56 International Journal of Essential Oil Therapeutics (2009) 3, 56-65 e International Journal of rc Essential Oil Therapeutics EORC www.ijeot.com Cymbopogon essential oils: Chemical compositions and bioactivities D. Ganjewala Plant Biotechnology Division, School of Biosciences and Technology, Vellore Institute of Technology (VIT) University, Vellore-632 014, Tamil Nadu, India Abstract The genus Cymbopogon (Poaceae) is most important from the point of view of their essential oils. Essential oils from these species are widely used in flavours, fragrances, cosmetics, soaps, detergents and perfumery owing to their typical lemon and rose-like aroma. Cymbopogon essential oils and constituents present therein e.g. citral, geraniol, citronellol, citronellal and piperitone, have been known to possess impressive antibacterial, antifungal, antiyeast, insecticidal and insect repellent activities for a long time. However, the biological and pharmacological significance of these essential oils has been rapidly expanded in the past ten years; anti-inflammatory, anticancer, allelopathic, free radical scavanging and other useful biological activities have now been demonstrated. Cymbopogon essential oils and constituents offer outstanding biological activities and therefore may be used in the treatment of several diseases, including cancers, and in applications of industrial importance particularly food packaging. The present review discusses the chemical compositions and biological activities essential oils from Cymbopogon species and emphasizing mechanisms of action. These details were gathered from reports on the bioactivities of essential oils of Cymbopogon species published during 1999-2009. Keywords: allelopathic, anticancer, anti-inflammatory, antioxidant, Cymbopogon species, essential oil, isointermedeol Introduction have been studied extensively, both previously and The genus Cymbopogon (Poaceae) is renowned for currently [1-9]. their essential oils of immense commercial significance The essential oils of Cymbopogon species mainly in flavours, fragrances, cosmetics, perfumery, soaps, consist of the monoterpene fractions. Several reports detergents and pharmaceuticals [1]. The genus comprises published earlier have revealed the presence of citral of about 140 species of which most are aromatic and yield (a mixture of geranial and neral), geraniol, citronellol, an essential oil upon the steam distillation of their aerial citronellal, linalool, elemol, 1,8-cineole, limonene, geraniol, parts [2]. β-caryophyllene, methyl heptenone, geranyl acetate and Some most important species of this genus are: geranyl formate in the essential oils of different species • Cymbopogon flexuosus Stapf. (East Indian lemongrass) with marked variations have been reported. Also, the • Cymbopogon citratus DC Stapf. (West Indian essential oil components are greatly influenced by genetic, lemongrass) environmental and geographical conditions [1-3]. The • Cymbopogon nardus (L) essential oils in Cymbopogon species are biosynthesized in • Cymbopogon winterianus Jowitt (citronella) the rapidly growing leaves and stored in specific oil cells in the parenchymal tissues [10,11]. • Cymbopogon martinii Roxb. (palmarosa) • C. nardus x C. jwarancusa (jamarosa hybrid ) [3]. For many years lemongrass (C. flexuosus) has been used as a culinary flavouring in Asia. The leaves are cooked with Essential oils from Cymbopogon species of diverse origin foods, especially curries, and the peeled stems are available in local markets. Fresh leaves crushed in water are used as * Corresponding author. hair wash and toilet water in India. Beside their traditional E-mail address: [email protected] uses, studies aimed to evaluate the biological activities of © Essential Oil Resource Consultants. All rights reserved. the essential oils and constituents of Cymbopogon species International Journal of Essential Oil Therapeutics (2009) 3, 56-65 57 have revealed their usefulness. Perhaps their significance extensively studied for their chemical composition by gas has been best realized in the past ten years. Studies have chromatography, GC-MS and NMR spectroscopy [1-9]. In revealed many useful biological activities of the essential recent years C. flexuosus, C. citratus, C. martinii, C. winterianus, oils and essential oil constituents of Cymbopogon species C. nardus, C. giganteus, C. schoenanthus and C. parkeri have in recent years such as anti-inflammatory, anticancer been investigated for their chemical compositions as well as and allelopathic activities [12-16]. There are few reports evaluated for biological activities The studies have revealed available describing other bioactivities of agricultural and that their essential oils mainly consist of monoterpenes ecological significance such as food packaging and insect (acyclic and acyclic), whilst those of C. flexuosus and C. repellent of essential oils of Cymbopogon species [17-20]. parkeri also consist of bicyclic monoterpenes, piperitone For example, C. martinii (palmarosa) essential oil is used as and sesquiterpenes such as isointermedeol [14, 21]. fumigation to control beetles like Callosobruchus chenesis Isointermedeol is a major component in the essential oil and Tribolium castaneum, which grow in stored grain [18]. of C. flexuosus that has anticancer properties [18]. Similarly, the insect repellent properties of C. winterianus (citronella) are used to protect cartons containing muesli and wheat germ from beetles [19]. It is also reported that the essential oils of Cymbopogon flexuosus, C. citratus, C. martinii, C. winterianus, C. nardus, C. khasianus, C. nervatus, C. schoenanthus, C. giganteus and C. densiflorus possess several useful bioactivities. In addition, individual chemical constituents such as citral, geraniol, citronellol, citronellal, linalool, limonene, piperitone, borneol, bisabolol and isointermedeol have demonstrated remarkable bioactivities, including anticancer activity [14]. The easy availability, pleasant olfactory properties and insignificant toxicity of the Cymbopogon essential oils make them most promising candidates for the treatment of chronic diseases [14]. In addition, their semio-chemical properties are useful as an alternative to synthetic chemical Figure 1. Mini Clevenger apparatus for extraction of essential oil. pesticides in an integrated pest management programme Figure 1. Mini Clevenger apparatus for essential oil [18]. extraction. Certainly, essential oils of the Cymbopogon species are Gas chromatographic analyses of essential oils of C. occupying increasingly and vastly varied significance in flexuosus cultivars OD-19 and GRL-1 has revealed the pharmaceuticals and medicine owing to their potential presence of several monoterpenes viz., citral (a and b), bioactivities. This trend, however, has been increased geraniol, borneol, isopulegol and 6-methyl hept-5-en-2- progressively in the past ten years. Despite the fact that one, geranyl acetate, γ-terpinene, α-thujene, α-pinene, the numbers of reports are increasing on the bioactivities sabinene, n-decanol, α-terpenyl acetate, β-caryophyllene, of Cymbopogon essential oils, these reports have not been α-humulene, germacrene D, β-bisabolene and γ-cadinene analyzed or reviewed at one place. In this review article, [1-9]. Structures of some of these monoterpenes are I have discussed chemical compositions and various presented in Figure 2. bioactivities of the essential oils of Cymbopogon species Our earlier study of essential oil compositions in eight from the collation of reports published in the past ten cultivars of C. flexuosus revealed that essential oils of the years. Also, the biosynthesis and accumulation of the seven cultivars consisted mainly of citral (75-85%), except essential oils has been briefly mentioned. that of cultivar GRL-1, which is mainly composed of Essential oil extraction from Cymbopogon species geraniol (90%) [1]. Citral is an isomeric mixture of geranial (citral a) and neral (citral b) and are major components Essential oils from members of the genus Cymbopogon are in the essential oils of several species of Cymbopogon usually extracted by steam or hydrodistillation of the aerial [10]. Both citral and geraniol have immense commercial parts, such as leaves and inflorescences in mini Clevenger significance due to their characteristic lemon and rose- apparatus (Figure 1). They yield an essential oil with a like smell in the flavour, fragrance, cosmetics, perfumery characteristic aroma due to the presence of the significant and pharmaceutical industries [1,22]. A study of essential monoterpene fractions. Cymbopogon flexuosus (East Indian oil composition and phylogenetic relationship in 19 lemongrass) oil is yellow to reddish-brown in colour and Cymbopogon taxa by Khanuja et al. 2005 [2] revealed marked the odour is powerful lemon like, while that of C. martinii variation in the essential oil content and compositions of (palmarosa) and C. flexuosus mutant cv. GRL-1 essential these taxa. Essential oils from C. confortiflorus and C. nardus oil has a rose-like aroma due to the higher proportion of var. confortiflorus were rich in geraniol with observed geraniol. values of 68% and 46%, respectively, whereas essential oils from C. nardus var. nardus and C. winterianus had very Chemical compositions of the essential oils little amount of geraniol. Essential oil extracted from C. Essential oils of a number of Cymbopogon species have been pendulus, C. flexuosus and C. citratus mainly consisted of 58 International Journal of Essential