Effect of the extraction solvent on the oleuropein content and antioxidant properties of olive leaf (cv. Oblica, Lastovka and Levantinka) extracts

In the last few decades numerous studies have proved that an olive leaf is a rich source of bioactive phenolic compounds, mainly oleuropein and its derivatives. The aim of this study was to investigate the influence of the extraction solvent on the phenolic and oleuropein content in the leaf extracts of Dalmatian autochthonic olive cultivars: Oblica, Lastovka and Levantinka. The antioxidant activity of leaf extracts was determined using FRAP method and by metal chelating activity evaluation. The recovery obtained using methanol and ethanol (50:50, v/v) was higher than by use of water solvents. The highest share of total phenols and oleuropein was detected in ethanolic extract of Lastovka, while almost two-fold lower amounts were obtained using water extracts, both hot water and room temperature water. The extremely significant correlation between the FRAP and oleuropein/phenolic content points out the importance of these compounds in the total reducing activity of the extracts. All tested extracts provided good chelating activity probably due to the high concentrations of oleuropein but also the presence of other compounds with catechol structure, which is the most important structural feature of strong chelating activity. According to the obtained results it can be concluded that the extraction of polyphenols from olive leaves, especially from Lastovka cultivar, could present an interesting means of increasing the value of this cheap plant material that often remains unused after the harvest

GA₄₊₇ plus benzyladenine in combination with sucrose improves postharvest leaf and inflorescence quality in Lilium ‘Alma Ata’

The interaction between foliar treatment with 100 mg∙dm–3 of both gibberellic acid 4+7 (GA4+7) and benzyladenine (BA) and vase solution containing 3% sucrose was analysed in cut Lilium ‘Alma Ata’. GA4+7+BA considerably delayed leaf senescence, suppressed anthocyanin accumulation in the leaves of plants held in the sucrose solution and improved the average longevity of the flowers and the vase life of the stems. Sucrose in the vase solution strongly reduced the abscission of leaves and contributed to the enlargement of the top flower. The number of significant interactions between the treatments indicated that the investigated factors acted dependently mainly on flower quality, while their action on leaf quality was mostly independent. Results show that combined treatment with growth regulators and sucrose may considerably increase postharvest quality of cut Lilium ‘Alma Ata’

Molecular characterization of Dalmatian cultivars and the influence of the olive fruit harvest period on chemical profile, sensory characteristics and oil oxidative stability

Four Dalmatian autochthonous olive cultivars (Buhavica, Drobnica, Lastovka and Oblica) were molecularly characterized by analyzing length variability of genomic DNA sequences encompassing 15 microsatellite repeats. Furthermore, several important parameters of olive oils were analyzed in relation to the harvest period. An analysis of major phenolics secoiridoids was done by qNMR, while the fatty acid profile of oils and squalene content was determined by GC–FID. Oxidative stability was evaluated by the Rancimat method and sensory evaluation was carried out by a trained professional panel. The results indicate that the effect of the harvest period on the phenolic profile of oils depends on the olive cultivar and is related to its genetic profile. Drobnica oil from the late harvest contained an extremely high concentration of oleocanthal + oleacein (966 mg/kg). The longest oxidative stability was achieved by Drobnica and Lastovka oils from the early harvest period (20.95 and 18.65 h). Squalene had no effect on the oil oxidative stability. This study shows that the content of phenolic secoiridoids depends mainly on the cultivar. In addition, some cultivars, such as Drobnica did not show significant change of phenolic secoiridoids content in relation to the harvest period. © 2017, Springer-Verlag GmbH Germany