Chemical Investigation Of Two Mangrove Plants Hibiscus Tiliaceus L. And Thespesia Populneoides (Roxb.) Kostel

This dissertation describes the isolation and structure elucidation of chemical constituents from two mangrove plants Hibiscus tiliaceus L. and Thespesia populneoides (Roxb.) Kostel. Some of the obtained compounds were preliminarily screened for antibacterial activity.The aerial parts of mangrove plants were collected at Hainan island of South China Sea, and the dried and powdered samples were extracted with 95% aqueous EtOH, and the residue was further extracted with CHCl3/MeOH (1:1, v/v) at room temperature. The concentrated extracts were combined, dissolved in water, and extracted with petroleum ether (PE) and EtOAc successively.The compounds were isolated by the combination of column chromatography on silica gel, RP-18, and Sephadex LH-20, as well as by preparative thin layer chromatography (pTLC) and re-crystallization. The structures of the obtained compounds were elucidated on the basis of spectroscopic analysis including IR, UV, MS, HR-MS, 1D-NMR and 2D-NMR. A total of 43 compounds were isolated with 38 of them were structurally elucidated. From the EtOAc-soluble fraction of H. tiliaceus, totally 22 compounds were isolated and 19 of them were structurally elucidated including three new triterpenoids (H1*–H3*). Fifteen compounds were isolated from this species for the first time. From the EtOAc-soluble fraction of T. populneoides, a totally of 21 compounds were isolated with 19 of them were structurally elucidated including one new sesquiterpene (T1*). All other compounds were isolated from this species for the first time. This is also the first report about the chemical constituents of T. populneoides.The antibacterial activities of some isolated compounds were evaluated. Most of the screened compounds showed no activity against the tested bacterial strains,while T1* showed weak inhibitory activity against Staphylococcus aureus.