Phytochemical profile of olive oil mill vegetative waters

Olive (Olea europaea L.) belongs to the Oleaceae family and it has been cultivated for olive oil, fine wood, olive leaf and its fruits from 2000 years ago and is one of the most diffused crops in the Mediterranean basin. Its fruits can be consumed as it is, but traditionally they are employed to produce olive oil, which is one of the cornerstones of the Mediterranean diet. It is a commercial good whose market is projected to reach a revenue of 1 billion of US dollars in 2022 worldwide and is a major contribution to Italian economy (1). The production of olive oil consists in several steps that produce, along the final product, several wastes among which pomace is a wet solid waste composed by peels, pulp residues and seed fragments. In modern implants (decanter multiphase) waste can include a dehydrated pomace containing peels and hazelnuts suitable for production of pellet for stoves and a second by-product, called "paté", consisting in hydrated pulp with a high humidity (75-80%) usually used to produce biogas. In the process for the latter, vegetative water is also produced, which is an aqueous toxic waste usually discarded (2). Olive mill wastes are toxic for both natural beneficial and pathogenic microrganisms. Nowadays, in the optic of a better employment of the natural resources, these approaches are no longer sustainable, and as such several national and international projects have been founded in order to use these waste materials for other applications. The aim of this project, which is the first step of the larger ABASA (Agricultural By-products into valuable Assets for Sustainable Agriculture) project founded by LazioInnova- Regione Lazio, is to characterize the phytochemical composition of patè and vegetative waters fractionated by various stages of membrane filtration in order to identify and quantify molecules with biological activity which could be employed in agriculture as phytopesticides, agents in crop protection, soil biofertilizers or as a source of bioactive compounds. In the present study, both pomace and vegetative waters fractions were analyzed by high-resolution NMR spectroscopy. The matrices have been treated with a multi-solvent extraction protocol, and both the hydro soluble and lyposoluble fractions have been analyzed. Mono and polyunsaturated fatty acid, triglycerides, triterpenes derived from ursolic acid, oleuropein, lingstroside and their aglycones, tyrosol and hydroxytirosol were observed in both matrices, with the major difference between them being the relative amount of triglycerides. Of great interest is the presence of oleuropein and lingstroside in waste waters since they are both seco-iridoids with a known antifungal and antimicrobical activity (3) Carbohydrate profile has been obtained for the same fractions. The presence of pectin and oligogalacturonides (OGs) were identified by anion exchange HPLC-Dionex. OGs are cell wall derived pectic fragments elicitors of plant immune responses (4). This finding highlights the high potential of these by-products as biostimulant of plant defense responses. The evaluation of the fractionation efficiency and the biological activity of the different fractions are in progress.