Biotic Elicitation Based Enhancement of Some Secondary Metabolites and Antioxidants in Sauropus androgynus (L.) Merr.

Author(s): Kirtana S. and N. Geetha

Abstract: In the present investigation, an attempt was made to test the hypothesis that whether biotic elicitor may enhance some secondary metabolites and antioxidants in S. androgynus. For this, B.subtilis strain was purchased from MTCC, Chandigarh, India and maintained in LB medium. After reaching the log phase, the bacterial culture was centrifuged, and extracellular biomass was collected (supernatant) and used for synthesis of AgNPs. Among five concentrations of AgNO3, a stable colour change was observed at 3mM concentration in 2:8 ratios (AgNO3 and cell filtrate). The visual formation of AgNPs was confirmed by UV-Vis spectrophotometer, XRD and SEM analyses. Phytotoxicity analysis was carried out to understand the positive and negative effects of synthesized AgNPs on seed germination and also for dose fixation for treatment of leaf derived calli of S. androgynus with synthesized AgNPs. It was observed that there is no negative effect on germination rate for seeds by treatment with 50 mg/L, 100 mg/L, and 150 mg/L AgNPs concentrations, whereas germination percentage was reduced by treatment with 200 mg/L and 250 mg/L AgNPs concentrations. For callus induction, MS medium was prepared with 2.0 mg/L 2, 4-D, and 0.5 mg/L of BAP along with different concentrations of AgNPs such as 50 mg/L, 100 mg/L, 150 mg/L, 200 mg/L and 250 mg/L individually and young leaf of S. androgynus were collected from field grown plants. After sterilization, the explants were inoculated onto different media. After 30 days of culture maintenance, the leaf derived calli were removed and aqueous calli extract was prepared using 0.5 g tissue and used for determination of some secondary metabolites and antioxidants. It was observed that a significant enhanced level of total phenolics and total antioxidant capacity compared to control calli. Higher level of free radical scavenging activities such as DPPH and FRAP was found in calli treated with AgNPs compared to control calli. This is the first report to exhibit an enhancement in these plant components of S. androgynus using extracellular biomass of B.subtilis as elicitor.

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