Phytochemical profiling of the Turkish plant Centaurea patula, a source of structurally diverse sesquiterpenoids

The first detailed phytochemical investigation of the aerial parts of the Turkish plant Centaurea patula DC. led to the isolation of 19 sesquiterpenoids belonging to the guaianolide (1-13), elemanolide (14-17), and germacrane (18-19) classes. These include the undescribed guaianolide cebellin Q (9), the glucosylated elemanolides 15-17, and the pair of germacrene diastereomers patulosins A (18) and B (19). The structures of the undescribed compounds were elucidated by detailed NMR-based spectroscopic analysis, while comparison of experimental 13C NMR data with those obtained by DFT-based quantum chemical calculations was used to define relative configurations. Based on the activity reported for the plant extract, all the isolated compounds were evaluated for their activity on Saccharomyces cerevisiae α-glucosidase.