Abstract: 15-¹⁴CArtemisinin(8) was prepared by the biosynthesis of15-¹⁴Cdihydroartemisic acid(14) which was synthesized from diketone in 6 steps. A supernatant liquidprepared from the tender leaves of ripe Shanghai Qinghao(Artemisia annua L.)was incubated with themixture of compounds l3 and l4(100 mg, total activity 3. 26 MBq, 13:14=1:1) at 30℃ or 37℃ for 4 hr. After the addition of natural artemisinin(100 mg) ,the mixture was heated at l00℃for5min , and extracted with chloroform(method A)or petroleum ether(bp. 60～90℃, method B).Theextract was evaporated and the residue was recrystallized(method B)or purified py preparative thinlayer chromatography(methed The crude product was recrystallized from methylene chloride—Petroleum ether to yield 8 with constant specific radioactivity. The mean rate of incorporation in runs1～8was l.17%。The possible influence factors of the biotransformation were studied. The incuhation temperaturewas considered as a key factor.