Influence of silybin on biophysical properties of phospholipid bilayers.
OBJECTIVE
Silybin (silibinin) is major biologically active flavonolignan extracted from milk thistle (Sylibum marianum). Its biological activities include hepato-protection, anticancer properties, and antioxidant- and membrane-stabilizing functions. Although membranes are postulated to be one of the cellular targets for silybin, little is known about its interaction with phospholipid bilayers.


METHODS
In the present work, the interactions of silybin with phosphatidylcholine bilayers were studied in detail using fluorescence spectroscopy, microcalorimetry and electron spin resonance techniques.


RESULTS
The results showed that silybin interacted with the surface of lipid bilayers. It affected the generalized polarization of the fluorescent probe Prodan, while not influencing the more deeply located Laurdan. Silybin lowered the main phospholipid phase transition temperature as judged by microcalorimetry, and caused the immobilization of spin probe Tempo-palmitate located on the surface of membranes. The mobility of spin probes 5- and 16-doxyl stearic acid was not affected by silybin. Silybin-induced quenching of 1,6-diphenyl-1,3,5-hexatriene fluorescence indicated that some flavonoid molecules partitioned into the hydrophobic region of membranes, which did not change significantly the biophysical properties of the deeper membrane regions.


CONCLUSIONS
Such a behavior of silybin in membranes is in accordance with its postulated biological functions and neglectable side effects of therapies using silybin.
Wesołowska
Olga
O
Department of Biophysics, Wroclaw Medical University, ul Chalubinskiego 10, 50-368 Wroclaw, Poland. olawes@biofiz.am.wroc.pl
Łania-Pietrzak
Barbara
B
Kuzdzał
Micha
M
Stanczak
Kamila
K
Mosiadz
Daniela
D
Dobryszycki
Piotr
P
Ozyhar
Andrzej
A
Komorowska
Małgorzata
M
Hendrich
Andrzej B
AB
Michalak
Krystyna
K
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D005453:Fluorescence; D008051:Lipid Bilayers / Q000737:chemistry*; D008958:Models, Molecular; D010743:Phospholipids / Q000737:chemistry*; D000077385:Silybin; D012838:Silymarin / Q000737:chemistry / Q000494:pharmacology
D008051:Lipid Bilayers; D010743:Phospholipids; D012838:Silymarin; D015060:1,2-Dipalmitoylphosphatidylcholine; D000077385:Silybin; D004134:Dimyristoylphosphatidylcholine