Green Extraction of Polyphenols from Olive Flesh, Pits and Leaves by Supercritical CO₂

Olive flesh, pits and olive leaves obtained from the olive tree (Olea europaea L.) contain compounds rich in polyphenols. Olive flesh, olive pomace and olive leaf oils and extracts are complex mixtures containing more than a hundred compounds with different chemical structures. Freeze drying is an effective preservation technique that produces high-quality dried materials while maintaining the integrity of heat-sensitive compounds. This study aimed to identify and quantify the active phenolic components of oils and extracts from olive flesh, olive pits and olive leaves using supercritical fluid extraction (SFE). An additional co-solvent was used in the SFE process. Extraction yields and total polyphenol contents were determined and are as follows; olive flesh CO2 (OF-1) 32.11%, 527 mg/kg, olive flesh CO2+ethanol (OF-2) 54.21%, 1470 mg/kg, olive pith CO2 (OP-1) 5.79%, 354 mg/kg, olive pith CO2+ethanol (OP-2) 5.85%, 1180 mg/kg and olive leaf CO2 (OL-1) 4.46%, 485 mg/kg, olive leaf CO2+ethanol (OL-2) 6.26%, 1275 mg/kg. Additionally, elevated concentrations of specific phenolic compounds—including 3-hydroxytyrosol, protocatechuic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, vanillin, ferulic acid, pinoresinol, oleuropein, kaempferol, and 2,5-dihydroxybenzoic acid—were exclusively detected in the OL-2 sample. Kaempferol was not detected in OL-1 and all other compounds were observed in small amounts in both analyses. OL-1 and OL-2 extracts showed antioxidant activity. In each case, extraction yields, total polyphenol contents and levels of phenolic compounds from olive leaves were relatively high. Polat SFE systems show promise as a sustainable and environmentally friendly extraction technology for future applications.