Agricultural and food waste is included in the biomass, providing a natural source for the production of energy and bioactive compounds. The scientific literature on the leaves and branches of Olive trees shows a good amount of nutraceuticals with high antioxidant properties. Therefore, the objective of the present research was to extract and characterize the main bioactive compounds from Olive pruning wastes, with a view to valorizing biomasses prior to their conversion into bio-energy. To achieve this goal, first three different ultrasound–assisted (UAE) procedures have been developed for the extraction of polyphenols, carotenoids and vitamin E, by using ethanol/water (8:2 v/v), acetone/methanol (1:1 v/v) and hexane, respectively. The extracts were then analyzed using hyphenated liquid chromatographic techniques (HPLC-PDA-MS, HPLC-FLD). The HPLC analyses confirmed that oleuropein was the predominant polyphenol in Olive pruning wastes, accompanied by minor amounts of glycosylated phenols. Lutein and β-carotene were the most abundant carotenoids. In addition, the presence of chlorophylls and tocopherols was detected. These results were then used to optimize a single-step supercritical fluid extraction (SFE) procedure for the simultaneous recovery of polyphenols, carotenoids, chlorophylls and vitamin E. The impact of several analytical parameters (e.g. modifier type and percentage, flow rate, back pressure, extraction time and temperature) was investigated. Using CO2 whit bio-ethanol as the modifier, the optimized method achieved recovery values of 76%, 84%, 88% and 90% for oleuropein, α-tocopherol, lutein and β-carotene, respectively. Although SFE provided lower yields compared to UAE, it showed advantages in terms of automation, sample throughput, operator safety and sustainability of materials. This finding was corroborated by the scores obtained through the AGREEprep tool for greenness assessment, which yielded values of 0.15 for UAE and 0.44 for SFE.
The results obtained for Olive pruning wastes highlight that the proposed SFE method was a scalable and sustainable strategy for the recovery of a wide range of bioactive compounds from biomass within the context of the circular economy.