Volatile composition of essential oils from major Egyptian Citrus cultivars: a multivariate chemometric approach

The essential oils extracted from the rind of Citrus spp. (F. Rutaceae) is abundant in chemical components of importance for the food and perfume industries, and therefore has been thoroughly researched during the past few decades. In this manuscript, we provide a comprehensive study of the volatile composition of this oils for the 12 most cultivated Citrus in Egypt: Citrus sinensis varieties: "Washington Navel (Navelina)", "Balady Seeded Orange", "Blood Orange", and "Sweet Orange Sukkari", Citrus reticulata Blanco varieties: "Yousfy Balady", "Ponkan Chinese Honey Mandarin", "Murcott Mandarin", "Clementine Mandarin", and "Dancy Tangerine", Citrus aurantifolia Swingle: "Key Lime", Citrus limettioides: "Sweet Lime", and Citrus paradisi Macf.: "Tangelo Seminole". All 12 varieties have been shown to contain 49 volatile chemical compounds, the majority of which are terpenoid (90-100%). However, some of the volatile compounds found in Citrus peel are non-terpenoid, and some of them may be helpful as species biomarkers. Multivariate data analysis was applied including unsupervised (PCA) and supervised multivariate approaches (PLS-DA, sPLS-DA) to profile volatile compounds across three Citrus groups (C. reticulate varieties, C. sinensis varieties, and other Citrus species). PCA revealed partial overlap between C. reticulata and C. sinensis, while C. paradisi and C. aurantifolia were clearly separated. PLS-DA and sPLS-DA confirmed these distinctions, with sPLS-DA achieving stronger discrimination. Variable Importance in Projection (VIP) analysis identified key discriminant metabolites, including α-ocimene, neryl acetate, and germacrene B, as primary contributors to varietal separation. These findings reveal distinct volatile profiles among Citrus groups and demonstrate the applicability of multivariate analysis for Citrus differentiation.