Separation of Bioactive Compounds in Olive Leaf witha Pyridyl-Functionalized Adsorbent and Hydroalcoholic Solvents

The separation of different types of bioactive compounds in olive leaf is demonstrated with a tailored adsorbent functionalized with pyridyl moieties and sorption–desorption processes developed to use only hydroalcoholic solvents. The competitive binding isotherms of mixtures of vanillic acid, oleuropein, quercetin, maslinic, and oleanolic acids in water/ethanol solvents, with the composition ranging from 50/50 up to 100% ethanol, prove the feasibility of the separation of such different classes of molecules. The bioactive compounds in two industrial olive leaf extracts with different crude compositions were separated with the pyridyl-based polymer particles in packed columns, employing multicycle sorption/desorption processes. A polyphenol-rich extract was subjected to separation, resulting in the isolation of fractions containing varying concentrations of specific compounds. For example, a fraction enriched with oleuropein exhibited a concentration of approximately 80% (an enrichment factor of ∼4 in comparison with the crude extract), while glycosylated flavonoids were present at a concentration of around 60% in another fraction (an enrichment factor of ∼12). Additionally, aglycone flavonoids were present in fractions at a concentration of approximately 83% (an enrichment factor of ∼49). On the other hand, the separation of polyphenols and triterpene acids in an olive leaf extract with a high triterpene content was also demonstrated, with a ratio of flavonoids to triterpenoids of approximately 23 in isolated fractions, as compared to approximately 1 observed in the crude extract. The developed approach yielded luteolin with an enrichment factor of approximately 7. These novel achievements are intended to contribute to sustainability and a circular bioeconomy through the efficient industrial valorization of agricultural byproducts.