Davana Oil is obtained by steam distillation of the overground parts of the flowering herb, Artemisia Pallens wall. The plant grows in the same parts of southern India where also sandalwood is grown. Davana Oil is very dark green or brownish green in color.
Artemisinin is a highly potent anti-malarial drug found in the medicinal plant Artemisia annua (A. annua). World Health Organization recommends artemisinin and its derivatives for the treatment of malaria (White 2008). Artemisia annua is a plant species of genus Artemisia L. and is used as a traditional medicine for the treatment of malaria and other diseases in China. A. pallens also known as “Davana” is an important aromatic herb of genus Artemisia L. and is mostly found in southern region of India. These plants are industrially important due to its anti-microbial, insecticidal, antioxidant, and anti-malarial properties as well as perfumery compounds (Haider et al. 2014). A. pallens has been employed by the local people as a herbal medicine in curing many disease like diabetes and some skin infections (Haider et al. 2014). The leaves and flowers of the A. pallens yield an essential oil known as “oil of Davana”. Further, it also indicates the presence of artemisinin and its derivatives which has been used as a drug for the treatment of malaria (Shukla et al. 2015). Recently, Agrobacterium tumefaciens mediated genetic transformation of A. pallens has been optimized, which suggested that genetic engineering of A. pallens could be the effective strategy for the production of artemisinin and its derivatives (Alok et al. 2016). Artemisinin and its derivatives are produced only in the aerial parts (especially leaves and floral parts) of the plant whereas non significant amount or absent in roots of some species of Artemisia (Ferreira and Janick. 1996; Mannan et al. 2010; Wang et al. 2016).
Hairy root culture of plants using the Agrobacterium rhizogenes, the causative agent of hairy root disease in several plants, has emerged as an important technique for the production of secondary metabolites (Sivakumar et al. 2010; Sujatha et al. 2013). Transformed hairy root cultures are biochemically and genetically stable model for scale-up of pharmaceutically important natural products (Souret et al. 2003). Hairy roots have been reported to yield higher amounts of artemisinin than intact plant tissue and cell suspension cultures (Sivakumar et al. 2010; Dilshad et al. 2015a). Growth of hairy roots can be scaled up using bioreactors and hence they can be exploited for commercial production of secondary metabolites (Liu et al. 1998; Patra and Srivastava 2014). Various biotic and abiotic elicitors such as endophytic fungi (Wang et al. 2001a), red light (Wang et al. 2001b) and methyl jasmonate (Baldi and Dixit 2008) have been reported to regulate cell metabolism of hairy root for enhanced production of artemisinin.
Among the plethora of phytochemicals, terpenes (terpenoids or isoprenoids) constitute the largest and most diverse class of specialized metabolites. Terpenoids, are the plant secondary metabolites which play an important role in plant–microbe, and plant–plant interactions (Dudareva et al. 2006). Terpenes are one of the largest groups of natural products; more than 25,000 terpene structures have been reported in different plant species (Gershenzon and Dudareva 2007). Terpene compounds have many functional roles in plants such as in photosynthesis (plastoquinones, chlorophylls, carotenoids), respiration (ubiquinone) as well as in growth and development of plant (sterols, cytokinins, gibberellins, abscisic acid, brassinosteroids) (Pulido et al. 2012). Natural bioactive compounds like alkaloids, flavonoids and polyphenols are the most important secondary metabolites in plants having properties that affect appearance, taste, odor and oxidative stability (Singh 2012). These compounds posses various important biological properties. Therapeutic potential of the extract of Artemisia species is directly related to the total polyphenolic and flavonoid content in those plants.
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Artemisinin is the drug of choice for the treatment of malaria and other diseases (White 2008). The highest artimisinin content has been reported in the leaves of A. annua (0.44–1.00 %), a Chinese variety of Artemisia plants (http://www.mmv.org/) (Mannan et al. 2010). It was introduced and cultivated in different regions of India, but artemisinin production was decreased (Singh et al. 1988; Baldi and Dixit 2008). There is a great concern that the artemisinin production at the current rate will not meet the increasing demand by the pharmaceutical industry. In past, various efforts have been made to enhance the level of these molecules in plants by the genetic engineering approach (Farhi et al. 2011). There are various strategies which are now being used to meet the increasing demand of artemisinin (Durante et al. 2011; Farhi et al. 2011; Singh et al. 2016).
Therefore, present study was aimed to investigate efficacy of the hairy root induction in cultures of A. pallens, an Indian Artemisia species. We quantified artesunate, an important derivative of artemisinin in the hairy roots of A. pallens and aerial extract of plant. To the best of our knowledge, this is the first report of A. rhizogenes mediated genetic transformation of A. pallens. Further, we also quantified the total content of alkaloids, flavonoids and phenolic comounds in different extracts prepared in aqueous, ethanolic and methanolic solvents.