Rhein suppresses esophageal cancer development by regulating cell cycle through DNMT3B gene.

The mechanism by which DNMT3B facilitates esophageal cancer (ESCA) progression is currently unknown, despite its association with adverse prognoses in several cancer types. To investigate the potential therapeutic effects of the Chinese herbal medicine rhubarb on esophageal cancer (ESCA), we adopted an integrated bioinformatics approach. Gene Set Enrichment Analysis (GSEA) was first utilized to screen active anti-ESCA components in rhubarb. We then employed Weighted Gene Co-expression Network Analysis (WGCNA) to identify key molecular modules and targets related to the active components and ESCA pathogenesis. This system-level strategy integrating multi-omics data provides a powerful means to unravel the molecular mechanisms underlying the anticancer activities of natural products, like rhubarb. To investigate module gene functional enrichment, Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were conducted. In addition, we evaluated the predictive impact of DNMT3B expression on ESCA patients utilizing the Kaplan-Meier method. Finally, we conducted experiments on cell proliferation and the cell cycle to explore the biological roles of DNMT3B. In this study, we identified Rhein as the main active ingredient of rhubarb that exhibited significant anti-ESCA activity. Rhein markedly suppressed ESCA cell proliferation. Utilizing Weighted Gene Co-expression Network Analysis (WGCNA) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, we determined that the blue module was associated with Rhein target genes and the cell cycle. Additionally, DNMT3B was identified as a Rhein target gene. Analysis of The Cancer Genome Atlas (TCGA) database revealed that higher DNMT3B levels were associated with poor prognosis in ESCA patients. Furthermore, Rhein partially reversed the overexpression of DNMT3B to inhibit ESCA cell proliferation. In vitro studies demonstrated that Rhein and DNMT3B inhibition disrupted the S phase of the cell cycle and affected the production of cell cycle-related proteins. In this study, we found that Rhein exerts its anti-proliferative effects in ESCA cells by targeting DNMT3B and regulating the cell cycle.

Revealing the anti-inflammatory ingredients in wine-processed Radix et Rhizoma Rhei using immobilized cysteinyl leukotriene receptor type 1 as the stationary phase.

Despite the tremendous progress of wine-processed Radix et Rhizoma Rhei (Jiudahuang, JDH) in removing toxic heat from the blood in the upper portion of the body for hundreds of years, the deep understanding of its functional material basis of the anti-inflammatory ingredients remains unclear due to the lack of high specific and efficient methods. Herein, taking Cysteinyl leukotriene receptor type 1(CysLT1R) as the target protein, we established a chromatographic method based on the immobilized CysLT1R using haloalkane dehalogenases (Halo) at the C-terminus of the receptor in one step. After careful characterization by X-ray photoelectronic spectroscopy, immune-fluorometric analysis, and chromatographic investigations, the immobilized receptor was used to screen the anti-inflammatory ingredients in JDH. Aloe-emodin, rhein, emodin, chrysophanol, and physcion were identified as the main anthraquinone exerting anti-inflammatory effects in the drug. The association constants for the five compounds to bind with the receptor were calculated as (0.30 ± 0.06)× 105, (0.35 ± 0.03)× 105, (0.46 ± 0.05)× 105, (1.05 ± 0.14)× 105, and (1.66 ± 0.17)× 105 M-1 by injection amount-dependent method. Meanwhile, hydrogen bonds were identified as the main driving force for the five compounds to bind with CysLT1R by molecular docking. Based on these results, we believe that the immobilized receptor chromatography preserves historic significance in revealing the functional material basis of the complex matrices.

Recent findings regarding the synergistic effects of emodin and its analogs with other bioactive compounds: Insights into new mechanisms.

CONTEXT: Emodin is a natural bioactive ingredient mainly extracted from traditional Chinese herbs. Increasing lines of evidence suggest that emodin and its analogs exert notable synergistic pharmacological effects with other bioactive compounds. OBJECTIVE: This review provides an overview of the pharmacological activity of emodin and its analogs in combination with other physiologically active substances, describes the related molecular mechanisms, and discusses future prospects in this field. METHODS: Information from multiple scientific databases, such as PubMed, the China Knowledge Resource Integrated Database from the China National Knowledge Infrastructure (CNKI), the Web of Science, Google Scholar, and Baidu Scholar, was collected between January 2006 and August 2022. The subject terms used in the literature search were emodin, pharmaceutical activities, analogs, aloe emodin, rhein, and synergistic effects. RESULTS: The comprehensive literature analysis suggested that combinations of emodin or its analogs with other bioactive compounds exert notable synergistic anticancer, anti-inflammatory, and antimicrobial effects and that such combinations improve glucose and lipid metabolism and central nervous system diseases. DISCUSSION AND CONCLUSIONS: Further assessments of the dose-effect relationship and the differences in the efficacy of emodin or its analogs with other bioactive compounds among various modes of administration are needed, and a drug safety evaluation of these combinations needs to be carefully performed. Future studies should also focus on determining the optimal drug combinations for specific diseases.

Design, synthesis, cytotoxic, and anti-inflammatory activities of some novel analogues of aloe-emodin isolated from the rhizomes of Rheum emodi.

In connection with our continuous efforts in the synthesis of derivatives from major compounds isolated from traditional medicinal plants, in the present study we have attempted to synthesize the furan-conjugated aloe-emodin derivatives (5a-j) using a three-component reaction. The synthesized derivatives were assessed for anticancer activity against five different cancer cell lines using the in vitro MTT assay and the results showed that most of the derivatives are potent against cancer cells comparing with the control. Compounds 5a and 5e showed excellent activity against all the cancer cells with less than 12.5 µM and arrested the cell cycle at the G0/G1 phase in both CAL27 and SCC9 cells. Compound 5e induces the early apoptosis in CAL27 cells and compounds 5a and 5e induce early and late apoptosis, respectively, in SCC9 cells. Moreover, compounds 5b, 5c, 5i, and 5j showed excellent anti-inflammatory activity in LPS-stimulated RAW 264.7 cells by inhibiting IL-6 production. The molecular docking studies revealed that compound 5e has strong interaction with the CLK kinase and protein kinase II through hydrogen binding Asp325 and Lys290.

The isomers, aloe-emodin and emodin, possess differential inhibitory activities against CYP1B1 enzyme.

Aloe-emodin, known as a 3-hydroxymethyl-chrysazin, is one of anthraquinones mainly found in Rheum officinale Baill, Rheum palmatum L and Rheum tanguticum Maxim. Ex BALF. In recent studies, aloe-emodin possesses many pharmacological effects, including antitumor, antibacterial, antiviral, anti-inflammatory, cardiovascular protection, liver protection, immune regulation, estrogenic activity as a phytoestrogen, and so on. Cytochrome P450 (CYP) 1B1 (CYP1B1), as a major estrogen metabolizing enzyme, can metabolize 17ß-estradiol (E2) to 4-hydroxy-E2 (4-OH-E2), which cause DNA damage and lead to tumor. Few studies have found that anthraquinones possess inhibitory activity against CYP1B1 enzyme. In this study, compared with emodin (3-Hydroxy-6-methyl-chrysazin, C15H10O5), the inhibition of aloe-emodin (3-hydroxymethyl-chrysazin, C15H10O5) on the activity of CYP1B1 was studied. The molecular mechanism of inhibition and the structure-activity relationship were also discussed. Although isomeric, the IC50 values of aloe-emodin and emodin were 0.192 ± 0.015 nM and 0.067 ± 0.003 µM, indicating the inhibition of aloe-emodin was about 350times stronger than that of emodin. Through structure-activity relationship analyses, it revealed the difference of inhibitory activity only due to different hydroxyl positions. When the hydroxyl group is transferred from the chrysazin skeleton to the methyl group, the hydrogen bond formed by this structure with the CYP1B1 protein can change the protein conformation, which may interfere with the binding of the substrate to CYP1B1 protein active site pocket and inhibit the catalytic activity of the CYP1B1 protein. Although the hydroxyl position changed, the inhibition mechanism did not change, all of which were mixed inhibition. This study reveals an anti-tumor mechanism of the anthraquinone compound aloe-emodin.

Network pharmacology combined with molecular docking to explore the potential mechanisms for the antioxidant activity of Rheum tanguticum seeds.

BACKGROUND: Rheum tanguticum (R. tanguticum) is an edible and medicinal plant that exhibits high antioxidant activity. The purpose of the present study was to investigate the bioactive components of its seeds and the potential mechanisms of antioxidant activity to provide a foundation for further developmental work on R. tanguticum seeds as a functional food. METHODS: In this study, the antioxidant activities of R. tanguticum seeds were measured using DPPH, ABTS and FRAP assays. LC-Q-TOF/MS was used to identify the active compounds in the seeds, and Swiss Target Prediction was used to identify their potential targets. The DisGENET, DrugBank, OMIM and GeneCard databases were used to search for antioxidant-related targets. RESULTS: The component-target-pathway network was constructed and included 5 compounds and 9 target genes. The hub genes included ESR1, APP, MAPK8, HSP90AA1, AKT1, MMP2, PTGS2, TGFB1 and JUN. The antioxidant activity signaling pathways of the compounds for the treatment of diseases were the cancer signaling pathway, estrogen signaling pathway, colorectal cancer signaling pathway, MAPK signaling pathway, etc. Molecular docking revealed that the compounds in R. tanguticum seeds could inhibit potential targets (AKT1, ESR1 and PTGS2). CONCLUSION: Molecular docking studies revealed that the binding energy score between liriodenine and PTGS2 was the highest (8.16), followed by that of chrysophanol (7.10). This result supports the potential for PTGS2-targeted drug screening and design.

Comparison of Three Species of Rhubarb in Inhibiting Vascular Endothelial Injury via Regulation of PI3K/AKT/NF-κB Signaling Pathway.

Background/Aim: Rhubarb, a traditional Chinese medicine derived from three species, is commonly used in the prescriptions for promoting blood circulation and removing blood stasis based on its traditional effects of removing blood stasis and dredging the meridians. It has been reported that rhubarb can protect blood vessels by reducing inflammation and inhibiting vascular endothelial injury (VEI), but the effective components and mechanism of rhubarb inhibiting VEI are still unclear. This study aimed to compare the differences in chemical compositions of the three species of rhubarb and their inhibitory effect on VEI, so as to explain the material basis and select the dominant species to inhibit VEI, and to elucidate the mechanism of rhubarb's inhibitory effect on VEI. Methods: Plant metabolomics was used to compare the chemical components of three species of rhubarb. The efficacy of three species of rhubarb in inhibiting VEI was compared through cell experiments in vitro. At the same time, combined with network pharmacology and molecular docking, the effective components and pathways of rhubarb involved in inhibiting VEI were screened. The mechanism of rhubarb inhibiting VEI was verified by molecular biology. Results: There were significant differences in the distribution of chemical components among the three species of rhubarb. We identified 36 different chemical components in the positive ion mode and 38 different chemical components in the negative ion mode. Subsequently, the results showed significant differences in inhibiting VEI among the three species of rhubarb based on the contents of inflammatory factors (such as IL-1ß, IL-6, and TNF-α), ROS, and NO and confirmed that R. tanguticum had the best inhibitory effect on VEI in the light of the comprehensive efficacy, compared with R. palmatum and R. officinale. Three species of rhubarb alleviated the inflammatory response in LPS-induced EA.hy926 cells by reducing the contents of inflammatory cytokines IL-6, IL-1ß, and TNF-α and decreasing expressions of PI3K, AKT, NF-κB p65, and STAT3 protein in the PI3K/AKT/NF-κB pathway and the inhibition of proteins phosphorylation. In addition, three species of rhubarb could lessen the contents of ROS and NO in EA.hy926 cells induced by LPS. All results indicated that the process of inflammation-induced cellular oxidative stress, which resulted in VEI, was obviously improved by three species of rhubarb. Conclusion: R. tanguticum was more effective among three species of rhubarb, and it had been proved that gallic acid, gallic-acid-O-galloyl-glucoside, procyanidin B-2,3,3'-di-O-gallatein, and other potential components could reduce the contents of inflammatory factors (such as IL-1ß, IL-6, and TNF-α), ROS, and NO by inhibiting the PI3K/AKT/NF-κB signaling pathway and protected the vascular endothelium and the blood vessels by improving the inflammation and oxidative stress reaction.

A high-value-added application of the stems of Rheum palmatum L. as a healthy food: the nutritional value, chemical composition, and anti-inflammatory and antioxidant activities.

Rhubarb has edible stems or stalks. In this paper, we investigated the nutritional value, chemical composition, and bioactivities of Rheum palmatum stems (SRP) and analyzed the mode of action. SRP exhibited biosafety and had nutritional value, with abundant essential amino acids and minerals. Based on network pharmacology and western blot tests, we found that it showed anti-inflammatory activity via the PI3K-Akt-mediated NF-κB pathway. Out of 20 compounds identified using UPLC-ESI-Q-TOF/MS analysis, cirsiliol and hydrangenol were active compounds and they inhibited NO production in RAW264.7 cells induced by LPS. The alleviation of an inflammatory response is combined with a decrease in oxidative stress, and SRP showed antioxidant activity via attenuating antioxidant enzymes, scavenging free radicals, improving the mitochondrial membrane potential, and decreasing the reactive oxygen species level. These results indicated that SRP, with abundant flavonoids and a good nutritional composition, could be used as a dietary supplement for food applications.

Herbal Medicines for Constipation and Phytochemical Comparison of Active Components.

Constipation is a very common medical condition worldwide, negatively affecting patients' quality of life and healthcare system. Rhubarb, senna leaf, and aloe are three frequently used herbal medications for achieving regular bowel movement. Rhubarb is also a key ingredient in MaZiRenWan, a Chinese medicine formula used every so often for constipation in oriental countries. We reviewed and summarized the major chemical components from these three botanicals, including dianthrones, anthraquinone glycosides, free anthraquinones, and other polyphenols. The purgative actions of these constituents have been compared. Anthraquinone, especially its dianthrone compounds such as sennoside A and sennoside B, as natural stimulant laxatives, possesses significant effects to promote gastrointestinal motility and relieve functional constipation. Furthermore, the safety, reported side effects, and other benefits of anthraquinone compounds are presented. To date, many anti-constipation natural products are being used but their research is relatively limited, and thus, more investigations in this field are indeed needed.

Molecular docking studies of phytocompounds of Rheum emodi Wall with proteins responsible for antibiotic resistance in bacterial and fungal pathogens: in silico approach to enhance the bio-availability of antibiotics.

Rheum emodi Wall. (Himalayan rhubarb) has many pharmacological activities such as antioxidant, antimicrobial, antiviral, anticancer and wound healing. The present study was aimed to understand if major phytocompounds of Rheum emodi could bind proteins responsible for antibiotic resistance in bacterial and fungal pathogens and enhance the potency of antibiotics. The major phytocompounds of R. emodi (emodin, rhein-13c6 and chrysophenol dimethy ether) were retrieved from the Pubchem and target proteins were retrieved from RCSB protein data bank. The docking study was performed by using AutoDock vina software and Molinspiration, swiss ADME servers were used for the determination of Lipinski rule of 5, drug-likeness prediction respectively, whereas, admetSAR and Protox-II tools were used for toxicity prediction. To study the docking accuracy of protein-ligand complexes, MD simulation for 100 ns was done by using Desmond program version 2.0 (Academic version). Among all the selected phytocompounds, emodin showed the best binding affinity against bacterial (Penicillin binding protein 3, 3VSL and fungal target (cytochrome P450 14 alpha-sterol demethylase 1EA1) with binding energy -8.2 and -8.0 Kcal mol-1 respectively. Similarly, rhein-13C6 showed the best binding affinity against fungal target (n-myristoyl transferase 1IYL) with binding energy -8.0 Kcal mol-1 which is higher than antibacterial and antifungal antibiotics. All the selected phytocompounds also fulfill Lipinski rule, non-carcinogenic and non-cytotoxic in nature. These compounds also showed high LD50 value showing non-toxicity of these phytocompounds. MD simulation studies of phytocompounds (emodin and rhein-13C6) define the stability of protein-ligand complexes with in 100 ns time scale.Communicated by Freddie R. Salsbury.

A systematic comparison of the effect of topically applied anthraquinone aglycones to relieve psoriasiform lesion: The evaluation of percutaneous absorption and anti-inflammatory potency.

The anthraquinones derived from rhubarb are reported to have anti-inflammatory activity. The present study aimed to assess the topical application of rhubarb anthraquinone aglycones for psoriasis treatment. The antipsoriatic effect of five anthraquinones, including aloe-emodin, rhein, emodin, physcion, and chrysophanol, was compared to elucidate a structure-permeation relationship. Molecular modeling was employed to determine the physicochemical properties. Both macrophages (differentiated THP-1) and keratinocytes (HaCaT) were used to examine the anti-inflammatory activity in the cell-based study. The in vitro pig skin absorption showed that chrysophanol was the compound with the highest cutaneous accumulation. Topically applied rhein was detected to be largely delivered to the receptor compartment. The absorption of rhein was increased by 5-fold in the barrier-deficient skin as compared to intact skin. By stimulating macrophages with imiquimod (IMQ) to model the inflammation in psoriasis, it was found that the anthraquinones significantly reduced IL-6, IL-23, and TNF. The cytokine inhibition level was comparable for the five compounds. The anthraquinones suppressed cytokines by inhibiting the activation of MAPK and NF-κB signaling. The anthraquinones also downregulated IL-6, IL-8, and IL-24 in the inflammatory keratinocytes stimulated with TNF. Rhein and chrysophanol were comparable to curtail the STAT3 phosphorylation in keratinocytes induced by the conditioned medium of stimulated macrophages. The IMQ-induced psoriasiform mouse model demonstrated the improvement of scaling, erythema, and epidermal hyperplasia by topically applied rhein or chrysophanol. The epidermal acanthosis evoked by IMQ was reduced with rhein and chrysophanol by 3-fold. The histological profiles exhibit that both anthraquinone compounds diminished the number of macrophages and neutrophils in the lesional skin, skin-draining lymph node, and spleen. Rhein and chrysophanol showed multifunctional inhibition, by regulating several targets for alleviating psoriasiform inflammation.

Emodin ameliorates antioxidant capacity and exerts neuroprotective effect via PKM2-mediated Nrf2 transactivation.

Pyruvate kinase M2 (PKM2) is overexpressed in neuronal cells. However, there are few studies on the involvement of PKM2 modulators in neurodegenerative diseases. Emodin, a dominating anthraquinone derivative extracting from the rhizome of rhubarb, has received expanding consideration due to its pharmacological properties. Our data reveal that emodin could resist hydrogen peroxide- or 6-hydroxydopamine-mediated mitochondrial fission and apoptosis in PC12 cells (a neuron-like rat pheochromocytoma cell line). Notably, emodin at nontoxic concentrations significantly inhibits PKM2 activity and promotes dissociation of tetrameric PKM2 into dimers in cells. The PKM2 dimerization enhances the interaction of PKM2 and NFE2-related factor 2 (Nrf2), which further triggers the activation of the Nrf2/ARE pathway to upregulate a panel of cytoprotective genes. Modulating the PKM2/Nrf2/ARE axis by emodin unveils a novel mechanism for understanding the pharmacological functions of emodin. Our findings indicate that emodin is a potential candidate for the treatment of oxidative stress-related neurodegenerative disorders.

The Health Benefits of Emodin, a Natural Anthraquinone Derived from Rhubarb-A Summary Update.

Emodin (6-methyl-1,3,8-trihydroxyanthraquinone) is a naturally occurring anthraquinone derivative found in roots and leaves of various plants, fungi and lichens. For a long time it has been used in traditional Chinese medicine as an active ingredient in herbs. Among other sources, it is isolated from the rhubarb Rheum palmatum or tuber fleece-flower Polygonam multiflorum. Emodin has a wide range of biological activities, including diuretic, antibacterial, antiulcer, anti-inflammatory, anticancer and antinociceptive. According to the most recent studies, emodin acts as an antimalarial and antiallergic agent, and can also reverse resistance to chemotherapy. In the present work the potential therapeutic role of emodin in treatment of inflammatory diseases, cancers and microbial infections is analysed.

Rhubarb granule promotes diethylnitrosamine-induced liver tumorigenesis by activating the oxidative branch of pentose phosphate pathway via G6PD in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Rhubarb is a natural herbal medicine widely used clinically with numerous pharmacological activities including anti-cancer. Specifically, several studies reported that free anthraquinones from Rhubarb suppressed the proliferation of hepatoma cells. Nonetheless, recent studies revealed that Rhubarb caused hepatotoxicity in vivo, confirming its "two-way" effect on the liver. Therefore, the efficacy and safety of Rhubarb in the in vivo treatment of liver cancer should be further elucidated. AIM OF THE STUDY: This study investigated the presence of hepatoprotection or hepatotoxicity of Rhubarb in diethylnitrosamine (DEN)-induced hepatocarcinogenesis. MATERIAL AND METHODS: A total of 112 male Sprague-Dawley rats weighing 190-250 g were enrolled. The rats were induced hepatocarcinogenesis using diethylnitrosamine (0.002 g/rat) until 17 weeks. Starting at week 11, Rhubarb granules (4 g/kg and 8 g/kg) were intragastrically administered daily for 7 weeks. All rats were euthanized at week 20 and the livers were analyzed via non-targeted metabolomics analysis. We established hepatic glucose 6 phosphate (6PG) levels and glucose 6 phosphate dehydrogenase (G6PD) activities to assess the pentose phosphate pathway (PPP). And the liver injuries of rats were analyzed via histological changes, hepatic function, as well as hepatic protein levels of alpha-fetoprotein (AFP), pyruvate kinase isozyme type M2 (PKM2), and proliferating cell nuclear antigen (PCNA). Furthermore, polydatin (0.1 g/kg/d) as a specific inhibitor of G6PD was used to treat rats. Notably, their histological changes, hepatic function, hepatic 6PG levels, hepatic G6PD activities, PCNA levels, and PKM2 levels were recorded. RESULTS: Non-targeted metabolomics revealed that Rhubarb regulated the PPP in the liver of Rhubarb-DEN-treated rats. Besides, Rhubarb activated the oxidative branch of the PPP by activating G6PD (a rate-limiting enzyme in the oxidative PPP) in the liver of Rhubarb-DEN-treated rats. Meanwhile, Rhubarb promoted DEN-induced hepatocarcinogenesis. Moreover, polydatin attenuated the promoting effect of Rhubarb on DEN-induced hepatocarcinogenesis. CONCLUSIONS: Rhubarb promoted DEN-induced hepatocarcinogenesis by activating the PPP, indicating that the efficacy and safety of Rhubarb in the treatment of liver cancer deserve to be deliberated.

Antioxidant Activity in Rheum emodi Wall (Himalayan Rhubarb).

Using natural products as antioxidant agents has been beneficial to replace synthetic products. Efforts have been made to profile the antioxidant capacities of natural resources, such as medicinal plants. The polyphenol content of Himalayan rhubarb, Rheum emodi wall, was measured and the antioxidant activity was determined using DPPH and ABTS+ assay, and the oxidative stress was assessed using SOD enzymatic assay. Five different solvent fractions, n-hexane, n-butanol, ethyl acetate, dichloromethane, and water, were used for screening the antioxidant capacity in effort to determine the optimum extraction solvent. The total phenolic contents for R. emodi fractions ranged from 27.76 to 209.21 mg of gallic acid equivalents (GAE)/g of dry weight. DPPH and ABTS+ assay results are presented into IC50 values, ranged from 21.52 to 2448.79 µg/mL and 90.25 to 1718.05 µg/mL, respectively. The ethyl acetate fraction had the highest antioxidant activity among other fractions. Also, n-butanol and water fractions showed significantly lower IC50 values than the positive control in DPPH radical scavenging activity. The IC50 values of SOD assay of fractions ranged from 2.31 to 64.78 µg/mL. A similar result was observed with ethyl acetate fraction showing the highest SOD radical scavenging activity. The study suggests that the ethyl acetate fraction of R. emodi possess the strongest antioxidant activity, thus the most efficient in extracting antioxidant contents. Moreover, a highly significant correlation was shown between total polyphenol content and antioxidant activity screening assays. The compounds related to the antioxidant activity of R. emodi were identified to myricitrin, myricetin 3-galloyl rhamnoside, and myricetin, which have not been reported in studies about R. emodi before.

Comparison of the Phytochemical Properties, Antioxidant Activity and Cytotoxic Effect on HepG2 Cells in Mongolian and Taiwanese Rhubarb Species.

The Mongolian rhubarb-Rheum undulatum L. (RU)-and Rumex crispus L. (RC)-a Taiwanese local rhubarb belonging to the family of Polygonaceae-are principal therapeutic materials in integrative medicine due to their rich quantities of bioactive compounds; however, their phytochemical and antioxidant properties, and anti-cancer activity is poorly investigated. Furthermore, the phytochemical characteristics of both species may be affected by their different geographical distribution and climatic variance. The current study aimed to compare RU with RC extracts in different polarity solvents (n-hexane, ethyl acetate, acetone, ethanol, and water) for their phytochemical contents including the total phenolic content (TPC), total anthraquinone content (TAC), total flavonoid content (TFC), antioxidant and free radical scavenging capacities, and anticancer ability on the HepG2 cell. Except for the n-hexane extract, all of the RU extracts had considerably higher TPCs than RC extracts, ranging from 8.39 to 11.16 mg gallic acid equivalent (GAE) per gram of dry weight, and the TPCs of each extract were also significantly correlated with their antioxidant capacities by ABTS, DPPH, and FRAP assays (p < 0.05). Moreover, there was no remarkable association between the antioxidant capacities and either TACs or TFCs in both the RU and RC extracts. Besides, high-performance liquid chromatography (HPLC) analysis revealed that both the RU and RC extracts contained chrysophanol, emodin, and physcion, and those bioactive compounds were relatively higher in the n-hexane solvent extracts. Additionally, we observed different levels of dose-dependent cytotoxic effects in all the extracts by cell viability assay. Notably, the ethanol extract of RU had a compelling cytotoxic effect with the lowest half-maximum inhibition concentration (IC50-171.94 ± 6.56 µg/mL at 48 h) among the RU extracts than the ethanol extract of RC. Interestingly, the ethanol extract of RU but not RC significantly induced apoptosis in the human liver cancer cell line, HepG2, with a distinct pattern in caspase-3 activation, resulting in increased PARP cleavage and DNA damage. In summary, Mongolian Rhubarb, RU, showed more phytochemical contents, as well as a higher antioxidant capacity and apoptotic effect to HepG2 than RC; thus, it can be exploited for the proper source of natural antioxidants and liver cancer treatment in further investigation.

Emodin Suppresses the Migration and Invasion of Melanoma Cells.

Emodin (1,3,8-trihydroxy-6-methylanthraquinone), as an active ingredient in rhubarb roots and rhizomes, has been reported to possess various pharmacological properties including anti-tumor effects. Recent studies have confirmed that emodin inhibited cell proliferation and induced apoptosis of cancer cells. However, the inhibitory effect of emodin on the migration and invasion of melanoma cells and its underlying mechanism are still unclear. In the study, we observed the impercipient effects of emodin in B16F10 and A375 melanoma cells with strong metastatic abilities, focusing on the functions and mechanisms of migration and invasion of B16F10 and A375 melanoma cells. Cell counting kit-8 (CCK-8), colony formation test and Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) staining tests confirmed that emodin possessed anti-proliferative and pro-apoptotic activities in B16F10 and A375 cells. The inhibitory effects on the migration and invasion of B16F10 and A375 cells were proved by wound healing assay and Transwell methods. Moreover, immunofluorescence assay approved the decrease in protein expression of matrix metalloproteinas (MMP)-2/-9 by emodin, and Western blot analyses revealed that emodin could increase the Bax/Bcl-2 ratio and inhibit the MMP-2/-9 protein expression and Wnt/ß-catenin pathway in a dose-depended manner. BML-284, as an agonist of Wnt/ß-catenin signaling pathway, reversed the effects of emodin on cell growth, migration and invasion in B16F10 cells. These findings may suggest that emodin treatment can be a promising therapeutic strategy for melanoma with highly metastatic abilities.

Assessment of the anti-inflammatory effects of three rhubarb anthraquinones in LPS-Stimulated RAW264.7 macrophages using a pharmacodynamic model and evaluation of the structure-activity relationships.

ETHNOPHARMACOLOGICAL RELEVANCE: Rhubarb (Rhei Radix et Rhizoma) is a traditional Chinese medicine, has been used as a strong astringent in China to treat inflammation-related diseases, such as acute pancreatitis, acute cholecystitis, appendicitis and so on. Rhein, emodin and aloe-emodin are the important active anthraquinone in rhubarb, and are considered to be the main ingredients contributing to anti-inflammatory. AIM OF THE STUDY: Rhein, emodin and aloe-emodin, anthraquinones with the same parent structure that are found in rhubarb, have beneficial anti-inflammatory effects in vitro and in vivo. Anthraquinone derivatives also have important clinical roles. However, their pharmacodynamic differences and the structure-activity relationships associated with their anti-inflammatory properties have not been systematically explored. The present study was designed to quantify the effects of three rhubarb anthraquinones on inflammation and to explore the structure-activity relationships of these compounds. MATERIALS AND METHODS: In this study, we detected NF-κB phosphorylation, iNOS protein expression, and IL-6 and NO production in LPS-stimulated RAW264.7 cells and then calculated median effect equations and built a dynamic pharmacodynamic model to quantitatively evaluate the efficacy of these three anthraquinones. Additionally, to determine the structure-activity relationships, we investigated the physicochemical properties and molecular electrostatic potentials of the drug molecules. RESULTS: We found that rhein, emodin, and aloe-emodin exerted at least dual-target (NF-κB, iNOS) inhibition of LPS-induced inflammatory responses. Compared with rhein and emodin, aloe-emodin had a stronger anti-inflammatory effect, and its inhibition of iNOS protein expression was approximately twice that of NF-κB phosphorylation. In addition, aloe-emodin had the strongest hydrophobic effect among the three anthraquinones. CONCLUSIONS: Overall, we concluded that the receptor binding the rhubarb anthraquinones had a hydrophobic pocket. Anthraquinone molecules with stronger hydrophobic effects had higher affinity for the receptor, resulting in greater anti-inflammatory activity. These results suggest that the addition of a hydrophobic group is a potential method for structural modification to design anti-inflammatory anthraquinone derivatives with enhanced potency.

The isolation of secondary metabolites from Rheum ribes L. and the synthesis of new semi-synthetic anthraquinones: Isolation, synthesis and biological activity.

Rheum ribes L. (Rhubarb) is one of the most important edible medicinal plants in the Eastern Anatolia region and is called "Iskin" by local people. Resveratrol and 6-O-methylalaternin were isolated from the Rhubarb for the first time in addition to well-known secondary metabolites including emodin, aloe-emodin, ß-sitosterol and rutin. The new semi-synthetic anthraquinone derivatives with the NαFmoc-l-Lys and ethynyl group were synthesized from the isolated anthraquinones emodin and aloe-emodin of Rhubarb to increase the bioactivities. Aloe-emodin derivative with NαFmoc-l-Lys shows the highest inhibition values by 94.11 ± 0.12 and 82.38 ± 0.00% against HT-29 and HeLa cell lines, respectively, at 25 µg/mL. Further, modification of the aloe-emodin with both the ethynyl and the NαFmoc-l-Lys groups showed an antioxidant activity-enhancing effect. From molecular docking studies, the relative binding energies of the emodin and aloe-emodin derivatives to human serum albumin ranged from -7.30 and -10.62 kcal/mol.

Rheum rhaponticum Root Extract Improves Vasomotor Menopausal Symptoms and Estrogen-Regulated Targets in Ovariectomized Rat Model.

Ovarian insufficiency and ovariectomy are characterized by deregulated heat loss mechanisms. Unlike hormone therapy, ERr 731 (a standardized botanical extract of Siberian rhubarb Rheum rhaponticum L. high in rhaponticin) acts like a selective estrogen receptor modulator for ERß receptors and may offer a higher degree of safety while maintaining the desired efficacy profile. In this study, we examined the relationship between oral administration of ERr 731 and the underlying components of skin vasomotion responses in an ovariectomized (OVX) rat model. ERr 731 dose-dependently reduced tail skin temperature (Tskin) values by an average of 1 °C. The rapid onset of this effect was observed in 1 and 3 mg/kg/day ERr 731 groups as early as day 2 of administration, and remained in place for the duration of the treatment (2 weeks). Substituting ERr 731 after E2 withdrawal helped maintain body temperature similarly to E2 alone, suggesting the usefulness of ERr 731 for replacing existing hormonal therapy in humans. ERr 731 also acted as a highly selective agonist for ERß in the hypothalamus of OVX rats, as well as in ERα/ß cell-based reporter assays. These data validate the OVX/Tskin rat model as a suitable screening platform to evaluate botanical and pharmaceutical treatments of menopause, while providing further evidence for the efficacy of ERr 731 towards alleviating vasomotor menopausal symptoms and improving wellbeing during the menopausal transition.