The Genus Artemisia: A Comprehensive Review

Abstract

Context: Medicinal plants are nature′s gift to human beings to make disease free healthy life, and play a vital role to preserve our health. They are believed to be much safer and proven elixir in the treatment of various ailments. The genus Artemisia (Astraceae) consists of about 500 species, occurring throughout the world. The present review comprises the ethnopharmacological, phytochemical and therapeutic potential of various species of Artemisia.

Objective: The aim of this this review is to bring together most of the available scientific research conducted on the genus Artemisia, which is currently scattered across various publications. Through this review the authors hope to attract the attention of natural product researchers throughout the world to focus on the unexplored potential of Artemisia species.

Methods: This review has been compiled using references from major databases such as Chemical Abstracts, Medicinal and Aromatic Plants Abstracts, ScienceDirect, SciFinder, PubMed, King′s American Dispensatory, Henriette′s Herbal Homepage, Dr. Duke′s Phytochemical and Ethnobotanical Databases.

Results: An exhaustive survey of literature revealed that the different species of Artemisia have a vast range of biological activities including antimalarial, cytotoxic, antihepatotoxic, antibacterial, antifungal and antioxidant activity. Some very important drug leads have been discovered from this genus, notably artemisinin, the well known antimalarial drug isolated from the Chinese herb Artemisia annua. Terpenoids, flavonoids, coumarins, caffeoylquinic acids, sterols and acetylenes constitute major classes of phytoconstituents of the genus.

Conclusion: Various species of Artemisia seems to hold great potential for in-depth investigation for various biological activities, especially their effects on the central nervous and cardiovascular systems.

Keywords::

• Antimalarial
• antimicrobial
• Artemisia
• cytotoxic
• flavonoids
• terpenoids.

Introduction

A survey by the World Health Organization reported that about 80% of the world′s populations rely on non-conventional medicines, especially herbal sources, in their primary healthcare (Chan, 2003). Medicinal herbs are the local heritage with global importance. The world is endowed with a rich wealth of medicinal herbs. Owing to the global trend towards improved “quality of life”, there is considerable evidence of an increase in demand for medicinal plants (Kotnis et al., 2004). Use of plants for treating various ailments of both humans and animal is a practice as old as human life itself. India is richly endowed with a wide variety of plants having medicinal value. These plants are widely used by all sections of society whether directly as folk remedies or indirectly as pharmaceutical preparations of modern medicine (Bhagwati, 2003). In the current scenario, focus on plant research has increased all over the world and a large body of evidence has collected to show the immense potential of medicinal plants used in various traditional systems. Medicinal plants are a major source of biodynamic compounds of therapeutic value, but the different variety of plants with different therapeutic properties is quite astonishing (Harsha et al., 2002).

The present review emphasizes the botanical, ethnopharmacological, phytochemical, and pharmacological reports and clinical studies on the various species of Artemisia. Through this review, the authors hope to attract the attention of natural product researchers throughout the world to focus on the unexplored potential of the Artemisia species. This genus needs to be investigated systematically so that potential species can be exploited as therapeutic agents.

The genus Artemisia

The genus Artemisia is one of the largest and most widely distributed genera of the family Astraceae (Compositae). It is a heterogenous genus, consisting over 500 diverse species distributed mainly in the temperate zones of Europe, Asia and North America. These species are perennial, biennial and annual herbs or small shrubs (Watson et al., 2002; Mehrdad et al., 2007).

General morphology

General morphological features of the genus Artemisia is described as leaves alternate, capitula small, usually racemouse, paniculate or capitate, inflorescence, rarely solitary; involucral bracts in few rows, receptacle flat to hemispherical, without scales and sometimes hirsute; florets all tubular, achenes obovoid, pappus absent or sometimes a small scarious ring (Heywood & Humphries, 1997; Mucciarelli & Maffel, 2002; Polyakov & Shishkin, 1995).

Ethnopharmacology

Traditionally, Artemisia absinthium (L.) has been used as an antispasmodic, febrifuge, stomachic, cardiac stimulant, anthelmintic, for the restoration of declining mental function and inflammation of the liver, and to improve memory (Wake et al., 2000; Guarrera, 2005). Artemisia afra (Jacq.) has been used in the treatment of a variety of ailments such as coughs, colds, headaches, dyspepsia, colic, malaria, diabetes, bladder and kidney disorders, and also used as a purgative (Thring & Weitz, 2006). Artemisia annua (L.) listed in the Chinese pharmacopoeia has been used as a remedy for various fevers including malaria (Mueller et al., 2000). Artemisia asiatica (Nakai) have been used in traditional oriental medicine for the treatment of cancer, inflammation, infections and ulcerogenic diseases (Lim et al., 2008). Artemisia douglasiana (Bess.) has been used to treat premenstrual syndrome and dysmenorrhea (Garcia & Adams, 2005). Artemisia dracunculus (L.) has been used as antidiabetic and anticoagulant (Swanston-Flatt et al., 1991; Shahriyary & Yazdanparast, 2007). Artemisia judaica (L.), an Egyptian medicinal plant has been used in the treatment of gastrointestinal disorders (Liu et al., 2004). In the western USA, Artemisia tripartite (Rydberg) (three-tip sagebrush) has been used in the treatment of colds, sore throats, tonsillitis, headaches and wounds by Native Americans (Moerman, 1998). Artemisia verlotorum (Lamotte) has been used in folk medicine of some countries of Tuscany, Italy, as a remedy for hypertension (Calderone et al., 1999). Artemisia vestita (Wall. ex Bess.) is a common traditional Tibetan medicinal plant which has been used widely in China for treating various inflammatory diseases (Ye et al., 2008). Artemisia vulgaris (L.) has been used as an analgesic, antiinflammatory, antispasmodic and in liver diseases (Gilani et al., 2005; Temraz & El-Tantawy, 2008).

Phytochemistry

An exhaustive literature survey on phytochemical reports of the genus Artemisia reveals that the Artemisia species comprise mainly terpenoids, flavonoids, coumarins, caffeoylquinic acids, sterols and acetylenes. Amongst various species of Artemisia, A. absinthium, A. afra, A. annua, A. maritima and A. scoparia (Waldst et Kit) are especially rich in terpenoids. Table 1 summarizes the phytoconstituents of various species of Artemisia, and Figure 1 represents the chemical structures of the most commonly occurring major volatile compounds.

Figure 1.  Chemical structures of the commonly occurring major volatile components of Artemisia species.

Table 1.  Phytoconstituents of various species of Artemisia.

Species	Phytoconstituents
A. absinthium	Essential oil containing (Z)-thujone, (E)-thujone (Guarrera, 2005), myrcene, trans-sabinyl acetate (Daise et al., 2008), chrysanthenyl acetate, β-pinene, sabinene, 1,8-cineole, artemisia ketone [1], linalool, hydrocarbon monoterpenes (Kordali et al., 2005), sesquiterpene lactones (Leung, 1980); polyphenolic compounds (Kordali et al., 2005), flavonoid (Oswiecimska et al., 1965); tannins (Slepetys, 1975); lignans (Greger & Hofer, 1980)
A. abrotanum	Volatile oil containing 1,8-cineole, linalool, davanone, thujyl alcohol (Tunon et al., 2006); flavonols (Remberg et al., 2004); tannins (Kolodziejski et al., 1959), caffeic acid (Kranen-Fiedler, 1956); coumarins (Tunon et al., 2006)
A. afra	Volatile and non volatile secondary metabolites such as monoterpenoids, sesquiterpenes; glaucolides, guaianolides; flavonoids (Liu et al., 2009)
A. annua	Volatile oil containing cineole, α-pinene, camphene, borneol, camphor, germacrene-D, hydroxyl amino isoartemisia ketone (Woerdenbag et al., 1994), sesquiterpene lactones artemisinin, artemisinic acid, arteanniun B, artemisinin derivatives artesunate, trioxanes, artemether artemisinin G and arteether (He et al., 2009; Bhakuni et al., 1990; Wei et al., 1992); phenolic compounds, flavones (Han et al., 2008; Han et al., 2007)
A. arborescens	Terpenes thujone, borneol, thujol (Rattu & Maccioni, 1953); flavone (Mazur & Meisels, 1955); fatty acids (Rattu & Maccioni, 1953)
A. asiatica	Volatile oil (Kordali et al., 2005); flavone (Min-Jung et al., 2005); alkaloids (Heo et al., 2000); artemisolide (Reddy et al., 2006)
A. capillaris	Volatile oil containing β-pinene (Cha et al., 2005), camphor, 1,8-cineole, β-caryophyllene, borneol (Kim et al., 2008); flavonoids (Min-Jung et al., 2005)
A. campestris	Volatile oil containing α- and β-pinene, 1,8-cineole, 1-thujone, thujyl alcohol, geraniol (Guven, 1963); flavonoids (Cavaleiro, 1986)
A. douglasiana	Monoterpenes such as cineole, camphor, linalool, isothujone, thujone (James & Cecilia, 2006), Sesquiterpene lactones such as vulgarin and psilostachyin (James & Cecilia, 2006)
A. dracunculus	Volatile oil containing menthol, anethole, anisol, anisic acid, d-sabinene, estragole, limonene, myrcene, ocimene, α-phellandrene, anisaldehyde (Bayrak et al., 1986), β-pinene, 1-methoxy-4-(2-Propenyl)-benzene, 1R-α-pinene (Zhang et al., 2005); coumarins (Hofer et al., 1986); polyphenolic compounds (Govorko et al., 2007); glucosides (Jakupovic et al., 1991)
A. judaica	Volatile components piperitone, trans-ethyl cinnamate (Abdelgaleil Samir et al., 2008), Judaicin (Saber & Khafagy, 1958b); phenolic contents (Saber & Khafagy, 1958a)
A. maritima	Volatile oil containing β-thujone, α-thujone, α-pinene, sabinene, p-cymene, sabinol cuminaldehyde, isobutyrate, isovalerate, sesquiterpene peroxysemiketal [2] (Ishibashi et al., 1965), 1,8-cineole, camphor, borneol, chrysanthenone (Jaitak et al., 2008), sesquiterpene lactones santonin [3] (Kaczmarek & Malek, 1955); fatty acids (Borsutzki, 1955)
A. mogoltavica (Poljakov)	Essential oil containing camphor, thujone, cineole (Goryaev & Shabanov, 1953), sesquiterpene lactone (Sinitsyn & Sinitsyn, 1960)
A. monospermal	Eudesmane sesquiterpenes (Stavri et al., 2005); coumarins (Hammoda et al., 2008)
A. nilagirica	Terpenoids; alkaloids; amino acids; flavonoids; quinines; tannins (Abdul & Waheeta, 2010)
A. scoparia	Volatile oil containing α-pinene, methylheptenone, 1,8-cineole, carvone, 1-thujone, α-thujadicarboxylic acid, 1-thujyl alcohol, geranyl acetate, eugenol, semicarbazone, (Z)-beta-ocimene, γ-terpinene (Singh et al., 2009), beta-myrcene, p-cymene and dl-limonene (Singh et al., 2008); fatty acids (Parihar & Dutt, 1950); coumarins (Ali et al., 2003); pyrogallol tannins (Maksudov et al., 1962); cholagogic components (Qi-Wei et al., 2002); flavonoids (Chandrasekharan et al., 1951), flavones (Lin et al., 2004)
A. tripartite	Guaianolides cumambrin B (Irwin & Geissman, 1969); biologically-active polysaccharides (Xie et al., 2008)
A. verlotorum	Volatile principles 1-camphene, cineole, fenchone, α-phellandrene, β-thujone, thujyl alcohol, cadinene; fatty acids valeric acid, palmitic acid (Covello, 1941)
A. vestita	Essential oil containing 1,8-cineole, α-, β-, γ-himachalene, caryophyllene, germacrene D, himachalol, santolina alcohol [4], thujones, thujanols (Weyerstahl et al., 1987); flavonoids (Trumpowskaand & Olszewski, 1968)
A. vulgaris	Terpenes p-cymene, fenchone, α- and β-thujone, cineole, camphor, β-pinene, 4-terpinenol, borneol (Trumpowskaand & Olszewski, 1968; Govindaraj et al., 2008), α-thujone, α-terpineol, geraniol, caryophyllene (Govindaraj et al., 2008); coumarins (Murray & Stefanovic, 1986); sterols (Ragasa et al., 2008); caffeoylquinic acids (Carnat et al., 2000)

Pharmacological and clinical reports

The essential oils distilled from the aerial parts of A. absinthium inhibited in vitro growth of Candida albicans and Saccharomyces cerevisiae (Juteau et al., 2003). Free-radical scavenging activity of A. absinthium extracts has been reported (Jasna et al., 2004). The antioxidative activity was tested by measuring their ability to scavenge stable 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical and reactive hydroxyl radical during the Fenton reaction trapped by 5,5-dimethyl-1-pyrroline-N-oxide, using electron spin resonance spectroscopy. It has been reported that crude aqueous extracts and crude ethanol extracts of the aerial parts of A. absinthium exhibit anthelmintic activity in comparison to albendazole against the gastrointestinal nematodes of sheep (Tariq et al., 2009). Recently, we have shown that A. absinthium exhibited neuroprotective effects against focal ischemia and reperfusion-induced cerebral injury in rats (Adams & Garcia, 2006).

Remberg et al. (2004) reported that a nasal spray formulation containing an extract characterised by a mixture of essential oils and flavonols from the A. abrotanum genotype “Tycho”, appear to be clinically useful and suitable for the prophylactic and therapeutic management of patients with allergic rhinitis and adjuvant symptoms. Flavonols isolated from the methanol extract of A. abrotanum exhibited spasmolytic activity against carbacholine-induced contraction of guinea-pig trachea (EC₅₀ value 20-30 µm) (Bergendorff & Sterner, 1995). Moreover, A. abrotanum extract exhibited in vitro antimicrobial activity against Malassezia spp., Candida albicans and Staphylococcus aureus.

A. afra has been reported to have a broad spectrum of inhibitory activity against microorganisms (Muyima et al., 2002). All other pharmacological activities of this species have been reported by Liu et al. (2009).

Artemisinin, an endoperoxide sesquiterpene lactone isolated from the Chinese medicinal plant A. annua, has provided a new class of highly effective antimalarials. Artemisinin-based combination therapies are now generally considered as the best current treatment for uncomplicated Plasmodium falciparum malaria (He et al., 2009). In addition, the essential oil has shown antioxidant activity equivalent to 18% of the reference compound (α-tocopherol). Dihydro-epideoxyarteannuin B and deoxyartemisinin isolated from the sequiterpene lactone-enriched fraction obtained from the crude ethanol extract of A. annua exhibited antiulcerogenic activity against ethanol and indomethacin-induced ulcer models in rats (Foglio et al., 2002). It has been reported that oral administration of artemisinin (35 or 75 mg/kg) isolated from A. annua can adversely affect post-implantation development and pregnancy in the rat (Boareto et al., 2008).

Essential oil isolated from Artemisia arborescens (L.) has been shown antiviral activity against HSV-1 and HSV-2 (Saddi et al., 2007).

DA-9601, a standardized extract of A. asiatica has been shown to exhibit chemopreventive effects against azoxymethane-initiated and dextran sulfate sodium-promoted mouse colon carcinogenesis (Ryu et al., 1998). The ethanol extract of A. asiatica has been reported to inhibit inflammatory activation of mouse microglial cells as determined by the production of nitric oxide and the expression of inducible nitric oxide synthase and inflammatory cytokine. The extract also protected nerve growth factor-differentiated PC12 cells against microglial cytotoxicity (Lim et al., 2008). The monoterpene alcohol fraction isolated from A. asiatica exhibited antibacterial and antifungal activity (Kalemba et al., 2002).

Extract of Artemisia campestris (L.) has been reported to scavenge radicals formed by carbon tetrachloride treatment resulting in protection against carbon tetrachloride-induced liver toxicity (Aniya et al., 2000).

Hong and Lee (2009) reported that the ethyl acetate fraction of Artemisia capillaris (Thunb.) (ACE) exhibit excellent protective effect by strengthening the antioxidant defense system, reducing the generation of reactive oxygen species (ROS) and damaging oxidative substances in the liver of high-fat diet induced obese mice. Moreover, ACE also exhibited significant ROS scavenging and protective effect against DPPH radical, superoxide, hydroxyl and nitric oxide radical (Hong et al., 2007). Chloroform extract of A. capillaris has been reported to have anticarcinogenic activity versus DMBA-induced mouse epidermal carcinogenesis (Kim et al., 2008). Flavonoids and a coumarin (6,7-dimethylesculetin) isolated from the buds of A. capillaris, showed significant antihepatotoxic activity by means of carbon tetrachloride-induced liver lesions in vivo and in vitro (Kiso et al., 1984). Tablets prepared from A. capillaris have potential antiviral activity against hepatitis B virus replication in vitro (Jin et al., 2005). Capillin, a component of the essential oil isolated from A. capillaris exhibited antimicrobial activity against Trichophyton mentagrophytes, Pyricularia oryzae, Candida albicans, Bacillus subtilis, Escherichia coli and Cochliobolus miyabeanus (Tanaka, 1961). Wu et al. (2001) reported that flavonoids, artemisidin A, coumarins, artemicapins A, B, C and D, and 70 other known compounds isolated and characterized from the aerial part of A. capillaris exhibited antiplatelet aggregation activity, and significant activity against HIV replication in H9 lymphocytic cells. It has been shown that water extract of A. capillaris greatly increased the volume of bile secreted and its dry weight without any significant change in the IR spectrum (Mashimo et al., 1963). A. capillaris extract has been shown to protect beta cells on cytokine-induced beta-cell damage, by suppressing NF-kappaB activation (Kim et al., 2007). A water extract of A. capillaris exhibited protective effects against oxidative stress induced by 2,2′-azobis (2-amidinopropane) dihydrochloride in Sprague-Dawley male rats (Han et al., 2006). It has been reported that β-pinene, β-caryophyllene and capillene isolated from A. capillaris exhibited antimicrobial activity against 15 different genera of oral bacteria (Cha et al., 2005).

A. douglasiana was, and still is, used to treat premenstrual syndrome and dysmenorrhea (Garcia & Adams, 2005). The tea prepared from A. douglasiana has been used to relieve premenstrual syndrome. Dysmenorrhea is treated by chewing A. douglasiana seeds (James & Cecilia, 2006).

Ethanol extract of A. dracunculus has shown antihyperglycemic activity in diabetic and non-diabetic animals (Ribnicky et al., 2006). Benli et al. (2007) reported that methanol, chloroform and acetone extracts of A. dracunculus exhibit antimicrobial activity against nine bacteria and four yeasts strains by the disc diffusion method. Methanol extract and chloroform fraction of A. dracunculus at a concentration of 200 mug/mL, inhibited platelet adhesion to laminin coated wells by 50% and 60%, respectively (Shahriyary & Yazdanparast, 2007).

Two flavones, 4′,6,7-trihydroxy-3′,5′-dimethoxy-flavone and 5′,5-dihydroxy-3′,4′,8-trimethoxyflavone isolated from A. giraldii showed antibiotic activity against Staphylococcus aureus, Sarcina lutea, Escherichia coli, Pseudomonas aeruginosa, Aspergillus flavus and Trichoderma viride (Zheng et al., 1996). Santolinylol, a monoterpene isolated from Artemisia giraldii (Pamp.) has been reported to have antifungal activity (Tan et al., 1999).

The ethanol-soluble part of a hot-water extract from Artemisia iwayomogi (Kitam.) has been reported to inhibit liver fibrosis induced by carbon tetrachloride in rats (Park et al., 2000).

Piperitone and trans-ethyl cinnamate isolated from A. judaica showed pronounced insecticidal and antifeedant activity against the third instar larvae of Spodoptera littoralis (Boisd), and antifungal activity against four plant pathogenic fungi (Abdelgaleil-Samir et al., 2008).

Aqueous methanol extract of Artemisia maritima (L.) at a dose of 500 mg/kg has been reported to exhibit hepatoprotective activity against acetaminophen and carbon tetrachloride-induced hepatic damage (Janbaz & Gilani, 1995). Cineole, a volatile oil isolated from the seeds of A. maritima shown to have more toxic effect as compared to that of santonin solution (0.0175%) (Janot & Mouton, 1930).

Essential oil isolated from flowering tops and leaves of Artemisia monospermal (Delile) has shown insecticidal activity against Musca domestica vicina and Drosophila melanogaster (Fahmy et al., 1968). Moreover, air-dried powdered drug of A. monospermal exhibited antispasmodic activity in the treatment of colic or in conditions associated with arterial hypertension (Sharaf et al., 1959).

The chloroform, diethyl ether, ethanol, hexane, methanol and petroleum ether extracts of Artemisia nilagirica (C.B. Clarke) leaf exhibited antibacterial activity against clinical and phytopathogenic bacteria. Methanol and hexane extracts showed high inhibition against clinical and phytopathogens, respectively (Abdul & Waheeta, 2010).

The monoterpenoid-rich essential oil isolated from A. scoparia (25-200 μg/mL) has shown a strong antioxidant and radical scavenging activity against hydroxyl ion and hydrogen peroxide (Singh et al., 2008). The essential oil isolated from A. scoparia exhibited strong insecticidal activity against stored-product insects (Negahban et al., 2006). A. scoparia has been reported to have anticholesterolemic, antipyretic, antiseptic, antibacterial, diuretic, purgative and vasodilator activity. Moreover, it has been used in the treatment of hepatitis, jaundice, and gall bladder inflammation (Yeung, 1985).

Artemisetin and chrysosplenetin isolated from A. sieversiana exhibited marked antitumor activity against melanoma B16, but only weakly retarded growth of Pliss lymphosarcoma (Chemesova et al., 1987). Moreover, essential oil isolated from A. sieversiana exhibited marked anti-inflammatory properties, apparently due to the azulenes in essential oil (Saratikov et al., 1986).

Biologically active polysaccharide fractions isolated from A. tripartita have been reported to exhibit macrophage-activating activity, enhancing production of intracellular ROS and release of nitric oxide, interleukin 6, interleukin 10, tumor necrosis factor alpha, and monocyte chemotactic protein 1. In addition, all fractions exhibited scavenging activity for ROS generated enzymatically or produced extracellularly by human neutrophils (Xie et al., 2008). Moreover, A. tripartite has been shown to have anti-fungal property (Tan et al., 1998).

Aqueous dried extract of A. verlotorum showed marked, but transient, hypotensive activity on the blood pressure of anaesthetized rats and on in vitro rat′s isolated aortae. This effect was mediated by a strong vasodilator action, closely linked to the release of endothelial nitric oxide and to the nitric oxide-guanosine 3′,5′-cyclic monophosphate pathway, caused by muscarinic receptor agonism (Calderone et al., 1999). Methanol and aqueous extracts of A. verlotorum exhibited in vitro antimycotic activity against Saprolegnia ferax (Macchioni et al., 1999).

The ethanol extract of the A. vestita exhibited significant inhibitory activity against the picryl chloride-induced contact hypersensitivity in mice. Cirsilineol, apigenin and 6-methoxytricin found to be responsible for the immunosuppressive activity of A. vestita (Ye et al., 2008). In addition, the potential of these three components suggested new effective remedies for the treatment of T cell-mediated inflammatory diseases.

The hydroalcohol extract of A. vulgaris at doses of 500 and 1000 mg/kg significantly inhibited abdominal contortions by 48 and 59%, respectively. Rutin, a flavonoid glycoside, and caffeic acid derivatives were identified in this hydroalcohol extract (Pires et al., 2009). Recently, antioxidant properties of this plant have shown correlation with oxidative stress defense and different human diseases. The aqueous extract exhibited scavenging potential with IC₅₀ value of 11.4 µg/mL for DPPH, the values were found to be close to those of standard rutin (10 µg/mL). On the other hand, A. vulgaris extract exhibited nitric oxide scavenging activity with IC₅₀ value of 125 mg/mL (Temraz & El-Tantawy, 2008). Both aqueous leaf extract, and essential oil obtained by steam distillation of the leaves of A. vulgaris have been shown to have insecticidal and larvicidal effects, whereas, the dry powder of A. vulgaris leaves was not found to be a contact poison for flies (Chopra et al., 1940; Ferrolino-Calumpang & Padolina, 1985). Aqueous leaf extract of A. vulgaris has been shown to have a protective effect on tissue damage brought about by ischemia-reperfusion injury in the rat mesentery (Tigno et al., 2000). The crude extract of the aerial parts of A. vulgaris exhibited hepatoprotective effects against d-galactosamine and lipopolysaccharide-induced hepatitis in mice (Gilani et al., 2005).

Discussion and conclusion

Herbal medicines are used worldwide in the traditional treatment of various ailments and diseases. Some of these have undergone in vitro screening but the efficacy of such herbal preparations has seldom been rigorously proven in controlled clinical trials. Conventional drugs provide effective therapeutic property for certain types of diseases, but for antibiotics there is an increasing issue of drug resistance, and consequently, a further need to discover new bioactive natural products. Although natural products are not necessarily safer than the synthetic analogues, still many patients undergoing treatment choose herbal medicines. Hence, health care professionals should be aware of the available pharmacological evidence of several herbal preparations.

The present review emphasizes the botanical, phytochemical, ethnopharmacological, pharmacological reports, clinical study and toxicological information on the various species of Artemisia. An exhaustive survey of literature revealed that sporadic information is available on more than 30 species. These species have been investigated for their phytoconstituents and pharmacological activities. Terpenoids, flavonoids, coumarins, caffeoylquinic acids and sterols constitute major classes of phytoconstituents of the genus. All species are rich in terpenoids but A. absinthium, A. afra, A. annua, A. maritima, A. scoparia and A. vulgaris possess high percentage of terpenoids. While A. capillaris, A. annua, A. dracunculus and A. scoparia are rich in flavonoids and coumarins.

A. absinthium, A. afra and A. nilagirica have been reported to have a broad spectrum of inhibitory activity against a variety of microorganisms due to presence of essential oil. Nasal spray formulation containing an extract characterised by a mixture of essential oils and flavonols from A. abrotanum is found to be clinically useful and suitable for the prophylactic and therapeutic management of patients with allergic rhinitis and adjuvant symptoms (Remberg et al., 2004).

A Chinese medicinal plant, A. annua, has provided a new class of highly effective antimalarials due to presence of an endoperoxide sesquiterpene lactone, artemisinin. Artemisinin-based combination therapies are now considered as the best current treatment for uncomplicated Plasmodium falciparum malaria (He et al., 2009). DA-9601, a standardized extract of A. asiatica exhibits hepatoprotective and chemopreventive effect; A. capillaries, A. scoparia and A. vulgaris exhibits significant ROS scavenging and protective effect against DPPH radical, superoxide and hydroxyl radicals (Aniya et al., 2000; Hammoda et al., 2008; Temraz & El-Tantawy, 2008) due to presence of flavonoids and volatile oil. Moreover, tablets of A. capillaris have potential antiviral activity (Jin et al., 2005).

Despite a long tradition of use of some species of Artemisia for treatment of various ailments, little pharmacological work so far has been carried out to validate their traditional uses. Some species of Artemisia seem to hold great potential for in-depth investigation for various biological activities, especially their effects on the central nervous system (CNS) and cardiovascular system. Presently, the authors are involved in evaluating the CNS effects of traditionally used medicinal plants with a view to isolating bioactive constituents following the bioactivity directed fractionation protocols.

Declaration of interest

Support from the L.L.R. Educational Trust, Solan, Himachal Pradesh, India, which runs the L.R. Institute of Pharmacy, is gratefully acknowledged.