1. A method of preventing a cytotoxic effect of amyloid beta protein on cells comprising: exposing the cells to an effective amount of an indole-3-propionic acid or a salt or ester thereof, wherein said acid, salt or ester have the antioxidant and antifibrillogenic properties which differ substantially from those of the indole-3-propionic acid. 2. A method according to claim 1, wherein the cytotoxic effect is cell death. 3. A method according to claim 1, wherein the cytotoxic effect is increased lipid peroxidation. 4. A method according to claim 1, wherein the cytotoxic effect is increased intracellular Ca&lt;2+&gt;. 5. A method according to claim 1, wherein the cytotoxic effect is increased oxygen free-radicals. 6. A method according to claim 1, wherein the cells are neuronal cells. 7. A method according to claim 1, wherein the cells are present in a human subject and wherein said exposing comprises: administering the indole-3-propionic acid or salt or ester thereof systemically. 8. A method according to claim 1, wherein the cells are present in a human subject having a fibrillogenic disease. 9. A method of treating a fibrillogenic disease in a human subject comprising: administering an amount of an indole-3-propionic acid or a salt or ester thereof effective to prevent or reverse fibrillogenesis in the human subject wherein said acid, salt or ester have the antioxidant and antifibrillogenic properties which differ substantially from those of the indole-3-propionic acid. 10. A method according to claim 9, wherein said administering is carried out systemically. 11. A method according to claim 9, wherein the fibrillogenic disease is Alzheimer&#39;s Disease. 12. A method according to claim 1, wherein the fibrillogenic disease is a prion-related encephalopathy. 13. A method of decreasing oxidation in a biological sample comprising: contacting the biological sample with an effective amount of an indole-3-propionic acid or a salt or ester thereof wherein said acid, salt or ester have the antioxidant and antifibrillogenic properties which differ substantially from those of the indole-3-propionic acid. 14. A method according to claim 13, wherein the biological sample is a cell. 15. A method according to claim 13, wherein said decreasing oxidation results in decreasing lipidperoxidat ion. 16. A method according to claim 13, wherein said decreasing oxidation results in decreasing oxygen free-radicals. 17. A method for treating diseases or other conditions where free radicals and/or oxidative stress play a role comprising: administering to a patient in need of such treatment an amount of an indole-3-propionic acid or a salt or ester thereof effective for the treatment of said disease or condition wherein said acid, salt or ester have the antioxidant and antifibrillogenic properties which differ substantially from those of the indole-3-propionic acid. 18. A method according to claim 17, wherein said administering is carried out systemically. 19. A method according to claim 17, wherein the disease or other condition is selected from the group consisting of Parkinson&#39;s Disease, Lewy body dementia, amyo lateral sclerosis, progressive supranuclear palsy, stroke, athrosclerosis, emphysema, and cancer. 20. Use of indole-3-propionic acid or a salt or ester thereof in the treatment of diseases associated with the cytotoxic effects of amyloid beta protein wherein said acid, salt or ester have the antioxidant and antifibrillogenic properties which differ substantially from those of the indole-3-propionic acid. 21. Use of indole-3-propionic acid or a salt or ester thereof in the treatment of fibrillogenic diseases wherein said acid, salt or ester have the antioxidant and antifibrillogenic properties which differ substantially from those of the indole-3-propionic acid. 22. Use of indole-3-propionic acid or a salt or ester thereof in the treatment of Alzheimer&#39;s Disease, a prion-related encephalopathy, or combinations thereof wherein said acid, salt or ester have the antioxidant and antifibrillogenic properties which differ substantially from those of the indole-3-propionic acid. 23. Use of indole-3-propionic acid or a salt or ester thereof in the treatment of diseases or other conditions where free radicals and/or oxidative stress play a role wherein said acid, salt or ester have the antioxidant and antifibrillogenic properties which differ substantially from those of the indole-3-propionic acid. 24. Use of indole-3-propionic acid or a salt or ester thereof in the treatment of Parkinson&#39;s Disease, Lewy body dementia, amyo lateral sclerosis, progressive supranuclear palsy, stroke, athrosclerosis, emphysema, cancer, or combinations thereof wherein said acid, salt or ester have the antioxidant and antifibrillogenic properties which differ substantially from those of the indole-3-propionic acid.