Abstract
Saikosaponin C (SSC) is one of the major active constituents of dried Radix bupleuri root (Chaihu in Chinese) that has been widely used in China to treat a variety of conditions, such as liver disease, for many centuries. The binding of SSC to human serum albumin (HSA) was explored by fluorescence, circular dichroism (CD), UV-vis spectrophotometry, and molecular docking to understand both the pharmacology and the basis of the clinical use of SSC/Chaihu. SSC produced a concentration-dependent quenching effect on the intrinsic fluorescence of HSA, accompanied by a blue shift in the fluorescence spectra. The Stern-Volmer equation showed that this quenching was dominated by static quenching. The binding constant of SSC with HSA was 3.72 × 103 and 2.99 × 103 L·mol−1 at 26 °C and 36 °C, respectively, with a single binding site on each SSC and HSA molecule. Site competitive experiments demonstrated that SSC bound to site I (subdomain IIA) and site II (subdomain IIIA) in HSA. Analysis of thermodynamic parameters indicated that hydrogen bonding and van der Waals forces were mostly responsible for SSC-HSA association. The energy transfer efficiency and binding distance between SSC and HSA was calculated to be 0.23 J and 2.61 nm at 26 °C, respectively. Synchronous fluorescence and CD measurements indicated that SSC affected HSA conformation in the SSC-HSA complex. Molecular docking supported the experimental findings in conformational changes, binding sites and binding forces, and revealed binding of SSC at the interface between subdomains IIA-IIB.
Highlights
Serum albumin is the most abundant plasma protein, being present in plasma at a concentration of approximately 40 mgmL1 (~0.6 mM) [1]
At an excitation of 280 nm, the maximum emission wavelength of human serum albumin (HSA) was 334 nm, which is in line with previous reports on the maximum emission wavelength of HSA was 334 nm, which is in line with previous reports on the binding of other drugs to HSA [3]
Albumin-binding events play an essential role in the transportation, The results showed that the Ka of the warfarin complex was much higher than that of SSC-HSA binding, distribution and free fraction of drugs
Summary
Serum albumin is the most abundant plasma protein, being present in plasma at a concentration of approximately 40 mgmL1 (~0.6 mM) [1]. Practice, it is very difficult to sciences, directly measure drug-protein binding in vivo. It is very difficult to directly measure drug-protein binding in vivo. The binding properties of HSA with drugs have extensively been characterized in vitro recent years, the spectroscopy. Binding properties of HSA with drugs have extensively been characterized in vitro by by fluorescence fluorescence spectroscopy. The contemporary clinical applications for Chaihu include a variety of diseases, especially liver diseases, for instance, jaundice, hepatitis and liver cirrhosis [12,13,14]. SSC is one of the major components in Chaihu, and possesses endothelial cells [12,15,16]. This study should provide useful information about the pharmacology and role of SSC/Chaihu in clinical medicine
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