Ground- and excited-state proton transfer and antioxidant activity of 3-hydroxyflavone in egg yolk phosphatidylcholine liposomes: absorption and fluorescence spectroscopic studies.
Excited-state intramolecular proton transfer (ESIPT) and dual luminescence behaviour of 3-hydroxyflavone (3-HF) have been utilized to monitor its binding to liposomal membranes prepared from egg yolk phosphatydilcholine (EYPC). Additionally, absorption spectrophotometric assay has been performed to evaluate the antioxidant activity of 3-HF against lipid peroxidation in this membrane system. When 3-HF molecules are partitioned into EYPC liposomes, a weak long-wavelength absorption band with lambda(abs)(max) approximately 410 nm appears in addition to the principal absorption at approximately lambda(abs)(max) = 345 nm. Selective excitation of the 410 nm band produces the characteristic emission (lambda(em)(max) approximately 460 nm) of the ground-state anionic species, whereas excitation at the higher energy absorption band leads to dual emission with predominatly ESIPT tautomer fluorescence (lambda(em)(max) = 528 nm). Both ESIPT tautomer and the anionic species exhibit fairly high fluorescence anisotropy (r) values (r = 0.122 and 0.180, respectively). Biexponential fluorescence decay kinetics are observed for the ESIPT tautomer as well as the ground-state anionic forms, indicating heterogeneity in the microenvironments of the corresponding emitting species. Furthermore, we demonstrate that lipid peroxidation of EYPC liposomes is significantly inhibited upon 3-HF binding, suggesting that 3-HF can be potentially useful as an inhibitor of peroxidative damage of cell membranes.
Biophysics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064, India.
Sudip
S
Chaudhuri
Kaushik
K
Basu
Bidisa
B
Sengupta
Anwesha
A
Banerjee
Pradeep K
PK
Sengupta
D000042:Absorption; D000818:Animals; D000975:Antioxidants / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002645:Chickens; D004530:Egg Yolk / Q000737:chemistry*; D004735:Energy Transfer; D005419:Flavonoids / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008081:Liposomes / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry*; D011522:Protons; D013050:Spectrometry, Fluorescence
D000975:Antioxidants; D005419:Flavonoids; D008081:Liposomes; D010713:Phosphatidylcholines; D011522:Protons; C041477:3-hydroxyflavone