 250 mL of 80% ethanol at 55°C for 5 h. 12,13 The mixture was filtered and completely evaporated in a rotary evaporator (N-21NS; EYELA, Tokyo, Japan) at 40°C before the concentrated mixture was freeze-dried.…”

Extraction by Subcritical and Supercritical Water, Methanol, Ethanol and Their Mixtures

“…Polyphenolic antioxidants were obtained by the application of pressurized water and ethanol to olive leaves. Water at 473 K and ethanol at 423 K were most effective [64]. A pressurized 50 mass% ethanol + water mixture at 473 K produced the best yield of phenolic antioxidants from black bamboo leaves [65].…”