Humicola sp. FO-2942, a soil isolate, was found to produce a series of new inhibitors of diacylglycerol acyltransferase (DGAT). Three active compounds, designated amidepsines A, B and C, were isolated from the fermentation broth of the producing strain by solvent extraction, silica gel column chromatography, ODS column chromatography and HPLC. Amidepsines inhibit DGAT activity with IC50 values of 10.2 approximately 51.6 microM in an enzyme assay system using rat liver microsomes. Amidepsines also showed specific inhibition of triacylglycerol formation in intact Raji cells, indicating that they inhibit DGAT activity in living cells.