Substituted cyclic imides as potential anti-gout agents

Development and characterization of liposomal formulations containing sesquiterpene lactones for the treatment of chronic gout

Gout and hyperuricemia are characterized by high uric acid levels, and their treatment involves medications that have adverse effects. In this study, we evaluated oral liposomal formulations with eremantholide C and goyazensolide as a novel approach to reduce the toxicity associated with these substances while maintaining their anti-hyperuricemic activity. We characterized the formulations and evaluated them based on encapsulation efficiency and stability over 12 months and under simulated physiological environments. We determined the toxicity of the liposomal formulations in Caco-2 cells and the anti-hyperuricemic activity in rats. The formulations exhibited nanometric size, a narrow size distribution, and a negative zeta potential, indicating their stability and uniformity. The efficient encapsulation of the sesquiterpene lactones within the liposomes emphasizes their potential for sustained release and therapeutic efficacy. Stability evaluation revealed a small decrease in the eremantholide C concentration and a remarkable stability in the goyazensolide concentration. In Caco-2 cells, the liposomes did not exert toxicity, but did exhibit an antiproliferative effect. In vivo assays demonstrated that the liposomes reduced serum uric acid levels. Our study represents an advancement in gout and hyperuricemia treatment. The liposomal formulations effectively reduced the toxicity associated with the sesquiterpene lactones while maintaining their therapeutic effects.

Anti-Hyperuricemic Effects of Extracts from Chaenomeles speciosa (Sweet) Nakai Fruits on Hyperuricemic Rats

Chaenomeles speciosa (Sweet) Nakai (C. speciosa) fruit has medicinal and food applications and exhibits beneficial pharmacological properties. This study aimed to explore the hypouricemic effect of C. speciosa fruit extracts on hyperuricemic rats and uncover potential protective mechanisms. The rats were given hypoxanthine (HX, 100 mg/kg) and potassium oxonate (PO, 300 mg/kg) for 14 days to induce hyperuricemia. Subsequently, the rats were orally administered C. speciosa fruits total extract (CSFTE, 250, 500, and 1000 mg/kg) and allopurinol (AP, 10 mg/kg) one hour after exposure to HX and PO. The results showed that CSFTE had significant xanthine oxidase (XOD) inhibitory activity in vitro (IC50 value of 334.2 μg/mL) and exhibited hypouricemic effects in vivo, reducing uric acid (UA), creatinine (CRE), and blood urea nitrogen (BUN) levels in serum. CSFTE increased UA excretion through the regulation of URAT1, GLUT9, OAT1, and OAT3 protein expression in the kidneys of hyperuricemic rats. Additionally, CSFTE (500 and 1000 mg/kg) was more effective than AP in improving renal injury and protecting kidney function in hyperuricemic rats. Our study demonstrated that CSFTE effectively reduced UA levels and protected the kidneys by inhibiting XOD expression in vitro and regulating UA, CRE, BUN, URAT1, GLUT9, OAT1, and OAT3 proteins in vivo.

Anti-Hyperuricemic, Anti-Arthritic, Hemolytic Activity and Therapeutic Safety of Glycoconjugated Triazole-Phthalimides

Hyperuricemia, the metabolic alteration that leads to gout or gouty arthritis, is increasing worldwide. Glycoconjugated triazole-phthalimides show potent anti-inflammatory activity. The aim of this study was to evaluate the anti-hyperuricemia effect of glycoconjugated triazole-phthalimides. To develop hyperuricemia, groups of mice received orally potassium oxonate (250 mg/kg) for 7 days, and F2, F3 and F4 glycoconjugated triazole-phthalimides (20 mg/kg), allopurinol (300 mg/kg), and 1% carboxymethylcellulose; indomethacin (2 and 4 mg/kg) was the positive control for anti-arthritic effect. Genotoxic and mutagenic effects were evaluated by the comet and micronucleus assays, respectively. The hemolytic action of the compounds was evaluated. Phthalimides F2, F3 and F4 significantly reduced the levels of serum uric acid, creatinine and urea in hyperuricemic animals. In addition, the compounds were efficient in reducing protein denaturation in a dose-dependent manner. In an interesting way, the histopathological analysis of kidneys from groups treated with F2, F3 and F4 showed a glomerular architecture, with the Bowman's capsule and renal tubules having a normal appearance and without inflammatory changes. Also, F2 and F4 showed a small increase in micronuclei, indicating a low mutagenic effect, whilst by comet assay only, we could infer that F4 affected the frequency and damage index, thus indicating a very small genotoxic action. Similarly, the phthalimides showed a low degree of erythrocyte hemolysis (<3%). Our data demonstrate that the new glycoconjugate triazole-phthalimides have potential to treat hyperuricemia and its secondary complications, such as gouty arthritis, with a low to non-significant rate of erythrocytes hemolysis, genotoxicity and mutagenicity making these molecules strong candidates as pharmaceutical agents for treatment requiring uric-acid-lowering therapy.

New Approach for the Identification of Isobaric and Isomeric Metabolites

The structural elucidation of metabolite molecules is important in many branches of the life sciences. However, the isomeric and isobaric complexity of metabolites makes their identification extremely challenging, and analytical standards are often required to confirm the presence of a particular compound in a sample. We present here an approach to overcome these challenges using high-resolution ion mobility spectrometry in combination with cryogenic vibrational spectroscopy for the rapid separation and identification of metabolite isomers and isobars. Ion mobility can separate isomeric metabolites in tens of milliseconds, and cryogenic IR spectroscopy provides highly structured IR fingerprints for unambiguous molecular identification. Moreover, our approach allows one to identify metabolite isomers automatically by comparing their IR fingerprints with those previously recorded in a database, obviating the need for a recurrent introduction of analytical standards. We demonstrate the principle of this approach by constructing a database composed of IR fingerprints of eight isomeric/isobaric metabolites and use it for the identification of these isomers present in mixtures. Moreover, we show how our fast IR fingerprinting technology allows to probe the IR fingerprints of molecules within just a few seconds as they elute from an LC column. This approach has the potential to greatly improve metabolomics workflows in terms of accuracy, speed, and cost.

Enantioselective and Chemoselective Phosphine Oxide-catalyzed Aldol Reactions of N-Unprotected Cyclic Carboxyimides

Asymmetric catalytic transformations of N-unprotected cyclic carboxyimides such as succinimides, hydantoins, oxazolidinediones, and glitazones, is a powerful way of directly accessing variety of biologically valuable chiral compounds. Herein, a bis(trichlorosilyl) nucleophilic intermediate formed from cyclic carboxyimides was reacted with aldehydes via (S)-SEGPHOS dioxide (SEGPHOSO), proceeding the aldol reaction in highly enantioselective fashion through a cyclic transition state. Furthermore, N-unprotected carboxyimides were chemoselectively activated, even in the presence of N-alkylated carboxyimides, to undergo stereoselective and chemoselective aldol reactions via in situ silicon tetrachloride activation. The functionalized cyclic carboxyimides is readily derived to the several synthetic units derivatization to various chiral building blocks without unnecessary protection/deprotection steps.

Anti-Inflammatory and Hypouricemic Effect of Bioactive Compounds: Molecular Evidence and Potential Application in the Management of Gout

Gout is caused by the deposition of monosodium urate crystals in the joint and represents the most common form of inflammatory arthritis in men. Its prevalence is rising worldwide mainly due to the increase of risk factors associated with the disease, in particular hyperuricemia. Besides gout, hyperuricemia leads to an increased inflammatory state of the body with consequent increased risk of comorbidities such as cardiovascular diseases. Increasing evidence shows that bioactive compounds have a significant role in fighting inflammatory and immune chronic conditions. In gout and hyperuricemia, these molecules can exert their effects at two levels. They can either decrease serum uric acid concentrations or fight inflammation associated with monosodium urate crystals deposits and hyperuricemia. In this view, they might be considered valuable support to the pharmacological therapy and prevention of the disease. This review aims to provide an overview of the beneficial role of bioactive compounds in hyperuricemia, gout development, and inflammatory pathways of the disease.

Hypouricemic Effect of Submerged Culture of Ganoderma lucidum in Potassium Oxonate-Induced Hyperuricemic Rats

Hyperuricemia is a disease caused by a high level of uric acid in the blood. It is an important factor for gout and may be linked to renal and hepatic failure. The objective of this study was to investigate the hypouricemic effects of submerged culture of Ganoderma lucidum. The lyophilized powder of mycelium (GM) and extracellular polysaccharides (GP) of the G. lucidum submerged culture were prepared. The contents of hypouricemic components, including phenolics and flavonoids, in GM (34.33 ± 0.41 mg/g and 0.32 ± 0.01 mg/g) were higher than that in GP (20.52 ± 1.49 mg/g and not detected). The hypouricemic effect of GM and GP was evaluated in potassium oxonate (PO)-injected rats. The average food intake (23.3 ± 1.2 g/day) and body weight (355.7 ± 28.0 g) were decreased, and the serum level of uric acid (5.56 ± 0.41 mg/dL) was increased in PO-injected rats. However, allopurinol (10 mg/kg b.w.) or GM treatment (200 or 400 mg/kg b.w) improved food intake (26.3 ± 2.7 g/day) and reduced the level of uric acid (4.45 ± 0.46 mg/dL). In parallel, the activity of hepatic xanthine oxidase (XOD) was downregulated from 841.29 ± 299.58 μU/mg protein to 540.80 ± 199.20 μU/mg protein. Moreover, GM and GP (200 or 400 mg/kg b.w) alleviated the level of blood urea nitrogen (BUN) from 30.49 ± 4.71 to 21.16 ± 4.25 mg/dL. GP treatment also diminished the level of alanine transaminase (ALT) from 52.63 ± 18.82 to 27.35 ±6.82 U/L. These results clearly demonstrated the hypouricemic effect of submerged G. lucidum culture and their potential against hyperuricemia-associated renal and hepatic damage. GM was more potent to alleviate hyperuricemia, and GP was more potent to improve renal and hepatic function.

Chemical Analysis of Eruca sativa Ethanolic Extract and Its Effects on Hyperuricaemia

In vivo assays and chemical analyses were performed on the ethanolic extract from leaves of Eruca sativa. UHPLC-ESI-QTOF analysis confirmed the presence of glucosinolates and flavonol glucosides. The major flavonoid of the ethanolic extract, kaempferol-3,4′-di-O-β-glucoside, was isolated, a HPLC-DAD method developed and validated to quantify its content in the extract. In vivo experiments were carried out on Wistar rats with hyperuricaemia induced by potassium oxonate and uric acid. A hypouricaemic effect was observed in hyperuricaemic Wistar rats treated with ethanolic extract at dose of 125 mg/kg and kaempferol-3,4′-di-O-β-glucoside at dose of 10 mg/kg. The main anti-hyperuricaemic mechanism observed in the extract was uricosuric. Kaempferol-3,4′-di-O-β-glucoside was identified as an important component responsible for the total activity of the ethanolic extract and was considered as a good chemical and biological marker of the ethanolic extract of E. sativa. The obtained results indicated the potential of E. sativa in the treatment of hyperuricaemia and its comorbidities.

Antihyperuricemia and antigouty arthritis effects of Persicaria capitata herba in mice

BACKGROUND

Hyperuricemia (HUA) is an important risk factor for gout, renal dysfunction and cardiovascular diseases. The whole plant of Persicaria capitata (Buch.-Ham. ex D. Don) H. Gross, namely Persicaria capitata herba, is a well-known ethnic herb with potent therapeutic effects on urinary tract infections and urinary calculus, yet previous reports have only focused on its effect on urinary tract infections.

PURPOSE

To evaluate the therapeutic potential of P. capitata herba against gout by investigating its antihyperuricemia and antigouty arthritis effects and possible mechanisms.

METHODS

The ethanol extract (EP) and water extract (WP) of P. capitata herba were prepared by extracting dried and ground whole plants of P. capitata with 75% ethanol and water, respectively, followed by removal of solvents and characterization by UHPLC-Q-TOF/MS. The antihyperuricemia and antigouty arthritis effects of the two extracts were evaluated in a potassium oxonate- and hypoxanthine-induced hyperuricemia mouse model and a monosodium urate crystal (MSUC)-induced acute gouty arthritis mouse model, respectively. The mechanisms were investigated by testing their effects on the expression of correlated proteins (by Western blot) and mRNAs (by RT-PCR).

RESULTS

UHPLC-HRMS fingerprinting and two chemical markers (i.e., quercetin and quercitrin) determination were used for the characterization of the WP and EP extracts. Both WP and EP extracts showed pronounced antihyperuricemia activities, with a remarkable decline in serum uric acid and a marked increase in urine uric acid in hyperuricemic mice. Unlike the clinical xanthine oxidase (XOD) inhibitor allopurinol, WP and EP did not show any distinct renal toxicities. The underlying antihyperuricemia mechanism involves the inhibition of the activity and expression of XOD and the downregulation of the mRNA and protein expression of glucose transporter 9 (GLUT9) and urate transporter 1 (URAT1). The extracts of P. capitata herba also demonstrated remarkable anti-inflammatory activity in MSUC-induced acute gouty arthritis mice. The mechanism might involve inhibitory effects on the expression of proinflammatory factors.

CONCLUSIONS

The extracts of P. capitata herba possessed pronounced antihyperuricemia and antigouty arthritis effects and were, therefore, promising natural medicines for hyperuricemia-related disorders and gouty arthritis. The use of P. capitata herba for the treatment of urinary calculus may be, at least to some degree, related to its potential as an antihyperuricemia and antigouty arthritis drug.

Eggshell Membrane Ameliorates Hyperuricemia by Increasing Urate Excretion in Potassium Oxonate-Injected Rats

Hyperuricemia is the primary cause of gouty arthritis and other metabolic disorders. Eggshell membrane (EM) is an effective and safe supplement for curing pain and stiffness connected with osteoarthritis. However, the effect of EM on hyperuricemia is unclear. This study determines the effects of EM on potassium oxonate-injected hyperuricemia. Uric acid, creatinine, blood urea nitrogen concentrations in the serum, and xanthine oxidase activity in the liver are measured. Protein levels of renal urate transporter 1 (URAT1), organic anion transporters 1 (OAT1), glucose transporter 9 (GLUT9), and ATP-binding cassette transporter G2 (ABCG2) in the kidney are determined with renal histopathology. The results demonstrate that EM reduces serum uric acid levels and increases urine uric acid levels in hyperuricemic rats. Moreover, EM downregulates renal URAT1 protein expression, upregulates OAT1 and ABCG2, but does not change GLUT9 expression. Additionally, EM does not change xanthine oxidase activity in the liver or the serum. EM also decreases uric acid uptake into oocytes expressing hURAT1. Finally, EM markedly reduces renal inflammation and serum interleukin-1β levels. These findings suggest that EM exhibits antihyperuricemic effects by promoting renal urate excretion and regulating renal urate transporters. Therefore, EM may be useful in the prevention and treatment of gout and hyperuricemia.

Identification of xanthine oxidase inhibitors through hierarchical virtual screening

As a critical enzyme for the uric acid production, xanthine oxidase (XO) has emerged as a primary drug target for antihyperuricemic therapy. A hierarchical virtual screening integrating both ligand-based and structure-based approaches was applied herein to identify potent XO inhibitors. Four compounds, which were previously reported as XO inhibitors, were recognized through the virtual screening protocol, and compound H3, which is distinct from the structures of known XO inhibitors, was identified as a new chemotype inhibitor with IC₅₀ of 2.6 μM. The binding mode of H3 was further investigated by molecular docking and molecular dynamics (MD) simulation. The results suggested the feasibility to discover new chemotypes of XO inhibitors via integrated virtual screening strategies.

Lychnophora pinaster ethanolic extract and its chemical constituents ameliorate hyperuricemia and related inflammation

ETHNOPHARMACOLOGICAL RELEVANCE

Lychnophora pinaster, known as "Brazilian arnica" is used in folk medicine as alcoholic extract to treat inflammation, pain, rheumatism and bruises.

AIM OF THE STUDY

Evaluate the effects of the Lychnophora pinaster's ethanolic extract and its chemical constituents on inflammation and hyperuricemia.

MATERIALS AND METHODS

Ethanolic and hexanic extracts were obtained from the aerial parts of L. pinaster. Sesquiterpene E-lychnophoric acid was isolated from hexanic extract and identified by RMN, GC/MS and IR. In vivo anti-hyperuricemic and anti-inflammatory effects of the ethanolic extracts from L. pinaster (40, 125, 375 mg/kg), E-lychnophoric acid and other constituents previous isolated from L. pinaster and identified in the ethanolic extract by HPLC/UV/DAD (rutin, quercetin and vitexina flavonoids, caffeic, cinnamic and chlorogenic acids, lupeol and stigmasterol, at dose of 15 mg/kg) were assayed by experimental model of oxonate-induced hyperuricemia in Swiss mice, liver xanthine oxidase (XOD) inhibition and by MSU-induced paw edema in mice.

RESULTS

Ethanolic extract and all its components presented anti-hyperuricemic activity by inhibiting the hepatic xanthine oxidase activity. Ethanolic extract and its chemical constituents, except quercetin and vitexin, were able to reduce paw edema size induced by urate crystals. Hypouricemic and anti-inflammatory results obtained for the ethanolic extract (40, 125, 375 mg/kg) and E-lychnophoric acid (15 mg/kg) were similar those obtained for standard drugs, allopurinol (10 mg/kg) and indomethacin (3 mg/kg).

CONCLUSION

Ethanolic extract and E-lychnophoric, chlorogenic, cinnamic and caffeic acids, rutin, lupeol and stigmasterol presented anti-inflammatory and anti-hyperuricemic actvities. These compounds are responsible for the activities presented by the ethanolic extract of L. pinaster. Ethanolic extract and its chemical constituents can be considered promising agents in the therapeutic of inflammation, hyperuricemia and gout.

Effects of ChondroT on potassium Oxonate-induced Hyperuricemic mice: downregulation of xanthine oxidase and urate transporter 1

Background

ChondroT, a new herbal medication, consists of the water extracts of Osterici Radix, Lonicerae Folium, Angelicae Gigantis Radix, Clematidis Radix, and Phellodendri Cortex (6:4:4:4:3). We previously reported that ChondroT showed significant anti-arthritis and anti-inflammatory effects.

Methods

This study was designed to evaluate the effect of ChondroT on hyperuricemia. First, the effect of ChondroT was evaluated on xanthine oxidase (XOD) activity in vitro. The anti-hyperuricemic effect of ChondroT was also studied in potassium oxonate (PO)-induced hyperuricemic model mice. Uric acid (UA) and XOD were evaluated in the serum, urine, and liver of the mice. In addition, we measured serum creatinine (Cr) and blood urea nitrogen (BUN) levels as well as mRNA expression of the mouse urate transporter 1 (mURAT1) to evaluate kidney function and urate excretion in hyperuricemic mice.

Results

ChondroT showed in vitro XOD inhibitory activity in a dose-dependent manner (P < 0.05). We demonstrated that ChondroT (37.5, 75 and 150 mg/kg) significantly reduced serum UA (P < 0.01 and P < 0.001, respectively), and upregulated urinary UA (P < 0.001, respectively) in PO-induced hyperuricemic mice. In addition, ChondroT (75 and 150 mg/kg) significantly reduced Cr (P < 0.05 and P < 0.01, respectively), BUN (P < 0.05 and P < 0.001, respectively), GOT (P < 0.05 and P < 0.01, respectively), and GPT (P > 0.05 and P < 0.05, respectively) levels in PO-induced hyperuricemic mice. ChondroT (75 and 150 mg/kg) also significantly downregulated serum (P < 0.05) and liver (P < 0.05) XOD activity. Compared to the hyperuricemic mice, the ChondroT (37.5, 75, and 150 mg/kg)-treated mice showed decreased mURAT1 protein expression level.

Conclusion

ChondroT displayed anti-hyperuricemic effects by regulating XOD activity and kidney mURAT1.

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.

An effort toward molecular neuroeconomics of food deprivation induced food hoarding in mice: focus on xanthine oxidoreductase gene expression and xanthine oxidase activity

The crucial role of xanthine oxidoreductase (XOR) gene and its active isoform, xanthine oxidase (XO), in purine metabolism and cellular oxidative status led us to investigative their fluctuations in food deprivation induced food hoarding in mice. After, 10 h food deprivation, mice that hoarded lesser than 5 g were considered as 'low-hoarders' while mice that hoarded higher than 20 g were considered as 'high-hoarders'. Mice who hoarded between 5 to 20 g of food were excluded from study. An increase (1.133-fold) in encephalic XOR expression has been found in high-hoarders compared with low-hoarders without sex consideration. An increase (~ 50-fold) in encephalic XOR in female high-hoarders vs. female low-hoarders while a decrease (0.026-fold) in encephalic XOR in male high-hoarders vs. male low-hoarders demonstrated that food deprivation is associated with sex-dependent alteration in XOR expression. The encephalic and hepatic XO activities were not different in male high-hoarders vs. male low-hoarders while encephalic XO activity has been also increased significantly in female high-hoarders (~ 4 times) compared to female low-hoarders. The plasma and hepatic XO activities tended to be increased in female high-hoarders as compared to female low-hoarders, however the uric acid levels in plasma, liver and brain tissues were not altered in female high-hoarders as compared to female low-hoarders. In sum, this study generally proposed that different gene expression space is behind of hoarding behavior in a food-deprived mouse model. Specifically, this is the first study that examined the levels of encephalic XO activity and XOR expression in hoarding behavior, although additional studies are requested.

The influence of seasonality on the content of goyazensolide and on anti-inflammatory and anti-hyperuricemic effects of the ethanolic extract of Lychnophora passerina (Brazilian arnica)

ETHNOPHARMACOLOGICAL RELEVANCE

Lychnophora passerina (Mart ex DC) Gardn (Asteraceae), popularly known as Brazilian arnica, is used in Brazilian folk medicine to treat pain, rheumatism, bruises, inflammatory diseases and insect bites.

AIM OF THE STUDY

Investigate the influence of the seasons on the anti-inflammatory and anti-hyperuricemic activities of ethanolic extract of L. passerina and the ratio of the goyazensolide content, main chemical constituent of the ethanolic extract, with these activities.

MATERIALS AND METHODS

Ethanolic extracts of aerial parts of L. passerina were obtained from seasons: summer (ES), autumn (EA), winter (EW) and spring (EP). The sesquiterpene lactone goyazensolide, major metabolite, was quantified in ES, EA, EW and EP by a developed and validated HPLC-DAD method. The in vivo anti-hyperuricemic and anti-inflammatory effects of the ethanolic extracts from L. passerina and goyazensolide were assayed on experimental model of oxonate-induced hyperuricemia in mice, liver xanthine oxidase (XOD) inhibition and on carrageenan-induced paw edema in mice.

RESULTS

HPLC method using aqueous solution of acetic acid 0.01% (v/v) and acetonitrile with acetic acid 0.01% (v/v) as a mobile phase in a gradient system, with coumarin as an internal standard and DAD detection at 270nm was developed. The validation parameters showed linearity in a range within 10.0-150.0µg/ml, with intraday and interday precisions a range of 0.61-3.82. The accuracy values of intraday and interday analysis within 87.58-100.95%. EA showed the highest goyazensolide content. From the third to the sixth hour after injection of carrageenan, treatments with all extracts at the dose of 125mg/kg were able to reduce edema. Goyazensolide (10mg/kg) showed significant reduction of paw swelling from the second hour assay. This sesquiterpene lactone was more active than extracts and presented similar effect to indomethacin. Treatments with ES, EA and EP (125mg/kg) and goyazensolide (10mg/kg) reduced serum urate levels compared to hyperuricemic control group and were able to inhibit liver XOD activity. One of the mechanisms by which ES, EA, EP and goyazensolide exercise their anti-hyperuricemic effect is by the inhibition of liver XOD activity. Goyazensolide was identified as the main compound present in ES, EA, EW and EP and it is shown to be one of the chemical constituents responsible for the anti-inflammatory and anti-hyperuricemic effects of the ethanolic extracts.

CONCLUSION

The anti-inflammatory and anti-hyperuricemic activities of the ethanolic extracts from L. passerina were not proportionally influenced by the variation of goyazensolide content throughout the seasons. The involvement of goyazensolide on in vivo anti-inflammatory and anti-hyperuricemic activities of L.passerina extracts was confirmed, as well as the possibility of participation of other constituents on these effects. This study demonstrated that the aerial parts of L. passerina may be collected in any season for use as anti-inflammatory agent. For use in hyperuricemia, the best seasons for the collection are summer, autumn and spring. The ethanolic extract of L. passerina and goyazensolide can be considered promising agents in the therapeutic of inflammation, hyperuricemia and gout.

Antioxidant Properties of a Parsley (Petroselinum crispum) Juice Rich in Polyphenols and Nitrites

Parsley (Petroselinum crispum) is an herbaceous vegetable used as foodstuff, spice and medicinal plant because it provides antioxidants especially flavonoids (apigenin), vitamins (K, C and A), and volatile oils, among other compounds. Because parsley has important concentrations of nitrates and flavonoids, very little vegetal pigment and a mild flavour profile, it was chosen for this study. The aim of this study was to obtain parsley juice rich in nitrite and polyphenols and to assess its antioxidant activity. To obtain nitrite from nitrate by enzymatic reaction, Staphylococcus xylosus ATCC 29971 was used as nitrate reductase source. To obtain the vegetable juice, fresh roots were minced and homogenized in aqueous solution. The sterile juice was filtered and then inoculated with S. xylosus and incubated at 37°C. The nitrate and nitrite concentrations (mg/L) were determined using a colorimetric method using salicylic acid and Griess reagent, respectively. The total polyphenols content (TPC) was measured with Folin-Ciocalteu reagent and expressed as mg gallic acid equivalent / 100 mL (mg GAE / 100 mL). The total flavonoids content (TFC) was measured with aluminium chloride reagent, and expressed as mg catechin equivalent / 100 mL (mg CE / 100 mL). To determine the antioxidant activity of parsley juice, the ability to reduce DPPH synthetic radical, reducing power of Fe3+ ion and the capacity of chelating transition metal ions were assessed. Maximum concentration of nitrites was achieved for parsley juice in the presence of S. xylosus after 24 hours; TPC was 14.87 mg GAE / 100 mL and TFC was 11.21 mg CE / 100 mL. The ability of parsley fermented juice to reduce DPPH synthetic radical was 79.45%, while the capacity to reduce Fe3+ was 0.758 ± 0.14 (absorbance at 700 nm) and to chelate Fe2+ ion was 23.64%. Parsley juice represents an important source of natural nitrate and flavonoids, with important antioxidant capacity.

Hypouricaemic action of mangiferin results from metabolite norathyriol via inhibiting xanthine oxidase activity

Context Mangiferin has been reported to possess a potential hypouricaemic effect. However, the pharmacokinetic studies in rats showed that its oral bioavailability was only 1.2%, suggesting that mangiferin metabolites might exert the action. Objective The hypouricaemic effect and the xanthine oxidase inhibition of mangiferin and norathyriol, a mangiferin metabolite, were investigated. Inhibition of norathyriol analogues (compounds 3-9) toward xanthine oxidase was also evaluated. Materials and methods For a dose-dependent study, mangiferin (1.5-6.0 mg/kg) and norathyriol (0.92-3.7 mg/kg) were administered intragastrically to mice twice daily for five times. For a time-course study, mice received mangiferin and norathyriol both at a single dose of 7.1 μmol/kg. In vitro, inhibition of test compounds (2.4-2.4 mM) against xanthine oxidase activity was evaluated by the spectrophotometrical method. The inhibition type was identified from Lineweaver-Burk plots. Results Norathyriol (0.92, 1.85 and 3.7 mg/kg) dose dependently decreased the serum urate levels by 27.0, 33.6 and 37.4%, respectively. The action was more potent than that of mangiferin at the low dose, but was equivalent at the higher doses. Additionally, the hypouricaemic action of them exhibited a time dependence. In vitro, norathyriol markedly inhibited the xanthine oxidase activities, with the IC50 value of 44.6 μM, but mangiferin did not. The kinetic studies showed that norathyriol was an uncompetitive inhibitor by Lineweaver-Burk plots. The structure-activity relationships exhibited that three hydroxyl groups in norathyriol at the C-1, C-3 and C-6 positions were essential for maintaining xanthine oxidase inhibition. Discussion and conclusion Norathyriol was responsible for the hypouricaemic effect of mangiferin via inhibiting xanthine oxidase activity.

Effects of Pimenta pseudocaryophyllus extracts on gout: Anti-inflammatory activity and anti-hyperuricemic effect through xantine oxidase and uricosuric action

ETHNOPHARMACOLOGICAL RELEVANCE

Leaves infusion of Pimenta pseudocaryophyllus (Gomes) Landrum is used in Brazilian folk medicine to treat the predisposition to arthritical and gouty affections of the joints, fever and other diseases. A refreshing drink prepared with the specie is also used due to its diuretic, sedative and aphrodisiac actions.

AIM OF THE STUDY

The study was undertaken to investigate the mechanisms of anti-hyperuricemic effect and anti-inflammatory activity of P. pseudocaryophyllus extracts.

MATERIALS AND METHODS

Anti-hyperuricemic effect was investigated using xanthine oxidase assay and uricosuric studies with rats in which hyperuricemia was induced by potassium oxonate and uric acid. Anti-inflammatory activity was investigated on MSU crystal-induced paw edema model. Ethyl acetate extracts of the leaves (EAL) and branches (EAB), ethanolic extracts of leaves (EEL) and branches (EEB) and aqueous extracts of leaves (AL) and branches (AB) were evaluated.

RESULTS

The extracts of P. pseudocaryophyllus evaluated showed expressive results regarding the inhibition of xanthine oxidase enzyme in vitro and they were also able to reduce serum uric acid levels in hyperuricemic rats. The investigation of the mechanism of action, it was found that EAL, EAB, EEB, AB (125 and 250 mg/kg) and AL (250 mg/kg) promoted an increase on the urinary excretion of uric acid and EEL, EEB, AB (125 and 250 mg/kg) and EAB (250 mg/kg) were capable to inhibit liver xanthine oxidase. Treatments with EEL (125 and 250 mg/kg) and EEB (250 mg/kg) were able to reduce edema at 48 th h. EAL and EAB (125 and 250 mg/kg) showed significant anti-inflammatory activity on monosodium urate crystal-induced paw edema model at all evaluated times.

CONCLUSIONS

The specie P. pseudocaryophyllus showed remarkable anti-hyperuricemic effects through uricosuric effects and inhibition of xanthine oxidase and therefore can be considered as a promise in the treatment of diseases related to hyperuricemia. Moreover, ethyl acetate extracts had significant anti-inflammatory activity.

Traditional Uighur Medicine Karapxa decoction, inhibits liver xanthine oxidase and reduces serum uric acid concentrations in hyperuricemic mice and scavenges free radicals in vitro

Background

Karapxa decoction (KD) is a Traditional Uighur Medicine used for hepatitis, cholecystitis, gastralgia, oedema, gout and arthralgia. Because of its purported effect in gout, its effects were tested in hyperuricemic mice models induced by yeast extract paste or potassium oxonate, as well as its capacity to scavenge free radicals in vitro.

Methods

Hyperuricemia was induced in mice by yeast extract paste or potassium oxonate. KD was given orally for 14 days at 200, 400 and 800 mg/kg/day, with Allopurinol 10 mg/kg/day as positive control. Serum uric acid (UA), and liver xanthine oxidase activity (XO) were measured. Scavenging activity of KD on 1, 1-diphenyl-2-picrylhydrazyl radicals (DPP•), nitric oxide (•NO), superoxide (O₂•-), efficiency against lipid peroxidation, and XO inhibition were determined in vitro.

Results

KD inhibited liver XO activity and reduced serum uric acid in hyperuricemic mice. KD also showed noticeable antioxidant activity, scavenging free radicals (DPP•, •NO and O₂•-). It was effective against lipid peroxidation and inhibited XO in vitro.

Conclusions

This study supports the traditional use of Karapxa decoction to treat hyperuricemia and gout.

ABCG2 dysfunction increases serum uric acid by decreased intestinal urate excretion

ATP-binding cassette transporter G2 (ABCG2), also known as breast cancer resistance protein (BCRP), is identified as a high-capacity urate exporter and its dysfunction has an association with serum uric acid (SUA) levels and gout/hyperuricemia risk. However, pathophysiologically important pathway(s) responsible for the ABCG2-mediated urate excretion were unknown. In this study, we investigated how ABCG2 dysfunction affected the urate excretion pathways. First, we revealed that mouse Abcg2 mediates urate transport using the membrane vesicle system. The export process by mouse Abcg2 was ATP-dependent and not saturable under the physiological concentration of urate. Then, we characterized the excretion of urate into urine, bile, and intestinal lumen using in vivo mouse model. SUA of Abcg2-knockout mice was significantly higher than that of control mice. Under this condition, the renal urate excretion was increased in Abcg2-knockout mice, whereas the urate excretion from the intestine was decreased to less than a half. Biliary urate excretion showed no significant difference regardless of Abcg2 genotype. From these results, we estimated the relative contribution of each pathway to total urate excretion; in wild-type mice, the renal excretion pathway contributes approximately two-thirds, the intestinal excretion pathway contributes one-third of the total urate excretion, and the urate excretion into bile is minor. Decreased intestinal excretion could account for the increased SUA of Abcg2-knockout mice. Thus, ABCG2 is suggested to have an important role in extra-renal urate excretion, especially in intestinal excretion. Accordingly, increased SUA in patients with ABCG2 dysfunction could be explained by the decreased excretion of urate from the intestine.

Effects of anthocyanins from purple sweet potato (Ipomoea batatas L. cultivar Eshu No. 8) on the serum uric acid level and xanthine oxidase activity in hyperuricemic mice

This study was aimed at evaluating the hypouricemic effect of the anthocyanin-rich purple sweet potato extract (APSPE).

Characterization of an Anti-gout Xanthine Oxidase Inhibitor from Pleurotus ostreatus

We selected Pleurotus ostreatus from among several edible mushrooms because it has high anti-gout xanthine oxidase (XOD) inhibitory activity. The maximal amount of XOD inhibitor was extracted when the Pleurotus ostreatus fruiting body was treated with distilled water at 40℃ for 48 hr. The XOD inhibitor thus obtained was purified by Sephadex G-50 gel permeation chromatography, ultrafiltration, C18 solid phase extraction chromatography and reverse-phase high-performance liquid chromatography with 3% of solid yield, and its XOD inhibitory activity was 0.9 mg/mL of IC50. The purified XOD inhibitor was a tripeptide with the amino acid sequence phenylalanine-cysteine-histidine and a molecular weight of 441.3 Da. The XOD inhibitor-containing ultrafiltrates from Pleurotus ostreatus demonstrated dose-dependent anti-gout effects in a Sprague-Dawley rat model of potassium oxonate-induced gout, as shown by decreased serum urated levels at doses of 500 and 1,000 mg/kg, although the effect was not as great as that achieved with the commercial anti-gout agent, allopurinol when administered at a dose of 50 mg/kg.

Hypouricemic effect of the methanol extract from Prunus mume fruit in mice

CONTEXT

The fruit of the Prunus mume Sieb. et Zucc (Rosaceae) is used as a health food or medicinal material in traditional herb medicine for a long time in Eastern Asian countries.

OBJECTIVE

Our present study investigated the hypouricemic effect of the methanol extract from P. mume fruit (MPMF) in mice with potassium oxonate-induced hyperuremia.

MATERIALS AND METHODS

Effect of MPMF (35, 70 and 140 mg/kg, p.o.) administrated for 7 days on the serum, liver, urinary uric acid levels and liver xanthine oxidase (XO) activity were assessed in mice.

RESULTS

Hyperuricemic mice induced by potassium oxonate demonstrated an elevation in serum and liver uric acid levels (11.0 mg/dL and 0.52 mg/g tissue) and a reduction in urinary uric acid levels (49.9 mg/dL). Oral administration of 140 mg/kg MPMF for 7 days reversed the abnormalities in serum, liver and urinary uric acid levels (7.1 mg/dL, 0.37 mg/g tissue and 69.7 mg/dL, respectively). In addition, 70 and 140 mg/kg MPMF (3.1 and 2.9 nmol/min per mg protein) inhibited liver XO activity compared with hyperuricemic mice (3.9 nmol/min per mg protein).

DISCUSSION AND CONCLUSION

The results indicated that the beneficial hypouricaemic effect of MPMF may be mediated, at least in part, by inhibiting XO activity in the liver. Our study suggests that P. mume and its extracts may have a considerable potential for development as an anti-gout agent for clinical application.

Reducing effect of mangiferin on serum uric acid levels in mice

CONTEXT

Mangiferin, a natural bioactive xanthone C-glycoside, is widely present in medicinal plants like the leaf of Mangifera indica L. (Anacardiaceae). It has been reported that mangiferin possesses a variety of biological activities, including antidiabetic, hepatoprotective, anti-inflammatory, antioxidant, and anticarcinogenic.

OBJECTIVE

The hypouricemic effect and xanthine oxidoreductase (XOR) inhibitory activity of mangiferin were investigated here for the first time.

MATERIALS AND METHODS

The hypouricemic effect of mangiferin was investigated in normal and hyperuricemic mice induced by potassium oxonate. Mangiferin at a dose of 0.75-100.0 mg/kg was given intragastrically to mice. The serum urate levels were determined using the phosphotungstic acid method. The hepatic activities of xanthine dehydrogenase (XDH) and xanthine oxidase (XOD) in hyperuricemic mice were assayed using commercially available kits.

RESULTS

The results showed that mangiferin at a dose of 1.5, 3.0, and 6.0 mg/kg significantly reduced the serum urate levels (148.7 ± 37.8, 142.2 ± 44.5, 121.7 ± 21.7 µmmol/L) in hyperuricemic mice, compared with untreated hyperuricemic mice (201.8 ± 71.2 µmmol/L). However, mangiferin did not decrease the serum urate levels in normal mice until mangiferin was up to 100 mg/kg. In addition, the hepatic activities of XDH in hyperuricemic mice were significantly decreased by mangiferin, while no changes of XOD were observed. Acute toxicity study in mice showed that mangiferin was very safe at a dose of up to 25 g/kg.

DISCUSSION AND CONCLUSION

These findings demonstrate that mangiferin has the potential to be developed as a new therapeutic agent for the treatment of hyperuricemia and gout.

Pharmacological basis for use of Lychnophora trichocarpha in gouty arthritis: anti-hyperuricemic and anti-inflammatory effects of its extract, fraction and constituents

ETHNOPHARMACOLOGICAL RELEVANCE

The ethanolic extract of Lychnophora trichocarpha Spreng. is used in Brazilian folk medicine to treat bruise, pain and inflammatory diseases.

AIM OF THE STUDY

The present study aimed at investigating whether ethanolic extract of L. trichocarpha, its ethyl acetate fraction and its main bioactive compounds could be useful to treat gouty arthritis by countering hyperuricemia and inflammation.

MATERIALS AND METHODS

L. trichocarpha ethanolic extract (LTE), ethyl acetate fraction from ethanolic extract (LTA) and isolated compounds were evaluated for urate-lowering activity and liver xanthine oxidase (XOD) inhibition in oxonate-induced hyperuricemic mice. Anti-inflammatory activity in monosodium urate crystal-induced paw oedema, an experimental model of gouty arthritis, was also investigated.

RESULTS

Crude ethanolic extract and its ethyl acetate fraction showed significant urate-lowering effects. LTE was also able to significantly inhibit liver xantine oxidase (XOD) activity in vivo at the dose of 250mg/kg. Luteolin, apigenin, lupeol, lychnopholide and eremantholide C showed the anti-hyperuricemic activities among tested compounds. Apigenin also showed XOD inhibitory activity in vivo. Luteolin, lychnopholide, lupeol and eremantholide C, in turn, did not shown significant inhibitory activity towards this enzyme, indicating that this mechanism is not likely to be involved in urate-lowering effects of those compounds. LTE, LTA, lupeol, β-sitosterol, lychnopholide, eremantholide, luteolin and apigenin were also found to inhibit monosodium urate crystals-induced paw oedema in mice.

CONCLUSIONS

Ethanolic extract of Lychnophora trichocarpha and some of its bioactive compounds may be promising agents for the treatment of gouty arthritis since they possesses both anti-hiperuricemic and anti-inflammatory properties.

Hypouricemic Effects of Phenylpropanoid Glycosides Acteoside ofScrophularia ningpoensison Serum Uric Acid Levels in Potassium Oxonate-Pretreated Mice

Phenylpropanoid glycoside acteoside was extracted from the traditional Chinese medicine Scrophularia ningpoenis Hemsl. In the present study, we investigated the effects of acteoside administration on serum uric acid levels in mice rendered hyperuricemic with the uricase inhibitor potassium oxonate. When administered orally for 3 days at doses of 50, 100 and 150 mg/kg, acteoside reduced serum uric acid levels by 15.2, 23.8 and 33.1%, respectively, relative to vehicle-treated hyperuricemic mice. Importantly, in non-hyperuricemic mice, the serum uric acid levels were not affected by acetoside treatment. Acteoside also inhibited mouse liver xanthine dehydrogenase XDH and xanthine oxidase XO activity at all three doses. These results suggest that the hypouricemic action of acteoside may be attributable to its inhibition of XDH/XO activity.

Decreased extra-renal urate excretion is a common cause of hyperuricemia

ABCG2, also known as BCRP, is a high-capacity urate exporter, the dysfunction of which raises gout/hyperuricemia risk. Generally, hyperuricemia has been classified into urate 'overproduction type' and/or 'underexcretion type' based solely on renal urate excretion, without considering an extra-renal pathway. Here we show that decreased extra-renal urate excretion caused by ABCG2 dysfunction is a common mechanism of hyperuricemia. Clinical parameters, including urinary urate excretion, are examined in 644 male outpatients with hyperuricemia. Paradoxically, ABCG2 export dysfunction significantly increases urinary urate excretion and risk ratio of urate overproduction. Abcg2-knockout mice show increased serum uric acid levels and renal urate excretion, and decreased intestinal urate excretion. Together with high ABCG2 expression in extra-renal tissues, our data suggest that the 'overproduction type' in the current concept of hyperuricemia be renamed 'renal overload type', which consists of two subtypes-'extra-renal urate underexcretion' and genuine 'urate overproduction'-providing a new concept valuable for the treatment of hyperuricemia and gout.

Effects of orange juice and hesperetin on serum paraoxonase activity and lipid profile in hyperuricemic rats

INTRODUCTION

Hypouricemic, antioxidant and xanthine oxidase inhibitory effects of orange juice and hesperetin have been already indicated. The objective of this study was to investigate the effects of orange juice and hesperetin on paraoxonase and arylesterase activity and lipid profile of hyperuricemic rats.

METHODS

Forty eight male Wistar rats were divided into 8 equal groups of healthy control, healthy+orange juice, healthy+hesperetin, healthy+allopurinol, hyperuricemic control, hyperuricemic+orange juice, hyperurice-mic+hesperetin and hyperuricemic+allopurinol. Hyperuricemia was induced using potassi-um oxonate (250 mg/kg ip). The treatments were carried out by daily gavage of 5 ml/kg orange juice, 5 mg/kg hesperetin and 5 mg/kg allopurinol for 2 weeks. Paraoxonase activi-ty in serum was measured spectrophotometrically using paraoxon and phenylacetate as substrates. Serum lipids levels were determined using enzymatic colorimetric methods.

RESULTS

Hyperuricemia-induced reduction of paraoxonase and arylesterase activity was restored after treatment with orange juice and hesperetin (p<0.05). The effect of both treatments on lipid profile was marginal and only orange juice could significantly increase the levels of HDL-C.

CONCLUSION

Supplementation of orange juice and hesperetin could restore paraoxonase and arylesterase activity in hyperuricemic rats. Orange juice could also partially improve the lipid profile. These effects could have major implications with respect to the prevention of cardiovascular disease in hyperuricemic patients. However, more studies are needed in future investigations.

Simiao pill ameliorates urate underexcretion and renal dysfunction in hyperuricemic mice

ETHNOPHARMACOLOGICAL RELEVANCE

Simiao pill is one of the most frequently prescription in traditional Chinese medicine to treat gout and hyperuricemia.

AIM OF THE STUDY

We investigated the effects of Simiao pill on urate excretion and renal function and examined whether renal organic ion transporters are involved in potassium oxonate-induced hyperuricemic mice.

MATERIALS AND METHODS

Water extract of Simiao pill at 507, 1014 and 2028mg/kg was orally administered to hyperuricemic and normal mice for 7 days, and allopurinol (5mg/kg) was given as a positive control. Serum and urine levels of uric acid and creatinine, and fractional excretion of uric acid (FEUA) were measured in hyperuricemic and normal mice treated with Simiao pill and allopurinol. Simultaneously, the mRNA and protein levels of mouse urate transporter 1 (mURAT1), glucose transporter 9 (mGLUT9) and organic anion transporter 1 (mOAT1) and organic cation/carnitine transporters (mOCT1, mOCT2, mOCTN1 and mOCTN2) in the kidney were analyzed by semi-quantitative RT-PCR and Western blotting methods, respectively.

RESULTS

Simiao pill significantly reduced serum uric acid levels and increased FEUA dose-dependently in hyperuricemic mice. And it effectively reversed oxonate-induced alterations in renal mURAT1, mGLUT9 and mOAT1 mRNA and protein levels, resulting in the enhancement of renal urate excretion in mice. Moreover, Simiao pill decreased serum creatinine levels, as well as increased renal mOCT1, mOCT2, mOCTN1 and mOCTN2 mRNA and protein levels, leading to improve renal dysfunction in this model.

CONCLUSION

These findings suggest that Simiao pill processes uricosuric and nephroprotective actions by regulating renal organic ion transporters in hyperuricemic animals.

The dual actions of Sanmiao wan as a hypouricemic agent: down-regulation of hepatic XOD and renal mURAT1 in hyperuricemic mice

ETHNOPHARMACOLOGICAL RELEVANCE

Sanmiao wan (SMW) is widely used for the treatment of gout and hyperuricemia in traditional Chinese medicine.

AIM OF THE STUDY

The aim of the present study was to investigate the hypouricemic effects of SMW and its possible mechanism in potassium oxonate-induced hyperuricemic mice.

MATERIALS AND METHODS

SMW at 489, 978 and 1956 mg/kg was orally administered to hyperuricemic and normal mice, and standard drug allopurinol (2.5mg/kg) was served as a positive control. The effects of SMW on serum, urine and liver levels of uric acid, serum levels of creatinine, and activity of hepatic xanthine oxidase (XOD) were measured in mice. Moreover, the effects of SMW on the mRNA and protein levels of hepatic XOD and renal urate transporter 1 (mURAT1) in mice were analyzed by semi-quantitative RT-PCR and Western blotting methods, respectively.

RESULTS

SMW significantly reduced uric acid levels in serum and liver, inhibited hepatic XOD activity, mRNA and protein levels in hyperuricemic mice. Furthermore, SMW could effectively down-regulate renal mURAT1 mRNA and protein levels of hyperuricemic mice. And it reversed oxonate-induced elevation in serum creatinine levels of mice. However, SMW did not show any effects in normal mice.

CONCLUSION

These findings suggested that SMW produced dual hypouricemic actions by suppressing hepatic XOD to reduce uric acid production and down-regulating renal mURAT1 to decrease urate reabsorption and enhance urate excretion in hyperuricemic mice.

Orange juice and hesperetin supplementation to hyperuricemic rats alter oxidative stress markers and xanthine oxidoreductase activity

Our objective was to examine the effect of orange juice and hesperetin on serum total antioxidant capacity (TAC), lipid peroxidation (MDA), uric acid and hepatic xanthine oxidase (XO) and xanthine dehydrogenase (XDH) activity in hyperuricemic rats. Experimentally hyperuricemia in rats was induced by intraperitoneal injection of potassium oxonate (250 mg/kg). Orange juice (5 ml/kg) and hesperetin (5 mg/kg) was given by oral gavage to rats for 2 weeks and biochemical data was measured. Data showed that orange juice supplementation increased serum TAC and decreased MDA concentration (p≤0.05). Orange juice also inhibited hepatic XO and XDH activity and decreased serum uric acid levels. Hesperetin, which is the main flavanone constituent in orange juice, also exhibited antioxidative and antihyperuricemic properties, but its effect was weaker than that of orange juice. Although the hypouricemic effect of allopurinol (5 mg/kg), as a positive control, was much higher than that of orange juice and hesperetin, it could not significantly change biomarkers of oxidative stress. These features of orange juice and hesperetin make them an attractive candidate for the prophylactic treatment of hyperuricaemia, particularly if these compounds are to be taken on a long-term basis.

Effects of onion on serum uric acid levels and hepatic xanthine dehydrogenase/xanthine oxidase activities in hyperuricemic rats

The aim of this study was to investigate the effects of onion on serum uric acid levels and hepatic Xanthine Dehydrogenase/Xanthine Oxidase activities in normal and hyperuricemic rats. Hyperuricemia was induced by intraperitoneal injection of 250 mg kg(-1) potassium oxonate in rats. Oral administration of onion at 3.5 and 7.0 mg kg(-1) day(-1) for 7 days was able to reduce serum uric acid levels in hyperuricemic rats with no significant effects on the level of this compound in the normal animals. In addition, onion when tested in vivo on rat liver homogeneities elicited significant inhibitory actions on the Xanthine Dehydrogenase (XDH) and Xanthine Oxidase (XO) activities. This effect resulted less potent than that of allopurinol. However, the hypouricemic effect observed in the experimental animal did not seem to parallel the change in XDH and XO activities, implying that the onion might be acting via other mechanisms apart from simple inhibition of enzyme activities. Such hypouricemic action and enzyme inhibitory activity of onion makes it a possible alternative for allopurinol, or at least in combination therapy to minimize the side-effects of allopurinol, in particular in long-term application.

Hypouricemic Action of Selected Flavonoids in Mice: Structure-Activity Relationships

Hyperuricemia and gout appear to be rapidly increasing worldwide and frequently cause symptoms of metabolic syndrome. Dietary flavonoids have their potential beneficial effects on human health. In the present study, 15 flavonoids (quercetin, morin, myricetin, kaempferol, icariin, apigenin, luteolin, baicalin, silibinin, naringenin, formonoetin, genistein, puerarin, daidzin and naringin dihydrochalcone) were selected to investigate for their hypouricemic action in mice. Oral administration of quercetin, morin, myricetin, kaempferol, apigenin and puerarin at 50 and 100 mg/kg for 3 d was able to elicit hypouricemic actions in hyperuricemic mice induced by potassium oxonate. Luteolin, formonoetin and naringenin showed the significant effects only at 100 mg/kg. Quercetin, puerarin, myricetin, morin and kaempferol significantly reduced liver uric acid level in hyperuricemic animals. In addition, quercetin, morin, myricetin, kaempferol and puerarin exhibited significant inhibition on the liver xanthine oxidase (XOD) activities. It seems to be likely that these flavonoids reduce serum urate levels by mainly inhibiting XOD activity. However, the hypouricemic effect of apigenin observed seemed not to parallel with the changes in liver uric acid level and liver XOD activity, implying that apigenin might act via other mechanisms apart from inhibiting enzyme activity simply. Analysis of the chemical structure showed that a planar structure with the hydroxyl groups played a crucial role in hypouricemic activity of flavonoids. The exact mechanism of the hypouricemic action of flavonoids in vivo should be investigated in the future.

Effect and mechanism of total saponin of Dioscorea on animal experimental hyperuricemia

In this study, we investigated the effects and mechanisms of Total Saponin of Dioscorea (TSD) on animal experimental hyperuricemia. Mouse and rat hyperuricemic models were made by orally administering yeast extract paste once a day (30 and 20 g/kg, respectively), for 7 days. Yeast would disturb normal purine metabolism by increasing xanthine oxidase (XOD) activity and generating large quantities of uric acid. This model is similar to human hyperuricemia, which is induced by high-protein diets, due to a purine and nucleic acid metabolic disturbance. Another mouse hyperuricemia model was generated by intraperitoneal injection once with uric acid 250 mg/kg or potassium oxonate 300 mg/kg. Potassium oxonate, a urate oxidase inhibitor, can raise the serum uric acid level by inhibiting the decomposition of uric acid. Likewise, injecting uric acid can also increase serum uric acid concentration. The concentration of uric acid in serum or urine was detected by the phosphotungstic acid method, and the activity of XOD was assayed by a test kit. The results showed that TSD (240, 120 and 60 mg/kg, ig) could significantly lower the level of serum uric acid in hyperuricemic mice. TSD (120 and 60 mg/kg, ig) could also lower the level of serum uric acid in hyperuricemic rats, reduce the activity of XOD in the serum and liver of hyperuricemic rats, and increase the level of urine uric acid concentration as well as 24-hour total uric acid excretion. In conclusion, TSD possesses a potent anti-hyperuricemic effect on hyperuricemic animals, and the mechanism may be relevant in accelerating the excretion and decreasing the production of uric acid.

Effects of cassia oil on serum and hepatic uric acid levels in oxonate-induced mice and xanthine dehydrogenase and xanthine oxidase activities in mouse liver

We investigated the hypouricemic effects of cassia oil extracted from Cinnamomum cassia using hyperuricemic mice induced by potassium oxonate, and its inhibitory actions against liver xanthine dehydrogenase (XDH) and xanthine oxidase (XOD) activities. Oral administration of cassia oil significantly reduced serum and hepatic urate levels in hyperuricemic mice in a time- and dose-dependent manner. At doses of 450 mg/kg of cassia oil or above, serum urate levels of the oxonate-pretreated mice were not different from the normal control mice. Cassia oil at 600 mg/kg was found to be as potent as allopurinol, which reduced hepatic urate levels to lower than normal. In normal mice, urate levels in liver, but not in serum, were altered with dose-dependent decrease after cassia oil treatment. Furthermore, the ratio, liver uric acid/serum uric acid, was determined after cassia oil administration with time- and dose-dependent decreases in hyperuricemic mice. The positive dose-dependent decrease ratio was also observed after cassia oil treatment in the normal animals. The decreased extent of ratio elicited by cassia oil in normal mice appeared to be greater than that in the hyperuricemic animal. In addition, cassia oil significantly exhibited marked reductions in liver XDH/XOD activities, with an apparent dose-dependence in the normal and hyperuricemic mice. The onset of inhibition in enzyme activities elicited by allopurinol was much higher than that elicited by cassia oil. These results suggested that hypouricemic effects of cassia oil could be explained, at least partly, by inhibiting liver in vivo activities of XDH/XOD.

Administration of procyanidins from grape seeds reduces serum uric acid levels and decreases hepatic xanthine dehydrogenase/oxidase activities in oxonate-treated mice

In this study we have investigated the effects of administration of procyanidins from grape seeds on serum uric acid levels in a model of hyperuricaemia in mice pretreated with oxonate, as well as the xanthine dehydrogenase and xanthine oxidase activities in mouse liver in vivo. The procyanidins, when orally administered to the oxonate-pretreated hyperuricaemic mice, were able to elicit a dose-dependent hypouricaemic effect. At a dose of 400 mg/kg for 3 days, the serum urate levels of the oxonate-pretreated mice were not different from the normal mice. In addition, the hepatic activities of xanthine dehydrogenase and xanthine oxidase in the procyanidins-treated mice were found to decrease significantly. However, the hypouricaemic effects observed in the experimental animals did not seem to parallel the changes in xanthine dehydrogenase and xanthine oxidase activities, implying that the procyanidins might be acting via other mechanisms apart from simple inhibition of enzyme activities. Furthermore, the procyanidin-treated animals exhibited normal growth while the allopurinol-treated animals exhibited some retarded growth. These results demonstrated for the first time that the procyanidins from grape seeds possess in vivo urate-lowering activities. The potential application of these natural compounds in the treatment of hyperuricaemia is discussed.