Effect of explant source, perlite nanoparticles and TiO/perlite nanocomposites on phytochemical composition of metabolites in callus cultures of Hypericum perforatum.

It appears that the biologically-synthesized nanoparticles (NPs) have potential to perform as effective elicitors for the production of valuable secondary metabolites in plants. Besides, it has been reported that the toxicity of the biologically-synthesized NP is not as much as that of the chemically-synthesized NPs. Therefore, it is necessary to test their advantages aspects. In this study, the physical synthesis of perlite NPs and biologically-synthesis of TiO/perlite nanocomposites (NCs) were conducted. Subsequently, their effects and explant source influence on the growth characteristics and secondary metabolite profiles of Hypericum perforatum callus cultures were evaluated. According to the obtained results, morphology of the synthesized perlite NPs and TiO/perlite NCs were mesoporous and spherical with sizes ranging about 14.51-23.34 and 15.50-24.61 nm, respectively. Addition of perlite NPs and TiO/perlite NCs to the culture medium at the concentration range of 25-200 mg/L showed no adverse impacts on the growth characteristics of H. perforatum calli. According to the GC-MS analysis, the stress caused by perlite NPs and TiO/perlite NCs led to an increase in the variety, amount and number of volatile compounds. The calli obtained from in vitro grown plants produced more volatile compounds relative to the calli obtained from field grown plants under the nanomaterial stress conditions. The production of hypericin and pseudohypericin were also determined in the callus cultures under desired nanomaterials elicitation. Accordingly, our results suggest that perlite NPs and TiO/perlite NCs can possibly be considered as effective elicitors for the production of volatile compounds, hypericin, and pseudohypericin in callus cultures of H. perforatum.