Metabolism of Rhaponticin and Activities of its Metabolite, Rhapontigenin: A Review

Qualitative and quantitative analysis methods for quality control of rhubarb in Taiwan's markets

Introduction: Rhubarb is a traditional Chinese medicine (TCM) used to release heat and has cathartic effects. Official rhubarb in Taiwan Herbal Pharmacopeias 4th edition (THP 4th) and China Pharmacopeia 2020 (CP 2020) are the roots and rhizomes of Rheum palmatum L., Rheum tanguticum Maxim. ex Balf., and Rheum officinale Baill. However, the Rheum genus is a large genus with many different species, and owing to the similarity in appearance and taste with official rhubarb, there needs to be more clarity in the distinction between the species of rhubarb and their applications. Given the time-consuming and complicated extraction and chromatography methods outlined in pharmacopeias, we improved the qualitative analysis and quantitative analysis methods for rhubarb in the market. Hence, we applied our method to identify the species and quality of official and unofficial rhubarb. Method: We analyzed 21 rhubarb samples from the Taiwanese market using a proposed HPLC-based extraction and qualitative analysis employing eight markers: aloe-emodin, rhein, emodin, chrysophanol, physcion, rhapontigenin, rhaponticin, and resveratrol. Additionally, we developed a TLC method for the analysis of rhubarb. KEGG pathway analysis was used to clarify the phytochemical and pharmacological knowledge of official and unofficial rhubarb. Results: Rhein and rhapontigenin emerged as key markers to differentiate official and unofficial rhubarb. Rhapontigenin is abundant in unofficial rhubarb; however, rhein content was low. In contrast, their contents in official rhubarb were opposite to their contents in unofficial rhubarb. The TLC analysis used rhein and rhapontigenin to identify rhubarb in Taiwan's markets, whereas the KEGG pathway analysis revealed that anthraquinones and stilbenes affected different pathways. Discussion: Eight reference standards were used in this study to propose a quality control method for rhubarb in Taiwanese markets. We propose a rapid extraction method and quantitative analysis of rhubarb to differentiate between official and unofficial rhubarb.

Targeting mitophagy for neurological disorders treatment: advances in drugs and non-drug approaches

Mitochondria serve as a vital energy source for nerve cells. The mitochondrial network also acts as a defense mechanism against external stressors that can threaten the stability of the nervous system. However, excessive accumulation of damaged mitochondria can lead to neuronal death. Mitophagy is an essential pathway in the mitochondrial quality control system and can protect neurons by selectively removing damaged mitochondria. In most neurological disorders, dysfunctional mitochondria are a common feature, and drugs that target mitophagy can improve symptoms. Here, we reviewed the role of mitophagy in Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, Huntington's disease, stroke, and traumatic brain injuries. We also summarized drug and non-drug approaches to promote mitophagy and described their therapeutic role in neurological disorders in order to provide valuable insight into the potential therapeutic agents available for neurological disease treatment. However, most studies on mitophagy regulation are based on preclinical research using cell and animal models, which may not accurately reflect the effects in humans. This poses a challenge to the clinical application of drugs targeting mitophagy. Additionally, these drugs may carry the risk of intolerable side effects and toxicity. Future research should focus on the development of safer and more targeted drugs for mitophagy.

Rhaponticin suppresses the hypoxia-induced factor-1 alpha-mediated aggressive phenotype of tongue squamous cell carcinoma

Background

Emerging evidence suggests that rhaponticin, a stilbene monomeric compound isolated from North China rhubarb, has been shown to exhibit significant biological activity against tumors. However, the anticancer effects and mechanisms of rhaponticin in tongue squamous cell carcinoma (TSCC) remain elusive.

Objective

We investigated the changes of migration and invasion abilities and EMT progression of TSCC cells treated with different concentrations of rhaponticin under hypoxia, as well as the possible mechanisms, in order to initially explore the effects of rhaponticin on the biological characteristics of TSCC cells under hypoxia.

Results

The number of cell migration and invasion was prominently increased, E-cadherin protein was down-regulated, and N-cadherin and HIF-1α protein expression was elevated under hypoxia. Rhaponticin intervention strikingly prevented the increased abilities of migration and invasion and EMT of TSCC cells under hypoxia. This was followed by further validation finding that rhaponticin indeed leads to reduced HIF-1α post-transcriptional activity. Mechanistically, rhaponticin may bind to aryl-hydrocarbon nuclear translocator (ARNT) domain of HIF-1α.

Conclusions

Rhaponticin repressed the invasion and migration abilities and EMT process of TSCC cells under a hypoxic environment in vitro by targeted suppression of HIF-1α.

Stilbene-based derivatives as potential inhibitors of trimethylamine (TMA)-lyase affect gut microbiota in coronary heart disease

Coronary heart disease (CHD) is defined by atherosclerosis, which may result in stenosis or blockage of the arterial cavity, leading to ischemic cardiac diseases such as angina and myocardial infarction (MI). Accumulating evidence indicates that the gut microbiota play a critical role in the initiation and progression of CHD. The gut microbial metabolite trimethylamine N-oxide (TMAO) is intimately linked to the pathophysiology of CHD. The hepatic flavin-containing monooxygenases (FMOs) convert trimethylamine (TMA) to TMAO. As a result, it is critical to prevent TMA generation. Stilbenes could reduce cardiovascular disease mortality. Twelve stilbenes with inhibitory activity against TMA-lyase were compiled and evaluated in this study. Docking results showed Resveratroloside had the highest Vina score, indicating that it was the most active and might be employed as a lead molecule for further structural modification.

Protective effect of rhaponticin on ovariectomy-induced osteoporosis in rats

Rhaponticin is a constituent isolated from numerous medicinal herbs. It has been reported earlier that rhaponticin possesses numerous biological effects like antiallergic, antidiabetic, hepatoprotective, and antithrombosis. The goal of this exploration was to scrutinize the therapeutic potential of rhaponticin on ovariectomy (OVX)-triggered osteoporosis in rats. Female Sprague Dawley rats were arbitrarily allocated to a sham-operated control group I, group II, which underwent OVX, and groups III and IV that underwent OVX were administered with rhaponticin (10 and 20 mg/kg). Rhaponticin was supplemented orally after 4 weeks of OVX and continued for about 16 weeks. Our findings exhibit that rhaponticin prevented the BMD diminution of femurs, induced by OVX, and protected the worsening of trabecular microarchitecture that are assisted through a noteworthy decline in skeletal remodeling as noticed through the diminished status of bone markers in a dose-dependent manner (10 and 20 mg/kg). OVX rats treated with rhaponticin efficiently enhanced body weight, lipid profiles, uterine index, bone turnover markers, inflammatory markers, and augmented the incidence of calcium in the OVX rats. Rhaponticin was established to restrain the functions of acid phosphatase, estradiol, and bone gla protein in OVX rats. Also, rhaponticin displayed some beneficial effects on histomorphometric and histopathological examination. It was observed that tabular area and thickness were reinstated in sham control and rhaponticin-treated OVX rats. We recognized that rhaponticin did not induce a damaging outcome on the skeletal organization of OVX rats. Moreover, we denote that rhaponticin can be an exceptional agent for the treatment and deal with associated bone diseases.

Anti-inflammatory effects of rhaponticin on LPS-induced human endothelial cells through inhibition of MAPK/NF-κβ signaling pathways

The untreated systemic chronic inflammation leads to autoimmune diseases, hyperglycemia, cardiovascular diseases, type 2 diabetes, hypertension, osteoporosis, and so on. Phytochemicals effectively inhibit the inflammation, and numerous studies have proved that the phytocomponents possess anti-inflammatory property via inhibiting the cyclooxygenase and lipoxygenase signaling pathways. Rhaponticin is one such phytochemical obtained from the perennial plant Rheum rhaponticum L. belonging to Polygonaceae family. We assessed the anti-inflammatory potency of rhaponticin in endothelial cells induced with lipopolysaccharides (LPS). Four different endothelial cells induced with LPS were treated with rhaponticin and assessed for the nitric oxide generation. The cytotoxic potency of rhaponticin was evaluated in endothelial cells using the 3-(4,5-dimethylthizaol-2yl)-2,5-diphenyl tetrazolium bromide assay. The tumor necrosis factor-α (TNF-α) synthesis was quantified using the commercially available assay kit. The inflammatory signaling protein gene expression of TNF-α, inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX2), and interleukin-1β (IL-1β) was analyzed with quantitative polymerase chain reaction (PCR) analysis. The gene expression of NADPH oxidase (NOX) cytoplasmic catalytic subunits gp91^phox , p47^phox , and p22^phox was assessed with real-time PCR analysis. Finally, to confirm the anti-inflammatory potency of rhaponticin, the nuclear factor kappa B (NFκB) and mitogen-activated protein kinase (MAPK) signaling protein expression was analyzed with immunoblotting analysis. Rhaponticin treatment significantly decreased the levels of nitric oxide and TNF-α synthesis in LPS-induced endothelial cells. It significantly decreased the gene expression of inflammatory proteins and NOX signaling protein. The protein expression of NFκB and MAPK signaling proteins was drastically decreased in rhaponticin-treated endothelial cells induced with LPS. Overall, our results confirm that rhaponticin effectively inhibited the inflammation triggered by LPS in endothelial cells via downregulating iNOS, COX2, and NFκB and MAPK signaling pathways.

New insights on Phyllanthus reticulatus Poir. leaves and stem bark extracts: UPLC-ESI-TOF-MS profiles, and biopharmaceutical and in silico analysis

Our results could provide a great scientific starting point on the way from the bench to functional applications through the use of P. reticulatus, namely novel nutraceuticals, pharmaceuticals and cosmeceuticals.

Neuroprotective effect of rhaponticin against Parkinson disease: Insights from in vitro BV-2 model and in vivo MPTP-induced mice model

Parkinson's disease (PD) is a complex neurodegenerative illness associated with the loss or damage to neurons of the dopaminergic system in the brain. Few therapeutic approaches and considerable side effects of conventional drugs necessitate a new therapeutic agent to treat patients with PD. Rhaponticin is a natural hydroxystilbene, found in herbal plants such as Rheum rhaponticum, and known to have desirable biological activity including anti-inflammatory properties. However, the neuroinflammation on rhaponticin levels has only been investigated partially so far. So, the current study explored whether rhaponticin could ameliorate the pathophysiology observed in both the in vitro microglial BV-2 cells and the in vivo (1-methyl-4-phenyl-1,2,3,5-tetrahydropyridine [MPTP])-mediated PD model. The results show rhaponticin significantly attenuated lipopolysaccharide (LPS)-mediated microglial activation by suppressing nitric oxide synthase in conjunction with abridged reactive oxygen species production together with proinflammatory mediator reduction. In vivo rhaponticin treatment improves motor impairments as well as the loss of dopaminergic neurons in MPTP-treated mice possibly through suppression via mediators of inflammation. Taken together, these results offer evidence that rhaponticin exerts anti-inflammatory effects and neuroprotection in an LPS-induced microglial model and the MPTP-induced mouse models of PD.