Isolation, Synthesis, and Bioactivity of Homoisoflavonoids from Caesalpinia pulcherrima

One new homoisoflavonoid, (3E)-2,3-dihydro-6,7-dimethoxy-3[(3-hydroxy-4-methoxyphenyl)methylene]-4H-1-benzopyran-4-one and four naturally new analogues, (3E)-3-(1,3-benzodioxol-5-ylmethylene)-2,3-dihydro-7-hydroxy-4H-1-benzopyran-4-one, (3E)-3-(1,3-benzodioxol-5-ylmethylene)-2,3-dihydro-7-methoxy-4H-1-benzopyran-4-one, (3E)-2,3-dihydro-7-hydroxy-3-[(3-hydroxy-4-methoxyphenyl)methylene]-4H-1-benzopyran-4-one and (3E)-2,3-dihydro-3-[(3,4-dimethoxyphenyl)methylene]-7-methoxy-4H-1-benzopyran-4-one, along with four known homoisoflavonoids, bonducellin, sappanone A, 2'-methoxybonducellin and 7-O-methylbonducellin were isolated from aerial parts of Caesalpinia pulcherrima. The structures of the new compounds were elucidated by interpretation of their 1D and 2D NMR spectra. Syntheses of the naturally new compounds and the known compounds have also been accomplished. The antibacterial and antifungal activities of the isolated homoisoflavonoids were studied.