Protein tyrosine phosphatase 1B (PTP1B) is an attractive molecular target for anti-diabetes, anti-obesity, and anti-cancer drug development. From the seeds of Silybum marianum, nine flavonolignans, namely, silybins A, B (1, 2), isosilybins A, B (3, 4), silychristins A, B (5, 6), isosilychristin A