Olive and Olive Oil Bioactive Constituents

Dimitrios Boskou

• Publisher: Academic Press and AOCS Press
• Year: 2015
• ISBN:
  9781630670429
• Topic: Technology & Engineering
• Subtopic: Food Science
• Index: Technology & Engineering

The market is flooded with products posing as elixirs, supplements, functional foods, and olive oil alternatives containing phenols obtained from multiple olive sources. This technically-oriented book will be of value to nutritionists and researchers in the biosciences. It unravels the body of science pertaining to olive minor constituents in relation to new chemical knowledge, technological innovations, and novel methods of recovery, parallel to toxicology, pharmacology, efficacy, doses, claims, and regulation.

Topics include: the biological importance of bioactive compounds present in olive products; developments and innovations to preserve the level of bioactives in table olives and olive oil; and importance of variety, maturity, processing of olives, storage, debittering of olives and table olives as a valuable source of bioactive compounds.

• Presents detailed information concerning the claimed benefits of olive oil and discusses the permitted health claim to EFSA on oils with natural phenolics
• Recovery of bioactive constituents from olive waste is comprehensively described
• Explores the relationship betwen phenolic levels and sensory evaluation
• Features chapters on the clinical and cellular mechanisms and health effects of olive, important for functional foods research

1

Olive Fruit, Table Olives, and Olive Oil Bioactive Constituents

Dimitrios Boskou, Aristotle University, Department of Chemistry, Thessaloniki, Hellas

Introduction

Phenolic compounds, widely distributed in the plant kingdom and abundant in our diet, are today among the most talked about classes of phytochemicals. In the last two decades, much work has been presented by the scientific community; this work focuses on:

Oxidation mechanisms and the real contribution of natural antioxidants in preventing free radical damage and oxidative stress

The levels and chemical structure of antioxidant phenols in different plant foods, aromatic plants, and various plant materials

The probable role of plant phenols in the prevention of various diseases associated with oxidative stress

The dietary intake of phenolic compounds and its effect on lipoprotein metabolism, oxidative damage, inflammation, endothelial dysfunction, and blood pressure

The potential of polyphenols in oncology based on the study of chemopreventive and cell-specific cytotoxic and apoptotic effects

The clarification of molecular mechanisms accounting for the antioxidant, anti-inflammatory, and anticancer properties through gene transcription profiling

The assessment and dissemination of strategies for the extraction of phenols and other bioactive compounds from fruits processing residues

Olive oil contains some minor constituents, including phenolic compounds, which contribute to the stability of the oil, antioxidant capacity, bitterness, and pungency, and have important biological properties. Published research work and ongoing studies are extended and their outcome may ultimately be used to make more specific dietary recommendations. These may regard the efficacy of olive oil phenolic fraction to counteract the burden of cardiovascular disease. One of the main factors that has delayed research on olive and olive oil phenols is the considerable diversity and complexity of their chemical structures. Therefore, new approaches should aim at integrating the results of past and future experiments in various disciplines, including food chemistry, biochemistry, pharmacology, and other biological sciences, and at validating most of the major individual phenols and other bioactives as new agents against various chronic and other human diseases.

Olive and Olive Oil Bioactive Ingredients

The Terms Polyphenols and Unsaponifiables

Olive and olive oil bioactives can be divided into two categories: (1) the nonpolar bioactives that are found in the unsaponifiable fraction of the oil, such as squalene, tocopherols, sterols, and triterpenic compounds, and (2) polar phenolic compounds usually characterized as “olive oil polyphenols,” which are contained in the fraction obtained by liquid–liquid extraction or solid phase extraction. The inaccurate term “polyphenols” is rather confusing because very few of the polar fraction compounds are polyphenols. Polyphenols contain two benzene rings joined by a linear three carbon chain. According to this definition, only flavonoids such as apigenin and luteolin are polyphenols. These compounds, however, are present only in trace amounts in olive oil. The rest of the olive oil polar phenols—hydroxytyrosol, tyrosol, dialdeydic forms of decarboxylmethyl elenolic acid linked to hydroxytyrosol and tyrosol, glycosides and aglycones, lignans, and phenolic acids—are not polyphenols. It is better to characterize them as olive oil bioactive phenols or as olive oil polar phenols to emphasize the difference from another class of phenols, tocopherols, which are the nonpolar phenols.

Unsaponifiables

In the literature, very often phenols such as hydroxytyrosol are categorized as unsaponifiables. This categorization is not correct because this term, according to IUPAC, is used for lipids. Unsaponifiables are components of an oily (oil, fat, wax) mixture that fail to form soaps when blended with sodium hydroxide. Squalene, sterols, tocopherols, linear alcohols, and triterpenic compounds are unsaponifiables. Polar phenols are not, because they are not lipids.

Phenolic Compounds Identified in Olives and Olive Oil

The composition of the polar phenolic fraction in olive fruit and virgin olive oil (VOO) is very complex, and there are minor compounds that have not yet been identified, despite a large number of studies aiming at elucidating their structure. The phenolic composition is not the same in every VOO because there is a variation due to agronomic, genetic, and environmental factors such as the variety of the olive fruit, the region and climatic conditions, the agricultural practices applied in the cultivation of the tree, the stage of maturity and harvest period, the mode of extraction, and storage and packaging (see Chapters 4, 5, 6, 7, 10).

Values reported in the literature vary significantly for another reason, too. Different methods are used (most of them not validated), peaks in the HPLC chromatograms are conventionally identified, some constituents have isomers, all the necessary standards needed for identification and quantitation are not available, and some of the constituents are present at very low levels. In the last two decades, remarkable progress has been observed in the preparation of the sample (solid-phase extraction techniques, semipreperative high-pressure chromatography, ultrasound-assisted emulsification–microextraction) and the identification and quantification of phenolic molecules. The latter are based on advanced techniques such as gas chromatography–mass spectrometry (GC–MS), high-pressure liquid chromatography–diode array detector/mass spectrometry (HPLC–DAD/MS), liquid chromatography diode array detector–electrospray time-of-flight mass spectrometry (HPLC–ESI-TOF/MS), and other hyphenated techniques and high-resolution mass spectrometry (HPLC-DAD-SPE-NMR/MS, ORBITRAP platform analyzers), as well as nuclear magnetic resonance techniques (see Chapters 6, 9, 10). So far, however, an official method for total phenolic content and individual phenols, which would be practical and would guarantee the comparison of results, does not exist. Therefore, some tables provided in the literature with sub-ppm quantities (micrograms per kg of oil), based mainly on conventional liquid–liquid extraction (for the preparation of sample) and high-performance liquid chromatography with UV detection (for identification and quantification of individual phenols), should be scrutinized for the parameters of analytical procedures (accuracy, repeatability, limit of detection) (Romero and Brenes, 2012). These remarks are important for oleuropein, which is encountered in sub-ppm quantities in olive oil and poses recovery problems; its quantification demands specific techniques such as isotope dilution method and specific mass spectroscopy providing the needed sensitivity and specificity (Sindona, 2010.)

Such analytical requirements should also be considered from the point of view of nutritional evaluation, taking into account the fact that since 2011, a European Food Safety Authority (EFSA) opinion exists that permits a health claim for olive oil phenols (hydroxytyrosol and its derivatives, e.g., oleuropein complex and tyrosol) and protection of blood lipids from ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Preface
• About the Editor
• Contributors
• List of Abbreviations
• Chapter 1: Olive Fruit, Table Olives, and Olive Oil Bioactive Constituents
• Chapter 2: Minor Bioactive Olive Oil Components and Health: Key Data for Their Role in Providing Health Benefits in Humans
• Chapter 3: Cellular and Molecular Effects of Bioactive Phenolic Compounds in Olives and Olive Oil
• Chapter 4: Olive Oil Phenolic Composition as Affected by Geographic Origin, Olive Cultivar, and Cultivation Systems
• Chapter 5: Effect of Fruit Maturity on Olive Oil Phenolic Composition and Antioxidant Capacity
• Chapter 6: From Drupes to Olive Oil: An Exploration of Olive Key Metabolites
• Chapter 7: Research and Innovative Approaches to Obtain Virgin Olive Oils with a Higher Level of Bioactive Constituents
• Chapter 8: Table Olives as Sources of Bioactive Compounds
• Chapter 9: Bioactive Phenolic Compounds from Olea europaea: A Challenge for Analytical Chemistry
• Chapter 10: Analysis of Bioactive Microconstituents in Olives, Olive Oil and Olive Leaves by NMR Spectroscopy: An Overview of the Last Decade
• Chapter 11: Recovery of High Added Value Compounds from Olive Tree Products and Olive Processing Byproducts
• Index