Inhibition of Protein Tyrosine Phosphatase 1β by Hispidin Derivatives Isolated from the Fruiting Body of Phellinus linteus

Protein tyrosine phosphatase 1β (PTP1β) acts as a negative regulator of insulin signaling. Selective inhibition of PTP1β has served as a potential drug target for the treatment of type 2 diabetes mellitus. We evaluated the inhibitory effect of Phellinus linteus against PTP1β as part of our ongoing search for natural therapeutic and preventive agents for diabetes mellitus. Fractions of the P. linteus extract were found to exhibit significant inhibitory activities against PTP1β. In an attempt to identify bioactive components, we isolated, from the most active ethyl acetate fraction, five hispidin derivatives (phelligridimer A, davallialactone, hypholomine B, interfungins A, and inoscavin A) and four phenolic compounds (protocatechuic acid, protocatechualdehyde, caffeic acid, and ellagic acid). The chemical structures of these compounds were elucidated from spectroscopic evidence and by comparison with published data. All the compounds strongly inhibited PTP1β activity in an in vitro assay; their IC50 values ranged from 9.0 ± 0.01 to 58.2 ± 0.3 μM. Our results indicated that the hispidin skeleton may be an important moiety for inhibitory activity of the above compounds against PTP1β. Thus, hispidin derivatives could be a potent new class of natural PTP1β inhibitors.

Methylenedisalicylic acid derivatives: New PTP1B inhibitors that confer resistance to diet-induced obesity

Methylenedisalicylic acid derivatives were synthesized and their inhibitory activities against protein tyrosine phosphatases (PTPases) examined. Two of the compounds, 8 and 9, showed K(i) values of 9.4 and 6.3microM against PTP1B, 4- and 7-fold lower values compared to those against TC-PTP. They were reversible and slow-binding inhibitors against PTP1B. When compound 8 was fed to a mouse model, the weight gain and adipocyte fat storage induced by a high-fat-diet were significantly suppressed.

PTP-1B inhibitors: Cyclopenta[d][1,2]-oxazine derivatives

A series of novel cyclopenta[d][1,2]-oxazine derivatives was prepared and evaluated for their inhibitory activity toward protein tyrosine phosphatase 1B (PTP-1B). Compound 6s was found to be an inhibitor of PTP-1B with nanomolar IC(50) value and high level of selectivity over other recombinant phosphatases.