A Trimeric Proanthocyanidin from the Bark of Acacia leucophloea Willd.

 (–)-Fisetinidol-(4α,8)-[(–)-fisetinidol-(4α,6) ]-(+)-catechin ( 1 ), a proanthocyanidin, was isolated from the bark of Acacia leucophloea . Its structure including absolute configuration was elucidated on the basis of spectroscopic analysis and chemical correlation . The 1H NMR spectrum of this compound, exhibiting exceptional complex signals attributable to rotational isomerism, and the reported data were obtained at elevated temperature in methyl ether acetate form. This work provided the 1H and 13C NMR assignments for 1 and its rotational isomer as the free phenolic form at ambient temperature for the first time. Compound 1 showed inhibitory activity against α-glucosidase type IV from Bacillus stearothermophilus with the IC 50 value of 102.3 μM.