Abstract

Graphical Abstract

Open in a separate window

Introduction

Cymbopogon is a genus with a lot of names, such as lemongrass, barbed wire grass, silky heads, Cochin grass, Malabar grass, oily heads, citronella grass, or fever grass. This grass species is widely distributed in more than 40 countries in the world (as shown in Figure 1) and is native to Asia, Africa, Australia, and tropical islands (Soenarko 1977; Toungos 2019). Cymbopogon is diverse in terms of names, species, and uses, with almost all of them being aromatic. It consists of 144 species, some of which include Cymbopogon nardus (L.) Rendle (C. nardus), Cymbopogon citratus (DC.) Stapf (C. citratus), Cymbopogon giganteus Chiov (C. giganteus), Cymbopogon flexuosus (Nees ex Steud.) W. Watson (C. flexuous), Cymbopogon martini (Roxb.) W. Watson (C. martinii), Cymbopogon schoenanthus subsp. proximus (Hochst. ex A. Rich.) Maire & Weiller (C. schoenanthus), etc. (Table 1 and Figure 2). The distribution of these species is astonishing as some of the same species can be found in different countries, but there no conclusive evidence to indicate whether or not their chemical composition is exactly the same. For example, C. citratus can be found in Bangladesh, Brazil, Tanzania, Ghana, Guadeloupe, French West Indies, Kenya, Mauritius, Argentina, Thailand, Uganda, Nigeria, India, Mexico, Singapore, Togo, Trinidad, etc. C. nardus can be hunted in Uganda, Brazil, Mauritius, Thailand, etc. While C. giganteus can be found in Ghana, Nigeria, Cameroon, Burkina Faso, Madagascar, etc. And C. jwarancusa can be found in Iran, Pakistan, etc (Jirovetz et al., 2007; Karami et al., 2021). The distribution of Cymbopogon species from different countries across the world is shown in Figure 1.

Open in a separate window

FIGURE 1

The distribution of Cymbopogon species from different countries across the world, with more than 10 species found in countries like India, China, Australia and countries found in East Africa.

Open in a separate window

FIGURE 2

Depiction of diversiform Cymbopogon species.

The ethnopharmacology of Cymbopogon species has been shown to possess a diverse set of characteristics that supports their traditionally applications in cosmetic, pharmaceuticals, insect repellants, insecticides, and perfumery, mainly due to their high level of essential oils (Khanuja et al., 2005; Aibinu et al., 2007). Several findings have confirmed the nutritional value of Cymbopogon species as well as their therapeutic and pharmacological properties. Many countries in the world use this species as an herbal remedy on urinary tract infection, detoxication effects on the kidney and liver, bone diseases, hypertension, hypercholesteremia, stomach ulcers, weight loss and indigestion (Takaisi-Kikuni et al., 2000; Jirovetz et al., 2007; Francisco et al., 2011; Kpoviessi et al., 2014; Karami et al., 2021). When it comes to dosage, in countries like Tanzania, it is believed that patients with stomach ulcers can have a cup of tea of this herb half an hour before eating in the morning, afternoon, and evening. In diabetic patients, you boil the lemongrass leaves and add ginger powder and take them before dinner. The doses and how it is consumed vary in other countries, as some consume it as tea or decoction with different dosages. C. citratus is one of the most extensively employed species in the world, with pharmacological effects such as anti-inflammatory, antitrypanosomal, and stomach discomfort treatments (Francisco et al., 2011; Kpoviessi et al., 2014). Other species with antimicrobial effects include C. giganteus (Jirovetz et al., 2007), C. pendulus and C. winterianus as antifungals (Pandey et al., 1996; Oliveira-Verbel et al., 2011), C. flexuosus as a chemo preventive (Sharma et al., 2009), C. densiflorus Stapf as an antibacterial (Takaisi-Kikuni et al., 2000).

Ethnopharmacology and traditional significance

Cymbopogon species has diverse uses in different countries, contributing to the discovery of traditional medicines and commercial applications. On continents like Asia, South America, and Africa, the Cymbopogon leaves have been traditionally utilized as tea or decoction. Different parts of the Cymbopogon plant embrace key bioactive chemicals which determine the anti-inflammatory, antiseptic, anti-dyspeptic, and anti-fever actions, antispasmodic, analgesic, antipyretic, tranquilizer, anti-hermetic, and diuretic characteristics of the plant (Ademuyiwa et al., 2015; Bayala et al., 2018). In Tanzania, lemongrass tea is utilized as an anti-fever to reduce fever and is used by women to ease dysmenorrhea. The tea is also believed to clean the fallopian tubes, which facilitates easier blood flow. In Singapore, C. citratus is employed to alleviate paronychia, cold and flu symptoms, bug bites, sore and itchy throats, flatulence, indigestion, and cancer prevention (Siew et al., 2014). Interestingly, several countries also choose C. citratus as an insect repellent against mosquitos, house flies, and fleas (Boaduo et al., 2014). In India, C. flexuosus is generally accepted to treat fever, rheumatism, and cancers (Sureshkumar et al., 2017). It has been argued that the aerial parts of Cymbopogon jwarancusa (Jones ex Roxb.) Schult (C. jwarancusa) are panacea for respiratory tract infections, while its root decoction has been demonstrated to exert superior roles on dyspepsia, typhoid, and fever in children (Kadir et al., 2014). In Gabon, the crushed leaves of Cymbopogon densiflorus (Steud.) Stapf (C. densiflorus) are recognized as a treatment for rheumatism, while its flowerhead is smoked in a pipe as a remedy for bronchial discomfort and asthma in Malawi and Congo. The aerial part and root of Cymbopogon distans (Nees ex Steud.) W. Watson (C. distans) are ingeniously utilized as carminatives to prevent heart disease in Pakistan (Ullah et al., 2014). The majority of Cymbopogon essential oils are consumed in aromatherapy because of their therapeutic benefits, which aid in body rejuvenation. It can also be found in a variety of items, including perfumes, local soaps, and candles (Dutta et al., 2016). In several Asian and African countries, the leaf has been shown to have some snake and reptile repellent functions. Figure 3 summarizes some of the ethnopharmacology observed in Cymbopogon species.

Open in a separate window

FIGURE 3

Ethnopharmacological applications of Cymbopogon species.

Phytochemistry

The presence of phytochemicals in medicinal herbs may be linked to their therapeutic potential. Many chemical compounds have been isolated from Cymbopogon species, including hydrocarbons, alcohols, ketones, esters, phenols (flavonoids, tannins), volatile and non-volatile terpenoids, acids, carotenoids, and other miscellaneous compounds (Table 2 and Table 3). Among which, essential oils, flavonoids, terpenoids, phenols, and tannins are the major phytoconstituents as shown in Figure 4 (Rahim et al., 2013; Avoseh et al., 2015). The chemical composition of essential oil is mainly composed of monoterpenes, monoterpenoids, sesquiterpenes, sesquiterpenoids (Figure 5), and a few fatty alcohols like 1-Octanol and 4-Nonanol (Piaru et al., 2012; Oladeji et al., 2019).

Open in a separate window

FIGURE 4

Major phytoconstituents extracted from Cymbopogon species.

Open in a separate window

FIGURE 5

The chemical structures of Cymbopogon essential oils. They include monoterpenes such as citral α, citral β, nerol, geraniol, myrcene, limonene, geranyl acetate and citronellal. Monoterpenoids: Cis-dihydrocarvone, eucalyptol. sesquiterpenes: α-farnesene, β-bisabolene, germacrene D, β-elemene, caryophyllene oxide, calarene. Monoterpene ketone: Piperitone. Sesquiterpenoids: Elemol and β-bourbonene.

Pharmacology

Most of the pharmacological investigations have been conducted based on the components present. These components have led to the discovery of different pharmacological effects, which are proved by the mechanism of action discovered. Figure 6 highlights some of the mechanisms of action observed in Cymbopogon species.

Open in a separate window

FIGURE 6

The involved mechanisms of action observed in Cymbopogon species for disease management.

Toxicology

Generally, Cymbopogon is safe when consumed orally, topically, or used as aromatherapy. However, there are some factors, like heavy metal contamination from the soil, interaction of Cymbopogon with some drugs, and wrong consumption that can cause an undesirable effect (Ekpenyong et al., 2015a). According to some studies, citronella oil derived from the species C. afronardus, C. nardus, C. validus, and C. winterianus, is one of the ingredients in insect repellents and is applied topically to prevent mosquito bites. However, some adverse effects have aroused public concern. This includes skin reactions or irritation in some people, lung damage prior to its inhalation, and some reports of child poisoning after ingesting citronella oil-contained insect repellent (RxList 2021a, November 6). Other negative effects documented prior to the use of lemon grass include skin allergies when used directly on the skin, toxic alveolitis when inhaled, an elevation in amylase, and bilirubin (RxList 2021b, February 9). Relevant findings suggest that toxicological biomarkers and genotoxicity of C. citratus essential oil have a low toxicity level but are suitable and safe in long-term treatment at doses up to 100 mg/kg (Bidinotto et al., 2011). Although the United States has classified lemongrass as relatively safe., it is not recommended for use during pregnancy and breast-feeding, considering its stimulation to uterine and menstrual flow (Nimenibo-Uadia and Nwosu, 2020).

Quality control

Quality control is important for medicinal herbs as it helps in identifying the herb, discovering the active and minimal components, and becoming acquainted with the extraction, separation, or isolation process of the herb (Wang et al., 2019). Figure 7 summarizes this process of Cymbopogon genus. This was conducive to assure the safety of the herb, its ethnopharmacology, and its pharmacological effects.

Open in a separate window

FIGURE 7

Plant collection, extraction, isolation, and analysis of constituents in Cymbopogon genus.

Discussion

The use of traditional medicines is widespread and dates back a long time before the increase in technology and knowledge that we have now (Wang et al., 2019 and, 2022). Cymbopogon species can also be termed as medicinal plants due to their many reported medical benefits, which mostly ascribe to their essential oils and the whole parts of the plant in general. Most Cymbopogon species are declared relatively safe to consume, except for some like C. winterianus, C. schoenanthus, C. pendulus, and obtectus, whose edible uses are unknown but are known to be used for medicinal purposes, perfumery products, cosmetics and household insecticides. Traditionally, the use of these species varies from simply being consumed as tea, drinks, or food flavoring. Medically, they have been argued to exhibit: a) anti-inflammatory, antiseptic, anti-dyspeptic, and anti-fever actions; b) antispasmodic, analgesic, antipyretic, tranquilizer, anti-hermetic, and diuretic anti-fever; c) ease dysmenorrhea; d) detoxication effects on the kidney and liver. The dosage used traditionally is not standard nor scientifically approved. However, it is believed in most countries that one tea cup of lemongrass daily can strengthen individual’s immunity. Clinically, citral, the main component in lemongrass, together with its other components, is thought to have anticancer ability and reduce the risk of various developing cancers by attacking the cancer cells or by boosting the immunity system. On the other hand, some cancer patients are given lemongrass tea after going through rounds of chemotherapy or radiation for relief. A study manifested that C. citratus tea can help get rid of gastric ulcers or even reduce the risk of gastric ulcers obtained from synthetic drugs like aspirin (Fernandes et al., 2012). Evidence also documented that drinking lemon grass tea every day for a month boosted the red blood cell count by increasing the amount of hemoglobin concentration, which was attributed to its superior antioxidant properties (Ekpenyong et al., 2015b).

Furthermore, many investigations have been dedicated to exploring the phytochemistry, phytotherapy and pharmacology of Cymbopogon species. In one of the studies, it has been reported that a dichloromethane extract of C. ambiguous was demonstrated to have antiplatelet activity, which is believed to be highly because of its eugenol content (Uddin et al., 2011). Another study substantiated that the methanolic extract of C. citratus can achieve a dose-dependent relaxant activity through endothelial vasoconstriction via the nitric oxide pathway (Pereira et al., 2013). As to adverse effects, it is generally safe to consume some of the Cymbopogon species, but several adverse effects have been reported by oral or topical administration. Adverse effects observed orally include fatigue, dry mouth, excessive urination, and vertigo. Noteworthily, lemongrass essential oil might harm the mucous membranes in the stomach and liver when excessive and unrestrained use. When applied topically, skin reactions or irritation can be observed. It is also advisable to avoid taking it with drugs that are glutathione-S-transferase substrates and cytochrome p450 substrates to prevent any risk of increased side effects of these drugs. Moreover, pregnant and breast-feeding mothers can also avoid consuming lemongrass tea, citronella oil and its related products, so as to prevent its effects on infant development (Memorial Sloan Kettering Cancer Center 2020, February 14).

Conclusion and future prospects

Cymbopogon species are very fascinating, diverse, and rich in every sense, from their simple traditional uses like culinary and tea. Of which some of the species like C. nardus are not edible due to their unpleasant nature, while some remain unknown as to whether they are edible or not. To their medicinal uses, the robust pharmacological activity is mainly attributed to their richness in essential oils, such as monoterpenes, monoterpenoids, sesquiterpenes, sesquiterpenoids, and certain fatty alcohols. This genus is widespread throughout the world, with species like C. giganteus and C. densiflorus found in tropical Africa, C. nardus in eastern Africa, C. caesius in southern and eastern Africa, C. martinii, C. flexuosus, C. distans, and C. coloratus in eastern Asia, among others, all of which have unique medicinal and commercial benefits. Lastly, more research is needed to improve the ones that are known and to reveal those with little knowledge. Researchers can come up with more essential products that can be made using natural ingredients to replace those manufactured with harsh chemicals, which cause a lot of side effects and negative health factors. In addition, the drug dosage and mode of drugs traditionally given to people should be effectively tested, and this will aid in the increase of certified medicinal drugs and enhanced pharmacological effects in the future. Meanwhile, the exact clinical efficacy and potential organ toxicity of some species or active ingredients also need to be further elucidated.

References