A Study on the Interaction of the DAS-K with Bovine Serum Albumin by On-line Ultrafiltration and Chemiluminescence

Potassium dehydroandrographolide succinate (DAS-K) has antibacterial and antiviral effects. It has been used widely for the treatment of virus pneumonia, malaria and respiratory infections. In this work, a novel flow-injection chemiluminescence (CL) method for the determination of DAS-K was proposed. The method is based on the reaction between DAS-K and hexacyanoferrate(III) in alkaline solution to give weak CL signal, which is enhanced by rhodamine B. The experimental conditions for the CL reaction were optimized and the possible reaction mechanism was discussed. Under the optimum conditions, the concentration of DAS-K is proportional to the CL intensity in the range of 0.1–80 μmol·L⁻¹ with a detection limit of 0.05 μmol·L⁻¹. The interaction of the DAS-K with bovine serum albumin by on-line ultrafiltration and flow-injection chemiluminescence was studied. The concentrations of unbound DAS-K from ultra filter tube were determined by the flow-injection CL method. The binding parameters were estimated by the Scatchard plot and Klotz plot. The proposed system proved that FIA-CL coupled with on-line ultrafiltration sampling was a fast and simple technique for the study of drug-protein interaction.