Читать книгу Secondary Metabolites of Medicinal Plants - Bharat Singh - Страница 47

Asparagus racemosus is facing the threat of being endangered due to several developmental, seasonal constraints and malpractices involved in its collection and storage. Due to the presence of steroidal sapogenins, the callus cultures of A. racemosus were established on modified MS medium with supplementation of NAA, 2,4-D, and BAP. The 15-day-old callus was harvested and the saponin production was estimated. In comparison, it was found that root calli produced more saponin compared to nodal calli. The 20-fold accumulation of shatavarins was found to be higher in in vitro cell cultures than in wild plants (Pise et al. 2011, 2015). Phosphorus in general is believed to support good growth and differentiation, and the same is true for potassium (Tsutomu and Katsuko 1987). It has also been established that the presence of exogenous additional phosphorus and potassium enhances secondary metabolite production, especially hecogenin, which is also a steroidal saponin (Kar and Sen 1985; Gyulai et al. 1992). Maximum levels of saponins and biomass production were obtained on day 25 of the culture cycle (pH 3.4–5.6). Saponin accumulation was not a biomass-associated phenomenon; cultures that showed the highest biomass accumulation were not the highest saponin accumulators. Maximum biomass and accumulation of shatavarin IV was found in a medium containing 2,4-D and casein hydrolysate and pectinase. The maximum production of sarsasapogenin, secreted and intracellular, accumulated in medium containing NAA, 2,4-D, BAP, casein hydrolysate, and pectinase after 25 days of inoculation (Pise et al. 2012). Fusarium oxysporum, Rhizopus stolonifer as abiotic elicitors, and UV and salicylic acid as abiotic elicitors were used for enhancement of shatavarins in cell cultures of A. racemosus. From this study, it was established that biotic elicitors show mild effects of accumulation of saponins, while abiotic elicitors (salicylic acid and UV) induced maximum accumulation of shatavarins (Pise et al. 2013). When cells of A. racemosus irradiated with UV-B (five minutes), the pH of the culture medium increases by 1.01 units within 10 minutes of irradiation. The UV-B irradiation increases the activity of the enzyme phenylalanine ammonia lyase in comparison to the control, which increased production of shatavarin (Pise and Upadhyay 2015).