New dihydrochalcones and anti-platelet aggregation constituents from the leaves of Muntingia calabura

Two new dihydrochalcones, 2,3-dihydroxy-4,3′,4′5′- tetramethoxydihydrochalcone (1) and 4,2′,4′-trihydroxy-3'- methoxydihydrochalcone (2), and a new flavanone, (2R,3R)-(-)-3,5-dihydroxy-6,7- dimethoxyflavanone (3), together with nineteen known compounds have been isolated from the leaves of Muntingia calabura. The structures of three new compounds were determined through spectral analyses including extensive 2D-NMR data. Among the isolates, 2,3-dihydroxy-4,3′,4′,5′- tetramethoxydihydrochalcone, 5,7-dihydroxy-3-methoxyflavone, 5,7-dihydroxy-6-methoxyflavone, 5,4′-dihydroxy-3,7-dimethoxyflavone, (2S)-7,8,3′,4′,5′-pentamethoxyflavan, (2S)-5′-hydroxy-7, 8,3′,4′-tetramethoxyflavan, and methyl gallate exhibited significant anti-platelet aggregation activity in vitro.