The nomenclature of three citrus varieties collected in Pakistan and chemicals in essential oils from the peels

Abstract

Some Citrus varieties are indigenous in Pakistan. In order to make use of these cherished genetic resources, a continuous study has been carried out on the essential oils from the peels. Three varieties were collected from Khyber Pakhtunkhwa, Pakistan, Their nomenclature were ascertained by the examination of the morphological characters of fruits, branches and leaves. They are identified as Citrus karna Raf. (Kharna khatta), C. pseudolimon Tanaka (Galgal), and C. paradisi var. Foster , respectively. The essential oils (EOs) extracted from the fresh peels by hydro-distillation were analyzed. In total, 40 components are identified and quantified, accounting for 98.4-99.7%. Limonene (92.1-97.7%) is the most abundant; nootkatone (tr-0.5%) is a chemical marker (CM) for Galgal and Foster; β -bisabolene (0-1.5%) and α -bergamotene (0-1.2%) are two CMs for Galgal; decanal (0.1-0.5%), valencene (0-0.3%) and selin-6-en-4 α -ol (0-0.2%) are two CMs of Foster. The other important CMs in peels EOs of Citrus such as γ -terpinene were undetected. α -Bergamotene and β -bisabolene are two important CMs for discriminating lemons, limes and citrons from the other Citrus species. Nootkatone most probably only originates from Citrus grandis . The results of CMs in these EOs also prove the results of nomenclature.