Metabolomics of Olive Fruit: A Focus on the Secondary Metabolites

Evaluating the Variability in the Phenolic Concentration of Extra Virgin Olive Oil According to the Commission Regulation (EU) 432/2012 Health Claim

The health benefits of extra virgin olive oil (EVOO) are associated to its fatty acids profile (with predominance of oleic acid) and to the minor components that include phenols, among others. Phenols are responsible for the only health claim of olive oil reported in the Commission Regulation (EU) 432/2012. Here, we have applied a liquid chromatography-tandem mass spectrometry method to determine the most abundant phenols included in the health claim (with special emphasis on secoiridoids) in 1239 EVOO samples produced in two consecutive agronomical seasons. The predominant cultivars in Spain ("Picual", "Arbequina", "Hojiblanca", and "Cornicabra") were evaluated. We also studied the influence of harvesting date and orchard location on the EVOO phenolic concentration. A great variability in phenolic content, from 1 to 2850 mg/kg, was found in these EVOOs, and not all of them (4.6 and 23.1% in the two seasons) reported a concentration above 250 mg/kg to certify the health claim.

EST-SNP Study of Olea europaea L. Uncovers Functional Polymorphisms between Cultivated and Wild Olives

BACKGROUND

The species Olea europaea includes cultivated varieties (subsp. europaea var. europaea), wild plants (subsp. europaea var. sylvestris), and five other subspecies spread over almost all continents. Single nucleotide polymorphisms in the expressed sequence tag able to underline intra-species differentiation are not yet identified, beyond a few plastidial markers.

METHODS

In the present work, more than 1000 transcript-specific SNP markers obtained by the genotyping of 260 individuals were studied. These genotypes included cultivated, oleasters, and samples of subspecies guanchica, and were analyzed in silico, in order to identify polymorphisms on key genes distinguishing different Olea europaea forms.

RESULTS

Phylogeny inference and principal coordinate analysis allowed to detect two distinct clusters, clearly separating wilds and guanchica samples from cultivated olives, meanwhile the structure analysis made possible to differentiate these three groups. Sequences carrying the polymorphisms that distinguished wild and cultivated olives were analyzed and annotated, allowing to identify 124 candidate genes that have a functional role in flower development, stress response, or involvement in important metabolic pathways. Signatures of selection that occurred during olive domestication, were detected and reported.

CONCLUSION

This deep EST-SNP analysis provided important information on the genetic and genomic diversity of the olive complex, opening new opportunities to detect gene polymorphisms with potential functional and evolutionary roles, and to apply them in genomics-assisted breeding, highlighting the importance of olive germplasm conservation.

Cultivar influence on variability in olive oil phenolic profiles determined through an extensive germplasm survey

Despite the evident influence of the cultivar on olive oil composition, few studies have been devoted to exploring the variability of phenols in a representative number of monovarietal olive oils. In this study, oil samples from 80 cultivars selected for their impact on worldwide oil production were analyzed to compare their phenolic composition by using a method based on LC-MS/MS. Secoiridoid derivatives were the most concentrated phenols in virgin olive oil, showing high variability that was significantly due to the cultivar. Multivariate analysis allowed discrimination between four groups of cultivars through their phenolic profiles: (i) richer in aglycon isomers of oleuropein and ligstroside; (ii) richer in oleocanthal and oleacein; (iii) richer in flavonoids; and (iv) oils with balanced but reduced phenolic concentrations. Additionally, correlation analysis showed no linkage among aglycon isomers and oleocanthal/oleacein, which can be explained by the enzymatic pathways involved in the metabolism of both oleuropein and ligstroside.