Sydowinin B (MS-347b) is a fungal xanthone that noncompetitively inhibits PTP1B.
Details
Sydowinin B (MS-347b) is a xanthone-type secondary metabolite isolated from fungal species including Aspergillus sp. and Malbranchea dendritica. Although originally reported as a minor component related to the MLCK inhibitor MS-347a but lacking MLCK inhibitory activity, subsequent biochemical studies demonstrated that sydowinin B moderately inhibits protein tyrosine phosphatase 1B (PTP1B) in a noncompetitive manner (IC50 = 0.081 mM), consistent with docking predictions of allosteric binding. Cytotoxicity studies in intestinal (HT-29) and neuroblastoma (SH-SY5Y) human cell models showed concentration-dependent effects and interaction profiles when combined with okadaic acid. Synthetic studies further confirmed its xanthone structure. These findings define sydowinin B as a bioactive fungal xanthone with phosphatase-inhibitory and cytotoxic properties.