Polar Lipids from Olives and Olive Oil: A Review on Their Identification, Significance and Potential Biotechnological Applications

Abstract

Polar lipids are minor components of olives and olive oil and include a myriad of molecules such as phospholipids and glycolipids. Even though sensitive and high-resolution analytical approaches have been used to unveil the polar lipidome of these matrices, new insights on their composition are needed. In this review, we will describe the findings on the identification and characterization of polar lipids from olives and olive oil and the underlying analytical challenges. The significance of polar lipids will also be discussed as potential markers of identity and traceability of olives and olive oil and in detecting adulteration of olive oil. Their potential impact on nutrition and health will be presented as a valuable source of bioactive compounds and as promising ingredients for different uses from olive-derived industrial by-products.

Keywords: authentication; bioactive; by-product; glycolipid; lipidomics; mass spectrometry; phospholipid; traceability.

Figure 1

Schematic representation of the methodological approaches used for studying polar lipids from olives and olive oil. Abbreviations: HPLC, high-performance liquid chromatography; HPLC-MS, high-performance liquid chromatography coupled to mass spectrometry; HPLC-MS/MS, high-performance liquid chromatography coupled to tandem mass spectrometry; HPLC-UV, high-performance liquid chromatography with ultraviolet detector; LLE, liquid/liquid extraction; NACE, non-aqueous capillary electrophoresis; NACE-MS, non-aqueous capillary electrophoresis coupled to mass spectrometry; NACE-MS/MS, non-aqueous capillary electrophoresis coupled to tandem mass spectrometry; NMR, nuclear magnetic resonance; SPE, solid-phase extraction.

Figure 2

Chemical structures of the classes of glycerophospholipids and glycolipids identified in olives and olive oil. Polar lipids include a broad range of molecules. Phospholipids are divided into two main classes depending on whether they contain glycerol (glycerophospholipids) or a sphingosyl (sphingophospholipids) backbone. Glycerophospholipids, besides the glycerol backbone, contain a polar phosphorus moiety. They derive mainly from sn-1,2-diacylglycerols and, thus, contain structures that are based on 3-sn-phosphatidic acid [31]. These lipids are grouped into classes based on the composition of their polar head group that is attached to the phosphate residue in sn-3 position. The polar head may be an amino acid, an amino-alcohol, a carbohydrate or another functional moiety. Each head group class is further differentiated into subclasses based on the sn-1 and sn-2 substituents on the glycerol backbone [31]. Glycolipids also include a wide variety of structures. These structures consist in acylglycerols (in the case of glycosylglycerides and sulfolipids) joined to a carbohydrate moiety by a glycosidic linkage at the sn-3 position [31]. Betaine lipids are ether-linked glycerolipids containing a betaine moiety. These lipids contain a polar group linked by an ether bond at the sn-3 position of the glycerol moiety, with the fatty acids esterified in the sn-1 and sn-2 positions [31]. 1,2-diacylglyceryl-3-O-4′-(N,N,N-trimethyl)-homoserine (DGTS) have been commonly found in lower plants, algae, fungi, and bacteria [32]. R, R1, and R2 represent fatty acyl chains.

Figure 3

Resume on the importance of polar lipids from olives, olive oil, and their by-products.