Three new hydronaphthalenone derivatives (1—3) and one new dihydroramulosin derivative (4), were isolated from the endophytic fungus PSU-N24 together with eight known compounds. Their structures were elucidated by spectroscopic methods. Griseofulvin (9) displayed strong antifungal activity against Microsporum gypseum SH-MU-4 with a minimum inhibitory concentration (MIC) value of 2 μg/ml while all metabolites exhibited very weak antibacterial activity (MIC value≥128 μg/ml) against Staphylococcus aureus, both standard and methicillin-resistant strains. 3-(2-Hydroxypropyl)benzene-1,2-diol (10) showed moderate antimalarial activity against Plasmodiun falciparum with an IC50 value of 6.68 μg/ml. For antimycobacterial activity against Mycobacterium tuberculosis, compound 3 gave the best activity with the MIC value of 12.50 μg/ml.