Silver nanoparticles elicited in vitro callus cultures for accumulation of biomass and secondary metabolites in Caralluma tuberculata.

Elicited plant in vitro cultures are gaining more interest worldwide for their potential in the uniform production of industrially important secondary metabolites. In the present study, different ratios of silver nanoparticles (AgNPs) and plant growth regulators (PGRs) were supplemented to in vitro cultures for the sustainable production of biomass and antioxidant secondary metabolites through callus cultures of Caralluma tuberculata. Results indicated that various concentrations of AgNPs significantly affected the callus proliferation and substantially increased the callus biomass, when combined with PGRs in the MS (Murashige and Skoog) media. The highest fresh (0.78 g/l) and dry (0.051 g/l) biomass accumulation of callus was observed in the cultures raised in vitro at 60 µg/l AgNPs in combination with 0.5 mg/l 2,4-D plus 3.0 mg/l BA. Phytochemical analysis of the callus cultures showed higher production of phenolics (TPC:3.0 mg), flavonoids (TFC:1.8 mg), phenylalanine ammonialyase activity (PAL: 5.8 U/mg) and antioxidant activity (90%), respectively, in the callus cultures established on MS media in the presence of 90 ug/l AgNPs. Moreover, enhanced activities of antioxidant enzymes such as superoxide dismutase (SOD: 4.8 U/mg), peroxidase (POD: 3.3 U/mg), catalase (CAT: 2.5 U/mg) and ascorbate peroxidase (APX: 1.9 U/mg) were detected at higher level (90 ug/l) of AgNPs tested alone for callus proliferation in the MS media. It may be concluded that the AgNPs can be effectively utilized for the enhancement of bioactive antioxidants in the callus cultures of C. tuberculata, a highly medicinal and threatened plant. This protocol can be scaled up for the industrial production of plant biomass and pharmacologically potent metabolites in C. tuberculata.