**3.4 Factors influencing the biosynthesis and accumulation of medicinal phytochemicals**

Knowledge about biosynthetic pathways for secondary metabolite production open avenues for the targeted production of medicinal compounds as reported by Varun et al. [34] where he proposed the biosynthetic pathways for the production of picroside-1 and picroside-2 of *Picrorhiza kurroa* an endangered herb of North-Western Himalayas, having hepatoprotective iridoid compounds. Varun et al. [35, 36] optimized preparative RP-HPLC method for the isolation and purification of picrosides in *Picrorhiza kurroa*.

For maximizing the production and accumulation of secondary metabolites through plant cell cultures, specific physical conditions such as type and composition of nutrient media, type and source of explant for initiating cell cultures, incubation temperatures and intensity of light, etc. are of paramount importance.
