title: Effect of Antioxidants and Carbohydrates in Callus Cultures of Taxus brevifolia: Evaluation of Browning, Callus Growth, Total Phenolics and Paclitaxel Production.
abstract: BACKGROUND
  To control the tissue browning phenomenon, callus growth, total phenolics and paclitaxel production, in the current investigation, we evaluated the effects of citric acid and ascorbic acid (as antioxidants) and glucose, fructose and sucrose in callus cultures of Taxus brevifolia.
  
  
  METHODS
  To obtain healthy callus/cell lines of Taxus brevifolia, the effects of two antioxidants ascorbic acid (100-1000 mg/L) and citric acid (50-500 mg/L), and three carbohydrates (glucose, fructose and sucrose (5-10 g/L)) were studied evaluating activities of polyphenol oxidase (PPO) and peroxidase (PO) enzymes, callus growth/browning, total phenolics and paclitaxel production.
  
  
  RESULTS
  These antioxidants (ascorbic acid and citric acid) failed to show significant effects on callus growth, browning intensity or paclitaxel production. However, the carbohydrates imposed significant effects on the parameters studied. High concentrations of both glucose and sucrose increased the browning intensity, thus decreased callus growth. Glucose increased paclitaxel production, but sucrose decreased it.
  
  
  CONCLUSIONS
  These results revealed that the browning phenomenon can be controlled through supplementation of the growth media with glucose, sucrose (5 g/L) and fructose (10 g/L), while increased paclitaxel production can be obtain by the optimized media supplemented with glucose (10 g/L), sucrose and fructose (5 g/L).
authors.affiliation: Department of Nanobiotechnology, Faculty of Biological Science, Tarbiat Modares University, Tehran, Iran.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Yari Khosroushahi
authors.forename: Hossein
authors.initials: H
authors.lastname: Naderi-Manesh
authors.forename: Henrik
authors.initials: H
authors.lastname: Toft Simonsen
keywords: Antioxidant; Browning; Carbohydrates; Paclitaxel; Taxus brevifolia