Oleuropein-Enriched Extract From Olive Mill Leaves by Homogenizer-Assisted Extraction and Its Antioxidant and Antiglycating Activities

Abstract

Olive oil consumption has increased in the last two decades and consequently, its wastes have increased, which generates a tremendous environmental impact. Among the by-products are the olive mill leaves, which are easier and inexpensive to treat than other olive by-products. However, little research has been done on their chemical composition and potential bioactivity. Hence, in this study, olive mill leaves were used to obtain Oleuropein-Enriched Extracts (OLEU-EE) using Conventional Extraction, Ultrasound-Assisted Extraction, and Homogenization-Assisted Extraction. These three techniques were evaluated using a Factorial Design to determine the parameters to obtain an OLEU-EE with high contents of Total Phenolic Compounds (TPC), Antioxidant Activity (AA), and Oleuropein concentration (OLEU). From the results, the Homogenizer-Assisted Extraction (HAE) technique was selected at 18,000 rpm, solid:liquid ratio 1:10, and 30 s of homogenization with 70% ethanol, due to its high TPC (5,196 mg GA/100 g), AA (57,867 μmol of TE/100 g), and OLEU (4,345 mg of OLEU/100 g). In addition, the antiglycating effect of OLEU-EE on the levels of (1) fluorescent Advanced Glycation End Products (AGEs) were IC50 of 0.1899 and 0.1697 mg/mL for 1λEXC 325/λEM 440 and 2λEXC 389/λEM 443, respectively; (2) protein oxidative damage markers such as dityrosine (DiTyr), N-formylkynurenine (N-formyl Kyn), and kynurenine (Kyn) were IC50 of 0.1852, 0.2044, and 0.1720 mg/mL, respectively. In conclusion, OLEU-EE from olive mill leaves has different capacities to inhibit AGEs evidenced by the IC50 of fluorescent AGEs and protein oxidation products, together with the scavenging free radical evidenced by the concentration of Trolox Equivalent. Therefore, OLEU-EE could be potential functional ingredients that prevent oxidative damage caused by free radicals and AGEs accumulation.

Antioxidant and Anti-Diabetic Properties of Olive (Olea europaea) Leaf Extracts: In Vitro and In Vivo Evaluation

“…The remarkable reducing power of the OLEs indicates the effectiveness of the phenolic compounds and flavonoids, which might be beneficial in the treatment and/or prevention of several human diseases and which might have health promoting properties. This result emphasized previous work, which reported the high antioxidant activity and oxidative stability of olive leaf extracts [ 34 , 35 , 36 ]. Several in vitro and in vivo studies have reported phenolic compounds as showing anti-inflammatory, anti-microbial, anti-diabetic and anti-tumoral properties.…”

Extractability of oleuropein, hydroxytyrosol, tyrosol, verbascoside and flavonoid-derivatives from olive leaves using ohmic heating (a green process for value addition)

“…In a recent paper, examining olive mill leaves (Arbequina variety), Márquez et al , 31 found substantial effectiveness of the homogenizer-assisted extraction approach in the recovery of oleuropein (4345 mg/100 g). Moreover, Ahmad-Qasem et al , 32 compared different drying and freezing methods used before the extraction process and detected the highest recovery of oleuropein (108.6 mg per g extract, d.w.) when the leaves, prior to being extracted in a shaking water bath (22 °C for 24 h), were initially hot air dried at 120 °C for 12 min.…”

“…In a recent paper, examining olive mill leaves (Arbequina variety), Márquez et al, 31 found substantial effectiveness of the homogenizer-assisted extraction approach in the recovery of oleuropein (4345 mg/100 g). Moreover, Ahmad-Qasem et al, 32 Fig.…”

Exploring the Bioactive Content of Liquid Waste and Byproducts Produced by Two-Phase Olive Mills in Laconia (Greece): Is There a Prospect for Added-Value Applications?

“…It was similar also to that found in a recent work of del Mar Contreras et al [36] (22 mg GA/g of dry leaf), which was obtained after optimization of the extraction process. The high value of phenols (~52 mg GA/g of dry leaf) has been reported only by Marquez et al [37]. Such value could be ascribed to the technique adopted (homogenizerassisted extraction at 18,000 rpm) which, after optimization, provided better results than conventional and ultrasound-assisted extraction.…”