The salt marsh plants live in characteristic environment such as tidal flats and salt marshes. They have a specific mechanism to adapt themselves to these environments and subsequently make specific secondary metabolites different from those of terrestrial plants. Therefore this study was focused on isolation and structure determination of secondary metabolites of the salt marsh plant Glehnia littoralis and their bioactivities.
Whole plants of Glehnia littoralis were collected by hand in September, 2002, at Pohang in Korea. The collected samples were dried under the shade and extracted twice with CH2Cl2 and MeOH, respectively. The combined crude extracts were concentrated in vacuo and then partitioned between CH2Cl2 and H2O. The organic layer was evaporated and re-partitioned between n-hexane and 85% aq. MeOH, and the aqueous layer was also further fractionated into n-BuOH and H2O.
Antioxidant activity of solvent fractions of Glehnia littoralis was evaluated using 1,1-Diphenyl-2-picryl-hydrazyl (DPPH) radical. In vitro scavenging effect of each fraction on DPPH radical increased in the order of n-BuOH > 85% aq. MeOH > H2O > n-hexane fraction. On the other hand, the scavenging effect of each fraction on reactive oxygen species (ROS) generated in HT1080 cells increased in the order of 85% aq. MeOH > n-hexane > H2O > n-BuOH fractions.
Cell growth inhibition effect of each of the solvent fractions was evaluated in HT1080, HT-29, AGS and U937 human cancer cells using MTT assay. The inhibitory effect of solvent fractions was increased in a dose-dependent manner. Among these fractions, 85% aq. MeOH and n-hexane fractions showed the potent inhibitory effect on the growth of human cancer cells and decreased the levels of mRNA expressions of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS).
On the basis of the above results, further purification of n-BuOH, 85% aq. MeOH, and n-hexane fractions led to the isolation of compounds 1-9. The chemical structure of these compounds was established by extensive 2D NMR experiments such as 1H gDQCOSY, TOCSY, NOESY, gHMQC, and gHMBC and by comparison with published spectral data.
In our measurements for evaluating antioxidant activity of compound 1-9 using in vitro DPPH radical and peroxynitrite systems, they exhibited high scavenging activities. In addition, their scavenging activities on the generation of ROS in HT1080 cell system were very high.
Cell growth inhibition effects of compound 1-9 were also evaluated in HT1080, HT-29, AGS and U937 human cancer cells using the MTT assay method. All of them exhibited good inhibitory effects in a dose-dependent manner and decreased the levels of mRNA expressions of cyclooxygenase-2 (COX-2) on the growth of HT-29 human cancer cells.