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, 1,200 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 the active EtOAc-soluble fraction of the root of this species has led to the isolation of three new compounds, including helicinol A (1) helicinol B (2) and helicinone (3), together with eleven known compounds, including one cyclophane, kermadecin H (4), three flavones, 5-hydroxy-3,7,4'-trimethoxyflavone (5), 5-hydroxy-3,6,7,4'-tetramethoxyflavone (6), and5-hydroxy-3,6,7,8,4'-pentamethoxyflavone (7), one fatty acid, stearic acid (8), one benzoquinone, α-tocopheryl quinone (9), and five steroids, β-sitostenone (10), a mixture of β-sitosterol (11) and stigmasterol (12), and a mixture of 3-O-β-D-glucopyranosyl β-sitosterol (13) and 3-O-β-D-glucopyranosyl stigmasterol (14). The structures of these new compounds were determined through spectroscopic analyses including 2D-NMR data. The successive isolation and antitubercular assay are still in progress.
Acknowledgement: National Science Council of the Republic of China (NSC 99–2320-B-037–010)