Characterization of the interaction between 3-Oxotabersonine and two serum albumins by using spectroscopic techniques

3-Oxotabersonine (OTAB) is a component of Voacanga africana, which is a type of traditional drug in Africa widely used for treating diseases. This study examines the interaction of OTAB with bovine serum albumin (BSA) and human serum albumin (HSA) under physiological conditions. The interaction between OTAB and BSA/HSA was investigated using fluorescence spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, circular dichroism (CD) spectroscopy, and molecular modeling under simulated physiological conditions. The experimental results confirm that the quenching mechanism is a static quenching process. The binding site number (n) and the apparent binding constant (K) were measured at various temperatures. The thermodynamic parameters, namely, enthalpy change (ΔH) and entropy change (ΔS), were calculated. Furthermore, the structural changes in the serum albumin that affected the OTAB binding were determined using FT-IR. The binding site was assumed to be located in site I of the BSA/HSA (subdomain IIA).