Abstract: High β-ecdysterone (β-EC) levels were contained in a cell suspension of Ajuga lobata. In order to further improve β-EC content, jasmonic acid methylester was added. The effects of adding jasmonic acid methylester was based on 4-10 generations of cell suspension of A. lobata and the influence of different MeJA concentrations and adding times on cell growth and β-EC accumulation was assessed. For β-EC content, high performance liquid chromatography (HPLC) was utilised. Results showed that the growth curve of the cell suspension and accumulative line of β-EC followed the Logistics model. Adding different concentrations of MeJA in the early (the 4th day of culture) or middle stages (the 7th day of culture) of the rapid cell growth period did not greatly affect cell growth; the growth curves were similar and each produced a peak. Adding MeJA on the 4th day and 7th day of culture resulted in peaks mostly occurring on the 5th and 3rd day after MeJA addition respectively. Dry weights of the cell suspension reached 0.60 g and 0.62 g respectively. Adding different concentrations of MeJA at the peak (the 10th day of culture) of rapid cell growth, resulted in a decline in growth in all cell cultures. The growth of suspended cells was significantly reduced by adding MeJA. Fresh and dry weights were usually significantly lower than that in the control group (P<0.05). The cell fresh weights were significantly correlated with β-EC contents after adding MeJA into the culture system during the early or middle stages of rapid cell growth. After adding 10-50 μmol·L^-1 MeJA cell fresh weights increased significantly compared with that of the control. Adding 50 μmol·L^-1 MeJA achieved the highest cell fresh weight (35.90 g), significantly higher than other treatments (P<0.05). Similarly β-EC content (0.5095 mg·g^-1) was also highest with 50 μmol·L^-1 MeJA. Adding 200 μmol·L^-1 MeJA, significantly reduced cell fresh weights compared with the control (38.88% reduction). After adding 100-200 μmol·L^-1 MeJA β-EC content was greatly increased, reaching 3.5315 mg·g^-1, 14.44 times the control treatment(P<0.01). At the peak of rapid cell growth (10th day of culture), adding 10-200 μmol·L^-1MeJA, reduced cell fresh weights compared with that of the control. The results illustrated that adding MeJA during cell growth could inhibit cell growth. Adding 10-50 μmol·L^-1 MeJA at the peak of rapid cell growth resulted in a massive surge in β-EC content shortly after adding, the highest level being 1.4136 mg·g^-1, 5.06 times the control (P<0.01). When the MeJA concentration reached 100-200 μmol·L^-1, the accumulation of β-EC was significantly reduced. We concluded that cell growth was mildly stimulated by adding 100 μmol·L^-1 MeJA treatment in the middle stage of cell rapid growth period with β-EC content reaching 3.5315 mg·g^-1.

Key words: jasmonic acid methylester (MeJA), Ajuga lobata, beta-ecdysterone (β-EC), cell growth, secondary metabolic products