Objective       To determine the effect of metal ions on the binding between arctiin and bovine serum albumin (BSA).       Methods       Fluorescence spectroscopy was used to determine the effect of Cu

2+

Mg

2+

or Zn

2+

on the interaction between arctiin and BSA under simulated physiological pH value.       Results       At the presence of metal ions (Cu

2+

Mg

2+

or Zn

2+

)

BSA fluorescence was enhanced with the increase of the concentration of arctiin

with electro-static forces still playing a major role between them. The binding constant was 7.899×10

4

(without metal ion)

8.557×10

4

(Cu

2+

)

6.724×104(Zn

2+

)

and 7.062×10

4

(Mg

2+

)

respectively

at 25 ℃. And it was 5.962×10

4

(without metal ion)

6.096×10

4

(Cu

2+

)

5.915×10

4

(Zn

2+

)

and 5.612×10

4

(Mg

2+

)

respectively

at 37 ℃.       Conclusion       Metal ions affect the binding between arctiin and BSA. Among the metal ions

Cu

2+

increases their binding constant

while

Mg

2+

and Zn

2+

decreases the binding constant.