Phenolic content, antioxidant and anti-inflammatory activities of some Algerian olive stone extracts obtained by conventional solvent and microwave-assisted extractions under optimized conditions

Kenza Djemaa-Landri,Stéphanie Cluzet,Stéphanie Krisa,Tristan Richard,Sabrina Hamri-Zeghichi,Khodir Madani,Wassila Belkhiri-Beder,Josep Valls,Nabil Kadri

doi:10.1007/s11694-021-00992-w

Abstract

The recovery of food waste is a stimulating opportunity for and competitive development of agroindustries. In this context, the objective of this study was to report the antioxidant potential and phenolic compounds content of olive stones (OS) of six Algerian cultivars. Two extraction methods were used: microwave assisted extraction (MAE) and conventional solvent extraction (CSE) in order to improve the recovery of total phenolic content (TPC) and the maximization of the two extraction processes by the Box-Behnken design (BBD) from olive stone of Olea Europaea L. cv Ayemele. The optimal processing parameters obtained were (i) for MAE: 22% (v/v) ethanol, 40 s, 500 W, and ratio 65:1 (mL/g) and (ii) for CSE: 33% (v/v) ethanol, 24 min, 71 °C, and ratio 60:1 (mL/g). Phenolic compounds were then extracted from olive stones of six Algerian cultivars with MAE best extraction conditions, as it was the best strategy in term of TPC recovery. The phenolic content was different according to the olive variety. The stones of Chemlale were the richest in TPC (7.23 mg GAE/g) followed by Azeboudj (6.33 mg GAE/g), Atefah (6.04 mg GAE/g), Agraraz (5.63 mg GAE/g), Azeradj (5.35 mg GAE/g) and Ayemel (5.14 mg GAE/g). A similar profile was observed with total flavonoids content and antioxidant activities. The anti-inflammatory effects of the optimized extracts by MAE were assessed regarding their ability to prevent lipopolysaccharide-induced of reactive oxygen species and nitric oxide production in a macrophage cell line (RAW 264.7). Olive stones that are issued from the production of olive oil, and table olives can therefore be considered as renewable by-products thanks to their compounds with high added value. These bioactive compounds can target the food natural additives markets, pharmaceutical and cosmetic industries, all of which are currently very receptive such natural products.

Highlights

Several studies have revealed a low incidence of many sicknesses among populations in the Mediterranean region such as heart disease and certain cancers [1, 2]
A statistical difference was noticed between the total phenolic content (TPC) contents ranging from 2.27 to 3.25 mg gallic acid equivalents (GAE)/g (Table 1)
It is generally accepted that in a milled form, the plant material has a greater surface area of contact with the solvent [25]. This is explained by the fact that the solvent diffuses more inside the small particles, which enhances the extraction of polyphenol molecules thanks to the establishment of a larger contact surface with the solvent

Summary

Introduction

Several studies have revealed a low incidence of many sicknesses among populations in the Mediterranean region such as heart disease and certain cancers [1, 2]. It has been often suggested that this reduced incidence of diseases can be related to a high consumption of fruits, vegetables and fats [3]. In the Mediterranean diet, olive oil is the main origin of fat in daily dishes and salads. The olive tree belongs to the Oleaceae family and the genus Olea, which includes about thirty different species in the world [4]. This tree is present in all four continents, and various cultivars are enumerated in Algeria. The majority (98%) of compounds are found in olive mill waste [10]. The olive pulp phenolic content has been evaluated and reviewed more than other fractions of the plant [13,14,15]

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