Your post seems to be referring to tryptophan, which is present within many foods, particularly eggs and fish. Some studies suggest that it can help people cope with depression (rather than actually cure it) but the evidence remains inconclusive.
For a list of foods containing tryptophan, see here:
http://en.wikipedia.org/wiki/Tryptophan
For dietary advice for depression sufferers, from the NHS website, see here:
http://www.nhs.uk/Liv...ionhealthyeating.aspx
Following that advice will probably be far more effective than taking fish oil supplements. Anyway, actually eating fish (rather than taking supplements) is far more likely to improve your mood (because of the high protein content). Dieticians recommend that everyone should eat fish at least three times a week. It needn't be expensive because things canned sardines, mackerel and pilchards all count.
Chris