Influence of silybin on biophysical properties of phospholipid bilayers
Abstract
Aim: 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. Conclusion:
Such a behavior of silybin in membranes is in accordance with its postulated
biological functions and neglectable side effects of therapies using silybin.
Keywords:
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. Conclusion:
Such a behavior of silybin in membranes is in accordance with its postulated
biological functions and neglectable side effects of therapies using silybin.