Secondary metabolites from the root of Helicia rengetiensis
Helicia rengetiensis Masamune (Proteaceae) is an endemic evergreen trees, growing in thickets at lower elevations in the central and southern parts of Taiwan. Flavonol glycosides, phenolic glycosides, benzenoid glycosides, and their derivatives distributed in plant of genus Helicia. In our studies on the antitubercular constituents of Formosan plants, 1200 species have been screened for in vitro antitubercular activity, and the H. rengetiensis has been found to be an active species. However, the chemical constituents and biological activities of this plant have never been studied. Bioassay-guided fractionation of active EtOAc-soluble fraction of the root of this species has led to the isolation of two new compounds, including helicinol A (1) and helicinol B (2), together with six known compounds, including one cyclophane, kermadecin H (3), one fatty acid, stearic acid (4), one triterpene, squalene (5), one chroman, α-tocopherol (6), and a mixture of β-sitosterol (7) and stigmasterol (8). The structures of these new compounds were determined through spectroscopic analyses including 2D-NMR data. The structural elucidation of these new compounds and the antitubercular activities of the isolates will be discussed in this symposium. The successive isolation and antitubercular assay are in progress.