Novel binding studies of human serum albumin with trans-feruloyl maslinic acid

Human serum albumin (HSA) is a predominant protein in the blood. Most drugs can bind to HSA and be transported to target locations of the body. For this study, we have extracted 3-trans-feruloyl maslinic acid (FMA) from the medicinal plant Tetracera asiatica, its a non-fluorescent derivative have potent anti-cancer, anti-HIV, anti-diabetic, and anti-inflammatory activities. The binding constant of the compound with HSA, calculated from fluorescence data, was found as K_FMA = 1.42 ± 0.01 × 10⁸ M^-1, which corresponds to 10.9 kcal M^-1 of free energy. Furthermore, microTOF-Q mass spectrometry data showed binding of FMA at nanomolar concentrations of FMA to free HSA. The study detected a mass increase from 66,560 Da (free HSA) to 67,919 Da (HSA + drug). This indicated a strong binding of FMA to HSA, resulting in an increase of the protein's absorbance and fluorescence. The secondary structure of HSA + FMA (0.1 mM) complexes showed the protein secondary structure became partially unfolded upon interaction of FMA with HSA, as well as indicating that HSA-FMA complexes were formed. Docking experiments uncovered the binding mode of FMA in HSA molecule. It was found that FMA binds strongly in different places with hydrogen bonding at IB domain of Arg 114, Leu 115 and Asp 173.