The effects of elicitors on cell growth and oleanolic acid (OA) accumulation in shaken cell suspension cultures of Calendula officinalis were investigated. Elicitors were added individually at various concentrations to 5-day-old cell cultures and their effects monitored at 24 h intervals for 4 days. Different effects on OA accumulation were observed depending on the clay of treatment. Jasmonic acid was the most efficient elicitor. After 72 h of treatment with 100 mu M JA, the intracellular content of OA reached its maximum value (0.84 mg g(-1) DW), which was 9.4-fold greater than that recorded in an untreated control cultures. The addition of chitosan at 50 mg l(-1) produced a 5-fold enhancement of OA accumulation (0.37 mg g(-1) DW) after 48 h of treatment. Treatment with yeast extract at 200 mg l(-1) for 96 h or with pectin at 2 mg l(-1) for 48 h produced identical cellular levels of OA (0.22 mg g(-1) DW). Lastly, 48 h elicitation with homogenate of the fungus Trichoderma viride produced a 1.8-fold increase in oleanolic acid content (0.12 mg g(-1) DW). In addition to significantly stimulating OA accumulation and its secretion into the culture medium, the elicitors also caused slight inhibition of cell growth. (C) 2009 Elsevier Inc. All rights reserved.