The corresponding author withdraws/retracts this article due to the mistaken inclusion of Fig. 1b from our previously 2011 paper in Acta Physiologiae Plantarum entitled "Hairy root culture of Picrorhiza kurrooa Royle ex Benth.: a promising approach for the production of picrotin and picrotoxinin". The authors accept the mistake and thank the anonymous complainant and the editor of PMBP for bringing it to their notice. The online version of this article contains the full text of the retracted article as electronic supplementary material