Gas and liquid chromatography of hydrocarbons in edible vegetable oils.

Hydrocarbons, an important part of the minor constituents belonging to vegetable oils are reviewed. Their importance, origin, characterization and detection in edible vegetable oils are considered. The determination of some of them as a means of establishing oil quality and genuineness is also highlighted. The official methodologies, as well as the most commonly procedures used for isolation and analysis are reviewed. Furthermore, novel procedures applying new techniques for determining those compounds are also presented.

Chromatographic analysis of minor constituents in vegetable oils.

The main group of minor constituents belonging to vegetable oils are reviewed. Their importance in the characterization, origin and detection of oil mixtures are considered. Also, the determination of these minor components is of great value in establishing the oil quality and their genuineness. The most commonly used procedures (including the Official methodologies) normally applying chromatographic techniques are reviewed. The interference of each component within the determination of the other minor constituents are discussed. Furthermore, novel procedures for determining those compounds are also presented.

Update on solid-phase extraction for the analysis of lipid classes and related compounds.

This article provides information on the different procedures and methodologies developed when solid-phase extraction (SPE) is used for lipid component separation. The analytical systematics, established by different authors and designed to separate groups of compounds and also specific components by using a combination of chromatographic supports and solvents are presented. The review has been divided into three parts, which we consider well defined: edible fats and oils, fatty foods and biological samples. Separations of non-polar and polar lipids is the most extensive systematic, although many other published methods have been established to isolate specific components or a reduced number of components from edible fats and oils, fatty foods or biological samples susceptible to further analysis by other quantitative techniques.

Simultaneous determination of long-chain aliphatic aldehydes and waxes in olive oils.

A procedure for the simultaneous determination of long-chain aliphatic aldehydes, and aliphatic and triterpenic waxes in virgin olive oils is described. A fraction containing these compounds was isolated from the oil using solid-phase extraction on silica-gel cartridges. The fraction was analyzed by capillary GC on 35%-dimethyl-65%-diphenylpolysiloxane phase using on-column injection. In extra virgin olive oils, the long-chain aliphatic aldehydes with even carbon atom numbers from C22 to C30 were identified by comparison of retention times and mass spectra with those of synthesized standards. The concentration of total aldehydes ranged from 20.2 to 108.0 mg/kg-n-hexacosanal being the most abundant aldehyde. The determination of aliphatic waxes was achieved with similar or better precision than that of the EU official methods.

Quantitative determination of hydroxy pentacyclic triterpene acids in vegetable oils.

A simple and precise analytical method for the determination of hydroxy pentacyclic triterpene acids (HPTAs) in vegetable oils was developed. The acidic fraction was isolated by solid-phase extraction using bonded aminopropyl cartridges, and the extract was silylated and analyzed by gas chromatography. Repeatability and recovery of the method were determined. In virgin olive oils, similar amounts of oleanolic (3beta-hydroxyolean-12-en-28-oic) and maslinic (2alpha,3beta-dihydroxyolean-12-ene-28oic) acids and traces of ursolic (3beta-hydroxyurs-12-en-28-oic) acid were found. The main factor affecting HPTA concentration was the oil quality since that increases as the quality decreases, while olive variety, olive ripeness, and oil extraction system had less influence. In crude olive pomace oils, the concentrations were very much higher than in virgin olive oils. During refining processes, total or significant losses of HPTAs were observed. Esterified derivatives of HPTAs were not found.

Effects of olive fruit quality and oil storage practices on the diacylglycerol content of virgin olive oils.

The evolution of 1,3- and 1,2-isomers of diacylglycerols (DGs) in olive oils obtained from healthy olives and the influence of the olive quality was studied. Healthy olive fruits yielded oils containing almost exclusively 1,2-isomers whereas altered olives produced oils with significant amounts of 1,3-isomers. Virgin olive oils obtained from various olive cultivars and stored at different temperatures showed triacylglycerol hydrolysis and diacylglycerol isomerization depending on the acidity and temperature. The results indicated that the relationship between acidity and total diacylglycerol content has scarce utility for detecting mild refined oil in virgin olive oil. On the other hand, the 1,3-/1,2-DG isomers ratio is useful for assessing the genuineness of virgin olive oils with low acidities during the early stages of storage.

Composition of fatty acids, triacylglycerols and polar compounds of different walnut varieties (Juglans regia L.) from Tunisia.

The chemical composition (total oil content, fatty acids, triacylglycerols (TAGs) and polar compounds) of six walnuts (Juglans regia L.) cultivars (Lauzeronne, Franquette, Hartley, Local pt, Local gd and Parisienne) collected from Mateur (north of Tunisia) was evaluated. The major fatty acids found in the walnut oils are linoleic acid (60.42-65.77%), oleic acid (13.21-19.94%) and linolenic acid (7.61-13%). The TAG species were mainly composed of trilinolein (LLL), dilinoleoyl-linolenoyl-glycerol, dilinoleoyl-oleoyl-glycerol and palmitoyl-dilinoleoyl-glycerol classes. The results revealed that Local pt variety has the highest level of oil (62.56%), linoleic acid (65.77%) and LLL (33.48%). Significant differences among oil samples were observed, therefore showing a great variability in the oil composition among cultivars.

Long-chain fatty alcohols from evening primrose oil inhibit the inflammatory response in murine peritoneal macrophages.

ETHNOPHARMACOLOGICAL RELEVANCE: Evening primrose (Oenothera biennis L., Onagraceae) is a wild medicinal plant of Central American origin that is now one of the most widely used herbal medicines in different parts of the world. Oil extracted from it seeds is traditionally used in the treatment of eczema, asthma, rheumatoid arthritis, breast problem, premenstrual and menopausal syndrome, all they have an inflammatory component. The present study demonstrates the in vitro anti-inflammatory effect of long-chain fatty alcohols, minor compounds isolated from Evening primrose oil (EPO). MATERIAL AND METHODS: A mixture of long chain fatty alcohols (LCFAs) was isolated from the non-triacylglycerol fraction of the EPO. Hexacosanol (C26OH: 38.65%), tetracosanol (C24OH: 31.59%), docosanol (C22OH: 11.36%) and octocosanol (C28OH: 7.64%), were the major constituents, identified and quantified by GC and GC-MS. LCFA was tested with LPS stimulated murine peritoneal macrophage. This fraction, significantly and dose-dependently decreased nitric oxide production induced by LPS (P<0.001) and the inhibitory effect seems to be consequence of an action at the level of the inducible nitric-oxide synthethase (iNOS) gene enzyme expression rather than to a direct inhibitory action on enzyme activity. The release of PLA2 and TXB2 also was significantly inhibited by LCFAs (P<0.001) although LCFAs did not affect to PGE2 generation, however the western blot assay showed that LCFAs reduced cyclooxygenase-2 enzyme gene expression at all doses assayed. In the same way, the secretion of inflammatory cytokines interleukin 1ß (IL-1ß) and tumour necrosis factor α (TNF-α) from LPS-stimulated murine macrophage, were also significantly reduced (P<0.001). CONCLUSION: These results demonstrates the anti-inflammatory activity of LCFAs, providing an additional value about the role of bioactive minor compounds in the beneficial effect of EPO and supports its traditional uses in inflammatory processes management.

Fatty acid alkyl esters presence in olive oil vs. organoleptic assessment.

The scientific work on the authenticity and quality of olive oil is an ever-growing area. Olive oil genuineness is not only valuable for the producers, but also for the consumers who expect an actual correspondence between the products they purchase and the information on the packaging labels. Sometimes oil's rejection by consumers is just a matter of taste, sometimes is a more objective question. Low quality olive oils with weak organoleptic defects are the targets of illegal blends that can be detected by determining the content of fatty acid alkyl esters (FAAEs). In this line we have established a relationship between the FAAEs concentration of olive oils and their sensory classification. Besides, a connection between the presence of large quantities of FAAEs and fermentative organoleptic defects has been proven.

Waxy fraction containing long-chain aliphatic aldehydes in virgin olive oils.

Long-chain aliphatic aldehydes are natural minor components occurring in the cuticle of numerous plant species and also evidenced in virgin olive oils. The fraction containing these compounds can be isolated from the oil samples by using a solid-phase extraction silica-gel cartridge and then directly analysed by GC on a 5% diphenyl-95% dimethylsiloxane capillary column, using an on column-injection system. The proposed methodology showed that extra virgin olive oils contain long-chain aliphatic aldehydes, with even carbon-atom numbers from C22 to C30. Quantitative results, using the synthesised aldehyde C21 as internal standard, give concentrations of total long-chain aliphatic aldehydes in a variable range below 116mgkg-1, being hexacosanal (C26-al) the most abundant aldehyde. The different experimental conditions utilised during olive oil extraction processes influence the total aldehydes concentration. Besides contribution to the knowledge of the minor-component composition present in olive oil, their interest and relationship with wax esters, aliphatic alcohols and n-alkanes are discussed.

Determination of the molecular species composition of diacylglycerols in human adipose tissue by solid-phase extraction and gas chromatography on a polar phase.

The free diacylglycerols (DAGs) in adipose tissue are involved in the metabolism of stored lipids and hence are related to the supply of fatty acids for other tissues. This paper describes a simple, fast, and reproducible method for the identification and quantification of different molecular species of DAGs in human adipose tissue. The method comprised solid-phase extraction on a diol-bonded phase column combined with capillary GC analysis of silylated DAG derivatives on a polar phase (65% phenylmethylsilicone). Separation of the DAGs was achieved based on chain length, isomeric structure (1,2- and 1,3-DAGs), and degree of unsaturation. The main DAGs were 1,2-OO, 1,2-OP, 1,2-LO and 1,2-LP. The composition was corroborated by analysis of the component fatty acids of the DAGs, 18:1(n-9), 16:0, and 18:2(n-6) being the three major fatty acids obtained.

Evaluation of hydrolysis and absorption of thermally oxidized olive oil in non-absorbed lipids in the rat.

The aim of this study was to investigate the contribution of hydrolysis and absorption to the reduced digestibility found for heat-oxidized oils. Indirect evaluation methods were designed to assess the hydrolysis and absorption undergone in vivo, based on the analysis of non-absorbed lipids in faeces. The results indicated difficulties in the hydrolysis of complex glyceridic molecules included in heat-oxidized fats. Also, the data suggested that the extension of hydrolysis undergone in vivo was closely dependent on the amount and alteration degree of the dietary fat. This fact was clearly shown specifically for non-altered fatty acids while in the case of non-polar dimer fatty acids the low digestibility value may be associated in part to difficulties during the absorption process.