Anthraquinone and stilbene derivatives from the cultivated Korean Rhubarb Rhizomes

Exploring Cassia mimosoïdes as a promising natural source of steroids with potent anti-cancer, urease inhibition, and antimicrobial properties

The genus Cassia is a rich source of physiologically active secondary metabolites, including a novel compound named 21-methylene-24-ethylidene lophenol, alongside 15 known compounds. These compounds were characterized using different spectroscopic techniques. They exhibited promising antimicrobial activity, particularly against bacteria causing gastrointestinal infections. Compound 1 showed strong anti-bacterial activity against H. pylori and S. aur with MIC values of 0.28 and 0.12 μg mL-1 respectively. The study investigated their impact on H. pylori, a contributor to ulcer development, by inhibiting the urease enzyme. Inhibiting urease can reduce H. pylori's pathogenic potential, evident from the fact that the compounds evaluated toward urease enzyme showed higher inhibitory activity (1.024 ± 0.43 6.678±0.11 μM) compared to standard thiourea (IC50 = 18.61 ± 0.11 μM). Molecular docking studies confirmed their inhibitory action, with compound 7 notably outperforming thiourea in inhibiting urease (-6.95 kcal mol-1vs. -3.13 kcal mol-1). Additionally, these compounds showed positive effects on liver functioning, which H. pylori can impair. Compound 9 shows the best response against human HepG2 liver cancer cell lines i.e., % viability is 14.47% ± 0.69 and IC50 is 7.8 μM ± 0.21. These compounds hold potential as lead compounds for addressing gastrointestinal and liver disorders caused by H. pylori.

Cardioprotective Effect of Rheum turkestanicum Against Doxorubicin-Induced Toxicity in Rats

Background: Doxorubicin as an anti-cancer drug causes cardiotoxicity, limiting its tolerability and use. The mechanism of toxicity is due to free radical production and cardiomyocytes injury. This research evaluated Rheum turkestanicum (R.turkestanicum) extract against doxorubicin cardiotoxicity due to its considerable in vitro antioxidant activity. Methods: Male Wistar rats received 2.5 mg/kg doxorubicin intraperitoneally every other day for 2 weeks to create an accumulative dose. R. turkestanicum was administrated at a dose of 100 and 300 mg/kg intraperitoneally from the second week for 7 days. On the 15th day, the animals were anesthetized and blood was collected from cardiac tissue for evaluation of alanine aminotransferase (ALT), cardiac muscle creatinine kinase (CK-MB), troponin T (cTn-T), lactate dehydrogenase (LDH), and B-type natriuretic peptide brain natriuretic peptide. A cardiac homogenate was also collected to determine superoxide dismutase (SOD), catalase Catalase Activity, malondialdehyde (MDA), and thiols. Histopathology was also performed. Results: Doxorubicin increased all cardiac enzymes and malondialdehyde, correlating with a reduction in SOD, catalase, and thiols. Histopathology revealed extracellular edema, moderate congestion, and hemorrhage of foci. In contrast, administration of R. turkestanicum ameliorated these doxorubicin-induced pathophysiological changes. Conclusion: This study revealed that the extract ameliorated doxorubicin-induced cardiac toxicity via modulation of oxidative stress-related pathways. Liquid chromatography-mass spectrometry analysis of R. turkestanicum indicated several components with potent pharmacological properties.

Matrix metalloproteinase inhibitor and sunscreen effective compounds from Rumex crispus L.: isolation, identification, bioactivity and molecular docking study

INTRODUCTION

Rumex (Polygonaceae) species are widely grown worldwide and their main compounds are anthranoids, tannins, naphthalenes and flavonoids. Matrix metalloproteinase (MMP) enzymes that cause the breakdown of the extracellular matrix and harmful ultraviolet (UV) rays are two important causes of skin ageing. Although there have been many studies on anthraquinones, there are not many studies on their anti-ageing effects.

OBJECTIVE

The aim of this study was to determine the anti-ageing effects of pure compounds isolated from Rumex crispus L. by measuring their MMP inhibitory and sunscreen activities.

METHODOLOGY

Molecular docking studies on anthranoid, flavonoid, tannin and naphthalene skeletons with MMP enzymes were applied for the first time. Various chromatographic methods were used for isolation studies. The structure elucidation was performed by spectroscopic [UV, infrared (IR), electrospray ionisation mass spectrometry (ESI-MS), nuclear magnetic resonance (NMR)] methods. To determine the anti-ageing capacity of compounds, MMP-1, MMP-8, MMP-13 enzyme inhibitory effects and sun protection factors (SPFs) were investigated for the first time.

RESULTS

Molecular docking results showed that skeletons had low binding energy to the target and were likely to inhibit MMP enzymes. Then, eight anthraquinones and a naphthalene glycoside were isolated from the underground parts of Rumex crispus L. According to the results, MMP inhibitory effects of compounds were found to be high. In vitro and molecular docking study results confirmed each other. All anthraquinones showed high sun protection and emodin showed highest UV capability with SPF of 30.59.

CONCLUSION

This study shows that anthraquinones may be evaluated as new potential MMP inhibitors, sun protective and anti-ageing agents.

Targeting severe acute respiratory syndrome-coronavirus (SARS-CoV-1) with structurally diverse inhibitors: a comprehensive review

Coronaviruses, which were discovered in 1968, can lead to some human viral disorders, like severe acute respiratory syndrome (SARS), Middle East respiratory syndrome-related (MERS), and, recently, coronavirus disease 2019 (COVID-19). The coronavirus that leads to COVID-19 is rapidly spreading all over the world and is the reason for the deaths of thousands of people. Recent research has revealed that there is about 80% sequence homology between the coronaviruses that cause SARS and COVID-19. Considering this fact, we decided to collect the maximum available information on targets, structures, and inhibitors reported so far for SARS-CoV-1 that could be useful for researchers who work on closely related COVID-19. There are vital proteases, like papain-like protease 2 (PL2pro) and 3C-like protease (3CLpro), or main protease (Mpro), that are involved in and are essential for the replication of SARS coronavirus and so are valuable targets for the treatment of patients affected by this type of virus. SARS-CoV-1 NTPase/helicase plays an important role in the release of several non-structural proteins (nsps), so it is another essential target relating to the viral life cycle. In this paper, we provide extensive information about diverse molecules with anti-SARS activity. In addition to traditional medicinal chemistry outcomes, HTS, virtual screening efforts, and structural insights for better understanding inhibitors and SARS-CoV-1 target complexes are also discussed. This study covers a wide range of anti-SARS agents, particularly SARS-CoV-1 inhibitors, and provides new insights into drug design for the deadly SARS-CoV-2 virus.

Acute and sub-acute toxicity evaluation of the root extract of Rheum turkestanicum Janisch

Despite the widespread use of Rheum turkestanicum in herbal medicine, no study has yet examined its in vivo toxicity. The aim of this study is to evaluate the acute and sub-acute toxicity of hydroalcoholic extract of R. turkestanicum root. In acute toxicity experiment, female and male mice (n = 5/group/sex) were orally administrated with the extract at single doses of 300, 2000 and 3000 mg/kg and observed for 14 days. In the sub-acute study, the extract was orally administered daily at doses of 100 and 400 mg/kg to male rats (n = 8) for 4 weeks. During the acute toxicity test, there were no deaths or any signs of toxicity observed after administration of the R. turkestanicum extract at 300 mg/kg, which was the no-observed-adverse-effect level (NOAEL). The extract at a dose of 3000 mg/kg led to the death of one female and one male mouse (LD₅₀ > 3000 mg/kg). In sub-acute toxicity experiment, the extract induced no mortality or significant changes in body weight, general behaviors, hematological parameters, serum biochemical factors (related to the kidney and liver function), and histopathology of the heart, liver, kidney, and brain up to the highest dose tested of 400 mg/kg (NOAEL). High-performance liquid chromatography-mass spectrometry revealed the presence of phenolic compounds, flavonoids, alkanes, and anthraquinones in the extract. In conclusion, short-term use of R. turkestanicum root does not appear to produce significant toxicity up to a dose of 400 mg/kg.

Neuroprotective naphthalene and flavan derivatives from Polygonum cuspidatum

Ten naphthalene derivatives including two unusual glycosides possessing a naphthalene-fused piceid via a [C8'-O-C6-C5-C7']-trans-dihydrofuran ring, two flavan derivatives, as well as sixteen known phenolic compounds, were isolated from Polygonum cuspidatum. The structures were determined by extensive NMR, MS, CD data, and chemical evidence. In the in vitro neuroprotective assays, at the concentration of 10 μM, five of these compounds exhibited significant effects against PC12 cells injured by rotenone.

Chrysophanol-8-O-glucoside, an anthraquinone derivative in rhubarb, has antiplatelet and anticoagulant activities

Rhubarb is a widely used traditional medicine and has been reported to elicit a number of biological effects including anti-inflammatory and antiplatelet effects. In the present study, we investigated the effects of anthraquinone derivatives isolated from rhubarb on platelet activity. Of four anthraquinone derivatives isolated from rhubarb examined, chrysophanol-8-O-glucoside (CP-8-O-glc) was found to have the most potent inhibitory effect on collagen- and thrombin-induced platelet aggregation. CP-8-O-glc-treated mice showed significantly prolonged bleeding times. Furthermore, CP-8-O-glc was found to have a significant inhibitory effect on rat platelet aggregation ex vivo and on thromboxane A(2) formation in vitro. In coagulation tests, CP-8-O-glc did not alter prothrombin time, and it prolonged the activated partial thromboplastin time. However, CP-8-O-glc only inhibited platelet phosphatidylserine exposure, but not exert direct inhibition on intrinsic factors. This study demonstrates the antiplatelet and anticoagulant effects of CP-8-O-glc and suggests that this compound might be of therapeutic benefit for the prevention of platelet-related cardiovascular diseases.

Rhapontigenin from Rheum undulatum protects against oxidative-stress-induced cell damage through antioxidant activity

The antioxidant properties of rhapontigenin and rhaponticin isolated from Rheum undulatum were investigated. Rhapontigenin was found to scavenge intracellular reactive oxygen species (ROS), the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, and hydrogen peroxide (H2O2). The radical scavenging effect of rhapontigenin was more effective than rhaponticin. Rhapontigenin protected against H2O2-induced membrane lipid peroxidation and cellular DNA damage, which are the main targets of oxidative stress-induced cellular damage. The radical scavenging activity of rhapontigenin protected Chinese hamster lung fibroblast (V79-4) cells exposed to H2O2 by inhibiting apoptosis. Rhapontigenin inhibited cell damage induced by serum starvation and was also found to increase the activity of catalase and its protein expression. Further, rhapontigenin increased phosphorylation of extracellular signal-regulated kinase (ERK) and inhibited the activity of activator protein 1 (AP-1), a redox-sensitive transcription factor. In summary, these results suggest that rhapontigenin protects V79-4 cells against oxidative damage by enhancing the cellular antioxidant activity and modulating cellular signal pathways.

Neuraminidase inhibitors from Reynoutria elliptica

In the course of screening neuraminidase inhibitors from herbal medicines, Reynoutria elliptica exhibited high inhibitory activity. Four active compounds were isolated from the ethyl acetate soluble fraction by consecutive purification using sillica gel, Sephadex LH-20 chromatography, and recrystallization. The chemical structures of these compounds were identified as 1,3,8-trihydroxy-6-methylanthraquinone (emodin) 1,8-dihydroxy-3-methoxy-6-methylanthraquinone (emodin 3-methyl ether; physcion), 1,3,8-trihydroxy-6-hydoxymethylanthraquinone (omega-hydroxyemodin), and 3,5,4'-trihydroxystilbene (trans-resvertrol) by spectral data including MS, 1H-, and 13C-NMR. The IC50 values of emodin, emodin 3-methyl ether, omega-hydroxyemodin, and trans-resvertrol were 2.81, 74.07, 10.49, and 8.77 microM, respectively. They did not inhibit other glycosidase such as glucosidase, mannosidase, and galactosidase, indicating that they were relatively specific inhibitors of neuraminidase.

Antithrombotic and antiallergic activities of rhaponticin from Rhei Rhizoma are activated by human intestinal bacteria

To evaluate the antithrombotic and antiallergic properties of rhaponticin extracted from Rhei Rhizoma, the in vitro and ex vivo inhibitory activities of rhaponticin and its metabolite, rhapontigenin, were measured. These compounds inhibited in vitro ADP- and collagen-induced platelet aggregation. Rhapontigenin was more potent, with IC50 values of 4 and 70 microg/ml, respectively. In ex vivo ADP- and collagen-induced rat platelet aggregation, these compounds also exhibited a potent inhibitory effect. The antiplatelet aggregation effects of rhaponticin and rhapontigenin were more potent than those of aspirin. Rhapontigenin showed significant protection from death due to pulmonary thrombosis in mice. Rhapontigenin also showed the strongest inhibitory activity against beta-hexosaminidase release induced by DNP-BSA. These compounds inhibited PCA reaction in mice. Rhapontigenin intraperitoneally administered showed the strongest inhibitory activity and significantly inhibited PCA at doses of 25 and 50 mg/kg, with inhibitory activities of 48 and 85%, respectively. The inhibitory activity of orally administered rhaponticin was stronger than that of intraperitoneally administered rhaponticin. These results suggest that rhaponticin, in the rhizome of Rhei Rhizoma, is a prodrug that has extensive antiallergic and antithrombotic properties.

Antioxidant constituents from rhubarb: structural requirements of stilbenes for the activity and structures of two new anthraquinone glucosides

The methanolic extracts from five kinds of rhubarb were found to show scavenging activity for DPPH radical and .O2-. Two new anthraquinone glucosides were isolated from the rhizome of Rheum undulatum L. together with two anthraquinone glucosides, a naphthalene glucoside, and 10 stilbenes. In the screening test for radical scavenging activity of rhubarb constituents, stilbenes and a naphthalene glucoside showed activity, but anthraquinones and sennosides did not. In addition, most stilbenes inhibited lipid peroxidation of erythrocyte membrane by tert-butyl hydroperoxide. Detailed examination of the scavenging effect on various related compounds suggested the following structural requirements; 1) phenolic hydroxyl groups are essential to show the activity; 2) galloyl moiety enhances the activity; 3) glucoside moiety reduces the activity; 4) dihydrostilbene derivatives maintain the scavenging activity for the DPPH radical, but they show weak activity for .O2-. In addition, several stilbenes with both the 3-hydroxyl and 4'-methoxyl groups inhibited xanthine oxidase.

A new stilbene diglycoside from Rheum undulatum

A new stilbene diglycoside, piceatannol-3, 4'-O-beta-D-diglucopyranoside (I), together with desoxyrhaponticin (II), emodin-1-O-beta-D-glucopyranoside (III), and physcion-8-O-b-D-glucopyranoside (IV), were isolated from the rhizomes of cultivated Korean rhubarb rhizomes (Rheum undulatum), Jong DaeWhang, and the structures of I-IV were identified on the basis of chemical and spectral evidences.

Effects of stilbene constituents from rhubarb on nitric oxide production in lipopolysaccharide-activated macrophages

Two new anthraquinone glucosides [chrysophanol 8-O-beta-D-(6'-galloyl)-glucopyranoside, aloe-emodin 1-O-beta-D-glucopyranoside] together with various known stilbenes and their glucosides, anthraquinone glucosides, and a naphthalene glucoside were isolated from the rhizome of Rheum undulatum L. Three stilbenes (rhapontigenin, piceatannol, resveratrol), a naphthalene glucoside (torachrysone 8-O-beta-D-glucopyranoside), and two stilbene glucoside gallates (rhaponticin 2''-O-gallate, rhaponticin 6''-O-gallate) showed inhibitory activity of NO production in lipopolysaccharide-activated macrophages, (IC50 = 11-69 microM). The oxygen functions (-OH,-OCH3) at the benzene ring were found to be essential to show the activity. Whereas, the glucoside moiety reduced the activity, while the alpha,beta-double bond did not affect the activity. Furthermore, the active stilbenes (rhapontigenin, piceatannol, resveratrol) inhibited iNOS induction.