Zinc oxide nanoparticles (ZnO NP) mediated regulation of bacosides biosynthesis and transcriptional correlation of HMG-CoA reductase gene in suspension culture of Bacopa monnieri

Abstract

Bacopa monnieri (L.) Wettst. is a well documented nootropic plant, extensive known for alleviating symptoms of neurological disorder, along with other symptomatic relief. This property is attributed to the active phytocompounds, saponins (bacoside A) present in the plant. However, lack of stringent validation guidelines in most of the countries bring to the market, formulations differing in phytocompounds yield, thereby suggesting possible variation in therapeutic efficacy. The in-vitro suspension cultures of the Bacopa monnieri, provide an ease of scale-up, but regulating saponin yield is a stringent task. The aim of the study is to explore the effects of different concentrations (0, 0.25, 0.50, 0.75 and 1.0 ppm) of zinc oxide nanoparticles (ZnO NP) (24 nm in size), in regulating growth rate, bacoside yield and transcriptional profile of HMG CoA reductasegene in the suspension cells of Bacopa monnieri. Results showed a linear correlation between Bacoside A yield and ZnO NP concentrations with around 2 fold increase in total bacoside A concentration at 1 ppm. Also, ZnO NP supplemented suspension cells showed variation in the specific growth rate. Neuroprotective properties, analyzed using methanolic extracts of suspension cells again obtrude the extract of ZnO NP supplemented (0.75 ppm and 1 ppm) culture for better response in alleviating oxidative stress mediated damage to neuronal cells. ZnO NP supplemented system showed lower expression of HMG CoA reductasegene (the rate limiting step in bacoside A biosynthesis) but higher concentration of bacoside A, suggesting possible role of ZnO NP in isoprenoid pathway than MVA pathways.

Keywords: Bacopa monnieri; Bacoside A; HMG CoA reductase gene; Neuroprotectivity; Specific growth rate.