Commercial Helichrysum italicum Essential Oils and Hydrosols from Adriatic and Continental Croatia: Quality Assessment and Chemical Composition

Immortelle (Helichrysum italicum (Roth) G. Don, family Asteraceae) essential oils (HiEOs) and hydrosols (HiHYs) are widely used in cosmetic, pharmaceutical, and agricultural formulations. However, their composition and quality vary depending on geographical origin and production practices, while standardized reference values—particularly for hydrosols—are still lacking. The aim of this study was to investigate and compare the physicochemical properties and chemical composition of commercial HiEOs and HiHYs from the Adriatic and continental regions of Croatia. Samples were analysed using standard pharmacopoeial methods and gas chromatography–mass spectrometry (GC–MS). Physicochemical analyses (relative density, acid value, refractive index, pH, turbidity, and essential oil content) showed that all samples were within generally accepted quality ranges, with no significant differences observed between regions using the Mann–Whitney U test. HiEOs were dominated by sesquiterpene hydrocarbons (53.15–55.60%), whereas HiHYs contained predominantly oxygenated monoterpenes (43.54–69.86%). The main compounds identified in both fractions were α-pinene, neryl acetate, γ-curcumene, and β-selinene, which formed a consistent chemical signature and served as practical biomarkers for the quality of H. italicum EO and hydrosol. Principal Component Analysis (PCA) distinguished sample groupings based on physicochemical properties and chemical composition, indicating regional variability without exceeding accepted quality limits. This study presents the first comparative dataset of Croatian commercial HiEOs and HiHYs, and defines practical parameter ranges to support standardized specifications, ensure consistent quality, and enhance the industrial applicability of immortelle-based products.