Unveiling the bioactive fingerprint driving the antioxidant and antimicrobial activities of Citrus essential oils from Morocco: a chemometric and mechanistic approach

Citrus processing in Morocco generates large quantities of peel waste, which are a valuable source of bioactive essential oils (EOs). This study aimed to characterize the volatile composition and evaluate the antioxidant and antimicrobial potential of EOs from five citrus species ( C. aurantium , C. limon , C. paradisi , C. reticulata , and C. sinensis) using an integrated chemometric approach. Gas chromatography-mass spectrometry (GC-MS) analysis revealed limonene (58.2–88.4%) as the predominant component, while unsupervised chemometric analysis (PCA and HCA) discriminated species into distinct metabolic clusters based on minor volatile components. Biological evaluation showed that C. reticulata EO exhibited the highest antioxidant capacity (IC 50 = 0.81 ± 0.02 mg/mL), whereas C. limon EO demonstrated broad-spectrum antimicrobial activity against all tested microorganisms (MIC = 0.78–1.56 mg/mL). Supervised OPLS-DA indicated that bioactivity was primarily associated with oxygenated monoterpenoids, particularly linalool and geranial, as well as the hydrocarbon monoterpenes α-pinene, p-cymene, and trans-α-ocimene, which emerged as key bioactivity-associated biomarkers (VIP > 1) rather than with overall hydrocarbon abundance. These results established a robust fingerprint-based framework for the selection and standardization of citrus EOs, highlighting their potential use as natural antioxidants and antimicrobial agents in food preservation and related fields.