Methyl jasmonate and salicylic acid elicit indole alkaloid production and modulate antioxidant defence and biocidal properties in Rauvolfia serpentina Benth. ex Kurz. in vitro cultures

In the present report, the effect of methyl jasmonate (MJ) and salicyclic acid (SA) elicitation, on the indole alkaloid production from micropropagated culture of the endangered Ayurvedic medicinal plant Rauvolfia serpentina Benth. ex Kurz, was investigated. The highest shoot multiplication was found in Murashige and Skoog (MS) media augmented with BAP (2.0 mg/l) following 4 weeks of culture. MS media fortified with cytokinins produced nodal explant-derived nodular base callus (NBC)/ nodular meristemoids (NMs) following 6 weeks. Maximum root length was found in half strength MS basal (½ MSO) media and maximum number of roots per shoot was noted in ½ MS media augmented with indole-3-butyric acid (IBA) (1.5 mg/l). Clonal fidelity of the in vitro plants was assessed by 10 inter-simple sequence repeat (ISSR) primers of which only 3 primers (UBC-810, UBC-820, and UBC-827) produced clear and reproducible bands. The content wise variation of indole alkaloids (reserpine and ajmalicine), post elicitor (MJ and SA) treatment (0.5-2 mg/l) was quantified via high-performance thin layer chromatography (HPTLC). In vitro raised R. serpentina root accumulated highest amount of reserpine (0.456% and 0.440%) followed by 1.5 mg/l MJ and SA mediated elicitation respectively. Ajmalicine content of in vitro root, grown on culture elicitated with MJ (1.5 mg/l and 2 mg/l), was 0.261%. The ascorbate peroxidase (APX) activity was the highest in MJ (1.5 mg/l) treated micropropagated plantlets (0.86 EU/min/mg protein) and comparatively lesser in root samples (0.77 EU/min/mg protein) following 9 days of treatment. In all tested concentrations, SA treated plant sample exhibited strong superoxide dismutase (SOD) activity but the MJ and SA mediated elicitation caused sharp decrease in catalase (CAT) activity in all plant samples. In elicitor treated plant samples, the 1,1-diphenyl2-picrylhydrazyl (DPPH) radical scavenging activity (%) as well as total phenolics and flavonoids contents were marginally higher than the untreated ones. In vivo and in vitro grown R. serpentina root extracts showed best response against the four evaluated ATCC strains of bacteria.