**1. Introduction**

Medicinal plants play an important role in a healthy society. Restoration of practices and knowledge related to medicinal plant resources is part of an important strategy related to biodiversity conservation, knowledge of new drugs and improving the living standards of rural populations [1]. The Gramineae family includes the genus *Cymbopogon*, which encapsulates herbs that are globally recognized for possessing high essential oil content. Its species are broadly distributed across the globe

where they are utilized for diverse purposes. Both the commercial and medicinal uses of its differential species have been well authenticated [2].

Additionally, the ethnopharmacology corroboration reveals the presence of an expansive array of properties possessed by these species, which establishes their utilization for pest control for cosmetics and anti-inflammatory media. Species of *Cymbopogon* may also envelope potentials as potent antitumor and chemopreventive drugs [3]. *Cymbopogon flexuosus* and *Cymbopogon citratus* are the two main species vastly farmed for their essential oils in various parts of the world [4]. It is cultivated in the subtropical and tropical regions of the world and widely used in the agriculture, cosmetics, flavor, food, pharmaceutical industries [1]. It is a member of the aromatic grasses containing essential oils with lemon flavor. Its species are tufted perennial C4 grasses with several hard stems emerging from a short, rhizomatous base [5] with a citrus flavor, dried to powder or freshly used. The name *Cymbopogon* is derived from the Greek words "kymbe" (boat) and "pogon" (beard), referring to the flower spike arrangement [5]. The species *C. citratus* is identified by many international common names, such as West Indian lemon grass or lemon grass (English), citronelle or verveine des indes (French), hierba limon or zacate de limón (Spanish), xiang mao (Chinese), capimcidrao, or capim-santo (Portuguese), and locally, there are more than 28 indigenous names identified from different countries of the world [4]. Other common names of *C. citratus* include lemongrass, barbed wire grass, citronella grass, fever grass, and tanglad [6]. *C. citratus* thrives best in sunny, warm, humid conditions of the tropics and grown in a wide range of soil types, from rich loam to poor laterite. Although calcareous and water-logged soils adversely affect growth [7], those cultivated on sandy soils have higher leaf oil yields and higher citral content [8]. *C. citratus* is believed to have originated from Malaysia, and it is now widely grown in Central and South America, regions in Africa, Southeast Asia, and the Indian Ocean Islands, both on subsistence and commercial scales particularly in South-east Asia. It is an aromatic, evergreen, perennial grass that produces multiple stiff stems emerging from a short rhizome-like rootstock and grows to approximately 1.5 m tall. Although it rarely produces florets, the leaflets are blue-green, erect, and linear and exude a characteristic lemon flavor when crushed [9]. The *C. citratus* is positioned as one of the most globally distributed genera that are usually utilized in all parts of the globe [3]. The plant, which can be dried and powdered, or used fresh, has been employed in diverse activities that include food flavoring, in teas, soups, with poultry, fish, beef, seafood, and curries. Reports have validated its global diverse health benefits, including the fact that lemongrass leaves and other parts can be infused to treat nausea, stomach aches, constipation, and a variety of stomach infections as well as to prevent ulcers [4]. *C. flexuosus* (Poaceae) is described as a native, tall perennial aromatic grass (sweet smelling sedge) with growth confined to specific patches of subtropical parts of Asia, Africa, and America. *Cymbopogon flexuous,* also known as the Cochin or Malabar grass*,* is native to Sri Lanka, India, Thailand, and Burma. It is naturalized in numerous parts of the tropical and subtropical Southeast Asia and Africa [10, 11]. Consequently, it has received significant global demand due its varied range of applications in differential industries. Reports reveal that *Cymbopogon* flexosus include more than 140 with 52 of them growing in Africa, 45 in India, 6 in Australia, 6 in South America, 4 in Europe (only in Montenegro), 2 in North America, and the others in South Asia. It is utilized as a medicinal tea, in preparation of soups, curries, and starting agent for vitamin A synthesis and has been known to be both perfumery and flavorful with the therapeutic

*Phytochemical Contents of Essential Oils from* Cymbopogon *Species: A Tropical Medicinal Plant DOI: http://dx.doi.org/10.5772/intechopen.105396*

characteristics [10]. *C. flexosus* is a C4 grass endowed with industrial importance and abundant medicinal properties, and utilized for its essential oil (EO) production [11]. India is a significant exporter and the major producer of lemongrass oil. The essential oil comprises citral (i.e., a mixture of neral and geranial), geraniol, limonene, and geranyl acetate among others and is well-recognized for their antimicrobial, anticancer, and allelopathic activities [11, 12]. These essential oils are employed in the production of eco-friendly pesticides [3, 11]. In addition, lemongrass is an important source of several vitamins (A, B1, B2, B3, B5, B6, folate, and vitamin C) and essential minerals (calcium, copper, iron, magnesium, manganese, potassium, phosphorous, zinc) [11]. The above-listed properties cause lemongrass to be an industrially preferred crop due to its enormous potential in the fields of medicine, cosmetics, food, and biotechnology [13]. In furtherance, a couple of studies published that lemongrass essential oil can be utilized as biofuel; thus, it is regarded as an energy grass [14].

## **2. Phytochemicals of essential oils of** *Cymbopogon* **species**

The essential oils of *Cymbopogon* are identified by monoterpene constituents including citral, limonene, geraniol, citronellol, elemol, b-carophyllene, citronellal, 1,8 cineole, linalool, methylheptenone, geranylformate, and geranyl acetic acid derivation. Essential oils are typically chemically characterized by GC-MS [1, 15–17]. The plant *C. citratus* is abundant in bioactive substances. Flavonoids, alkaloids, saponins, tannins, and phenolic compounds, such as quercetin, luteolin, apiginin, isoorientin 2'-O-rhamnoside, and kaempferol, have been isolated and identified from the plant's leaves [18, 19]. These phytochemicals have been reported to be beneficial, especially in the pharmaceutical, food, health, and agricultural industries [20, 21]. Alcohols, aldehyde, ketones, esters, and terpenes are predominantly the other compounds found in *C. citratus* [20]. It also consists of 1–2 percent essential oil on a dry basis with the chemical composition varying greatly depending on the habitat, genetic diversity, and agricultural treatment of the crops. Longifolene (V4) (56.67%) and selina-6-en-4-ol (20.03%) are the constituents of volatile oil from the roots [22]. Although the primary chemical constituent of lemongrass essential oil is citral, borneol, geranial, geraniol, β-myrcene, limonene, neral, geranyl acetate, alpha-terpeniol, estragole, methyleugenol, citronellal, careen-2, farnesol, (+)-cymbodiacetal, proximadiol, methyl heptenone, terpinolene, pinene, linalool, linalyl acetate, and β-caryophyllene have also been reported [5, 22]. Citral (3, 7-dimethyl-2, 6-octadien-2-al) refers to the natural mixture of two isomeric acyclic monoterpene aldehydes, that is, geranial (citral A or trans citral) and neral (citral B or ciscitral) [20], which have same molecular formula (C10H16O) but different structures [23–26]. The various components of *C. flexosus* are significantly recognized due to the high concentration of aromatic essential oil, which contain many secondary metabolites, particularly monoterpenes (citral) and sesquiterpenes (caryophyllene) [11, 27]. Lemongrass is used in a variety of traditional Asian dishes and beverages, and also in high-end perfumes, pharmaceuticals, and biomedical applications [28]. The antibacterial, insecticide, larvicide, antitumoral, and cytotoxic characteristics of C. flexuosus' essential oil make it popular in alternative medicine [20]. The main constituents of the essential oil of C. flexuosus are Z-citral (-citral), geraniol, and -geranial (-citral), with citral contributing significantly to the oil's antibacterial properties.
