Artemisinin (AN), a potent antimalarial drug that has been used for centuries as a folk remedy in China, is an effective treatment against quinine-resistant strains of Plasmodium. It can be produced through the in vitro culture of genetically transformed (hairy) roots. The effect of gibberellic acid (GA3) on the growth and secondary metabolite production of hairy roots of Artemisia annua was investigated. Six different concentrations of GA 3 were tested in shaker flasks to determine the optimum concentration. GA3 levels of 0.01-0.001 mg/l (28.9-2.89 ~tM) provided the most significant increase in biomass, and 0.01 mg/1 (28.9 laM) produced the highest amount of AN. Investigation of growth kinetics showed that the use of GA 3 at 0.01 mg/1 (28.9 ~tM) increased the growth rate of hairy roots ofA. annua by 24.9%. Thus, the cultures treated with GA s reached stationary phase faster than control cultures.

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We analyzed four factors (phosphate and nitrate salts, sucrose, and culture inoculum age), simultaneously at three levels using a fractional factorial design method to determine the most suitable conditions for maximizing both root biomass and terpenoid production in transformed Artemis& annua root cultures. Optimal growth conditions were determined to be: nitrate (15 mM), phosphate (1.0 nrM), sucrose content (5% wt/vol), and inoculum age (8 d-old). Determination of optimal conditions for sesquiterpene production was more complicated than for biomass production. For most experiments artemisinic acid was undetectable especially in experiments where phosphate was greater than 0.5 mM and for nearly all culture inoculum ages of 14 d. Artemisinic acid was also never detected whenever arteannuin B was present. Arteannuin B was the major artemisinic compound detected in these experiments, sometimes at levels exceeding 300 ~tg/g fresh weight. When the sum of artemisinin and its three precursors is analyzed, three factors (sucrose, nitrate, and inoculum age) are heavily dependent on one another, and in conjunction with possible degradation of artemisinin by peroxidase, the current analysis does not provide a clear picture regarding the most effective conditions for maximizing the production of artemisinin.

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In the above paper, Figures 1 and 3 (on pages 308 and 310, respectively) were inadvertently transposed, but the figure legends are correct as printed.