Ghayth Rigane

Phenolic Composition, Isolation, and Structure of a New Deoxyloganic Acid Derivative from Dhokar and Gemri‐Dhokar Olive Cultivars

Two rare olive cultivars, Dhokar and Gemri-Dhokar, growing in the south of Tunisia were investigated to identify their phenolic profile and evaluate their sugar content and antioxidant activity. The highest value of phenolic content was detected in Gemri-Dhokar cultivar extract (6.97 g gallic acid equivalents/kg of fresh olive). In addition, sugar content was quantified; glucose (45.17 g/kg of fresh olive) was the predominant sugar in Dhokar cultivar, followed by fructose (40.83 g/kg of fresh olive). The identification of phenolic compounds was based on separation by high-performance liquid chromatography equipped with a diode array detector followed by liquid chromatography-mass spectrometry analysis. In both cultivars, Oleuropein aglycon derivatives and elenolic acid were the main phenolic components. Oleuropeins were the major compounds quantified in the Gemri-Dhokar drupes olives (61.04 mg/100 g of fresh olive), while 0.25 mg/100 g were found in fresh Dhokar. A new iridoid compound, isolated as pure compound, was not previously reported in the literature. Its structure was established by spectroscopic analyses (NMR, UV, MS, and IR). DPPH, ABTS, and FRAP assays showed that the most important antioxidant capacity of olive extracts was found in with Gemri-Dhokar cultivar.

Analytical evaluation of two monovarietal virgin olive oils cultivated in the south of Tunisia: Jemri-Bouchouka and Chemlali-Tataouin cultivars

BACKGROUND The characterisation of virgin olive oils from two Tunisian cultivars, growing in the Tataouin zone, namely Jemri-Bouchouka, a rare olive cultivar, and Chemlali-Tataouin, was carried out. Several analytical parameters were evaluated; these include quality index, fatty acids, phenolic, chlorophyll, carotenoid, squalene, α-tocopherol compositions and oxidative stability. RESULTS Jemri-Bouchouka olive oil had the highest value of oleic acid (74.50%) while Chemlali-Tataouin olive oil had the highest value of oleic acid (69.39 %) and also was characterized by a high percentage of palmitic acid (14.75 %) which makes this oil freeze at a low temperature [corrected]. On the other hand, Jemri-Bouchouka oil was characterised by a low phenolic and α-tocopherol content (267.72 mg GAE kg⁻¹ and 278.34 mg kg⁻¹, respectively). Ten phenolic compounds were identified. The main phenols found in the two olive oils were oleuropein aglycon and pinoresinol. All phenolic compounds showed significant correlations with oxidative stability. CONCLUSION The analytical parameters of virgin olive oil that were determined in this study were greatly influenced by cultivar.

Characterisation and phenolic profiles of two rare olive oils from southern Tunisia: Dhokar and Gemri‐Dhokar cultivars

BACKGROUND The aim of this work was to study the chemical characteristics of two Tunisian cultivars, namely Dhokar and Gemri-Dhokar, to analyse the fatty acids, sterols, triacylglycerols, triterpenic alcohols, and to determine the phenolic composition and oxidative stability. RESULTS Among the rare varieties, Gemri-Dhokar olive oil had the highest value of oleic acid (69.39%) whereas Dhokar oil was noteworthy for its lower content of phenolic compounds (94.56 mg kg(-1) gallic acid equivalents of oil) and presented the highest level of palmitic acid (19.37%). The main sterols found in all olive oil samples were β-sitosterol and Δ5-avenasterol, whereas cholesterol and 24-methylenecholesterol were also found in all samples but in lower amounts. Two triterpenic dialcohols (erythrodiol and uvaol) were also detected and their content ranged from 1.45 to 2.30%, in Gemri-Dhokar and Dhokar olive oil, respectively. Ten phenolic compounds were identified. In all samples, the main phenols found were oleuropein aglycon and pinoresinol. These phenolic compounds showed significant correlations with oxidative stability. CONCLUSION The analytical parameters of two oils that were determined in this study were greatly influenced by genetic factors (cultivar).

Identification and characterization of a new iridoid compound from two-phase Chemlali olive pomace

From ethyl acetate fraction of olive pomace, solid residue from olive oil extraction, a new compound was isolated and purified through solid-phase extraction using silica Cartridge column chromatography. The structure of the new compound was established as a deoxyloganic acid lauryl ester by spectroscopic data including one- and two-dimensional NMR, electrospray ionization mass spectrometry, infrared analysis and UV spectra. The antioxidant activity of the purified compound was evaluated by measuring the radical-scavenging effect on 2,2-diphenyl-1-picrylhydrazyl and by using the ferric reducing antioxidant power assays. The pure compound has not been previously identified in the genus Olea and could be used as for studying the biosynthetic pathway of oleuropein aglycon.

Microwave Heating of Different Commercial Tunisian Olive Oil: Regarding to Exposure Times on Physical and Chemical Parameters Properties

In this work the effect of different microwave heating times, that simulate the usual times used to cooking, on Tunisian olive oils was investigated. Traditional parameters, including free acidity, peroxide value, ultraviolet absorbance values at 232 and 270 nm, phenolic, chlorophyll and carotenoid compositions, were determined in four extra-virgin olive oil samples before and after microwave treatment. The results showed that heating by microwave apparatus produce losses in the quality of the different analyzed olive oils. The heating time did not promote the occurrence of hydrolysis in the samples since no changes in free acidity values were found. All other parameters were affected by exposure time in a similar way: in the first 3 min no marked changes were observed, after that the quality of the oil decrease significantly. Globally, the microwave heating time also affects the total chlorophylls, carotenoids and phenolic contents which clearly decreased as long as the exposure time increases. The use of extra-virgin olive oil may be encouraged especially at short microwave treatment times for both domestic and food catering applications.