Antioxidant activity of in vitro propagated Stevia rebaudiana Bertoni plants of different origins

An efficient in vitro protocol for propagation of Stevia rebaudiana Bertoni is described. Multiple shoots were induced in vitro from shoot tip and nodal segments on Murashige and Skoog medium containing 6-benzylaminopurine, zeatin, or thidiazuron alone and in combination with naphthalene acetic acid or indole-3-acetic acid. A high frequency of shoot induction as well as maximum number of shoots per shoot tip explant was observed on Murashige and Skoog medium supplemented with 6-benzylaminopurine (1.0 mg L^–1) alone and combined with indole-3-acetic acid (0.1 mg L^–1). For root induction, in vitro shoots were transferred to rooting media containing naphthalene acetic acid, indole-3-acetic acid, or indole-3 butyric acid. The highest rooting frequency and the highest number of roots was observed in half-strength Murashige and Skoog medium supplemented with 0.1 mg L^–1 indole-3-butyric acid. The rooted in vitro plants were successfully acclimatized in a growth chamber and transferred to the field. Leaf extracts of plants propagated in vitro and adapted to field conditions are characterized by high levels of water soluble antioxidant capacity (expressed as equivalents of ascorbic acid), phenols, and flavonoids, and therefore by high total antioxidant potential, expressed as DPPH radical scavenging activity.