Recent years have seen an explosion of scientific
papers that deal with drugs from the fruits of milk thistle and its
active substances silymarin (standardized mixture of flavonolignanes),
thus justifying an updated systematic review. Methods:
Electronic databases identified silymarin, silibinin, silicristin
or milk thistle as descriptors in >700 papers (34% published
in last 5 years; 92% dealt with animal pharmacological).
Only papers adequately reporting on experimental conditions,
dosing, variables tested and statistics were analysed. Results:
Silymarin was found to modify specifically the functions related
to various transporters and receptors located in the cell membranes;
that is, organic anion uptake transporter peptides
(OATP), ABC transporters (P-gp), bile salt export pump, as well
as TNF-a-dependent and possibly selectin-dependent phenomena.
In the cytoplasm, some antioxidant properties and the inhibition
of the lipoxygenase pathway seem quite selective and
could concur to the antitoxic effects. Some effects like the inhibition
of inducible nitric-oxide synthase, of nuclear factor κ B,
and reduction of collagen synthesis are indicative of DNA/RNAmediated
effects. Several studies using ‘in vitro’ and ‘in vivo’
cancer models suggest a potential of silymarin in such diseases.
Topical and systemic silymarin has skin protective properties
against UV-induced damage in epidermis and causes an
up-regulation of tumour-suppressor genes p53- and p21CIP1.
There were no data on hepatic viral replication, viremia or
spontaneous tumours in the data examined. Conclusions: Data
presented here do not solve the question about the complex
mechanism(s) of action of the medicinal herbal drug silymarin.
Silymarin may be a natural multi-functional and multi-target
drug.