Effect of Chinese medicine alpinetin on the structure of human serum albumin

• Published in: Bioorganic & medicinal chemistry Vol. 13; no. 5; pp. 1837 - 1845
• Main Authors: He, Wenying, Li, Ying, Xue, Chunxia, Hu, Zhide, Chen, Xingguo, Sheng, Fenling
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-03-2005; Elsevier Science
• Subjects: Alpinetin; Binding Sites; Biological and medical sciences; Circular Dichroism; Circular dichroism (CD); Drugs, Chinese Herbal; Flavanones; Flavonoids - metabolism; Flavonoids - pharmacology; Fluorescence spectroscopy; Fourier transform infrared (FT-IR) spectroscopy; General pharmacology; Human serum albumin; Humans; Medical sciences; Models, Molecular; Pharmacognosy. Homeopathy. Health food; Pharmacology. Drug treatments; Protein Conformation; Secondary structure; Serum Albumin - chemistry; Serum Albumin - drug effects; Serum Albumin - metabolism; Spectrometry, Fluorescence; Spectrophotometry, Ultraviolet; Fluorescence spectroscopy; Human serum albumin; Circular dichroism (CD); Secondary structure; Alpinetin; Fourier transform infrared (FT-IR) spectroscopy; Monocotyledones; Fourier transformation; Seeds; Fluorescence; Hydrophobic interaction; Binding site; Flavonoid; Modeling; Chinese medicine; Folk medicine; Angiospermae; Molecular model; Human; Pharmacognosy; Antiinflammatory agent; Serum albumin; Serum protein; Ultraviolet spectrometry; β-Structure; Circular dichroism; Flavanone derivatives; Infrared spectrometry; Absorption spectrometry; Biological fixation; Plant origin; Spermatophyta; Antibacterial agent; Thermodynamic properties; Zingiberaceae
• ISSN: 0968-0896; 1464-3391
• DOI: 10.1016/j.bmc.2004.11.038

Alpinetin is the bioactive component of a traditional Chinese medicine. This study is designed to examine the effect of alpinetin on the solution structure of HSA using UV–visible spectroscopic, circular dichroism (CD), Fourier transform infrared (FT-IR), and fluorescence spectroscopic methods at four temperatures under physiological conditions. Attempts were made to investigate the binding mechanism of alpinetin to HSA and the effect of alpinetin on the protein secondary structure. The partial binding parameters of the reaction were calculated through SGI FUEL workstations.
Alpinetin (7-hydroxy-5-methoxyflavanone), one of the main constituents from the seeds of
Alpinia katsumadai Hayata, belongs to flavonoids with its usefulness as antibacterial, anti-inflammatory and other important therapeutic activities of significant potency and low systemic toxicity. In this paper, the interaction of alpinetin to human serum albumin (HSA) has been studied for the first time by spectroscopic method including Fourier transform infrared (FT-IR) spectroscopy, circular dichroism (CD), and UV-absorption spectroscopy in combination with fluorescence quenching study under physiological conditions with drug concentrations of 3.3
×
10
−6–2.0
×
10
−5
mol/L. The results of spectroscopic measurements and the thermodynamic parameters obtained (the enthalpy change Δ
H
0 and the entropy change Δ
S
0 were calculated to be −10.20
kJ/mol and 53.97
J/mol
K
−1 according to the Van’t Hoff equation) suggest that hydrophobic interaction is the predominant intermolecular forces stabilizing the complex, which is also good agreement with the results of molecule modeling study. The alterations of protein secondary structure in the presence of alpinetin in aqueous solution were quantitatively estimated by the evidences from FT-IR and CD spectroscopy with reductions of α-helices about 24%, decreases of β-sheet structure about 2%, and increases of β-turn structure about 21%. The quenching mechanism and the number of binding site (
n
≈
1) were obtained by fluorescence titration data. Fluorescent displacement measurements confirmed that alpinetin bind HSA on site III. In addition, the effects of common ions on the constants of alpinetin–HSA complex were also discussed.