Composition of Turkish Bitter Orange and Lemon Leaf Oils

Abstract

Bitter orange (Citrus aurantium L.) and lemon (Citrus limon (L.) Burm. f.) leaf oils were obtained from bitter orange tree leaves and lemon tree leaves by steam distillation. The oils were analyzed by high-resolution gas chromatography (HRGC) and high-resolution gas chromatography mass spectrometry (HRGC/MS). In total, 50 and 60 components have been identified in bitter orange and lemon leal oils, respectively. Bitter orange leaf oil showed a high content of oxygenated compounds (89.6%) with linalyl acetate (50.1%) and linalool (24.8%) being the main components. Lemon leaf oil was characterized by higher content of monoterpene hydrocarbons (64.2%) of which limonenc (44.2%)) and [beta]-pinene (10.6%) were the major components. It contained a lower content oxygenated compounds (33.5%) than the bitter orange leaf oil.

Key Word Index

Citrus aurantium, Citrus limon, Rutaceae, bitter orange leaf oil, lemon leaf oil, petitgrain oil, linalyl acetate, linalool, limonene.

Plant Name

Citrus aurantium L., Citrus limon (L.) Burm. f.

Introduction

Bigarade (family Rutaceae, genus Citrus), commonly named bitter orange, is cultivated in Central and South America (Haiti and Paraguay) and in Mediterranean countries (1). Bitter orange tree is very resistant to cold, to excess of water and to several diseases. Bitter orange leaf or petitgrain oil possesses more desirable organoleptic properties than other leaf oils obtained from the other Citrus trees (lemon, mandarin, sweet orange, bergamot, etc.), the production of which is very limited (2). The bitter orange leaf oil is mainly produced by France, Italy, Spain and Paraguay. It is widely used in perfumery for the sweet and fresh note it gives to colognes and lotions. The oil is also used for the fabrication of soaps because of its good resistance to an alkaline medium. Studies concerning the chemical composition of bitter orange leaf oil have been reviewed (3-8). Lawrence has also reviewed most of the papers about bitter orange, lemon, mandarin, bergamot and sweet orange leaf oils (9).

Lemon (Citrus limon) originated in Southeast Asia, China, and the Malayan Archipelago. Lemon is the an important crop, grown in coastal sites of southern California, Argentina, Sicily, Greece, Spain and Turkey. Lemon oil is widely used as aroma flavor enhancers for soft and alcoholic beverages and food. In pharmaceutical industries, it used as flavoring agents to mask unpleasant tastes of drugs. In perfumery, it forms the base of many compositions. Lemon oil has a higher market value per pound than orange, grapefruit or tangerine oils. Most of the published data were directed towards true lemon leaf oil [Citrus limon (L.) Burm.] (9-16), while some papers dealt with the composition of the leaf oil of C. jambhiri Lush. (Rough lemon) (17), C. limon x C. sinensis (Meyer lemon) (18) and C. volkameriana (19) Eureka lemon (20).

Although the composition of the bitter orange and lemon leaf oils have been thoroughly studied by many researchers, data regarding the composition of Turkish origin bitter orange and lemon leaf oils have not been reported. This study was part of a research program on the Turkish origin citrus oils. In this paper, the composition of Turkish origin bitter orange and lemon leaf oils are reported.

Experimental

The samples of bitter orange and lemon leaves were collected from a commercial citrus plantation (Antalya) 15 May 2001. The leaves were carefully cleaned then cut for steam distillation.

Steam distillation: Steam distillation was carried out by passing steam atmospheric pressure for 2 h through a 2-L round-bottomed flask containing 300 g of fresh leaves. The oil was separated from the condensed and dried over anhydrous Na^sub 2^SO^sub 4^ and stored at -18°C until analysis.

Analysis

For gas chromatographic analysis, a 60 x 0.25 mm, 0.25 µm film thickness, DD-5 capillary column was used. The column was installed in a HP 5890 CC equipped with an injection splitter with a split ratio 1/30 and flame ionization detector (FID). The oven temperature was programmed from 40°C (4-min isothermal) to 280°C at 5°C/min and at 280°C (10-min isothermal). The temperatures of the injector and detector were 230°C and 240°C, respectively. Helium (1 mL/min) was used as carrier gas. The injected volume of the samples was 0.2 µL of neat oil. The quantitative composition was obtained by peak area normalization, and the response factor for each component was considered to equal 1.

Gas chromatography/mass spectrometer (GC/MS) analysis of the oils were performed on the same Chromatograph equipped with a Micromass Zabspec (double focusing, magnetic sector), Ionization voltage 70 eV, electron multiplier 1700 V, interface temperature 250°C, ion source temperature 200°C, scan mass range 35-500 amu; GC column and conditions were the same as above. Mass spectra and individual GC peaks were identified by a computer search of the commercial libraries (WILEY, NIST), followed by matching of MS data and published data (21-23).