Volatile compounds of volatile oils and hydrosols: intra-specific comparison in seven Lamiaceae species

Aromatic plants of the Lamiaceae family are widely recognized as major natural sources of volatile oils (VOs), with broad applications in pharmaceutical, cosmetic, and food systems. In contrast, hydrosols (HYDs)-the aqueous co-products of hydrodistillation-have received comparatively less attention, despite growing industrial relevance and the potential to provide distinct, water-compatible aromatic signatures. In the present work, the volatile signatures of VOs and taxon-matched HYDs from seven Lamiaceae species (Lavandula × intermedia, Melissa officinalis, Mentha × piperita, Origanum onites, Salvia rosmarinus, Salvia fruticosa, and Salvia officinalis) were profiled and contrasted using GC/FID-MS for VOs and SPME-GC/FID-MS for HYDs. HYDs were produced in a separate HYD-oriented hydrodistillation run; thus, VO-HYD differences reflect protocol- and matrix-dependent profiles rather than phase partitioning within a single distillation. By profiling both distillation products across seven taxa, this study helps characterize recurring matrix- and protocol-dependent compositional fingerprints of VO and HYD. Because HYDs and VOs were analyzed using different sampling modes and matrices, peak-area percentages are reported as within-matrix distributions and are not treated as directly comparable concentrations. Across taxa, oxygenated terpenes dominated both products, typically driven by oxygenated monoterpenes. VOs were generally characterized by a stronger presence of less polar and highly volatile compounds (e.g., monoterpene hydrocarbons and selected esters/ketones), whereas HYDs showed a more pronounced contribution of polar oxygenated compounds, including alcohols, oxides, and oxygenated sesquiterpenes. Several moderately water-soluble volatiles were consistently prominent in HYDs, highlighting the recurrent representation of several moderately polar oxygenated volatiles in HYDs. Overall, under the applied protocol, HYDs appeared as chemically distinct distillates with a stronger relative representation of polar oxygenated volatiles, supporting their potential use as complementary aromatic resources for aqueous-oriented formulations.