Serotonin (aka 5-hydroxytryptamine) has long been known as an important neurotransmitter with implications in depression and sleep disorders but according to research published in the April 7th, 2006 issue of Science; it is also an important hormone that may be very important in regenerating damaged liver tissue. The use of tryptophan or 5-HTP (5-Hydroxytryptophan) although not prominently mentioned in the article (they only talk about drugs to improve platelet carrying of serotonin), may be crucial in helping people with impaired liver function (excessive toxicity) or alcoholism.
While there was some evidence that mice injected with 5-HTP received benefits the focus unfortunately was more on receptor agonists than natural agents. Further study is necessary on the benefits of 5-HTP on liver regeneration.