It is noteworthy that, only (1) and (2) were secreted into the liquid media. This may be due to the large molecular size of (3), making it release difficultly through the cell membrane. MJ treatment at 600 µM markedly diminished growth of the root cultures, as well as production levels of (1) and (2). At this high concentration of MJ browning of the cultures and cell death was extensive. An increase of NQ content in the cultured media leads to the low viability of the root cultures, possibly due to a cytotoxic effect of (2) that is released into the media (Ding et al., 2008). This browning effect and cell growth retardation has also been reported in Panax ginseng cultures treated with high concen trations of MJ (Lu et al., 2000). It has been suggested that browning coloration could also be due to other phenolic compounds as a response to elicitor-induced stress (Zhao et al., 2001). A two-phased culture, or in situ extraction, may have to be introduced in further studies to improve the cell viability and NQ production from the root cultures. It has been reported that the simultaneous use of in situ extraction and elicitation cell treatment had a synergistic effect on the stimulation of shikonin production in suspension cultures of Arnebia euchroma (Fu and Lu, 1999). Since MJ was capable of increasing total NQs to the highest extent, it was used to elicitate I. balsamina root cultures to optimize elicitor conditions, including optimum concentration, period of contract and age of root cultures for elicitation.