BACKGROUND: Rheum palmatum (RP) is a widely used traditional herb, which possesses antioxidant properties, inhibits ROS production and reduces fever.
OBJECTIVE: The aim of this study was to examine the antioxidative properties of the water extract of RP on oxidative-stressed mice.
METHODS: Forty mice were administered with DL-homocysteine (DL-Hcy) to induce oxidative stress and were divided into four groups: 1) CK: NaCl and water; 2) DL-Hcy: DL-Hcy and water; 3) DL-Hcy+50RP: DL-Hcy with 50 mg kg-1 body weight (BW) d-1 RP; and 4) DL-Hcy+150RP: DL-Hcy with 150 mg kg-1 BW d-1 RP. Rhein (0.3 mg g-1 dry matter) was the main active ingredient in RP.
RESULTS: When compared with Dl-Hcy mice, the mice with supplementary RP mitigated oxidative stress by reducing the liver concentrations of superoxide dismutase (SOD) by 27% and glutathione peroxidase (GSH-Px) by 32%, and the reactive oxygen species (ROS) in the kidney and spleen. These responses were more pronounced in DL-Hcy+150RP than DL-Hcy+50RP mice. RP also exhibited therapeutic effects on liver steatosis, chronic kidney nephritis and intestinal villus width shortening caused by oxidative stress, and concomitantly decreased the serum glucose concentration (RP vs. DL-HCY, 2.3 vs. 4.1 mmol L-1).
CONCLUSIONS: It was concluded that RP possesses antioxidant and therapeutic properties that can mitigate lesions on organs and prevent diabetes in oxidative-stressed mice. This study highlights the potential of RP as a medicinal supplement for animals in the future.

BACKGROUND: Rheum palmatum L. has important medicinal value because it contains biologically active anthraquinones. However, the key genes and TFs involved in anthraquinone biosynthesis and regulation in R. palmatum remain unclear.
METHODS: Based on full length transcriptome data, in this study, we screened the differentially expressed genes in the anthraquinone biosynthesis pathway. The R2R3-MYB family genes of R. palmatum were systematically identified based on full-length transcriptome sequencing followed by bioinformatics analyses. The correlation analysis was carried out by using co-expression analysis, protein interaction analysis, and real-time fluorescence quantitative analysis after MeJA treatment. The RpMYB81 and RpMYB98 genes were amplified by RT-PCR, and their subcellular localization and self-activation characteristics were analyzed.
RESULTS: Comparative transcriptome analysis results revealed a total of 3525 upregulated and 6043 downregulated DEGs in the CK versus MeJA group; 28 DEGs were involved in the anthraquinone pathway. Eleven CHS genes that belonged to the PKS family were differentially expressed and involved in anthraquinone biosynthesis. Twelve differentially expressed MYBs genes were found to be co-expressed and interact with CHS genes. Furthermore, 52 MYB genes were identified as positive regulators of anthraquinone biosynthesis and were further characterized. Three MYB genes including RpMYB81, RpMYB98, and RpMYB100 responded to MeJA treatment in R. palmatum, and the levels of these genes were verified by qRT-PCR. RpMYB81 was related to anthraquinone biosynthesis. RpMYB98 had an interaction with genes in the anthraquinone biosynthesis pathway. RpMYB81 and RpMYB98 were mainly localized in the nucleus. RpMYB81 had self-activation activity, while RpMYB98 had no self-activation activity.
CONCLUSIONS: RpMYB81, RpMYB98, and RpMYB100 were significantly induced by MeJA treatment. RpMYB81 and RpMYB98 are located in the nucleus, and RpMYB81 has transcriptional activity, suggesting that it might be involved in the transcriptional regulation of anthraquinone biosynthesis in R. palmatum.

BACKGROUND: Pancreatic lipase is one of the most important key targets in the treatment of obesity. Inhibition of pancreatic lipase can effectively reduce lipid absorption and treat obesity and other related metabolic disorders.
OBJECTIVE: The goal of this study is the efficient screening of pancreatic lipase inhibitors in the root and rhizome of Rheum palmatum using affinity ultrafiltration-high-performance liquid chromatography (AUF-HPLC) combined with high-resolution inhibition profiling (HRIP).
METHODS: Potential pancreatic lipase ligands and pancreatic lipase inhibitors in ethyl acetate fraction of R. palmatum were screened using AUF-HPLC and HRIP, respectively. All screened compounds were identified by HPLC- quadrupole time-of-flight (Q-TOF)/MS. Eight compounds were screened out by both AUF-HPLC and HRIP, and six compounds were screened out by either AUF-HPLC or HRIP alone. The pancreatic lipase inhibitory activities of all screened compounds were verified by enzyme inhibition assay and molecular docking.
RESULTS: Five new potent pancreatic lipase inhibitors were discovered, namely procyanidin B5 3,3\'-di-O-gallate (IC50 = 0.06 ± 0.01 μM), 1,6-di-O-galloyl-2-O-cinnamoyl-β-D-glucoside (IC50 = 12.83 ± 0.67 μM), 1-O-(1,3,5-trihydroxy)phenyl-2-O-galloyl-6-O-cinnamoyl-β-D-glucoside (IC50 = 17.84 ± 1.33 μM), 1,2-di-O-galloyl-6-O-cinnamoyl-β-D-glucoside (IC50 = 18.39 ± 1.52 μM), and 4-(4\'-hydroxyphenyl)-2-butanone-4\'-O-β-D-(2\"-O-galloyl-6\"-O-cinnamoyl)-glucoside (IC50 = 2.91 ± 0.40 μM). It was found that procyanidin B5 3,3\'-di-O-gallate showed higher pancreatic lipase inhibitory activity than the positive control orlistat (IC50 = 0.12 ± 0.02 μM).
CONCLUSIONS: The combination of affinity ultrafiltration-high-performance liquid chromatography (AUF-HPLC) and high-resolution inhibition profiling (HRIP) could reduce the risk of false-negative screening and missed screening and could achieve more efficient screening of bioactive compounds in complex natural products.

Tyrosinase (TYR) plays a key role in the enzymatic reaction that is responsible for a range of unwanted discoloration effects, such as food browning and skin hyperpigmentation. TYR inhibitors could, therefore, be candidates for skin care products that aim to repair pigmentation problems. In this study, we used a metabolomics approach combined with the isobologram analysis to identify anti-TYR compounds within natural resources, and evaluate their possible synergism with each other. Rheum palmatum was determined to be a model plant for observing the effect, of which seven extracts with diverse phytochemicals were prepared by way of pressurized solvent extraction. Each Rheum palmatum extract (RPE) was profiled using nuclear magnetic resonance spectroscopy and its activity of tyrosinase inhibition was evaluated. According to the orthogonal partial least square analysis used to correlate phytochemicals in RPE with the corresponding activity, the goodness of fit of the model (R2 = 0.838) and its predictive ability (Q2 = 0.711) were high. Gallic acid and catechin were identified as the active compounds most relevant to the anti-TYR effect of RPE. Subsequently, the activity of gallic acid and catechin were evaluated individually, and when combined in various ratios by using isobologram analysis. The results showed that gallic acid and catechin in the molar ratios of 9:5 and 9:1 exhibited a synergistic inhibition on TYR, with a combination index lower than 0.77, suggesting that certain combinations of these compounds may prove effective for use in cosmetic, pharmaceutical, and food industries.

Rheum palmatum, a well-known Traditional Chinese Medicines (TCM), has been used for medical purposes for thousand years in China. However, endophyte diversity of R. palmatum among different tissues and ages is still not revealed. In this study, we used 16S and ITS amplicon sequencing and combined with PICRUSt and FUNGuild to compare endophyte diversity and ecological function among different tissues and ages of R. palmatum. The results showed that the diversity and OTUs (Operational taxonomic units) abundance of endophytic fungi and bacteria of R. palmatum differed among different tissues and ages. The predictive function analysis showed that metabolism was main function of endophytic bacteria in different tissue and year samples, while saprotroph was dominant trophic mode of endophytic fungi in different year samples. The dominant trophic modes of endophytic fungi were saprotroph, pathotroph-symbiotroph and symbiotroph, and relative abundances differed in the different tissue samples. Our results elucidated the comprehensive diversity and composition profiles of endophytes in different tissues and year of R. palmatum. Our data offered pivotal information to clarify the role of endophytes in the production of R. palmatum and its important metabolites.

Trichoderma spp. are an important plant-growth-promoting fungi. Trichoderma citrinoviride HT-1 was isolated from Rheum palmatum root, which has beneficial effects on growth and metabolite accumulation. However, the improvement mechanisms for growth and metabolite accumulation of T. citrinoviride HT-1 are unclear. In this study, RNA sequencing (RNA-seq) and high-performance liquid chromatography (HPLC) were used to measure the effect of different concentrations of conidial suspension of the HT-1 strain on the growth promotion and metabolite accumulation of R. palmatum seedlings. The results showed that the highest biomass and metabolites of R. palmatum seedlings were obtained through treatment with the HT-1 strain at a final spore concentration of 107 spores/mL. RNA sequencing indicated that 1662 genes were upregulated and 2155 genes were downregulated after inoculation with 107 spores/mL of the HT-1 strain. This strain induced significant upregulation of related genes in the phenylpropanoid biosynthesis pathway, plant hormone signal transduction pathway, biosynthesis of secondary metabolites pathway, and plant-pathogen interaction pathway in R. palmatum. The gene expression trends were revealed through quantitative real-time polymerase chain reaction (qRT-PCR) and were consistent with those determined by RNA-seq. Our results will help us to understand the growth-promoting mechanisms of the HT-1 strain on R. palmatum and provide a theoretical basis for the application of T. citrinoviride HT-1 as a biological fertilizer.

UNASSIGNED: Rheum palmatum is an endangered and important medicinal plant in Asian countries, especially in China. However, there is little knowledge about the codon usage bias for R. palmatum CDSs. In this project, codon usage bias was determined based on the R. palmatum 2,626 predicted CDSs from R. palmatum transcriptome.
UNASSIGNED: In this study, all codon usage bias parameters and nucleotide compositions were calculated by Python script, Codon W, DNA Star, CUSP of EMBOSS.
UNASSIGNED: The average GC and GC3 content are 46.57% and 46.6%, respectively, the results suggested that there exists a little more AT than GC in the R. palmatum genes, and the codon bias of R. palmatum genes preferred to end with A/T. We concluded that the codon bias in R. palmatum was affect by nucleotide composition, mutation pressure, natural selection, gene expression levels, and the mutation pressure is the prominent factor. In addition, we figured out 28 optimal codons and most of them ended with A or U. The project here can offer important information for further studies on enhancing the gene expression using codon optimization in heterogeneous expression system, predicting the genetic and evolutionary mechanisms in R. palmatum.

Rheum palmatum has a long history in medicine, which is one of the main export medicinal herb in China. The complete chloroplast genome of R. palmatum was assembled and reported in this study. The R. palmatum chloroplast genome was 161,541 bp in length as the circular and consisted a large single-copy (LSC) region of 86,519 bp, a small single-copy (SSC) region of 13,112 bp and a pair of inverted-repeat (IR) regions of 30,955 bp. The nucleotide composition was asymmetric 31.2% A (Adenine), 31.5% T (Thymine), 19.0% C (Cytosine), and 18.3% G (Guanine) with an overall G + C content of 37.3%. It encoded 131 genes, including 86 protein-coding genes (76 PCG species), 37 transfer RNA genes (26 tRNAs species), and eight ribosomal RNA genes (four rRNAs species). The Phylogenetic relationships used neighbour-joining (NJ) method and the result showed that R. palmatum and Rheum officinale are phylogenetically related to each other in the family Polygonaceae. This study will be very important for Chinese medicinal herb research value and clinical drug development for future in China.

The pharmacological activities of medicinal plants are reported to be due to a wide range of metabolites, therein, the concentrations of which are greatly affected by many genetic and/or environmental factors. In this context, a metabolomics approach has been applied to reveal these relationships. The investigation of such complex networks that involve the correlation between multiple biotic and abiotic factors and the metabolome, requires the input of information acquired by more than one analytical platform. Thus, development of new metabolomics techniques or hyphenations is continuously needed.
Feasibility of high performance thin-layer chromatography (HPTLC) were investigated as a supplementary tool for medicinal plants metabolomics supporting 1H nuclear magnetic resonance (1H NMR) spectroscopy.
The overall metabolic difference of plant material collected from two species (Rheum palmatum and Rheum tanguticum) in different geographical locations and altitudes were analyzed by 1H NMR- and HPTLC-based metabolic profiling. Both NMR and HPTLC data were submitted to multivariate data analysis including principal component analysis and orthogonal partial least square analysis.
The NMR and HPTLC profiles showed that while chemical variations of rhubarb are in some degree affected by all the factors tested in this study, the most influential factor was altitude of growth. The metabolites responsible for altitude differentiation were chrysophanol, emodin and sennoside A, whereas aloe emodin, catechin, and rhein were the key species-specific markers.
These results demonstrated the potential of HTPLC as a supporting tool for metabolomics due to its high profiling capacity of targeted metabolic groups and preparative capability.

BACKGROUND: Hepatocellular carcinoma (HCC) is among the most common malignancies. Signal transducer and activator of transcription 3 (STAT3), with abnormal expression and constitutive activation, has been reported to promote proliferation, metastasis, survival and angiogenesis of HCC cells. Rheum palmatum (RP), a traditional Chinese medicinal herb, exhibited tumor-suppressing effects in multiple human cancers, but its potential functions in HCC remain unexplored.
OBJECTIVE: This study aimed to examine the involvement of STAT3 signaling in the anti-HCC effects of RP extract.
METHODS: SMMC-7721 and HepG2 HCC cell lines were treated with RP extract for 24 h, and then viability, migration, and invasion of HCC cells and angiogenesis of human umbilical vein endothelial cells (HUVECs) were analyzed using MTS, wound-healing, Transwell invasion and tube formation assays, respectively. Western blotting and immunohistochemistry (IHC) were used to examine the activation of key molecules in STAT3 signaling, including STAT3, JAK2, and Src. Additionally, we explored the in vivo antitumor effects of RP extract in a xenograft tumor nude mouse model of HCC.
RESULTS: The result showed that RP extract reduced viability, migration, and invasion of SMMC-7721 and HepG2 cells and angiogenesis of HUVECs. It suppressed the phosphorylation of STAT3 and its upstream kinases including JAK2 and Src. In addition, RP extract treatment downregulated STAT3 target genes, including survivin, Bcl-xL, Mcl-1, Bcl-2, MMP-2, MMP-9, Cyclin D1, CDK4, c-Myc, and VEGF-C. Furthermore, RP extract suppressed the xenograft tumor growth and activation of STAT3 in xenograft tumor mice.
CONCLUSIONS: Collectively, the results showed that RP extract prevented HCC progression by inhibiting STAT3, and might be useful for the treatment of HCC.