PTPN1 and Insulin resistance: Other synthetic OA derivatives, such as (26) (3β-O-α-d-mannuronopyranoside), (27) (3β-O-α-d-mannuronopyranosyl-6-methyl ester), (28) (3β-O-β-D-lactopyranoside), and (29) (3β-O-β-D-glucuronopyranoside), have demonstrated inhibitory activity against protein tyrosine phosphatase 1B (PTP-1B), which is involved in insulin resistance.