Vanillic acid derivatives from the green algae Cladophora socialis as potent protein tyrosine phosphatase 1B inhibitors

A novel vanillic acid derivative (1) and its sulfate adduct (2) were isolated from a green algae, Cladophora socialis. The structures of 1 and 2 were elucidated from NMR and HRESIMS experiments. Both compounds showed potent inhibitory activity against protein tyrosine phosphatase 113 (PTP1B), an enzyme involved in the regulation of insulin cell signaling. Compounds I and 2 had IC50 values of 3.7 and 1.7 mu M, respectively.