Essential Oil of Carpolobia lutea

Abstract

Carpolobia lutea G. Don (Polygalaceae) is a shrub or small tree native to West and Central tropical Africa [1]. It is known by many common names such as cattle stick (English), Abekpok Ibuhu (Eket), Ikpafum, Ndiyan, Nyayanga (Ibibio), Agba or Angalagala (Igbo), and Egbo oshunshun (Yoruba). Herbalists from these tribes use the root decoction in locally-made alcohol as an aphrodisiac and also for the treatment of genitourinary infections, gingivitis, and waist pains. The root decoction is also said to be useful in the treatment of internal heat. The plant Carpolobia lutea has been reported to possess anti-inflammatory, anti-arthritic [2], antimicrobial [3, 4], antidiarrheal [5], anti-ulcerogenic [5, 6], anti-nociceptive [7], antimalarial [8], and analgesic properties [9]. The plant is known to contain triterpene saponins [10] and glycosides [11]. No report on its oil constituents could be found in the literature. Leaves of C. lutea (herbarium number: FHI 109066) used for this study were collected in Igbesa, Ogun State (Southwest) and Minna, Niger State (North central), Nigeria, in August 2011. The air-dried samples (300 g each) were hydrodistilled in a Clevenger-type apparatus [12] for 3 h to afford oils with yield 0.06% v/w and 0.10% v/w, respectively, for Igbesa and Minna samples. Both oils were greenish yellow in coloration. GC analysis was performed on HP-5890 series II instrument equipped with HP-wax and HP-5 capillary columns (both 30 m 0.25 mm, 0.25 m film thickness). Analytical conditions: temperature program; 60 C for 10 min, rising from 5 C·min–1 to 220 C; injector and detector temperature 250 C; carrier gas nitrogen (2 mL/min); detector, FID; split ratio, 1:30; volume injected 0.5 L. Gas Chromatography-electron ionization mass spectroscopy (GC-EI-MS) was performed with a Varian CP-3800 gas chromatography equipped with an HP-5 capillary column and a Varian Saturn 2000 ion trap mass detector. Analytical conditions: injector and transfer line temperature 220 C and 240 C, respectively; oven temperature programmed from 60 C to 244 C at 3 C·min–1; carrier gas helium at a flow rate of 1 mL/min; volume injected 0.2 L (10% hexane solution); split ratio 1:30. Mass spectra were recorded at 70 eV. The acquisition mass range was m/z 30–300 at a scan rate of 1 scan·s–1. Identification of the constituents (Table 1) was based on comparison of the linear retention indices with those of authentic samples, and by the use of a self-constructed spectral library built up from pure substances and components of known oils and MS literature data [13, 14]. Moreover, the molecular weights of all the identified substances were confirmed by gas chromatography-chemical ionization mass spectrometry using methanol as CI ionizing gas. Although the composition of both oils of C. lutea looks similar, it is evident that some quantitative differences could be seen among them. The ubiquitous terpenoids were mostly represented in the oils. The major oil contents were hexahydrofarnesyl acetone (22.5 and 20.0%), (E)-geranyl acetone (11.8 and 11.5%), (E)-2-decenal (4.5 and 4.3%), farnesyl acetone (5.8 and 4.8%), germacrene B (3.6 and 5.4%), and -calacorene (2.7 and 2.5%). The results indicate that there seems to be homogeneity in the volatile oils of C. lutea grown in Nigeria. The essential oils from other plant species around the world have been the subject of literature discussions [15, 16].