ACE and platelet aggregation inhibitors from Tamarix hohenackeri Bunge (host plant of Herba Cistanches) growing in Xinjiang

Abstract

Background: Tamarix hohenackeri Bunge is a salt cedar that grows widespread in the desert mountains in Xinjiang. T. hohenackeri has not been investigated earlier, although there are many reports of phytochemical work on other Tamarix species.Materials and Methods: To fi nd out natural angiotensin-converting enzyme (ACE) inhibitor and platelet aggregation inhibitors, the bioactive extract (ethyl acetate [EtOAc] fraction) from the dried aerial parts of T. hohenackeri were investigated. The active fraction was purifi ed by repeated column chromatography, including silica gel, Sephadex LH-20 column, medium-pressure liquid chromatography (MPLC) (polyamide column) and high-performance liquid chromatography (HPLC). The isolated major constituents were tested for their anti-platelet aggregation activity.Results: Bioassay-directed separation of the EtOAc fraction of the 70% ethanol extract from the air-dried aerial parts of T. hohenackeri led to the isolation of a new triterpenoid lactone (1), together with 13 known compounds (2-14). It was the fi rst time to focus on screening bioactive constituents for this plant. The chemical structures were established on the basis of spectral data (ESI-MS and NMR). The results showed that the fl avonoid compounds (7 and 8) and phenolic compounds (9, 10, 11, and 14) were potential ACE inhibitors. And the fl avonoid compounds (5 and 7) showed signifi cant anti-platelet aggregation activities.Conclusion: On the basis of the chemical and biological data, the material basis of ACE inhibitory activity for the active part was the phenolic constituents. However, the fl avonoid compounds were responsible for the anti-platelet aggregation. The primary structure and activity relationship were also discussed respectively.

Keywords: ACE inhibitors; bioassay-directed separation; new triterpenoid lactone; platelet aggregation inhibitors; Tamarix hohenackeri Bunge