Identification Of New Anti-Gastric Cancer Natural Compounds From Radix Glycyrrhizae (RG), A Traditional Chinese Medicinal Herb (TCMH)

Although techniques for early diagnosis and the treatment of gastric cancer have been established, standard treatments for gastric cancer have not. In order to improve gastric cancer chemotherapeutic effects, scientists are trying to discover new drugs. The aim of this study was to identify new natural compounds having anti-gastric cancer properties that target stomach cancer-specific signal/metabolic pathways from Traditional Chinese Medicinal herbs (TCMH).The anticancer medicinal herbal fraction library built up in Northeast Normal University in Changchun, Jilin province, China was valuable in this study. This library is composed of 500 samples of Traditional Chinese medicinal herbs. We screened the herbal small molecules fractions library against the human gastric cancer cell line MGC-803. Among 214 96-wells plates screened, we obtained 52 positives plates, contaning 790 positives fractions. Toxicity analysis of the 790 positives fractions on mouse splenocytes revealed 140 nontoxic fractions from 21 plates. These fractions were assumed to be tumor-specific and some were confirmed as having a very high activity. We chose F4-F7, F11, and G2-G9 positives fractions of Radix Glycyrrhizae for further study.After determining that RG possesses an activity on MGC-803 cells and is of no action on mouse splenocytes, we isolated the active compounds from RG ethanol extract using solvent extraction and high performance liquid chromatography (HPLC). Three single compounds RG-X1-3 were isolated. The chemical structure of RG-X1 was identified and confirmed to be 7-Hydroxyflavanone 4'-O-glucoside or 4', 7-Dihydroxyflavanone 4'-beta-D-glucoside (Liquiritin, LQ). The doses responses of the three single compounds on MGC-803 cells were studied. The biological activity of LQ and RG-X2-3 was reverified again on MGC-803 cells. For mechanism study, MTT assay was applied to detect the cell proliferation. This test offered a quantitative and convenient method in evaluating a cell population's response to external factors, whether it is an increase in cell growth, no effect, or a decrease in growth due to necrosis or apoptosis. The IC50 of each compound was 30.81μΜfor LQ; 36.62μM for RG-X2 and 40.02μΜfor RG-X3. The apoptotic morphological changes in the nuclear chromatin of cells were detected via Hoechst 33258 staining. Flow cytometry was also performed to detect the apoptosis of the cells and revealed that LQ, and RG-X2-3 compounds could induce apoptosis of MGC-803 cells in dose-dependent manner. Hence, we concluded that LQ and RG-X2-3 compounds from Radix Glycyrrhizae could inhibit the growth of human gastric cancer cells effectively in vitro by inducing apoptosis. Therefore, the Radix Glycyrrhizae-derived anticancer natural compounds might be promising chemopreventive and chemotherapeutic agents against human gastric cancers and other malignant tumors.