Scopoletin from the flower buds of Magnolia fargesii inhibits protein glycation, aldose reductase, and cataractogenesis Ex Vivo

Five compounds previously known structures, scopoletin ( 1 ), northalifoline ( 2 ), stigmast-4-en-3-one ( 3 ), tiliroside ( 4 ), and oplopanone ( 5 ) were obtained from the flower buds of Magnolia fargesii using chromatographic separation methods. The structures of 1 – 5 were identified by the interpretation of their spectroscopic data including 1D- and 2D-NMR as well as by comparison with reported values. Three compounds 1 – 3 were found from M. fargesii for the first time in this study. All the isolates ( 1 – 5 ) were subjected to in vitro bioassays to evaluate the inhibitory activity on advanced glycation end products formation and rat lens aldose reductase (RLAR). Compound 1 showed a remarkable inhibitory activity on advanced glycation end products formation with IC 50 value of 2.93 μM (aminoguanidine: 961 μM), and showed a significant RLAR inhibitory activity with IC 50 value of 22.5 μM (3.3-tetramethyleneglutaric acid: 28.7 μM). Compound 4 exhibited potent inhibitory activity against RLAR (IC 50 = 14.9 μM). In the further experiment ex vivo , cataractogenesis of rat lenses induced with xylose was significantly inhibited by compound 1 treatment.