The antidiabetic effect of 6-formylumbelliferone (14) has been attributed to the blocking of enzymes that play a crucial role in diabetes mellitus type 2 including protein tyrosine phosphatase 1B (PTP1B) (IC50 = 1.13 μM), α-glucosidase (IC50 = 58.36 μM), and human recombinant aldose reductase (HRAR) (IC50 = 5.11 μM). This evidence concerns the gene PTPN1 and diabetes mellitus.