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The major obstacles for treatment of intracellular infections with clarithromycin are poor gastrointestinal solubility, short half-life (3–4 h), low oral bioavailability and hepatotoxicity.

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Picrorhiza (Picrorhiza kurrooa) is an endangered medicinal plant with well-known hepatoprotective activity attributed to monoterpenoid picrosides. The present article details on regulatory genes of terpenoid metabolism, 3-hydroxy-3-methylglutaryl coenzyme A reductase (pkhmgr) and 1-deoxy-D-xylulose-5-phosphate synthase (pkdxs) from picrorhiza. Since no molecular information was available, these genes were cloned to full-length by degenerate primers and rapid amplification of cDNA ends, followed by cloning of the upstream sequences that showed the presence of core sequences for light and temperature responsiveness. Electrophoretic mobility shift assay confirmed binding of protein to these motifs. Expression of pkhmgr and pkdxs was up-regulated at 15 degrees C as compared to at 25 degrees C as well as under light as compared to dark conditions. Picrosides content exhibited the trend similar to gene expression. To rule out the possible limitation of carbon pool under dark condition, plantlets of picrorhiza were raised in vitro in Murashige and Skoog medium supplemented with 3% sucrose. Results showed similar up-regulation of both the genes and the higher picrosides content in in vitro raised plantlets in the presence of light. Data suggested the important roles played by light and temperature in regulating pkhmgr and pkdxs, and the picrosides level in picrorhiza.

Shikonins are commercially important secondary compounds, known for array of biological activities such as antimicrobial, insecticidal, antitumor, antioxidants, etc. These compounds are usually colored and therefore have application in food, textiles and cosmetics. Shikonin and its derivatives, which are commercially most important of the naphthoquinone pigments, are distributed among members of the family Boraginaceae. These include different species of Lithospermum, Arnebia, Alkanna, Anchusa, Echium and Onosma. The growing demand for plant-based natural products has made this group of compounds one of the enthralling targets for their in vitro production. The aim of this review is to highlight the recent progress in production of shikonins by various biotechnological means. Different methods of increasing the levels of shikonins in plant cells such as selection of cell lines, optimization of culture conditions, elicitation, in situ product removal, genetic transformation and metabolic engineering are discussed. The experience of different researchers working worldwide on this aspect is also considered. Further, to meet market demand, the needs for continuous and reliable production systems, as well as future prospects, are included.

Cell suspension cultures of Arnebia euchroma were raised from in vitro leaf-derived friable callus on liquid MS [Murashige and Skoog] medium supplemented with BAP (6-benzylaminopurine) (10.0 μM) and IBA (indole-3-butyric acid) (5.0 μM). A two-stage culture system was employed using growth and production medium for cell biomass and shikonin derivatives, respectively. Factors such as light, temperature, sucrose and pH (hydrogen ion concentration) were studied to observe their effect on the shikonin derivative production. Light conditions completely inhibited shikonin derivative production. Out of different temperature regimes tested, the highest yield (586.17 μg/g FW) was found at 25°C. Maximum production (656.14 μg/g FW) was observed in 6% sucrose. An alkaline pH (7.25-9.50) favoured shikonin derivative production. The results showed that physical and chemical factors greatly influence the production of shikonin derivatives in cell suspension cultures of A. euchroma. Therefore, by employing optimum culture conditions, it is possible to enhance the production of secondary compounds from the cells. The factors optimized for in vitro production of shikonin derivatives during the present study can successfully be employed for their large-scale production in bioreactors.

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