Composition and Antimicrobial Activity of Cymbopogon giganteus (Hochst.) Chiov. Essential Flower, Leaf and Stem Oils from Cameroon[dagger]

Abstract

The essential oils of fresh flowers (2 samples), leaves and stems of Cymbopogon giganteus (Hochst.) Chiovenda from Cameroon were investigated by GC and GC/MS. More than 55 components have been identified in the samples 1 (flowers 1), 2 (leaves), 3 (stems) and 4 (flowers 2) with main compounds possessing the p-menthathene skeleton as follows: cis-p-mentha-1(7),8-then-2-ol (1: 22.8%, 2: 27.7%, 3: 29.1%, 4: 20.5%), trans-p-mentha-1(7),8-dien-2-ol (1: 24.9%, 2: 21.6%, 3: 28.1%, 4: 26.5%), trans-p-mentha-2,8-then-1-ol (1: 17.3%, 2: 22.1%, 3: 21.4%, 4: 16.3%) and cis-p-mentha-2,8-dien-1-ol (1: 8.3%, 2: 5.4%, 3: 4.6%, 4: 9.7%). Additional components in higher concentrations, responsible for the characteristic aroma impressions of these samples are especially limonene, trans-verbenol and carvone as well as some other mono- and sesquiterpenes. Antimicrobial activities of the four oils were found against Gram-(+)- and Gram-(-)-bacteria as well as the yeast Candida albicans, and these results were discussed with the compositions of each sample.

Key Word Index

Cymbopogon giganteus, Poaceae, essential oil compositions, cis-p-mentha-1(7),8-dien-2-ol, trans-p-mentha-1(7),8-dien-2-ol, trans-p-mentha-2,8-dien-1-ol, antimicrobial activity.

Plant Name

Cymbopogon giganteus (Höchst.) Chiovenda syn. Andropogon giganteus Höchst., Poaceae.

Source

Fresh plants of C. giganteus were coUected at the Waza-Park near Mora-City, North-Province, Cameroon, during February 2005 (dry season, morning-time). The plants were identified by botanists of the University of Yaounde (Cameroon) and a voucher specimen (no. 13971 SFRCAM) has been deposited in the specially maintained Herbarium of Yaounde.

Plant Part

Fresh flowers, leaves and stems were hydrodistdled for 4 h using a Clevenger-type apparatus. The flower sample was separated into two parts. The ods of leaves, stems and one part of the flowers were obtained by décantation of water and dried by filtration over anhydrous sodium sulfate. Od yields were 0.4% for leaves (sample 2), 0.01% for stems (sample 3) and 1.4% for flowers (sample 1). The second part of the collected flower distdlate was extracted with diethyl etiler (2 x 100 mL). The ether extract was dried over anhydrous sodium sulphate. After evaporation of the ether the yield of the flower oil (sample 4) was 1.1%.

Previous Work

Cymbopogon giganteus (Höchst.) Chiov. syn. Andropogon giganteus Höchst, (common names: Tsauri grass; Cameroon: wadjalo; French: beignefata; German: Großes Lemongrass (1), Poaceae) is growing in the Asian and African tropical Savannahs (2). Cymbopogon giganteus is a loosely tufted perennial herb, the basal sheadis soon fading away; culms are robust and l-3m high, are erect, sometime supported by stilt roots at the base; leaf blades are linear to narrowly lanceolate, 15-60cm long and 8-30cm wide, smoodi, mostly dark green, firm. False panicles are linear 20- 70cm and racemes are 10- 15mm long; the lower most inter node and pedicel are connate (3). Cymbopogon giganteus plant parts are used in local African medicine for various treatments, such as against rheumatism, fever, cough, skin disorders (decoctions of leaves and flowers) and arterial hypertension (2,4). Some antimalarial activities have also been studied in animal experiments (5). The essential oils of this as wed as of other Cymbopogon species (e.g. the more common C. citratus) are important aromatic substances, used for food flavoring (1) andperfumery/cosmeticproducts (6), and also show antioxidative and antiradical (6) as wed as anti-inflammatory and analgesic properties (7). Analyses of the od composition of C. giganteus samples from Africa, such as Burkina Faso, Ivory Coast and Mali, showed p-menthadienols as main constituents (2,4,6-8). Only few papers discuss the composition of oils of C. giganteus from Cameroon (9). To the best of our knowledge, no information is available on the od composition of different plant parts of C. giganteus from Cameroon and tiieir antimicrobial activities against various microorganisms.

Present Work

The essential oils of C. giganteus from Cameroon were described as being intense fresh, green-herbal, spicy and weak floral (leaves); fresh-green, floral and weak herbal (flowers); fresh-spicy, weak floral-fruity and herbal-musty in the background (stems) as wed as fresh-floral, green-herbal and weak spicy (flowers, ether-sample). The oil composition was analyzed by a combination of GC and GC/MS. GC analysis of the oil was carried out on a Shimadzu GC-14A (FID) and a Varían GC-3700 (FID) gas Chromatograph fitted with a 30 m ? 0.32 mm (film thickness: 0.25 pm) chemicady bonded apolar FSOT-RSL-200 (Biorad) and with a 30 m ? 0.32 mm (film thickness: 0.50 pm) Stabdwax (Restek) fused silica column, respectively. The sample was injected by splitter using H as carrier gas. The column temperature was programmed from 40°C (5 min) to 280°C (20 min) at 6°C/min. The compound identification was partly possible by coinjection of pure compounds and correlation with published retention-time data (10-13). GC/MS analysis was carried out on a Shimadzu GC-17A/QP5000, on a HP-5890GC/HP-5970MSD and on a Finnigan MAT GCQ (carrier gas: He, EI mode, 70 eV, scanrange: 40-450 amu and ion-source temperature 200°C each, columns see GC-part) equipped widi Wdey/NBS- and NIST libraries. For additional mass spectral correlations, published data (10,12-14) were used.