A cultured endophytic fungus, Guignardia mangiferae, isolated from the toxic plant Gelsemium elegans yielded five new sesquiterpenes (1-5), two new polyketones (6 and 7), and two known terpene polyketones (8 and 9). Their structures were elucidated using spectroscopic methods. On the basis of circular dichroism, the absolute configurations of the new compounds were determined. Compounds 1, 3, 4, and 9 inhibited lipopolysaccharide-induced NO production in BV2 cells with IC50 values of 15.2, 6.4, 4.2, and 4.5 μM, respectively (positive control curcumin, IC50 = 3.9 μM).