Studies On Chemical Constituents And Bioactivities Of Three Medicinal Plants, Juncus Effusus, Caesalpinia Sappan And Caesalpinia Bonduc

The dissertation deals mainly with chemical and pharmacological investigations of three medicinal plants, Juncus effusus, Caesalpinia sappan and Caesalpinia bonduc.A total of 133, including 46 new compounds were isolated from these plants through column chromatography over MCI, Silica gel, Sephadex LH-20, and preparative HPLC. Their structures were elucidated on the basis of spectroscopic methods including UV, IR, ESI-MS, HR-ESI-MS, 1D and 2D NMR, CD, and single crystal X-Ray diffraction. The structural types of the isolates include phenanthrenoids, cassane diterpenoids, flavonoids, homoisoflavonoids, sesquiterpenoids, and phenylpropanoids, etc.36 compounds, including 22 new were isolated from Juncus effusus, and the charateristics chemical constituents are phenanthrenoids(16 monomeric and 12 dimeric). Compound 5 and 11 are found to be a rarely nitrated and chlorinated phenanthrenoid derivative, respectively. Compound 6 represents the first naturally occurring conjugate of a phenanthrene unit and an alkaloid unit. Compound 13 possesses an unprecedented skeleton featuring a new six-membered ring formed presumably via a [4 + 2] Diels-Alder cycloaddition between two phenanthrene units. Four new types of dimeric linking styles, including C3-C5′(17–19), C8-C5′(20), C14-C3′(21) and C14-C8′(22) were found. ECD measurements and TDDFT-ECD calculations were used for the determination of the absolute configurations of two phenanthrenoid dimers. All the phenanthrenoid isolates were evaluated for their neuroprotective activity against Aβ25–35-induced neurotoxicity in cultured SH-SY5 Y cells, among them, three compounds showed potent neuroprotective activity, and a brief structure-activity relationship(SAR) were discussed. These results show for the first time that phenanthrene skeleton structures could be used as potential drug leads for the discovery and development of novel neuroprotective therapeutic agents.97 compounds, including 54 new were isolated from two Caesalpinia species(Caesalpinia sappan and Caesalpinia bonduc), and the characteristics chemical constituents are cassane diterpenoids. 17 cassane diterpene alkaloids were isolated from these two plants, five of which could be regarded as the first naturally occurring conjugates of a cassane diterpenoid and an amino acid. We proposed a method for the fast isolation of cassane diterpene alkaloids, and we also proposed a plausible biosynthetic pathway for them. 80 isolated cassane diterpenoids were evaluated for their anti-malarial activity against 3D7 strain of Plasmodium falciparum, and five of them showed potent inhibitory activity.