Azathioprine hepatotoxicity and the protective effect of liquorice and glycyrrhizic acid

Whole-chromosome oligo-painting in licorice unveils interspecific chromosomal evolutionary relationships and possible origin of triploid genome species

Licorice is one of the most extensively studied medicinal plants in the world, whose roots and rhizomes have long been used as both a sweetener and an essential component in numerous herbal preparations. However, the genus Glycyrrhiza has a complex composition, and the interspecies chromosomal relationships, origin, and evolution are still largely unclear. Here, we develop a set of whole-chromosome painting probes that allowed identification of all eight chromosomes of licorice on same metaphase chromosomes. Comparative chromosome painting analyses in seven different Glycyrrhiza species revealed that the genus Glycyrrhiza maintained extraordinarily conserved chromosomal synteny after about 3-12 million years of divergence. No cytologically visible inter-chromosomal rearrangements were identified in any species. By comparative chromosomal karyotype analyses, we revealed interspecific chromosome evolutionary relationships and dramatic variable chromosomal karyotype after independent divergence and demonstrated that G. prostrate was the most closely related to the ancestral type among the seven Glycyrrhiza species. Furthermore, we also discovered a G. glandulosa seed with distinct triploid-genome for the first time in China, suggesting the existence of a polyploid evolutionary pathway in the genus Glycyrrhiza, which challenges the previous notion that only diploids of licorice existed in nature. This study expands our knowledge of the chromosome evolution of licorice and will lay an important foundation for the genome origin and evolution studies in the genus Glycyrrhiza.

Glycyrrhizin protects against diosbulbin B-induced hepatotoxicity by inhibiting the metabolic activation of diosbulbin B

Diosbulbin B (DIOB), isolated from herbal medicine Dioscorea bulbifera L. (DB), could induce severe liver injury, and its toxicology was closely associated with CYP3A4-mediated metabolic oxidation of furan moiety to the corresponding cis-enedial reactive metabolite. Glycyrrhizin (GL), the major bioactive ingredient in licorice, can inhibit the activity of CYP3A4. Thus, GL may ameliorate hepatotoxicity of DIOB when GL and DIOB are co-administrated. The study aimed to investigate the protective effect of GL on DIOB-induced hepatotoxicity and the underlying mechanism. Biochemical and histopathological analysis demonstrated that GL alleviated DIOB-induced hepatotoxicity in a dose-dependent manner. In vitro study with mouse liver microsomes (MLMs) demonstrated that GL reduced the formation of metabolic activation-derived pyrrole-glutathione (GSH) conjugates from DIOB. Toxicokinetic studies showed that the pretreatment with GL caused the increase of AUCs and Cmax of DIOB in blood of mice, resulting in accelerating the accumulation of DIOB in the circulation. In addition, the pretreatment with GL alleviated DIOB-induced hepatic GSH depletion. In summary, GL ameliorated DIOB-induced hepatotoxicity, possibly related to the inhibition of the metabolic activation of DIOB. Thus, development of a standardized combination of DIOB with GL may protect patients from DIOB-induced liver injury.

Chromosome-scale genome assembly of Glycyrrhiza uralensis revealed metabolic gene cluster centred specialized metabolites biosynthesis

A high-quality genome assembly is imperative to explore the evolutionary basis of characteristic attributes that define chemotype and provide essential resources for a molecular breeding strategy for enhanced production of medicinal metabolites. Here, using single-molecule high-fidelity (HiFi) sequencing reads, we report chromosome-scale genome assembly for Chinese licorice (Glycyrrhiza uralensis), a widely used herbal and natural medicine. The entire genome assembly was achieved in eight chromosomes, with contig and scaffold N50 as 36.02 and 60.2 Mb, respectively. With only 17 assembly gaps and half of the chromosomes having no or one assembly gap, the presented genome assembly is among the best plant genomes to date. Our results showed an advantage of using highly accurate long-read HiFi sequencing data for assembling a highly heterozygous genome including its complexed repeat content. Additionally, our analysis revealed that G. uralensis experienced a recent whole-genome duplication at approximately 59.02 million years ago post a gamma (γ) whole-genome triplication event, which contributed to its present chemotype features. The metabolic gene cluster analysis identified 355 gene clusters, which included the entire biosynthesis pathway of glycyrrhizin. The genome assembly and its annotations provide an essential resource for licorice improvement through molecular breeding and the discovery of valuable genes for engineering bioactive components and understanding the evolution of specialized metabolites biosynthesis.

Sunitinib induced hepatotoxicity in L02 cells via ROS-MAPKs signaling pathway

Sunitinib is a multi-targeted tyrosine kinase inhibitor with remarkable anticancer activity, while hepatotoxicity is a potentially fatal adverse effect of its administration. The aim of this study was to elucidate the mechanism of hepatotoxicity induced by Sunitinib and the protective effect of glycyrrhetinic acid (GA). Sunitinib significantly reduced the survival of human normal hepatocytes (L02 cells), induced the increase of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH). Chloroquine (CQ) and Z-VAD-FMK were applied to clarify the cell death patterns induced by Sunitinib. Sunitinib significantly induced L02 cells death by triggering apoptosis and autophagy acted as a self-defense mechanism to promote survival. Sunitinib exposure caused excessive ROS generation which activated mitogen-activated protein kinases (MAPKs) signaling. Mechanistically, SP600125 (JNK inhibitor) and SB203580 (p38 inhibitor) respectively blocked apoptosis and autophagy induced by Sunitinib. And inhibition of ROS by NAC pretreatment ameliorated the effect of Sunitinib on MAPKs phosphorylation. GA alleviated Sunitinib-induced cell damage by inhibiting apoptosis and autophagy. These results suggested ROS/MAPKs signaling pathway was responsible for Sunitinib-induced hepatotoxicity and GA could be a preventive strategy to alleviate liver injury caused by Sunitinib.

Natural products in licorice for the therapy of liver diseases: Progress and future opportunities

Liver diseases related complications represent a significant source of morbidity and mortality worldwide, creating a substantial economic burden. Oxidative stress, excessive inflammation, and dysregulated energy metabolism significantly contributed to liver diseases. Therefore, discovery of novel therapeutic drugs for the treatment of liver diseases are urgently required. Licorice is one of the most commonly used herbal drugs in Traditional Chinese Medicine for the treatment of liver diseases and drug-induced liver injury (DILI). Various bioactive components have been isolated and identified from the licorice, including glycyrrhizin, glycyrrhetinic acid, liquiritigenin, Isoliquiritigenin, licochalcone A, and glycycoumarin. Emerging evidence suggested that these natural products relieved liver diseases and prevented DILI through multi-targeting therapeutic mechanisms, including anti-steatosis, anti-oxidative stress, anti-inflammation, immunoregulation, anti-fibrosis, anti-cancer, and drug-drug interactions. In the current review, we summarized the recent progress in the research of hepatoprotective and toxic effects of different licorice-derived bioactive ingredients and also highlighted the potency of these compounds as promising therapeutic options for the treatment of liver diseases and DILI. We also outlined the networks of underlying molecular signaling pathways. Further pharmacology and toxicology research will contribute to the development of natural products in licorice and their derivatives as medicines with alluring prospect in the clinical application.

Phytochemical Constituents and Pharmacological Effects of Licorice: A Review

Licorice (or “liquorice”) is one of most widely used in foods, herbal medicine, and extensively researched medicinal plants of the world. In traditional medicine licorice roots have been used against treating many ailments including lung diseases, arthritis, kidney diseases, eczema, heart diseases, gastric ulcer, low blood pressure, allergies, liver toxicity, and certain microbial infections. Licorice extract contains sugars, starch, bitters, resins, essential oils, tannins, inorganic salts, and low levels of nitrogenous constituents such as proteins, individual amino acids, and nucleic acids. A large number of biological active compounds have been isolated from Glycyrrhiza species, where triterpene saponins and flavonoids are the main constitutes which show broad biological activity. This review examines recent studies on the phytochemical and pharmacological data and describes some side effects and toxicity of licorice and its bioactive components.

Pharmacological Activities and Phytochemical Constituents

Glycyrrhiza glabra is one of the most popular medicinal plants and it has been used in traditional herbal remedy since ancient times (Blumenthal et al. in Herbal medicine: expanded commission E monographs. Integrative Medicine Communications, Newton, 2000; Parvaiz et al. in Global J Pharmocol 8(1):8–13, 2014; Altay et al. in J Plant Res 129(6):1021–1032, 2016). Many experimental, pharmacological and clinical studies show that liquorice has antimicrobial, antibacterial, antiviral, antifungal, antihepatotoxic, antioxidant, antiulcer, anti-hemorrhoid antihyperglycemic, antidiuretic, antinephritic, anticarcinogenic, antimutagenic, anticytotoxic, anti-inflammatory, and blood stopper activity.

Folic Acid and Grape Seed Extract Prevent Azathioprine-induced Fetal Malformations and Renal Toxicity in Rats

Azathioprine (AZA) is an important drug commonly used in the therapy of the autoimmune system disorders. It induces many hazard effects that restrict its use. The present study was designed to investigate the influence of AZA on the fetal development and renal function and its co-administration with either folic acid (FA) or grape seed extract (GSE). The effects of administration of GSE or FA on AZA toxicity by gavage simultaneously for 4 weeks were studied by determining the changes in kidney histology, the glutathione level (GSH), and lipid per oxidation content as malondialdehyde in the kidney tissue. Additionally, their effects on the fetal development were investigated. Azathioprine induced a renal damage as indicated from the pronounced changes in histological structure, a significant increase in serum urea and creatinine, and malondialdehyde content in the kidney tissue. Meanwhile, the GSH activity was significantly decreased. Co-treatment with GSE significantly minimized the previously mentioned hazard effects of AZA by ameliorating the antioxidant activity. At this point, FA induced a nonsignificant protective activity. The results also revealed that administration of FA or GSE at 6th to 15th day of gestation did not altered fetal development. While, AZA administration clearly disturbed fetal development as indicated from a significant decrease in fetal weights. Furthermore, co-administration of both drugs significantly minimized similarly the hazards of AZA on the fetal development. It may be concluded that GSE and FA are a useful remedies. Maternal administrations of either both are protective agents against AZA-induced fetal malformations. Grape seed extract was more active than FA in potentiating the antioxidative defenses for controlling AZA-induced oxidative renal damages. Copyright © 2016 John Wiley & Sons, Ltd.

Hepatoprotective triterpene saponins from the roots of Glycyrrhiza inflata

Two novel oleanane-type triterpene saponins, licorice-saponin P2 (1) and licorice-saponin Q2 (3), together with nine known compounds 2, 4-11, have been isolated from the water extract of the roots of Glycyrrhiza inflata. The structures of these compounds were elucidated on the basis of spectroscopic analysis, including 2D-NMR experiments (1H-1H COSY, HSQC, HMBC and ROESY). In in vitro assays, compounds 2-4, 6 and 11 showed significant hepatoprotective activities by lowering the ALT and AST levels in primary rat hepatocytes injured by D-galactosamine (D-GalN). In addition, compounds 2-4, 6, 7 and 11 were found to inhibit the activity of PLA2 with IC50 values of 6.9 μM, 3.6 μM, 16.9 μM, 27.1 μM, 32.2 μM and 9.3 μM, respectively, which might be involved in the regulation of the hepatoprotective activities observed.

Evaluation of azathioprine-induced cytotoxicity in an in vitro rat hepatocyte system

Azathioprine (AZA) is widely used in clinical practice for preventing graft rejection in organ transplantations and various autoimmune and dermatological diseases with documented unpredictable hepatotoxicity. The potential molecular cytotoxic mechanisms of AZA towards isolated rat hepatocytes were investigated in this study using “Accelerated Cytotoxicity Mechanism Screening” techniques. The concentration of AZA required to cause 50% cytotoxicity in 2 hrs at 37°C was found to be 400 μM. A significant increase in AZA-induced cytotoxicity and reactive oxygen species (ROS) formation was observed when glutathione- (GSH-) depleted hepatocytes were used. The addition of N-acetylcysteine decreased cytotoxicity and ROS formation. Xanthine oxidase inhibition by allopurinol decreased AZA-induced cytotoxicity, ROS, and hydrogen peroxide (H₂O₂) formation and increased % mitochondrial membrane potential (MMP). Addition of N-acetylcysteine and allopurinol together caused nearly complete cytoprotection against AZA-induced hepatocyte death. TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl), a known ROS scavenger and a superoxide dismutase mimic, and antioxidants, like DPPD (N,N′-diphenyl-p-phenylenediamine), Trolox (a water soluble vitamin E analogue), and mesna (2-mercaptoethanesulfonate), also decreased hepatocyte death and ROS formation. Results from this study suggest that AZA-induced cytotoxicity in isolated rat hepatocytes may be partly due to ROS formation and GSH depletion that resulted in oxidative stress and mitochondrial injury.

Bioactive constituents of oleanane-type triterpene saponins from the roots of Glycyrrhiza glabra

Three new oleanane-type triterpene saponins, namely licorice-saponin M3 (1), licorice-saponin N4 (2), and licorice-saponin O4 (3), an artificial product (4), as well as five known triterpene glucuronides (5-9), were isolated from the roots of Glycyrrhiza glabra L. Their structures were established using 1D and 2D NMR spectroscopy, mass spectrometry, and by comparison with spectroscopic data reported in the literature. The inhibitory effects of the selected compounds on neuraminidase were evaluated, and the preliminary structure-activity relationship was also predicted.

18α-glycyrrhizin ameliorates oxidative stress in rats with CCl4-induced liver fibrosis

AIM: To investigate the effect of 18α-glycyrrhizin (18α-GL) on oxidative stress in rats with experimental liver fibrosis.

METHODS: Male SD rats were randomly divided into five groups: control group, fibrosis group, low-, medium-, and high-dose GL groups. Except the control group, liver fibrosis was induced by subcutaneous injection of 40% CCl₄ for 8 weeks in rats of the other groups. The three GL groups were treated with different doses of GL (6.25, 12.5, 25 mg/kg, respectively). All the rats were sacrificed at the end of the 8th week. Histopathological changes in the liver tissue were evaluated by HE staining and Masson collagen staining. The contents of MDA and HNE and the activity of SOD and GSH-PX in liver tissue homogenate were determined.

RESULTS: 18α-GL could inhibit CCl₄-induced liver fibrosis. The contents of MDA and HNE were elevated in the liver fibrosis group (both P < 0.05), but 18α-GL could markedly increase SOD and GSH-PX activity (both P < 0.05) and reduce the levels of MDA and HNE to protect the liver from damage.

CONCLUSION: 18α-GL can ameliorate hepatic histopathological changes and reduce hepatic lipid peroxidation, thus exerting antioxidant and antifibrotic effects in rats with experimental liver fibrosis.

Ginseng (Panax quinquefolius) and Licorice (Glycyrrhiza uralensis) Root Extract Combinations Increase Hepatocarcinoma Cell (Hep-G2) Viability

The combined cytoactive effects of American ginseng (Panax quinquefolius) and licorice (Glycyrrhiza uralensis) root extracts were investigated in a hepatocarcinoma cell line (Hep-G2). An isobolographic analysis was utilized to express the possibility of synergistic, additive or antagonistic interaction between the two extracts. Both ginseng and licorice roots are widely utilized in traditional Chinese medicine preparations to treat a variety of ailments. However, the effect of the herbs in combination is currently unknown in cultured Hep-G2 cells. Ginseng (GE) and licorice (LE) extracts were both able to reduce cell viability. The LC50 values, after 72 h, were found to be 0.64 ± 0.02 mg/mL (GE) and 0.53 ± 0.02 mg/mL (LE). An isobologram was plotted, which included five theoretical LC50s calculated, based on the fixed fraction method of combination ginseng to licorice extracts to establish a line of additivity. All combinations of GE to LE (1/5, 1/3, 1/2, 2/3, 4/5) produced an effect on Hep-G2 cell viability but they were all found to be antagonistic. The LC50 of fractions 1/3, 1/2, 2/3 were 23%, 21% and 18% above the theoretical LC50. Lactate dehydrogenase release indicated that as the proportion of GE to LE increased beyond 50%, the influence on membrane permeability increased. Cell-cycle analysis showed a slight but significant arrest at the G1 phase of cell cycle for LE. Both GE and LE reduced Hep-G2 viability independently; however, the combinations of both extracts were found to have an antagonistic effect on cell viability and increased cultured Hep-G2 survival.

Structural characterization and identification of oleanane-type triterpene saponins in Glycyrrhiza uralensis Fischer by rapid-resolution liquid chromatography coupled with time-of-flight mass spectrometry

Oleanane-type triterpene saponins (OTS) are major active ingredients in Glycyrrhiza uralensis. In this work, a rapid-resolution liquid chromatography with time-of-flight mass spectrometry (RRLC/TOF-MS) method has been developed to characterize and identify OTS from G. uralensis. The major diagnostic ions and fragmentation pathways from thirteen OTS have been characterized for the first time. At a low fragmentor voltage of 120  V in positive ion mode, the precursor ion [M + H](+) or/and [M + Na](+) was obtained for accurate determination of molecular formula. When the fragmentor voltage was increased to 425  V, abundant characteristic fragment ions were observed for structural characterization. Neutral losses of sugar moieties, such as glucuronic acid (GlcA, 176  Da), glucose (Glc, 162  Da) and rhamnose (Rha, 146 Da), were commonly observed in the MS spectra for prediction of the sugar number and sequences. Other typical losses included AcOH (60  Da), CH(2)O (30  Da), 2 × H(2)O (2 × 18  Da) and HCOOH (46  Da) from [Aglycone + H-H(2)O](+) (named [B](+)), corresponding to the presence of a C(22)-acetyl group, C(24)-hydroxyl group, C(22)-hydroxyl group or C(30)-carboxyl group on the aglycone moiety, respectively. In particular, characteristic ring cleavages of the aglycone moieties on A- and B-rings were observed. Based on the fragmentation patterns of reference compounds, nineteen OTS have been identified in an extract of G. uralensis, thirteen of which were unambiguously identified and the other six were tentatively assigned.

Analysis of phenolic and triterpenoid compounds in licorice and rat plasma by high-performance liquid chromatography diode-array detection, time-of-flight mass spectrometry and quadrupole ion trap mass spectrometry

High-performance liquid chromatography with diode-array detection (HPLC/DAD), time-of-flight mass spectrometry (HPLC/TOFMS) and quadrupole ion trap mass spectrometry (HPLC/QITMS) were used for separation and identification of several compounds in licorice and rat plasma after oral administration of the herbal extract. Three phenolic compounds and one triterpenoid in licorice extract were unambiguously identified by comparing with the standard compounds. A formula database of known compounds in licorice was established, against which the other 42 compounds were identified effectively based on the accurate extract masses and formulae acquired by HPLC/TOFMS. In order to differentiate the isomers, tandem mass spectrometry was also used. The deduced fragmentation behaviors in QITMS were used to distinguish seven groups of isomers in licorice. By means of the three detectors, 46 compounds in licorice were identified. After oral administration of the extract, 25 compounds in rat plasma were detected and identified by comparing and contrasting the compounds measured in licorice with those in the plasma samples by HPLC/TOFMS. It is concluded that a rapid and effective method based on three analytical techniques was established, which is useful for identification of multiple compounds in licorice in vitro and in vivo. The result should be very useful for the quality control and curative mechanism study of licorice.

Chemical analysis of the Chinese herbal medicine Gan-Cao (licorice)

Gan-Cao, or licorice, is a popular Chinese herbal medicine derived from the dried roots and rhizomes of Glycyrrhiza uralensis, G. glabra, and G. inflata. The main bioactive constituents of licorice are triterpene saponins and various types of flavonoids. The contents of these compounds may vary in different licorice batches and thus affect the therapeutic effects. In order to ensure its efficacy and safety, sensitive and accurate methods for the qualitative and quantitative analyses of saponins and flavonoids are of significance for the comprehensive quality control of licorice. This review describes the progress in chemical analysis of licorice and its preparations since 2000. Newly established methods are summarized, including spectroscopy, thin-layer chromatography, gas chromatography, high-performance liquid chromatography (HPLC), liquid chromatography/mass spectrometry (LC/MS), capillary electrophoresis, high-speed counter-current chromatography (HSCCC), electrochemistry, and immunoassay. The sensitivity, selectivity and powerful separation capability of HPLC and CE allows the simultaneous detection of multiple compounds in licorice. LC/MS provides characteristic fragmentations for the rapid structural identification of licorice saponins and flavonoids. The combination of HPLC and LC/MS is currently the most powerful technique for the quality control of licorice.

The extract ofPrunus persica flesh (PPFE) attenuates chemotherapy-induced hepatotoxicity in mice

Cisplatin (cis-diamminedichloroplatinum II) is one of the most effective chemotherapeutic agents used in the treatment of a variety of human solid tumors. However, its clinical use is limited due to severe toxicity. The pathogenesis of liver damage caused by cisplatin is generally considered to be oxidative damage. The aim of this study was to evaluate the protective effect of the ethanol extract of Prunus persica flesh (PPFE) against cisplatin-induced hepatotoxicity in animal models. In a xenograft model with the repeated administration of a low-dose cisplatin (5 mg/kg body weight) for 15 days, and in an acute toxicity model with a single administration of a high-dose cisplatin (45 mg/kg body weight) over a 16 h period, the consecutive administration of PPFE in combination with and prior to the cisplatin injection reversed the cisplatin-induced decrease in the liver weight as a percentage of total body weight, and the cisplatin-induced increases in the serum alanine aminotransferase and aspartate aminotransferase levels caused by liver damage. Moreover, the oral administration of PPFE significantly recovered the reduced glutathione level and inhibited lipid peroxidation in the cisplatin-treated mice. These results demonstrate that supplementation with PPFE might protect against cisplatin-induced toxicity in cancer patients.