Volatile Constituents of Redblush Grapefruit (Citrus paradisi) and Pummelo (Citrus grandis) Peel Essential Oils from Kenya

The volatile constituents of cold-pressed peel essential oils of redblush grapefruit (Citrus paradisi Macfadyen forma Redblush) and pummelo (Citrus grandis Osbeck) from the same locality in Kenya were determined by GC and GC−MS. A total of 67 and 52 compounds, amounting to 97.9 and 98.8% of the two oils, respectively, were identified. Monoterpene hydrocarbons constituted 93.3 and 97.5% in the oils, respectively, with limonene (91.1 and 94.8%), α-terpinene (1.3 and 1.8%), and α-pinene (0.5%) as the main compounds. Sesquiterpene hydrocarbons constituted 0.4% in each oil. The notable compounds were β-caryophyllene, α-cubebene, and (E,E)-α-farnesene. Oxygenated compounds constituted 4.2 and 2.0% of the redblush grapefruit and pummelo oils, respectively, out of which carbonyl compounds (2.0 and 1.3%), alcohols (1.4 and 0.3%), and esters (0.7 and 0.4%) were the major groups. Heptyl acetate, octanal, decanal, citronellal, and (Z)-carvone were the main constituents (0.1−0.5%). Perillene, (E)-carveol, and perillyl acetate occurred in the redblush grapefruit but were absent from the pummelo oil. Nootkatone, α- and β-sinensal, methyl-N-methylanthranilate, and (Z,E)-farnesol were prominent in both oils. Keywords: Kenyan Citrus fruits; redblush grapefruit; Citrus paradisi Macfadyen forma Redblush; pummelo; Citrus grandis Osbeck; essential oil constituents