Pallidifloside D from Smilax riparia enhanced allopurinol effects in hyperuricemia mice

Herbal remedies in the management of hyperuricemia and gout: A review of in vitro, in vivo and clinical evidences

Gout, or hyperuricemia is a multifactorial and multi-faceted metabolic disease that is quite difficult to manage and/or treat. Conventional therapies such as non-steroidal anti-inflammatory drugs (NSAIDs) such as allopurinol, corticosteroids and colchicine amongst others, have helped in its management and treatment to some extent. This study aimed to compile and analyze the different herbal remedies used in the management of hyperuricemia and gout. A literature search was conducted from key databases (PubMed, ScienceDirect, Cochrane Library, Google Scholar) using relevant keywords via the PRISMA model. Smilax riparia A.DC. from Traditional Chinese Medicine is used in many countries for its therapeutic effect on lowering serum urate levels. No single study was able to establish the efficacy of a specific traditionally used herb via in vitro, in vivo, and clinical studies. Patients were found to use a panoply of natural remedies, mainly plants to treat hyperuricemia and gout, which have been validated to some extent by in vitro, in vivo, and clinical studies. Nonetheless, further research is needed to better understand the ethnopharmacological relationship of such herbal remedies.

A Review of Medicinal Plants and Phytochemicals for the Management of Gout

Gout, characterized by elevated uric acid levels, is a common inflammatory joint disease associated with pain, joint swelling, and bone erosion. Existing treatments for gout often result in undesirable side effects, highlighting the need for new, safe, and cost-effective anti-gout drugs. Natural products, including medicinal plants and phytochemicals, have gained attention as potential sources of anti-gout compounds. In this review, we examined articles from 2000 to 2020 using PubMed and Google Scholar, focusing on the effectiveness of medicinal plants and phyto-chemicals in managing gout. Our findings identified 14 plants and nine phytochemicals with anti-gout properties. Notably, Teucrium polium, Prunus avium, Smilax riparia, Rhus coriaria, Foenic-ulum vulgare, Allium cepa, Camellia japonica, and Helianthus annuus exhibited the highest xa-thine oxidase inhibitory activity, attributed to their unique natural bioactive compounds such as phenolics, tannins, coumarins, terpenoids, and alkaloids. Herbal plants and their phytochemicals have demonstrated promising effects in reducing serum urate and inhibiting xanthine. This review aims to report recent studies on plants/phytochemicals derived from herbs beneficial in gout and their different mechanisms.

Action mechanisms of two key xanthine oxidase inhibitors in tea polyphenols and their combined effect with allopurinol

BACKGROUND

Tea polyphenols have been reported to have the effect of lowering uric acid. However, there are few studies on the inhibitory effects and molecular mechanisms of specific catechins on the urate-metabolizing enzyme xanthine oxidase (XO). In this research, multiple spectroscopic methods and computer simulations were used to determine the inhibitory ability and mechanisms of epigallocatechin gallate (EGCG) and gallocatechin gallate (GCG) on XO.

RESULTS

Herein, EGCG and GCG reversibly inhibited XO activity in a mixed manner, with IC₅₀ values of 40.50 ± 0.32 and 33.60 ± 0.53 μmol L^-1 , and also decreased the superoxide anion radical (O₂ ^- ) of the catalytic system by reducing the XO molecule and inhibiting the formation of uric acid. The combination of EGCG or GCG with allopurinol showed synergistic inhibition on XO. The binding of EGCG or GCG to XO with moderate affinity formed a stable complex by hydrogen bonds and van der Waals forces. The presence of EGCG and GCG made the structure of XO more stable and compact. The two inhibitors bound to the vicinity of flavin adenine dinucleotide (FAD) in XO, hindering the entry of substrate; thus the activity of XO was suppressed.

CONCLUSION

Both EGCG and GCG are excellent natural XO inhibitors, and inhibited the activity of XO by occupying the channel of the substrate to enter the active center and interfering with the dual substrate reaction catalyzed by XO. These findings provide a scientific basis for the application of catechins in dietary supplements and medicines with lowering uric acid effects. © 2022 Society of Chemical Industry.

Effect of Different Molecular Weights of Chitosan on Formulation and Evaluation of Allopurinol-Loaded Nanoparticles for Kidney Targeting and in Management of Hyperuricemic Nephrolithiasis

Present research study was conducted to formulate kidney-targeted allopurinol (AO)-loaded chitosan nanoparticles (ANPs) for management of hyperuricemic related nephrolithiasis. Different molecular weights of chitosan were used for fabricating ANP formulation by adopting modified ionotropic gelation method. The prepared batches were than evaluated for particle size analysis, entrapment efficiency, transmission electron microscopy, X-ray diffraction, Differential Scanning Calorimetry, in vitro release and in vivo animal study. The in vivo study depicted that post 2 h of administration of different formulations and pure drug; ANPs prepared from low molecular weight chitosan showed maximum concentration of AO in kidney signifying successful kidney targeting of drug (25.92 fold) whereas no or very less amount of AO was seen in other animal groups. Effectiveness (p < 0.01) of formulation in management of hyperuricemia-associated nephrolithiasis was also evaluated via estimation of urine pH and serum and urine uric acid levels of mice. Further histological study was also performed on kidney samples which again affirmed these results. Present investigation demonstrated that ANPs prepared from low MW chitosan depicted maximum kidney-targeting ability that might be due to its specific uptake by the kidneys as well as its higher solubility than other two polymers, which results in enhanced release rate from the formulation and also offers an efficient strategy for the management of hyperuricemic nephrolithiasis.

Dapagliflozin and xanthine oxidase inhibitors improve insulin resistance and modulate renal glucose and urate transport in metabolic syndrome

Disturbance in glucose and uric acid metabolism is the major disorder of metabolic syndrome (MetS). The kidneys play an important role in the management of glucose and uric acid. The aim of our study was to investigate alterations in renal glucose and uric acid transporters in animals with MetS after treatment with dapagliflozin and xanthine oxidase inhibitors (allopurinol and febuxostat). Sprague-Dawley rats were fed normal chow or a high fructose diet for the first 3 months. The fructose-fed animals were then treated with dapagliflozin, allopurinol, febuxostat, or no treatment for the next 3 months. Fasting glucose, insulin resistance, and hyperuricaemia were improved in all treatment groups except that in the fructose group (all p < 0.05). Both allopurinol and febuxostat reversed the increase in levels of sodium glucose cotransporter (SGLT) 1, SGLT2, and glucose transporter (GLUT) 2 (all p < 0.05). Dapagliflozin alleviated hyperuricaemia and induced uricosuria without affecting serum xanthine oxidase activity. Dapagliflozin suppressed the expression of GLUT9, urate transporter, and urate anion exchanger 1 (all p < 0.05), which was similar to the effects of allopurinol and febuxostat. The results suggest that treatment with dapagliflozin and xanthine oxidase inhibitors improved insulin resistance and reversed the increased expression of glucose and urate transporters in the kidney.

The Efficacy and Mechanism of Chinese Herbal Medicines in Lowering Serum Uric Acid Levels: A Systematic Review

Background. Chinese herbal medicines are widely used to lower serum uric acid levels. However, no systemic review summarizes and evaluates their efficacies and the underlying mechanisms of action. Objectives. To evaluate the clinical and experimental evidences for the effectiveness and the potential mechanism of Chinese herbal medicines in lowering serum uric acid levels. Methods. Four electronic databases PubMed, Wed of Science, the Cochrane Library and Embase were used to search for Chinese herbal medicines for their effects in lowering serum uric acid levels, dated from 1 January 2009 to 19 August 2020. For clinical trials, randomized controlled trials (RCTs) were included; and for experimental studies, original articles were included. The methodological quality of RCTs was assessed according to the Cochrane criteria. For clinical trials, a meta-analysis of continuous variables was used to obtain pooled effects. For experimental studies, lists were used to summarize and integrate the mechanisms involved. Results. A total of 10 clinical trials and 184 experimental studies were included. Current data showed that Chinese herbal medicines have promising clinical efficacies in patients with elevated serum uric acid levels (SMD: −1.65, 95% CI: −3.09 to −0.22; p = 0.024). There was no significant difference in serum uric acid levels between Chinese herbal medicine treatments and Western medicine treatments (SMD: −0.13, 95% CI: −0.99 to 0.74; p = 0.772). Experimental studies revealed that the mechanistic signaling pathways involved in the serum uric acid lowering effects include uric acid synthesis, uric acid transport, inflammation, renal fibrosis and oxidative stress. Conclusions. The clinical studies indicate that Chinese herbal medicines lower serum uric acid levels. Further studies with sophisticated research design can further demonstrate the efficacy and safety of these Chinese herbal medicines in lowering serum uric acid levels and reveal a comprehensive picture of the underlying mechanisms of action.

Formulation, Optimization, and Evaluation of Allopurinol-Loaded Bovine Serum Albumin Nanoparticles for Targeting Kidney in Management of Hyperuricemic Nephrolithiasis : Formulation, optimization, and evaluation of ABNPs for kidney targeting

The aim of present research work was to design, fabricate, optimize, and evaluate allopurinol (ALLO)-loaded bovine serum albumin nanoparticles (ABNPs) for kidney targeting of the drug and exploring the potential of fabricated ABNPs for management of hyperuricemia-related nephrolithiasis. ABNP formulation was prepared by employing desolvation technique, and its optimization was conducted by 2-factor-3-level central composite design (CCD) in order to achieve minimum particle size (PSA) and polydispersity index (PDI), maximum entrapment efficiency (EE), and zeta potential (ZP). Further, the optimized formulation (ABNPs_opt) was also assessed for in vitro drug release study, TEM, DSC, XRD analysis, FTIR spectroscopy, and in vivo animal study. The in vivo study revealed that after 2 h of ABNPs_opt administration, a significant concentration of ALLO was present in kidney (21.26-fold) as compared with serum while in case of standard pure drug group; no drug was seen in mice kidney and serum post 2 h administration, which indicates successful targeting of ALLO by formulating its albumin nanoparticles. Also, uric acid and pH levels were measured in serum and urine samples of mice which showed significant (P < 0.01) efficacy of ABNPs_opt formulation in management of hyperuricemia-related nephrolithiasis. Histological studies on kidney samples also confirmed these outcomes. Findings of present study indicate higher kidney uptake of allopurinol from formulated ABNPs_opt, which could be due to the specificity of albumin polymer for cubilin and megalin receptors, and it also serves as effective strategy in management of hyperuricemic-related nephrolithiasis.

Reinvestigation of Herniaria glabra L. saponins and their biological activity

Twelve undescribed triterpenoid pentacyclic glycosides, medicagenic acid (3-O-β-D-glucuronopyranosyl-28-O-{[β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)]-[α-L-rhamnopyranosyl-(1 → 3)]-4-O-acetyl-β-D-fucopyranosyl-(1→)}-2β,3β-dihydroxyolean-12-ene-23,28-dioic acid, 3-O-β-D-glucuronopyranosyl-28-O-{[α-L-rhamnopyranosyl-(1 → 2)]-[β-D-apiofuranosyl-(1 → 3)]-4-O-acetyl-β-D-fucopyranosyl-(1→)}-2β,3β-dihydroxyolean-12-ene-23,28-dioic acid, 3-O-β-D-glucuronopyranosyl-28-O-{[α-L-rhamnopyranosyl-(1 → 2)]-3,4-O-diacetyl-β-D-fucopyranosyl-(1→)}-2β,3β-dihydroxyolean-12-ene-23,28-dioic acid, 28-O-{[6-O-acetyl-β-D-glucopyranosyl-(1 → 2)]-[2-O-acetyl-α-L-rhamnopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 6)]-β-D-glucopyranosyl-(1→)}-2β,3β-dihydroxyolean-12-ene-23,28-dioic acid, 28-O-{[6-O-acetyl-β-D-glucopyranosyl-(1 → 2)]-[3-O-acetyl-α-L-rhamnopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 6)]-β-D-glucopyranosyl-(1→)}-2β,3β-dihydroxyolean-12-ene-23,28-dioic acid, 28-O-{[6-O-acetyl-β-D-glucopyranosyl-(1 → 2)]-[4-O-acetyl-α-L-rhamnopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 6)]-β-D-glucopyranosyl-(1→)}-2β,3β-dihydroxyolean-12-ene-23,28-dioic acid, 28-O-{[6-O-acetyl-β-D-glucopyranosyl-(1 → 2)]-[β-D-glucopyranosyl-(1 → 6)]-β-D-glucopyranosyl-(1→)}-2β,3β-dihydroxyolean-12-ene-23,28-dioic acid, 28-O-{[β-D-glucopyranosyl-(1 → 2)]-[β-D-glucopyranosyl-(1 → 6)]-β-D-glucopyranosyl-(1→)}-2β,3β-dihydroxyolean-12-ene-23,28-dioic acid), zanhic acid (3-O-β-D-glucuronopyranosyl-28-O-{[β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)]-[α-L-rhamnopyranosyl-(1 → 3)]-4-O-acetyl-β-D-fucopyranosyl-(1→)}2β,3β,16α-trihydroxyolean-12-ene-23,28-dioic acid, 3-O-β-D-glucuronopyranosyl-28-O-{[β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)]-β-D-fucopyranosyl-(1→)}-2β,3β,16α-trihydroxyolean-12-ene-23,28-dioic acid), 29-hydroxy-medicagenic acid (3-O-β-D-glucuronopyranosyl-28-O-{[β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)]-[α-L-rhamnopyranosyl-(1 → 3)]-4-O-acetyl-β-D-fucopyranosyl-(1→)}-2β,3β,29β-trihydroxyolean-12-ene-23,28-dioic acid) and herniaric acid (28-O-{[6-O-acetyl-β-D-glucopyranosyl-(1 → 2)]-[α-L-rhamnopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 6)]-β-D-glucopyranosyl-(1→)}-2β,3β-dihydroxyolean-18-ene-23,28-dioic acid) were isolated from the whole plant extract of Herniaria glabra L. (Caryophyllaceae), wild growing in the Ukraine. In addition, five known triterpenoid saponins; i.e. herniariasaponins 1, 4, 5, 6, and 7 were also isolated. Their structures were elucidated by HRESIMS, 1D and 2D NMR spectroscopy, as well as by comparison with the literature data. Twelve herniariasaponins, the purified crude extract, and the saponin fraction were evaluated in vitro for their xanthine oxidase, collagenase, elastase, and tyrosinase inhibitory activity. Moreover, herniariasaponins 4, 5, and 7 were screened for their cholinesterase inhibitory potential. As a result, no or low inhibition towards the mentioned enzymes was observed.

Targeting kidneys by superparamagnetic allopurinol loaded chitosan coated nanoparticles for the treatment of hyperuricemic nephrolithiasis

PURPOSE

The major short coming of conventional therapy system is that they can't deliver the therapeutics specifically to a site within the body without producing nonspecific toxicity. Present research aimed at developing kidney targeted allopurinol (AP) loaded chitosan coated magnetic nanoparticles (A-MNPs) for the management of hyperuricemic nephropathy manifested in the form of nephrolithiasis.

METHODS

The work includes preparation of magnetic nanoparticles by chemical co-precipitation method and evaluation of the prepared batches for particle size analysis, Transmission electron microscopy, entrapment efficiency, in-vitro release study etc. Further, FTIR spectroscopy, X-ray diffraction, Differential Scanning Calorimetry, Vibrational sample magnetometer (VSM) and in-vivo animal studies were also performed.

RESULTS

VSM analysis demonstrates that the prepared nanoparticles exhibit superparamagnetic magnetic behaviour which was retained even after coating by chitosan. In-vivo studies of A-MNPs showed 19.07-fold increase in kidney uptake of AP as compared to serum post 2 h of administration in mice whereas no drug was detected in kidney and serum post 2 h administration of pure drug (free-form) indicating successful targeting to kidney as well as sustained release of AP from the formulated A-MNPs. The significant (p < 0.01) effectiveness of A-MNPs in management of hyperuricemic nephrolithiasis was observed through estimating pH and uric acid levels in urine and serum samples of mice. These findings were also confirmed by histological examination of isolated kidney samples.

CONCLUSION

Present investigation signifies that a simple external magnetic field is enough for targeting allopurinol to kidneys by formulating A-MNPs which further offers an effective approach for management of hyperuricemic nephrolithiasis. Graphical Abstract.

Screening the Best Compatibility of Selaginella moellendorffii Prescription on Hyperuricemia and Gouty Arthritis and Its Mechanism

Objectives

The Selaginella moellendorffii prescription (SMP) consists of S. moellendorffii Herba (SM), Smilacis glabrae Rhizoma (SGR), and Plantaginis Semen (PS). It has been commonly used to treat hyperuricemia and acute gouty arthritis as a hospital preparation. This study was aimed at investigating the best compatibility ratio of SMP on hyperuricemia and gouty arthritis and getting better insight of the possible mechanism. Methods. In vitro, anti-inflammatory activity of SMP was evaluated by lipopolysaccharide (LPS) induced RAW264.7 cells. The release of nitric oxide (NO) was screened by Griess assay, and NF-κB p65 and NLRP3 proteins expression was examined by immunofluorescence assay. Then, the levels of creatinine (Cr), blood urea nitrogen (BUN), and uric acid (UA) were detected in mice induced by potassium oxonate, and the paw oedema, inflammatory mediators, and histological examination were analyzed in rats induced by monosodium urate (MSU). HPLC method was employed to investigate the chemical profile of this preparation. Results. In vitro, SMP-3 (the ratio of SMP:SGR:PS was 3:1:1) exhibited the most potent anti-NO production activity without obvious toxicity. This anti-inflammatory effect was associated with suppression of NF-κB p65 nuclear translocation and NLRP3 protein expression. In animal experiments, the levels of BUN and Cr in SMP-3 group were lower than other extract groups, and the level of UA was also remarkably decreased by SMP-3 in hyperuricemic mice (P<0.01). Besides, SMP-3 extract was able to prevent the paw edema, reduce gouty joint inflammatory features, and decrease the levels IL-1β, PGE-2, IL-8, and NO in gouty arthritis rats. Furthermore, 6-C-β-D-xylopyranosyl-8-C-β-D-glucopyranosyl, apigenin, and astilbin were identified from SMP-3 extract.

Conclusions

In summary, SMP-3 may be a potential therapeutic agent for the prevention of hyperuricemic and gout.

Antihyperuricemic effect of mangiferin aglycon derivative J99745 by inhibiting xanthine oxidase activity and urate transporter 1 expression in mice

A mangiferin aglycon derivative J99745 has been identified as a potent xanthine oxidase (XOD) inhibitor by previous in vitro study. This study aimed to evaluate the hypouricemic effects of J99745 in experimental hyperuricemia mice, and explore the underlying mechanisms. Mice were orally administered 600 mg/kg xanthine once daily for 7 days and intraperitoneally injected 250 mg/kg oxonic acid on the 7th day to induce hyperuricemia. Meanwhile, J99745 (3, 10, and 30 mg/kg), allopurinol (20 mg/kg) or benzbromarone (20 mg/kg) were orally administered to mice for 7 days. On the 7th day, uric acid and creatinine in serum and urine, blood urea nitrogen (BUN), malondialdehyde (MDA) content and XOD activities in serum and liver were determined. Morphological changes in kidney were observed using hematoxylin and eosin (H&E) staining. Hepatic XOD, renal urate transporter 1 (URAT1), glucose transporter type 9 (GLUT9), organic anion transporter 1 (OAT1) and ATP-binding cassette transporter G2 (ABCG2) were detected by Western blot and real time polymerase chain reaction (PCR). The results showed that J99745 at doses of 10 and 30 mg/kg significantly reduced serum urate, and enhanced fractional excretion of uric acid (FEUA). H&E staining confirmed that J99745 provided greater nephroprotective effects than allopurinol and benzbromarone. Moreover, serum and hepatic XOD activities and renal URAT1 expression declined in J99745-treated hyperuricemia mice. In consistence with the ability to inhibit XOD, J99745 lowered serum MDA content in hyperuricemia mice. Our results suggest that J99745 exerts urate-lowering effect by inhibiting XOD activity and URAT1 expression, thus representing a promising candidate as an anti-hyperuricemia agent.

Renal organic anion transporters in drug-drug interactions and diseases

The kidney plays a vital role in maintaining systemic homeostasis. Active tubular secretion and reabsorption, which are mainly mediated by transporters, is an efficient mechanism for retaining glucose, amino acids, and other nutrients and for the clearance of endogenous waste products and xenobiotics. These substances are recognized by uptake transporters located in the basolateral and apical membranes of renal proximal tubule cells and are extracted from plasma and urine. Organic anion transporters (OATs) belong to the solute carrier (SLC) 22 superfamily and facilitate organic anions across the plasma membranes of renal proximal tubule cells. OATs are responsible for the transmembrane transport of anionic and zwitterionic organic molecules, including endogenous substances and many drugs. The alteration in OAT expression and function caused by diseases, drug-drug interactions (DDIs) or other issues can thus change the renal disposition of substrates, induce the accumulation of toxic metabolites, and lead to unexpected clinically outcome. This review summarizes the recent information regarding the expression, regulation, and substrate spectrum of OATs and discusses the roles of OATs in diseases and DDIs. These findings will enables us to have a better understanding of the related disease therapy and the potential risk of DDIs mediated by OATs.

Steroidal Saponins from the Genus Smilax and Their Biological Activities

The Smilax species, widely distributed in tropical region of the world and the warm areas of East Asia and North America, are extensively used as folk medicine to treat inflammatory disorders. Chemical investigation on Smilax species showed they are rich sources of steroidal saponins with diversified structure types, including spirostane, isospirostane, furostane, pregnane, and cholestane. This review mainly summarizes the steroidal saponins (1-104) reported from the genus Smilax between 1967 and 2016, and their biological activities. The relationship between structures of steroidal saponins and related biological activities were briefly discussed.

Natural Products Improving Hyperuricemia with Hepatorenal Dual Effects

This review aims to put forth an overview of natural products reducing uric acid level with hepatorenal dual effects. The prevalence of hyperuricemia increased rapidly in recent years and has closely interdependent relationship with other metabolic disorders. Current therapeutically used drugs including a few uricostatic and uricosuric chemical drugs are proved efficient to control serum uric acid level. However, their side effects as well as contraindication in some cases with liver, kidney injury, or other conditions frequently limit their clinic application. More attention thus has been paid to natural products as an alternative means in treating hyperuricemia. Many natural products have been proved efficient in downregulating uric acid level, among which some can improve hyperuricemia with hepatorenal dual effects. It means these natural products can regulate both the production and the excretion of uric acid by targeting the key metabolic enzymes mainly in liver or uric acid transporters in kidneys. Thus, these natural products could have stronger efficacy and broader application, which may be developed for the treatment of hyperuricemia in clinic.

Hypouricemic effect of allopurinol are improved by Pallidifloside D based on the uric acid metabolism enzymes PRPS, HGPRT and PRPPAT

Allopurinol is a commonly used medication to treat hyperuricemia and its complications. Pallidifloside D, a saponin glycoside constituent from the total saponins of Smilax riparia, had been proved to enhanced hypouricemic effect of allopurinol based on uric acid metabolism enzyme XOD. In this study, we evaluated whether Pallidifloside D (5mg/kg) enhanced hypouricemic effect of allopurinol (5mg/kg) related to others uric acid metabolism enzymes such as PRPS, HGPRT and PRPPAT. We found that, compared with allopurinol alone, the combination of allopurinol and Pallidifloside D significantly up-regulated HGPRT mRNA expression and down-regulated the mRNA expression of PRPS and PRPPAT in PC12 cells (all P<0.01). These results strongly suggest that hypouricemic effect of allopurinol are improved by Pallidifloside D via numerous mechanisms and our data may have a potential value in clinical practice in the treatment of gout and other hyperuricemic conditions.