Aluminum chloride elicitation (amendment) improves callus biomass growth and reserpine yield in Rauvolfia serpentina leaf callus

The biotechnological approach of exploiting cell culture elicitation (amendment) offers an attractive alternative strategy to overcome the limited availability of biologically active and medicinally important secondary metabolites. The present study investigated the influence of abiotic aluminum chloride (AlCl3) elicitation on alkaloid yield in Rauvolfia serpentina. This metallic ion was used to enhance the biosynthesis of reserpine in leaf-derived callus, cultured in 1.0 mg l−1 BAP + 0.5 mg l−1 IAA amended Murashige and Skoog (MS) medium and this study revealed the increased yield of reserpine in cultivated tissues. This enhanced yield could help in minimizing the indiscriminate harvest of endangered flora for natural alkaloid extraction. The elicitor’s impact on callus biomass, alteration of biochemical attributes and reserpine yield at 0.05 mM (A1), 0.10 mM (A2), 0.15 mM (A3) and 0.20 mM (A4) was evaluated at periodic intervals. Maximum callus biomass was observed in 0.15 mM AlCl3 amended medium with a highest fresh weight of 1.24 g and dry weight of 0.14 g at day 6. To understand the role of AlCl3 in plant defense mechanism, various antioxidant enzymes i.e. superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities were assayed in in vitro cultivated calli with or without AlCl3 treatment. The above enzymes activities increased linearly with increasing AlCl3 level, i.e. 5.10 enzyme unit (EU) min−1 mg−1 protein SOD, 3.93 EU min−1 mg−1 protein CAT and 0.83 EU min−1 mg−1 protein APX, all being maximum at A4 treatment. The yield of reserpine was quantified in callus tissues by using HPTLC method, indicating that the reserpine synthesis was enhanced with increasing elicitor treatment up to A3 and maximum being at 0.15 mM AlCl3 amended medium (0.129 mg g−1 DW). Higher elicitation level (0.20 mM) had a very little influence on callus biomass and reserpine synthesis. Besides, the role of genes encoding pyroline-5-carboxylate synthetase (P5CS) and tryptophan decarboxylase (TDC), which participate in reserpine biosynthetic pathway is also discussed.