and eco-friendly source of artemisinin (Acton and Roth 1992; Haynes and Vonwiller 1994). The genetic engineering of Saccharomyces cerevisiae to produce higher yield of artemisinic acid was attempted. The mevalonate pathway, amorphadiene synthase, and a novel cytochrome P450 monooxygenase (CYP71AV1) genes from A. annua were transferred into yeast cells to enhance the production of amorpha-4,11-diene to artemisinic acid by genetic engineering (Ro et al. 2006).
Artemisinin is an effective against both drug-resistant and cerebral malaria-causing organism such as P. falciparum. The low yield of artemisinin from aerial parts is a limitation to the commercial production of drug. So, to increase the production of artemisinin, the cell culture studies of this species are highly desirable. The production can be increased by better understanding of pathways of synthesis. The genetic engineering tools can be used for the overexpression of genes to link to the artemisinin synthesis. The synthesis can be overcome by changing fully or partially in the pathway of artemisinin production (Abdin et al. 2003).
The methanolic extract of Artmisia aucheri possessed antileishmanial and cytotoxic activities. The different concentrations of growth hormones, thiamine HCl, showed better synthesis of artemisinin in the callus cultures of this species. The methanolic extract of callus also demonstrated cytotoxic activity (Gharehmatrossian et al. 2014; Mohammad et al. 2014). The different concentrations of BA, kinetin, IAA, and 2,4-D were added to the MS culture medium for obtaining callus in Artmisia absinthium. The lower concentration of BA with higher level of NAA and kinetin increased the callus growth. The best callus growth was obtained from the leaf explants in this plant species (Nin et al. 1996). The adventitious shoots regenerated and maintained on MS culture medium supplemented with gibberellic acid and casein hydrolysate. In these shoots, the synthesis of artemisinin was reported as higher in concentration. The hormone when used as elicitors during the synthesis of artemisinin was reduced. So, it is suggested that higher or lower synthesis of artemisinin is hormone specific and dependent on the presence or absence of nutrients in culture medium (Zia et al. 2007b).
The estimation of phenylalanine lyase enzyme activity and their relationship with artemisinin synthesis in callus cultures of A. annua were studied. The synthesis of higher concentration of artemisinin is linked to the enzyme activity. Maximum enzyme activity and synthesis of artemisinin were reported in a four-week-old callus but, after this, the enzyme activity started to decrease. In decreased synthesis of enzymatic stage, it was also observed that artemisinin synthesis was found to be lower in concentration. Therefore, it is predicted that artemisinin synthesis is dependent on phenylalanine synthase enzymatic activity (Jhansi Rani et al. 2012).
Cell suspension cultures developed from A. annua exhibited antimalarial activity against P. falciparum in vitro both in the n-hexane extract of the plant cell culture medium and in the chloroform extract of the cells. Trace amounts of the antimalarial sesquiterpene lactone artemisinin may account for the activity of the n-hexane fraction, but only the methoxylated flavonoids artemetin, chrysoplenetin, chrysosplenol D, and cirsilineol can account for the activity of the chloroform extract (Liu et al. 1992; Ferreira and Janick 2002).
The commercial production of artemisinin by hairy roots in bioreactors remains considered as challenging job. A. annua is a rich source of artemisinin and its derivatives. For the enhancement of production of artemisinin, two types of bioreactors were used. The mist bioreactor provided a more appropriate environment for the hairy roots; hence, maximum accumulation of artemisinin was observed (Nin et al. 1997). Similarly, other bubble column bioreactor was more suitable for production of biomass of hairy roots but not for artemisinin production. The gene expression mechanism of biosynthetic pathways of 3-hydroxy-3-methylglutaryl coenzyme A reductase, 1-deoxy-D-xylulose-5-phosphate synthase, 1-deoxy-D-xylulose-5-phosphate reductoisomerase, and farnesyl diphosphate synthase in culture conditions was also studied. In case of shake flasks, out of four genes, only farnesyl diphosphate synthase gene was correlated with artemisinin production. The effects of light was also studied, and it was found that it controls the process of transcription of genes (Souret et al. 2002, 2003). It has been reported that an A. annua HDRcDNA was cloned from leaves and their expression profiles were estimated in different parts of this plant species. The overexpression of AaHDR1 enhanced the contents of artemisinin, arteannuin B and other sesquiterpenes, and multiple monoterpenes (Ma et al. 2017).
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19 Fulzele,
