Two new compounds, lasdiplactone (1) and lasdiploic acid (2) and one known compound 3 were isolated from the chloroform extract of cell free filtrate of the endophytic fungus Lasiosdiplodia pseudotheobromae. The structures of new compounds were determined by interplay of spectral techniques (IR, mass, 1H NMR, 13C NMR, DEPT, and 2D NMR). The absolute configuration at C-4 position of 1 was established as S using a process similar to modified Mosher's method. The absolute configuration of 2 was established by comparing its ECD spectrum with the calculated ECD spectra of all possible isomers. In the in vitro XO inhibition assay, the highest inhibition was exhibited by 3 with an IC50 of 0.38 ± 0.13 μg/ml, followed by 2 with an IC50 of 0.41 ± 0.1 μg/ml and the least in 1. The oxidized form of 1 also showed high XO inhibition with IC50 of 0.35 ± 0.13 μg/ml.