Two new naturally dimers constituent from Indonesian Sesbania grandiflora plant and their bioactivity

A new dimer of natural isoflavonoid along with some known flavonoid compounds was successfully isolated from the roots of Indonesian Sesbania grandiflora plant using ethyl acetate extraction. The new compound specified as naturally bi-isoflavonoid with (4→6) inter-isoflavanyl linkage and four known flavonoids xenognosin B, liquiritigenin, 7,2′4′-trihydroxyisoflavone, demethylvestitol, and 1,1′-bi-2-naphthol was isolated and the antituberculosis activity of the compounds was studied. The structure of all compounds was elucidated with the aid of 1D and 2D NMR, UV spectroscopy, and HRESI mass spectrometry. The data obtained were also compared with the previous published data. Among compounds, 1,1′-bi-2-naphthol was found to exhibit the highest activity against Mycobacterium tuberculosis H37Rv with the MIC’s value of 10.9 µM while the biisoflavonoid with (4→6) inter-isoflavanyl linkage showed moderate activity with the MIC’s value of 92.2 nM, compared with isozianid as a positive control with the MIC’s value of 0.569 nM. It is worth to note that 1,1′-bi-2-naphthol and biisoflavonoid with (4→6) inter-isoflavanyl linkage were isolated for the first time from a natural source. Both compounds have been previously reported as synthetic compounds, which is synonymous with 3,4- trans-4-[(3S)-7,2′-dihydroxy-4′-methoxyisoflavan-6-yl]-7,2′-dihydroxy-4′-methoxyisoflavan and 1,1′-bi-2-naphthol, respectively. In this respect, the results of this study suggest that the roots of S. grandiflora is a potential source of new natural product compounds, with promising bioactivities.