Effect of growing seasons on the leaf essential oil composition of Citrus species that are cultivated in Egypt

Abstract

ABSTRACT Essential oil (EO) of Citrus has some biological and pharmaceutical properties; thus, it can be used in food and drug industries. Changes in growing seasons play important roles in physiological processes of Citrus EO especially that extracted from young leaves. The aim of this study was to evaluate the EO extracted from young leaves of twelve Citrus species in different seasons (winter, spring, summer and autumn) under Egyptian conditions. The Citrus species in this investigation were Valencia Orange, Navel Orange, Sour Orange, Lemon, Volkamer Lemon, Lime, Persian Lime, Sweet Lime, Mediterranean Mandarin, Dancy Tangerine, Grapefruit and Shaddock. The EOs of young leaves were extracted by hydrodistillation method (HD), and then analyzed by GC and GC/MS. Data were statistically analyzed using ANOVA. Sabinene was identified as the major component in EO isolated from Valencia Orange, Navel Orange and Grapefruit while linalool was the main compound in EO of Sour Orange, Mediterranean Mandarin and Dancy Tangerine. The major constituent of EO produced from Lemon, Volkamer Lemon, Lime, Persian Lime and Sweet Lime was limonene, but it was E-phytol in Shaddock EO. The greatest contents (%) of EO isolated from young leaves and major constituents of all Citrus species were detected in the samples harvested during the spring season. The EO constitutes that detected in leaf EO were classified into five chemical groups “monoterpene hydrocarbons (MH), oxygenated monoterpenes (OM), sesquiterpene hydrocarbons (SH), oxygenated sesquiterpenes (OS) and oxygenated diterpenes (OD)”. It was found that the detected compounds of EO extracted from various Citrus species belonged to MH, OM, SH and OS, except the compounds of Dancy Tangerine and Shaddock were belonged to MH, OM, SH, OS and OD. Different changes were observed in the minor components and various chemical groups in different growing seasons.