New amides from seeds of Silybum marianum with potential antioxidant and antidiabetic activities

Abstract Two new amide compounds, mariamides A and B (1–2), were obtained together with fourteen known compounds from the seeds of milk thistle ( Silybum marianum ). Their structures were established on the basis of extensive 1D and 2D NMR analyses, as well as HR-ESI-MS data. Most of the compounds showed significant antioxidant activities than positive control in ABTS and FRAP assays. However, only amide compounds 1–4 showed moderate DPPH radical scavenging activity and compounds 7 and 16 showed the most potent activity against DPPH. Most of the compounds showed moderate to stronger α -glucosidase inhibitory activities. Nevertheless, only flavonoids showed strong PTP1B inhibitory activities. These results indicate a use of milk thistle seed extracts as promising antioxidant and antidiabetic agents.