The effect of o-phthalic acid (o-PA) on the production of the anti-tumor polyketide compound aspergiolide A by the marine fungus Aspergillus glaucus was investigated. o-PA at 12 mM increased the aspergiolide A production by 77%. A combination of 12 mM acetate with 12 mM o-PA increased the production by 126%, i.e., from 27.1 mg/l to 60.9 mg/l, which was 27% and 75% higher than adding either 12 mM o-PA or 12 mM acetate, respectively. It was also found that A. glaucus could use o-PA as the sole carbon source on Minimal Medium. Ninety percent of o-PA was degraded by the fungus strain, especially when 12 mM acetate was supplemented simultaneously. In culture medium supplemented with o-PA addition, sugar consumption decreased with increasing o-PA concentration, at the same time, the oxalacetate and pyruvate levels increased and the concentration of fumarate decreased. The results indicated that o-PA could stimulate biosynthesis of aspergiolide A effectively by regulating the metabolic pathway. (c) 2010 Elsevier Ltd. All rights reserved.