Confirming the presence of 3,4-dihydroxyphenylglycol (DHPG) in olive leaves via thermal extraction and mass spectrometry

Olive leaves, a significant byproduct of Olea europaea cultivation, are a rich source of phenolic compounds. Among these, 3,4-dihydroxyphenylglycol (DHPG) stands out for its potent antioxidant capacity, reportedly surpassing hydroxytyrosol. Despite its potential, DHPG has been consistently elusive in conventional olive leaf extracts, often going undetected or appearing in negligible amounts in literature, which predominantly relies on organic solvent methods. This study investigates the efficient recovery of DHPG from 21 diverse olive cultivars, comparing a thermal extraction method against traditional ethanolic extraction. Our results unequivocally demonstrate that thermal treatment (120 °C, 30 min in autoclave) vastly superiorly enhances DHPG yields across all cultivars, confirming its crucial role in DHPG release. Mass spectrometry analysis indicates that this process mediates the hydrolysis and conversion of DHPG precursors. This robust and sustainable thermal strategy unlocks the full potential of olive leaf biomass, providing a high-value source of DHPG for nutraceutical, pharmaceutical, and functional food applications, thereby addressing a critical gap in olive leaf valorization.