Water as a solvent of election for obtaining oleuropein-rich extracts from olive (Olea europaea) leaves

Leaves from Olea europaea represent one of the main by-products of the olive oil industry, containing a plethora of bioactive compounds with several promising activities for human health. An organic solvent-free extraction method was developed for the recovery of olive leaf phenols, which obtained an extract containing oleuropein in high amounts. A comparison of various extraction media is reported, together with the total phenolic content, DPPH (2,2-Diphenyl-1-picrylhydrazyl) content, ORAC (oxygen radical absorbance capacity), and polyphenol oxidase activity of the corresponding extracts. The polyphenol profiles and content of the most representative extracts have also been studied. Extraction solvent and temperature significantly influenced the phenolic content and antioxidant activity of the extracts, with hot water representing the solvent of election for the extraction of bioactive compounds from this matrix. All the extracts obtained showed reasonably high total phenol content (TPC) and good DPPH radical scavenging activity; among them, the water extract is characterized by desirable traits and could be used for many industrial applications and human consumption

Edible coatings incorporating pomegranate peel extract and biocontrol yeast to reduce Penicillium digitatum postharvest decay of oranges

This study investigated the potential use of two edible coatings, chitosan (CH) and locust bean gum (LBG), which incorporated chemically characterized water pomegranate peel extract (WPPE) or methanol pomegranate peel extract (MPPE) and the biocontrol agent (BCA) Wickerhamomyces anomalus, to control the growth of Penicillium digitatum and to reduce the postharvest decay of oranges. CH and LBG including pomegranate peel extracts (PPEs) at different concentrations were tested in vitro against P. digitatum to determine their antifungal efficacy; at the same time, the tolerance of viable cells of W. anomalus to increasing concentrations of WPPE and MPPE extracts was assessed. The potential application of selected bioactive coatings was evaluated in vivo on oranges, which had been artificially inoculated with P. digitatum, causal agent of green mold decay. CH incorporating MPPE or WPPE at all concentrations was able to inhibit in vitro P. digitatum, while LBG was active only at the highest MPPE or WPPE concentrations. W. anomalus BS91 was slightly inhibited only by MPPE-modified coatings, while no inhibition was observed by WPPE, which was therefore selected for the in vivo trials on oranges artificially inoculated with P. digitatum. The experimental results proved that the addition of 0.361 g dry WPPE/mL, both to CH and LBG coatings, significantly reduced disease incidence (DI) by 49 and 28% respectively, with respect to the relative controls. Besides the combination CH or LBG + WPPE, the addition of W. anomalus cells to coatings strengthened the antifungal effect with respect to the relative controls, as demonstrated by the significant reduction of DI (up to 95 and 75% respectively). The findings of the study contribute to the valorization of a value-added industrial byproduct and provide a significant advancement in the development of new food protectant formulations, which benefit from the synergistic effect between biocontrol agents and natural bioactive compounds