BACKGROUND: To provide the scientific evidence for a possible new mechanism of hypolipidemic effects of gallic acid (GA) and tannic acid (TA), the binding capacity of GA and TA with blood lipid level-related biological molecules, including fat, cholesterol and cholates, were investigated in vitro. Additionally, we attempted to study the interactions of cholates with GA and TA by spectroscopic methods, high-performance liquid chromatography electrospray-ionization mass spectrometry (HPLC-ESI-MS) analysis and molecular modeling studies. RESULTS: Our results demonstrated that both GA and TA were capable of binding with the blood lipid level-related biological molecules in vitro. The fat-binding capacity of TA was 122.1% that of GA when the addition of polyphenol was 90 mg. The inhibitory effects of GA and TA on the cholesterol solubility in mixed micelles and liquid egg yolk exhibited a dose-dependent relationship (0.5-2.0 mg mL-1 ). In cholate-binding tests, TA showed higher affinity for sodium cholate than GA at a concentration of 2.0 mg mL-1 , while no significant difference in the affinity for sodium deoxycholate was found between GA and TA. Moreover, the data of spectroscopic methods, HPLC-ESI-MS analysis and molecular modeling studies indicated that GA and TA might precipitate cholates through hydrophobic interactions and intermolecular hydrogen bonds rather than covalent bonds. CONCLUSION: The findings of the present study suggested that the binding capacity of GA and TA with blood lipid level-related biological molecules might play a crucial role in their hypolipidemic effects in animals.
BACKGROUND: To provide the scientific evidence for a possible new mechanism of hypolipidemic effects of gallic acid (GA) and tannic acid (TA), the binding capacity of GA and TA with blood lipid level-related biological molecules, including fat, cholesterol and cholates, were investigated in vitro. Additionally, we attempted to study the interactions of cholates with GA and TA by spectroscopic methods, high-performance liquid chromatography electrospray-ionization mass spectrometry (HPLC-ESI-MS) analysis and molecular modeling studies. RESULTS: Our results demonstrated that both GA and TA were capable of binding with the blood lipid level-related biological molecules in vitro. The fat-binding capacity of TA was 122.1% that of GA when the addition of polyphenol was 90 mg. The inhibitory effects of GA and TA on the cholesterol solubility in mixed micelles and liquid egg yolk exhibited a dose-dependent relationship (0.5-2.0 mg mL-1 ). In cholate-binding tests, TA showed higher affinity for sodium cholate than GA at a concentration of 2.0 mg mL-1 , while no significant difference in the affinity for sodium deoxycholate was found between GA and TA. Moreover, the data of spectroscopic methods, HPLC-ESI-MS analysis and molecular modeling studies indicated that GA and TA might precipitate cholates through hydrophobic interactions and intermolecular hydrogen bonds rather than covalent bonds. CONCLUSION: The findings of the present study suggested that the binding capacity of GA and TA with blood lipid level-related biological molecules might play a crucial role in their hypolipidemic effects in animals.