Freezing effect on the oleuropein content of olive leaves extracts obtained from microwave-assisted extraction

Abstract

This work aimed to investigate the effect of freezing on the oleuropein content obtained from olive leaves extracts. The extracts were obtained by microwave-assisted extraction using different solvents, pH, temperatures and microwave irradiation time. Afterward, HPLC was used to identify and quantify the amount of oleuropein in the extracts. A part of the extracts was immediately analyzed, and another was frozen for a week. The experimental results highlighted that the storage condition has a significant ( p < 0.05) effect on the oleuropein content. Regardless of the extraction condition, the frozen storage was responsible for a decrease in the oleuropein content, ranging from 5.38 to 70.09%. These results indicate that it is important to consider the degradation of oleuropein in frozen olive leaf extracts so that subsequent applications are suitable.

Valorization of Olive Leaves through Polyphenol Recovery Using Innovative Pretreatments and Extraction Techniques: An Updated Review

“…In the majority of studies [29,[32][33][34][35][36][37][38][39][40][41], drying was conducted prior to polyphenol extraction from olive leaves. However, few papers have compared drying techniques and their effect on polyphenols [42,43].…”

“…The aqueous and hydroalcoholic MAE of polyphenols from dried and ground olive leaves (particle size < 0.272 mm to 0.5 mm) were tested with microwave powers ranging from 150 to 1500 W. Most of the studies used response surface methodology to optimize the operating conditions, including treatment time (0.5-40 min), temperature (50-150 • C), pH (3)(4)(5)(6)(7)(8)(9), and ethanol percentage (0-100%). Total phenolic content ranged between 10.45 mg GAE/g DM and 103.87 mg GAE/g DM, while oleuropein content varied from 11.59 mg/g DM to 60 mg/g DM [38][39][40]69] (see Table 3).…”

Oleuropein and Hydroxytyrosol as Antidiabetics: A Review on Extraction Method, Effectiveness and Toxicity Effect

“…The increase in body weight in obesity (5) is in line with a chronic increase in free fatty acids (FFA), which significantly affects the function of adipose tissue as a fat storage site. Infiltrating macrophages (6) cause adipose dysfunction, which in turn controls the release of hormones that cause inflammation (cytokines) (7).…”