Seseli L. species from the Apiaceae family are well-known medicinal plants with rich bioactive components. In the present study, the phytochemical investigation of the n-hexane extract of the aerial parts from Seseli petraeum M. Bieb., a fairly narrow growing plant on the northern side of Turkey, led to the isolation of one new pyranocoumarin called 3'-isovaleryl-4'-oxo-lomatin (petracoumarin, (1) along with 12 known coumarins octanoyllomatin (2), selinidin (3), anomalin (4), 3'-isobutryl-lomatin (5), 3'-angeloyl-4'-isovaleryl-ciskhellactone (6), 3'-isovaleryl-4'-angeloyl-cis-khellactone (7), calipteryxin (8), samidin (9), 4'-senecioyl-cis-khellactone (10), 3'-senecioyl-cis-khellactone (11), cis-khellactone (12) and angelicin (13), and six plant sterols (campesterol, stigmasterol, beta-sitosterol, stigmastanol, stigma-7-en-3-ol and gamma-ergosterol, 14-19). The structures of the coumarins were elucidated by spectroscopic methods, including extensive 1D/2D NMR, and MS techniques. In addition, several coumarins have been tested for their inhibitory activity against alpha-amylase and alpha-glucosidase enzymes. The coumarins exhibited notable inhibitory activity against the alpha-glucosidase enzyme and low inhibitory potential against alpha-amylase. Among the tested compounds, octanoyllomatin (2) was found to be the best inhibitor of alpha-glucosidase with IC50 = 69.00 +/- 0.43 mu g/mL. The promising results will guide our future studies and suggest that more detailed studies can be done on in vivo models. (C) 2021 SAAB. Published by Elsevier B.V. All rights reserved.