Seasonal Variation of Leaf, Stem and Umbel Ray Essential Oils of Bupleurum gibraltarium Lam.

Journal of Essential Oil Research: JEOR, Jul/Aug 2006 by Fernández-Ocaña, Ana M, Fernández-López, Carlos, Camacho-Simarro, Ana M, Velasco-Negueruela, Arturo, Et al

Abstract

The yield and composition of essential oils from leaves, stems, umbel rays and also from whole aerial parts of Bupleurum gibraltarium Lam. (Apiaceae) were determined during the pre-flowering, full flowering, late flowering, and fruiting vegetative periods. A fruit sample was also studied for comparative purposes. Leaves (0.8-1.8% yield) and stems (0.3-0.7%) reached their maximum oil content during the late flowering period, whereas umbel rays (2.2-3.7%) reached it in full flowering. Oil samples were analyzed by capillary GC and GC/MS: components which were found in amounts greater than 2% were selected to carry out a seasonal study. In the leaf oils, sabinene (12.0-33.9%) and limonene (7.8-23.4%) were the main components, the sabinene level being minimum in full flowering and maximum in fruiting. In stem oils, sabinene (4.7-21.6%) and 2,3,4-trimethylbenzaldehyde (9.3-13.6%) were the main components, the sabinene level being minimum in pre-flowering and maximum in full flowering. In umbel ray oils, sabinene (20.7-43.1%) was the first component in all the phenological periods, followed by α-pinene (7.3-28.2%). Both monoterpenes increased their levels in late flowering and reached minimum amounts in fruiting.

Key Word Index

Bupleurum gibraltarium, Apiaceae, essential oil composition, seasonal variation, sabinene, α-pinene, limonene, 2,3,4-trimethylbenzaldehyde.

Introduction

Bupleunim gibraltarium Lam. (Apiaceae) is an evergreen shrub that grows wild in calcareous and shady areas of central and southern Spain and northwestern Africa (1,2). The species name for this plant more frequently appears in the literature as Bupleurum gibraltaricum Lam. than as B. gibraltarium Lam. However, the specific epithet used herein is "gibraltarium" as it was the term originally coined by J.-B. A.P. Monnet de Lamarck in 1785, and also compiled in Flora Europaea (1) and Flora Iberica (2). As this species name was introduced before the International Code of Botanical Nomenclature had accepted the Latin adjective "gibraltaricum" to mean "from Gibraltar," the valid complete name for this plant is that assumed in this article. ) Stems measure up to 200 cm, and the coriaceous leaves have very marked veins. Flowers are in compound umbels, with yellow petals. It can be found in bloom during July and August, and reaches the fruiting period from September to November.

A survey of the literature reveals a number of studies concerning the chemical composition of B. gibraltarium. From the root extract diverse acetylenic compounds, monoterpenes, angelic acid esters (3), and several saikosaponins have been isolated (4,5). From the aerial part extract flavonoids and cinnamic acids have been detected (6), and from a non-polar leaf extract two new monoterpene aldehydes along with known terpenoids were characterized ( 7). In regard to the composition of the essential oil, it has been studied on a few occasions. Cabo et al. found ca. 20 monoterpenoids in the oil from the plant in bloom, the major constituents being β-pinene/δ-3-carene, α-pinene, terpinen-4-ol and limonene (8,9). Gil et al. continued this work with a comparative study of the fruiting apex oils of plants collected in different areas within the province of Granada (Spain), δ-3-carene and α-pinene being again the main components (10).

Rural inhabitants of the areas where the plant grows wild have used it in folk medicine (11), and it has been described its application as analgesic and antirrheumatic (12) as well as disinfectant and vulnerary in human medicine and veterinary (13). In the laboratory, the anti-inflammatory activity of the essential oil (10,11) and of a root extract (4), and the in vitro antimicrobial activity of an oil sample ( 14) have been investigated. Some years ago we studied the oil composition from the umbel rays, stems, leaves, fruits and the whole aerial parts of B. gibraltarium harvested in the province of Jaén, southern Spain (15). The oils of the umbels, leaves and fruits were dominated by sabinene and α-pinene, and stems and aerial parts by sabinene and 2,3,4-trimethylbenzaldehyde, among others. More recently, the in vivn antifungal activity of an oil sample from aerial parts has been studied by us against Plasmopara halstedii, a pathogen capables of causing important losses in the world production of sunflower ( 16). Continuing with our work on B. gihraltarium we would like to describe herein the composition and variation in essential oils obtained from different plant parts of B. gibraltarium from the pre-flowering phenological stage until the fruiting period of the plant.

Experimental

Plant material: Samples of B. gihraltaritim were gathered in November 1995 during the fruiting period (F), in May 1996 during the pre-flowering period (PF), in July 1996 during the full flowering period (FF), and in September 1996 during the late flowering period (LF) from El Zumbel area (UTM: 30SVG3278) near the city of Jaén. Every sample consisted in the whole aerial parts of five single plants growing wild near one to another. Botanical identification of samples was performed by one of us (C. F.-L.), and a voucher specimen (JAEN950910) was deposited at the Herbarium JAEN of the University of Jaén. Once the plants reached the laboratory, they were air-dried for seven to 15 days, and separated by parts, i.e., leaves, stems, umbel rays and, when present, fruits.