Folic acid plays an important role in neuronal development. A series of newly synthesized bioactive compounds (NSCs) was reported to exhibit immunoactive and neuroprotective functions. The isolated and combined effects of folic acid and NSCs against beta-amyloid (Abeta)-induced cytotoxicity are poorly understood. These effects were tested using human microglia cells (C13NJ) subjected to Abeta(25-35) challenge. According to an MTT assay, treatment of C13NJ cells with Abeta(25-35) at 10-100 microM for 48 h induced 18%-43% cellular death in a dose-dependent manner (p < 0.05). Abeta(25-35) treatment at 25 microM induced nitrite oxide (NO) release, elevated superoxide production, and reduced the distribution of cells in the S phase. Preincubation of C13NJ with 100 microM folic acid protected against Abeta(25-35)-induced cell death, which coincided with a reduction in NO release by folic acid supplements. NSC47 at a level of 50 microM protected against Abeta(25-35)-induced cell death and reduced Abeta-promoted superoxide production (p < 0.05). Folic acid in combination with NSC47 at their cytoprotective doses did not synergistically ameliorate Abeta(25-35)-associated NO release, superoxide production, or cell cycle arrest. Taken together, folic acid or NSC treatment alone, but not the combined regimen, protected against Abeta(25-35)-induced cell death, which may partially, if not completely, be mediated by free radical-scavenging effects.