Journal of Food Quality Evaluation of Effect of Extraction Solvent on Selected Properties of Olive Leaf Extract

Abstract

The quest for natural preservatives and functional foods with health benefits has seen an increasing demand for natural products having therapeutic value. Herein, we investigated the influence of ethanol, methanol, acetone (50%, 70%, and 90% v/v), and distilled water on selected properties of olive leaf extract and determined the yield, total phenolic content (TPC), antioxidant activity, and antimicrobial activity. Extracts were analyzed for their oleuropein, hydroxytyrosol, and tyrosol contents by high-performance liquid chromatography (HPLC). The highest extraction yield of 20.41% was obtained when using 90 vol% methanol, while the highest total polyphenol contents of 232 and 231 mggallic-acid-equivalent/100 g were obtained for 90 vol% methanol and 90 vol% ethanol, respectively. Antioxidant activity was determined using the α,α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging assay, by determining the ferric reducing antioxidant power (FRAP), and using the Fe2+-chelating activity assay, which provided the highest values when 90 vol% methanol was used (33.84%, 0.75, and 12.91%, respectively). HPLC analysis showed that the highest oleuropein contents corresponded to the extracts obtained using 90 and 70 vol% methanol (26.10 ± 0.20 and 24.92 ± 1.22 g/L, respectively), and the highest antimicrobial activity was observed for 90 vol% methanol and distilled water. Olive leaf extracts using 90 vol% methanol had high levels of polyphenols and were highly antioxidant and antimicrobial. The results of this study facilitate the commercial applications of natural extracts with antioxidant and antibacterial activities and are expected to establish a foundation for further optimization studies.

Antioxidant Activity of Moringa oleifera and Olive Olea europaea L. Leaf Powders and Extracts on Quality and Oxidation Stability of Chicken Burgers

“…The olive leaves showed a maximum yield of 24.65%, compared to the Moringa leaves, which showed a smaller extraction yield of 20.94%. The results obtained for the olive leaves were similar to those reported in Cho et al (2020) [56], where the extract was obtained using 90% methanol, and the yield obtained was 20.41%. The results for the Moringa leaves were similar to those reported by do Nascimento et al (2017) [57], who used 95% ethanol to obtain 25.022% (Table 1).…”

Olive byproducts and their bioactive compounds as a valuable source for food packaging applications

“…Many solvents, such as water, ethanol, methanol, acetone, ethyl acetate, and hexane, have been used for polyphenols extraction from olive pomace and leaves and parameters, including solvent type, solvent‐solid ratio, pH, and extraction temperature and duration, have been optimized (Čepo et al., 2017; Goldsmith et al., 2014). Methanol:water solvent (90:10) provided the highest extraction yield from olive leaves (20.4%), total polyphenol content (231.98 mg gallic acid equivalent/100 g dry basis), oleuropein content (26.1 g/L), and antioxidant and antimicrobial activities (Cho et al., 2020). Ethanol:water solvent (50:50) was found effective in extracting polyphenols from olive‐oil filter cake (Lozano‐Sánchez et al., 2014).…”

Oleuropein: Methods for extraction, purifying and applying

“…These authors used maceration at 25 °C for 2 h with a mixture of ethanol and water (70:30 v / v) and 1% acetic acid, and observed that the highest oleuropein content was reached with an olive leaf: solvent ratio equal to 1: 3, while the proportions 1: 8 and 1: 6 were also tested, with or without acetic acid present. Cho et al, (2020) determined optimal conditions for olive leaf extraction by examining the effect of extraction solvent (water, aqueous methanol, aqueous ethanol, and aqueous acetone) on selected extract properties. The highest extraction efficiency of 20.41% was obtained using 90 vol% methanol.…”