ARPI, ß-AS, and UGE regulate glycyrrhizin biosynthesis in Glycyrrhiza uralensis hairy roots.

KEY MESSAGE: ARPI, ß-AS, and UGE were cloned from G. uralensis and their regulatory effects on glycyrrhizin biosynthesis were investigated. ß-AS and UGE but not ARPI positively regulate the biosynthesis of glycyrrhizin. Glycyrrhiza uralensis Fisch. has been used to treat respiratory, gastric, and liver diseases since ancient China. The most important and widely studied active component in G. uralensis is glycyrrhizin (GC). Our pervious RNA-Seq study shows that GC biosynthesis is regulated by multiple biosynthetic pathways. In this study, three target genes, ARPI, ß-AS, and UGE from different pathways were selected and their regulatory effects on GC biosynthesis were investigated using G. uralensis hairy roots. Our data show that hairy roots knocking out ARPI or UGE died soon after induction, indicating that the genes are essential for the growth of G. uralensis hairy roots. Hairy roots with ß-AS knocked out grew healthily. However, they failed to produce GC, suggesting that ß-AS is required for triterpenoid skeleton formation. Conversely, overexpression of UGE or ß-AS significantly increased the GC content, whereas overexpression of ARPI had no obvious effects on GC accumulation in G. uralensis hairy roots. Our findings demonstrate that ß-AS and UGE positively regulate the biosynthesis of GC.

Molecular mechanisms underlying the anticancer activities of licorice flavonoids.

ETHNOPHARMACOLOGICAL RELEVANCE: Licorice has been commonly used in traditional Chinese medicine for treatment of gastric, liver, and respiratory disease conditions for more than two thousand years. It is a major component of several Chinese patent medicines certificated by National Medical Products Administration that possess great anticancer activities. AIM OF THE STUDY: To comprehensively summarize the anticancer activities of licorice flavonoids, explain the underlying molecular mechanisms, and assess their therapeutic potentials and side-effects. METHODS: PubMed, Research Gate, Web of Science, Google Scholar, academic journals, and Science Direct were used as information sources, with the key words of "anticancer", "licorice", "flavonoids", and their combinations, mainly from 2000 to 2019. RESULTS: Sixteen licorice flavonoids are found to possess anticancer activities. These flavonoids inhibit cancer cells through blocking cell cycle and regulating multiple signaling pathways. The major pathways targeted by licorice flavonoids include: the MAPK pathway, PI3K/AKT pathway, NF-κB pathway, death receptor - dependent extrinsic signaling pathway, and mitochondrial apoptotic pathway. CONCLUSION: Licorice flavonoids are a group of versatile molecules that have pleiotropic effects on cell growth, survival and cell signaling. Many of the flavonoids possess inhibitory activities toward cancer cell growth and hence have a great therapeutic potential in cancer treatment. However, additional preclinical studies are still needed to assess their in vivo efficacy and possible toxicities. It is also imperative to evaluate the effects of licorice flavonoids on the metabolism of other drugs and explore the potential synergistic mechanism.

The anti-diabetic activity of licorice, a widely used Chinese herb.

ETHNOPHARMACOLOGICAL RELEVANCE: A great deal of valuable experience has been accumulated in the traditional Chinese medicine (TCM) system for the treatment of "Xiaoke" disease which is known as diabetes mellitus now. As the most-commonly used Chinese herb, licorice has been used in TCM for more than two thousand years. It is often used in combination with other herbs to treat metabolic disorders, especially diabetes mellitus. AIM OF THE STUDY: To summarize the characteristics, mechanisms, and clinical use of licorice and its active components for treating diabetes mellitus. METHODS: PubMed, Web of Science, Research Gate, Science Direct, Google Scholar, and Academic Journals were used as information sources by the inclusion of the search terms 'diabetes', 'licorice', 'licorice extracts', 'flavonoids', 'triterpenoids', and their combinations, mainly from 2005 to 2019. RESULTS: Licorice extracts, five flavonoids and three triterpenoids isolated from licorice possess great antidiabetic activities in vivo and in vitro. This was done by several mechanisms such as increasing the appetency and sensitivity of insulin receptor site to insulin, enhancing the use of glucose in different tissues and organs, clearing away the free radicals and resist peroxidation, correcting the metabolic disorder of lipid and protein, and improving microcirculation in the body. Multiple signaling pathways, including the PI3K/Akt, AMPK, AGE-RAGE, MAPK, NF-кB, and NLRP3 signaling pathways, are targets of the licorice compounds. CONCLUSION: Licorice and its metabolites have a great therapeutic potential for the treatment of diabetes mellitus. However, a better understanding of their pharmacological mechanisms is needed for evaluating its efficacy and safety.

RNA-Seq based transcriptome analysis reveals the molecular mechanism of triterpenoid biosynthesis in Glycyrrhiza glabra.

Licorice is a frequently-used medicinal plant worldwide. Two triterpenoids, 18α-glycyrrhizic acid (18α-GC) and 18ß-glycyrrhizic acid (18ß-GC), are the key medicinal components accumulated in licorice. Biosynthesis of triterpenoids is a complex process that involves many secondary metabolic pathways. In this study, we tried to identify the key enzymes and pathways for the triterpenoid biosynthesis in licorice by analyzing the gene expression patterns in samples containing different GC levels. Glycyrrhizia glabra (one of the original species used as licorice in Chinese Pharmacopoeia) seeds were irradiated by X-ray and cultivated for one year, and samples with different GC contents were selected by HPLC analysis. RNA-Seq was performed to determine the gene expression in three X-ray irradiated G. glabra samples (H1, H2, and H3) with the highest GC content and one control G. glabra sample (L1) with the lowest GC content. 28.44 Gb raw data was generated and 47.7 million, 45.4 million, 43.3 million, and 45.9 million clean reads were obtained in samples H1, H2, H3, and L1, respectively. Approximately 48.53% of genes were annotated searching against GO and KEGG databases. A total of 1376 core differentially expressed genes (DEGs) were identified, which mainly enriched in phenylpropanoid metabolism, glycometabolism, plant circadian rhythm, and terpenoid biosynthetic pathway. 15 core DEGs selected from the 1376 DEGs were further verified by qRT-PCR, which confirmed that the RNA-Seq results were accurate and reliable. This study provides a basis for future functional genes mining and molecular regulatory mechanism elucidation of triterpenoid biosynthesis in licorice.