Isolation,Structures,and Antitumor Activity Of Triterpenoids From Pleurotus Eryngii

Pleurotus eryngii(P. eryngii), which contains many biologically active compounds, has been widely consumed by humans as food ingredients in recent years not only because of its good flavor and texture, but also substantial nutritional value and potential medicinal value. In our previous study, an acetic ether(EtOAc) fraction from sporocarp of P. eryngii exhibited significant tumor cell growth inhibition in vitro and in vivo.Consequently, the purpose of this study was to examine the isolation and characterization of triterpenoids existing in P. eryngii extract. Additionally, the growth inhibition activity against breast cancer MCF-7 cells and ovarian cancer SK-OV-3 cells of these isolated compounds was also investigated to provide a theoretical basis for the development of new drugs. The main results are as follows:1. The optimal parameters of vanillin-glacial acetic acid colorimetry to measure the content of triterpene compounds were determined: After adding 0.2 m L of 5% vanillin-glacial acetic acid solution and 0.8 m L of perchloric acid solution, the test sample was under water bath for 15 min at 60℃. Then after adding 5 mL of glacial acetic acid, let stand for 10 min, absorbance values were measured at 547 nm. The colorimetric test in this condition presented high sensitivity, good stability and reproducibility.2. The triterpenes from P. eryngii were extracted by ultrasonic assisted digestion. According to single factor experiment, the optimal parameters were determined: extracting time was 30 min, the frequency of ultrasonic wave was 150 W and the solid-liquid ratio was 1:3. Compared with the experimental group only processed by methanol extraction for 8h, the terpene extraction rate increased from 1.02% to 2.67%.3. The conent of triterpene compounds exsiting in different solvent extract was not the same. Among them, the content of triterpene compounds in ethyl acetate extract, which was relatively the richest, presented 131.47 ± 0.73mg·g-1. Three triterpene monomer compounds 1-3 were obtained from ethyl acetate extract through various separation and purification technologies such as silica gel column chromatography, gel chromatography and preparative thin layer chromatography, which were combined with thin layer chromatography(TLC) to qualitative analysis of the purified samples. Their structures were identified by nuclear magnetic resonance(NMR) and mass spectrometry(MS) as 2,3,6,23-tetrahydroxy-urs-12-en-28 oic acid(compound 1), 2,3,23-trihydroxy-urs-12-en-28 oic acid(compound 2) and lupeol(compound 3). These triterpenoids have never been previously reported in P. eryngii.4. In vitro experiment,the MTT assay was taken to measure the antitumor activities of the three purified triterpenes, all of which showed significant inhibition activity against breast cancer MCF-7 and ovarian cancer SK-OV-3 cell lines, with the greatest activity of compound 1, followed by compound 2 and 3. Under the same concentration, all three compounds presented higher inhibit activity against MCF-7 cells than against SK-OV-3 cells. Their IC50 values towards breast cancer MCF-7 cells were 15.71 μM, 48 μM and 66.89 μM, towards ovarian cancer SK-OV-3 cells were 67.98 μM, 89.64 μM and 147.25 μM, respectively. Therefore, these constituents may be considered as valuable molecules for use as cancer chemopreventive or chemotherapeutic agents. And the study also provides a scientific and theoretical basis for P. eryngii to develop in functional food.