Constituents of Rhizome Essential Oils of Two Types of Cyperus articulatus L. Grown in Nigeria

Journal of Essential Oil Research: JEOR, Nov/Dec 2006 by Olawore, Nureni O, Usman, Lamidi A, Ogunwande, Isiaka A, Adeleke, Kasali A

Abstract

The essential oils of the rhizomes of the red and black types of Cyperus articulatus L. were investigated by GC and GC/MS. Oxygenated sesquiterpenes constituted the bulk of both oils (54.2% and 52.1% for the red and black types, respectively). The major components of the oil of the red type were cyperotundone (42.3%), piperitone (10.1%), β-maaliene (8.4%) and germacrone (5.3%), while the oil of the black type had an abundance of cedrol (19.0%), guaia-5-en-11-ol (14.9%) and cyperotundone (9.6%).

Key Word Index

Cyperus articulatus, Cyperaceae, essential oil composition, cyperotundone, piperitone, cedrol, guaia-5-en-11-ol.

Introduction

Cyperus articulatus L. (family Cyperaceae) is tropical sedge widely grown in Nigeria, where it is commonly known as 'kajiji' by the Hausas, 'woire' by the Fulanis and 'ifin' by the Yorubas (1). The plant is used in traditional medicine for the treatment of several ailments like epilepsy, malaria and dysentery in different parts of the world (1). The therapeutic properties of this plant have been established by various workers. For instance, the non-volatile extracts of the rhizomes of C. articulatus are known to possess anticonvulsant, anti-malaria and antimicrobial properties (2-4). Repellant and anti-feedant properties of these extracts have also been reported (5).

Nyasse et al. (6,7) have isolated the sesquiterpenic ketones, mandassidione, mustakone, corymbolone and the alcohol corymbolol, from Cameroonian grown C. articulatus. Earlier work on the essential oils from the Canadian grown C. articulatus has led to the isolation and characterization of a bicyclic ketone, articulone, which was later, renamed cyperotundone and isopatchoul-4(5)en-3-one (8).

Literature information is scant on the chemical composition of the oil from C. articulatus. However, research works on the oil composition of other Cyperus species have been reported. Ekundayo et al. (9) had reported that the main constituents of the essential oil of C. tuberosus were α-humulene (30.04%), humulene eporide II (16.91%), β-caryophyllene (12.13%) and caryophyllene oxide (10.75%), while C. rotundus L. had cyperene (19.19%) and α-cyperone (17.72%) in abundance. On the other hand, Sonwa and Koenig (10) had isolated (-) nor-rotundone, (-)-isorotundone, (-)-cypera-2,4(15)-diene and ( )-cyperadione from C. rotundus.

In continuation of our systematic study of the essential oils of Nigerian medicinal plants, we investigated the rhizome oils of the red and black types of C. articulatus.

Experimental

Plant materials: The dried rhizomes of the red and black types of C. articulatus were obtained in Ilorin, Kwara State, Nigeria. Identification was carried out at the herbarium of the Forestry Research Institute of Nigeria (FRIN), Ibadan, where voucher specimens were deposited.

Oil isolation: Pulverized rhizomes of the red and black types of C. articulatus (500 g) were separately hydrodistilled for 3 h in a Clevenger-type apparatus, according to the British Pharmacopoeia specification (11). The resulting oils were collected, preserved in a sealed sample tube and stored under refrigeration until analysis.

Gas chromatography: GC analyses were performed on an Orion micromat 412 double focusing gas chromatography system fitted with two capillary columns coated with CP-Sil 5 and CP-Sil 19 (fused silica, 25 m x 0.25 mm, 0.15 μm film thickness) and flame ionization detector (FID). The volume injected was 0.2 μL and the split ratio was 1:30. Oven temperature was programmed from 50°-230°C at 3°C/min using hydrogen as carrier gas. Injection and detector temperatures were maintained at 200°C and 250°C, respectively. Qualitative data were obtained by electronic integration of FID area percents without the use of correction factors.

Gas chromatography/mass spectrometry: A Hewlett-Packard HP5890A GC, interfaced with a VG Analytical 70-250s double focusing mass spectrometer was used. Helium was the carrier gas at 1.2 mL/min. The MS operating conditions were: ionization voltage 70 eV, ion source 230°C. The GC was fitted with a 25 m x 0.25 mm, fused silica capillary column coated with CP-Sil 5. The film thickness was 0.15 μm. The GC operating conditions were identical with those of GC analyses. The MS data were acquired and processed by on-line desktop computer equipped with disk memory.

The percentage compositions of the oils were computed in each case from GC peak areas. The identification of the components was based on the comparison of retention indices (determined relative to the retention times of series of n-alkanes) and mass spectra with those of authentic samples and with data from literature (12-14).

Results and Discussion

Pulverized rhizomes of the red and black types of C. articulatus on hydrodistillation afforded oils in yields of 0.62% and 0.60% v/w, respectively.

Table I shows the retention indices, relative percentages and the identities of the constituents. A total of 37 and 43 compounds representing 93.1% and 94.7% of the rhizome oils of the red and black types, respectively, were identified from their mass spectra. The constituents of the oils were monoterpenoids 21.4% and 34.1% for the red and black types, respectively, and sesquiterpenoids 71.7% and 60.6%, respectively. The overall chemical composition seems to be different from each other and from that of other Ctjperus species previously studied.