I was wondering about the same topic. I bought the Liver Tonic tincture by Herbs (the name of the company), and the main component is milk thistle.
My friend said he read somewhere on Internet, that Milk Thistle is said to be really good or really bad for the liver depending on ??? (he doesn't remember what) maybe time of the day? I guess it would have to do with some principles of Ayurveda, which I am not too familiar with so far.
Anyone has any insight?