Quantification of the enzymatic browning and secondary metabolites in the callus culture system of Nigella glandulifera Freyn et Sint.

To investigate browning prevention in the callus culture system of Nigella glandulifera Freyn et Sint., the changes of polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) activity, cell biomass, extracellular total phenolics and total saponin content were examined by selecting three concentrations of MS medium, four kinds of antioxidants, vitamin C, sodium thiosulfate (Na2S2O3), L-glutamine and citric acid, and three kinds of adsorbents, activated carbon, polyvinylpyrrolidone (PVP) and macroporous resin. In liquid static culture, several culture methods were proved to be effective to prevent callus browning. In the 1/2MS + NAA 3.0 mg/L + 6-BA 0.3 mg/L + 6 mg/L Na2S2O3 medium, the callus cultured for 14 days showed the most potent browning-inhibiting effect. The activity of PAL (275 U/(g·h)), the dry weight of cell biomass (0.51 g), the content of extracellular phenolics (124.5 U/ml) and total saponins (37.59 %) were all significantly increased by 9.8-, 4.6-, 2.9-, and 4.7-fold, respectively, compared with the callus in MS medium in the absence of antioxidants or adsorbents.