Isolation and Crystal Structure of Ent-kaurane Diterpenes from Rubus corchorifolius L. f.

In this study, ent-Kaurane-3β,16β,17-trioi （1） and ent-kaurane-2a,16β,17-triol （2）, were isolated from the leaves ofRubus corchorifolius L. f. Their structures were elucidated based on extensive spectroscopic analysis. NMR experiments identified the two compounds and X-ray crystallographic analysis confirmed their crystal structures. The crystal of 1 belongs to monoclinic with space group P21 and a = 10.7641（3）, b = 7.2789（3）, c = 11.7862（4） A, β = 95.275（3）°, V = 919.55（6） A3, Z = 2, C20H34O4, Mr = 322.49 g/mol, Dc = 1.230 g/m3, F（000） = 376, 2 = 1.54178 A,μ = 0.661 mm-1, R = 0.0319, and wR = 0.0811 for 10889 observed reflections （I〉 2σ（I））. The crystal of 2 is classified as orthorhombic with space group P212121 and a = 10.7641（3）, b = 12.72224（19）, c = 21.3929（3） A, V= 1748.94（4） A3, Z= 4, C20H3404, Mr = 322.47, De = 1.225 Mg/m3 F（000） = 712, λ = 1.54184 A,μ = 0.625 mm-1, R = 0.0303 and wR = 0.0759 for 10470 observed reflections （1〉 2σ（I））. Meanwhile, the compound revealed low inhibitory activities toward HepG2, MCF-7, and SCG-7901 cells.

Structure analysis of ethyl ferulate from Rubus corchorifolius L.f.leaves and its inhibitory effects on HepG2 liver cancer cells

The tender leaves of Rubus corchorifolius L.f.(R.corchorifolius)have been made into herbal tea for relieving coughs in East and Southeast Asia from ancient times.Herein,we obtained an ethyl acetate extract from R.corchorifolius leaves and isolated a major bioactive compound within.Structural analysis of the isolated compound was performed by spectroscopic methods and the compound was identified as ethyl ferulate.Effect of ethyl ferulate on the growth and proliferation of human liver cancer HepG2 cells and normal human liver LO2 cells was determined by MTT assay.We found that ethyl ferulate significantly suppressed the cell proliferation of HepG2 cells(IC_(50)26.4μM),while it did not cause cytotoxicity on LO2 cells.In addition,flow cytometry analysis demonstrated that ethyl ferulate inhibited HepG2 cell growth via inducing cellular apoptosis.Specifically,ethyl ferulate reduced the electrical potential of the mitochondrial membrane and increased the concentration of calcium ions inside cells.Moreover,these changes were accompanied by increases in the expression of the pro-apoptotic proteins,such as cleaved caspase-3 and Bax.In contrast,cell morphology and growth of LO2 cells remained unaffected.In conclusion,for the first time,our observations demonstrated that ethyl ferulate possesses great potential as an effective and safe antitumor agent for cancer chemoprevention in humans.