Two isocoumarin derivatives, stoloniferol A (1) and B (2), a known $5{alpha}$, $8{alpha}-epidioxy-23-methyl-(22E, 24R)-ergosta-6$, $22-dien-3{eta}-ol$ (3), and a known dihydrocitrinone (4) were isolated from the ethyl acetate extract of the sea squirt-derived fungus, Penicillium stoloniferum QY2-10, and a halophilic fungus, Penicillium notatum B-52, respectively. Their structures were elucidated by spectroscopic methods and optical rotation. The stereochemistry of 2 was determined on the basis of different NOE experiments and chemical transformation. Compound 3 showed cytotoxicity against P388 cells, with an $IC_{50}$ value of 4.07 ${mu}M$.