Impatiens balsamina root cultures were treated with yeast extract (YE), Candida albicans homogenate (CAH), Trichophyton rubrum homogenate (TRH), chitosan (CHI) and methyl jasmonate (MJ). Different elicitors, depending on concentrations used exerted differential effects on the production of the three main naphthoquinones, lawsone (2-hydroxy-1,4-naphthoquinone), lawsone methyl ether and methylene-3,3'-bilawsone. Treatment with MJ (400 mu M) was capable of increasing production of lawsone, and lawsone methyl ether up to 8.6- and 11.3-fold higher, respectively, compared to the level in untreated cultures. Treatment of 21-day-old root cultures with 300 mu M MJ for 36 h resulted in the production of 10.0, 0.78 and 0.23 mg/g DW of lawsone, its methyl ether and methylene-3,3'-bilawsone, respectively. Such levels are sufficient for commercial production. (C) 2010 Elsevier Ltd. All rights reserved.