Dehydroandrograpolide Succinate (PDS) is a drug, widely used to treat viral pneumonia, viral upper respiratory tract infection such as anti-inflammatory drugs, known as the “Chinese medicine antibiotics”. Herein, Under the optimal conditions，fluorescence and absorption spectroscopy were used to study the interaction of PDS with bovine serum albumin (BSA) and effects of metal ions at different temperatures. The rate constant (Kq), apparent quenching constant (Ksv), binding constant (KA) and static fluorescence quenching association constant (KLB) and binding site number(n) were calculated using Stern-Volmer, Lineweaver–Burk and Double logarithm equations. The results show that PDS is able to bind to BSA. The probable quenching mechanism of BSA by PDS was mainly static quenching due to the formation of a PDS-BSA complex. The results of thermodynamic parameters indicate that electrostatic force plays the main role in the binding process and the binding process was spontaneous. The obtained data for binding sites of n approximately equal to 1 indicated that there was a single class of binding site for the BSA with PDS. The primary binding site for PDS was located at sub-domain ⅡA and ⅢA of BSA and near by tyrosine residue. There was almost no cooperative effect. The results obtained from synchronous fluorescence showed that the interaction between BSA and PDS caused the conformational changes of BSA. Pb2+, Mn2+, Ni2+and Cu2+ competed with the interaction of PDS with BSA, increasing medical effectiveness. Cr3+ promoted on interaction and prolonged drug effect time. The obtained results not only provided a theoretical basis for revealing the pharmacokinetics and further research on development of new anti virus herbs drugs.
