[Fluorescence investigation on interaction between artemisinin (qinghaosu) and hemin and its analytical application]

Hemin-catalytic decomposition of artemisinin (qinghaosu, QHS) was studied using pyronine B (PB) as an indicator. The interaction between hemin and QHS was an enzyme-substrate model, and the action sites were the endoperoxide moiety of QHS and the central metal ion of enzyme respectively. The kinetic catalytic constant depends upon enzyme and substrate concentrations, and the Michaelis-Menten parameters Km, Vmax and Kcat was 8.4 x 10(-5) mol x L(-1), 7.4 x 10(-6) mol x L(-1) s(-1) and 50.23 s(-1) respectively. The catalytic activity of hemin was inhibited in the presence of deactivated agents and at high temperature. Under optimal conditions, the change in fluorescence intensity (Fo-F) of pyronine B was proportional to the QHS concentration from 0.0 to 1.27 x 10(-6) mol x L(-1), and the detection limit (3sigma) was as low as 2.3 x 10(-8) mol x L(-1). The proposed method was applied to detect the concentration of QHS in the media of plasma and urine.