Inhibition of xanthine oxidase by Rhodiola crenulata extracts and their phytochemicals

Ferulic acid ameliorates hyperuricemia by regulating xanthine oxidase

Hyperuricemia is characterized by elevated uric acid (UA) level in the body. The xanthine oxidase (XO) inhibitory ability is an important way to evaluate the anti-hyperuricemia effect of natural products. Ferulic acid (FA) is a phenolic acid compound, and it is a free radical scavenger with many physiological functions. The aim of this study was to investigate the structure-activity relationship, potential mechanism and interaction of FA as XO's inhibitor. In the cell experiment, using 1.25 mM adenosine to incubate for 24 h under the optimal conditions (37 °C, pH = 7.2) can increase the UA production by 1.34 folds. PCR analysis showed that FA could reduce the mRNA expression level of XO. FA inhibited XO in a mixed mode (IC50 = 13.25 μM). The fluorescence quenching of XO by FA occurs through a static mechanism, with an inhibition constant of Ki = 9.527 × 10-5 mol L-1 and an apparent coefficient of α = 1.768. The enthalpy and entropy changes were found as -267.79 KJ mol-1 and - 860.85 KJ mol-1, indicating that both hydrogen binding and hydrophobic are involved in the interaction of this polyphenolic natural compound with XO. Thus, FA supplementation may be a potential therapeutic strategy to improve hyperuricemia by reducing UA production.

Design and synthesis of salidroside analogs and their bioactivity against septic myocardial injury

Cardiac tissue suffers much from sepsis, and the incidence of myocardial injury is high in septic patients. The treatment of sepsis myocardial injury (SMI) has been the focus of clinical medicine. Salidroside shows myocardial cell protection, anti-oxidation and anti- inflammation effects, and it is thought as one of the potential compounds to treat sepsis myocardial injury. However, its anti-inflammatory activity is lower and its pharmacokinetic properties are not ideal, which is far from clinical application. Here, a series of salidroside analogs were synthesized, and their bioactivities were evaluated from several aspects, including their anti-oxidant and anti-inflammatory activities in vitro and anti-sepsis myocardial injury activities in vivo. Of all the compounds which synthesized, compounds 2 and 3 exhibited stronger anti-inflammatory activities than the others; after treating LPS-stimulated RAW264.7 or H9c2 cells with each of them, the levels of IL-1β, IL-6 and TNF-α were down-regulated in a dose-dependent manner. In the anti-oxidative stress injury test, compounds 2 and 3 not only markedly increased the survival rate of cells, and but also improved the cellular oxidative stress-related indicators MDA, SOD and cell damage marker LDH in a dose-dependent manner. In the LPS-induced septic rat myocardial injury models (in vivo), the two compounds also showed good bioactivities. They also reduced the expression of IL-1β, IL-6 and TNF-α, and blocked cell damage by suppressing overhauled oxidation in septic rats. In addition, the myocardial injury was significantly improved and the inflammatory infiltration was reduced after treatment with the two compounds. In conclusion, the salidroside analogs (2 and 3) showed promising therapeutical effect on septic myocardial injury in LPS-model rats, and they could be good candidates for clinical trials against inflammation and septic myocardial injury.

Preparation, Purification, and Identification of Novel Feather Keratin-Derived Peptides with Antioxidative and Xanthine Oxidase Inhibitory Activities

Feather keratin is an underappreciated protein resource of high quality, with limited bioavailability, and it urgently requires eco-friendly methods to enhance its value. Here, we report on the preparation, purification, and identification of novel peptides with antioxidant and xanthine oxidase (XOD) inhibitory activities from fermented feather broth, using Bacillus licheniformis 8-4. Two peptides, namely, DLCRPCGPTPLA (DA-12) and ANSCNEPCVR (AR-10), displayed remarkable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging abilities with half-maximal inhibitory concentrations (IC₅₀) values of 0.048, 0.034, and 0.95, 0.84 mg/mL, respectively. These values exceed those of the previously reported feather keratin-derived antioxidant peptides. Another peptide, GNQQVHLQSQDM (GM-12), demonstrated XOD activity inhibition, with an IC₅₀ value of 12.15 mg/mL, and it quenched the fluorescence of XOD. Furthermore, after simulating gastrointestinal digestion, DA-12, AR-10, and GM-12 retained their biological activities. Meanwhile, DA-12 and GM-12 showed an unexpected synergistic inhibition on XOD activity accompanied by fluorescence quenching. This study provides new insights into the potential applications of feather keratin, including functionalized feed with antioxidative and antigout (anti-hyperuricemia) activities.

Function of Uric Acid Transporters and Their Inhibitors in Hyperuricaemia

Disorders of uric acid metabolism may be associated with pathological processes in many diseases, including diabetes mellitus, cardiovascular disease, and kidney disease. These diseases can further promote uric acid accumulation in the body, leading to a vicious cycle. Preliminary studies have proven many mechanisms such as oxidative stress, lipid metabolism disorders, and rennin angiotensin axis involving in the progression of hyperuricaemia-related diseases. However, there is still lack of effective clinical treatment for hyperuricaemia. According to previous research results, NPT1, NPT4, OAT1, OAT2, OAT3, OAT4, URAT1, GLUT9, ABCG2, PDZK1, these urate transports are closely related to serum uric acid level. Targeting at urate transporters and urate-lowering drugs can enhance our understanding of hyperuricaemia and hyperuricaemia-related diseases. This review may put forward essential references or cross references to be contributed to further elucidate traditional and novel urate-lowering drugs benefits as well as provides theoretical support for the scientific research on hyperuricemia and related diseases.

Natural Products and Extracts as Xantine Oxidase Inhibitors - A Hope for Gout Disease?

Xanthine oxidase (EC 1.17.3.2) (XO) is one of the main enzymatic sources that create reactive oxygen species (ROS) in the living system. It is a dehydrogenase enzyme that performs electron transfer to nicotinamide adenine dinucleotide (NAD+), while oxidizing hypoxanthin, which is an intermediate compound in purine catabolism, first to xanthine and then to uric acid. XO turns into an oxidant enzyme that oxidizes thiol groups under certain stress conditions in the tissue. The last metabolic step, in which hypoxanthin turns into uric acid, is catalyzed by XO. Uric acid, considered a waste product, can cause kidney stones and gouty-type arthritis as it is crystallized, when present in high concentrations. Thus, XO inhibitors are one of the drug classes used against gout, a purine metabolism disease that causes urate crystal storage in the joint and its surroundings caused by hyperuricemia. Urate-lowering therapy includes XO inhibitors that reduce uric acid production as well as uricosuric drugs that increase urea excretion. Current drugs that obstruct uric acid synthesis through XO inhibition are allopurinol, febuxostat, and uricase. However, since the side effects, safety and tolerability problems of some current gout medications still exist, intensive research is ongoing to look for new, effective, and safer XO inhibitors of natural or synthetic origins for the treatment of the disease. In the present review, we aimed to assess in detail XO inhibitory capacities of pure natural compounds along with the extracts from plants and other natural sources via screening Pubmed, Web of Science (WoS), Scopus, and Google Academic. The data pointed out to the fact that natural products, particularly phenolics such as flavonoids (quercetin, apigenin, and scutellarein), tannins (agrimoniin and ellagitannin), chalcones (melanoxethin), triterpenes (ginsenoside Rd and ursolic acid), stilbenes (resveratrol and piceatannol), alkaloids (berberin and palmatin) have a great potential for new XO inhibitors capable of use against gout disease. In addition, not only plants but other biological sources such as microfungi, macrofungi, lichens, insects (silk worms, ants, etc) seem to be the promising sources of novel XO inhibitors.

Screening of Xanthine Oxidase Inhibitors by Liquid Crystal-Based Assay Assisted with Enzyme Catalysis-Induced Aptamer Release

Small-molecule drugs play an important role in the treatment of various diseases. The screening of enzyme inhibitors is one of the most important means in developing therapeutic drugs. Herein, we demonstrate a liquid crystal (LC)-based screening assay assisted with enzyme catalysis-induced aptamer release for screening xanthine oxidase (XOD) inhibitors. The oxidation of xanthine by XOD prevents the specific binding of xanthine and its aptamer, which induces a bright image of LCs. However, when XOD is inhibited, xanthine specifically binds to the aptamer. Correspondingly, LCs display a dark image. Three compounds are identified as potent XOD inhibitors by screening a small library of triazole derivatives using this method. Molecular docking verifies the occupation of the active site by the inhibitor, which also exhibits excellent biocompatibility to HEK293 cells and HeLa cells. This strategy takes advantages of the unique aptamer-target binding, specific enzymatic reaction, and simple LC-based screening assay, which allows high-throughput and label-free screening of inhibitors with high sensitivity and remarkable accuracy. Overall, this study provides a competent and promising approach to facilitate the screening of enzyme inhibitors using the LC-based assay assisted with the enzyme catalysis-induced aptamer release.

Exploring the potential of novel xanthine oxidase inhibitory peptide (ACECD) derived from Skipjack tuna hydrolysates using affinity-ultrafiltration coupled with HPLC-MALDI-TOF/TOF-MS

This study aimed to isolate and investigate the potential of the peptide alanine-cysteine-glutamic acid-cysteine-aspartic acid (ACECD), a novel xanthine oxidase inhibitory (XODI) peptide derived from Skipjack tuna hydrolysate (HS). Ultrafiltration membranes were used to obtain HS-based peptides as successive ultrafiltration fractions (of decreasing molecular weight) of UF-1, UF-2, UF-3, and UF-4. Their antioxidant and xanthine oxidase (XOD) inhibitory activities were determined and further characterized by affinity-ultrafiltration coupled with HPLC-MALDI-TOF/TOF-MS and in silico techniques. The results showed that peptides with a molecular weight (MW) cutoff of 600-1000 Da (UF-2) exhibited the highest antioxidant and XODI activities. A novel XODI peptide (ACECD) was identified with an IC₅₀ value of 13.40 mmol/L, which decreased by 21.24% and 51.40% compared to those of UF-2 and HS, respectively. Molecular docking indicated that ACECD inserted into the active center of Mo atoms in XOD, which led to competitive attachment with XOD and caused inhibition. The study findings indicated that the ACECD peptide could be useful as a safe XODI substance to alleviate hyperuricemia.

Phloroglucinol Derivatives from Dryopteris crassirhizoma as Potent Xanthine Oxidase Inhibitors

Dryopteris crassirhizoma rhizomes are used as a traditional medicine in Asia. The EtOAc extract of these roots has shown potent xanthine oxidase (XO) inhibitory activity. However, the main phloroglucinols in D. crassirhizoma rhizomes have not been analyzed. Thus, we investigated the major constituents responsible for this effect. Bioassay-guided purification isolated four compounds: flavaspidic acid AP (1), flavaspidic acid AB (2), flavaspidic acid PB (3), and flavaspidic acid BB (4). Among these, 1 showed the most potent inhibitory activity with a half-maximal inhibitory concentration (IC₅₀) value of 6.3 µM, similar to that of allopurinol (IC₅₀ = 5.7 µM) and better than that of oxypurinol (IC₅₀ = 43.1 µM), which are XO inhibitors. A comparative activity screen indicated that the acetyl group at C3 and C3' is crucial for XO inhibition. For example, 1 showed nearly 4-fold higher efficacy than 4 (IC₅₀ = 20.9 µM). Representative inhibitors (1-4) in the rhizomes of D. crassirhizoma showed reversible and noncompetitive inhibition toward XO. Furthermore, the potent inhibitors were shown to be present in high quantities in the rhizomes by a UPLC-QTOF-MS analysis. Therefore, the rhizomes of D. crassirhizoma could be used to develop nutraceuticals and medicines for the treatment of gout.

Arylsulfonyl histamine derivatives as powerful and selective α-glucosidase inhibitors

A series of simple N-arylbenzenesulfonyl histamine derivatives were prepared and screened against α-glucosidase. Inhibition was in the micromolar range for several N α,N τ-di-arylsulfonyl compounds, with N α,N τ-di-4-trifluorobenzenesulfonyl histamine (IId) being the best inhibitor. Compound IId is a reversible and competitive α-glucosidase inhibitor, and presented good selectivity with respect to other target enzymes, including β-glucosidase and α-amylase, and interesting predicted physicochemical properties. Docking studies have been run to postulate ligand-enzyme interactions to account for the experimental results. In vivo, compound IId produced a similar hypoglycemic effect to acarbose with half of its dose.

Inhibition and molecular mechanism of diosmetin against xanthine oxidase by multiple spectroscopies and molecular docking

Studying the inhibition and molecular mechanism of diosmetin against xanthine oxidase helps to develop natural product xanthine oxidase inhibitors.

Termipaniculatones A-F, chalcone-flavonone heterodimers from Terminthia paniculata, and their protective effects on hyperuricemia and acute gouty arthritis

Terminthia paniculata (Sanyeqi) is widely used for treating inflammation and rheumatic arthritis in the folk areas of Yunnan province, China. Its total extract was first revealed with xanthine oxidase (XO) inhibitory activity in vitro and anti-hyperuricemic effect in vivo. Bioassay-guided separation on Fr. A5 yielded six chalcone-flavonone heterodimers, termipaniculatones A-F. Their structures were elucidated based on extensive spectroscopic analyses involving HRESIMS, 1D and 2D NMR, UV, IR and [α]_D, and the absolute configuration of termipaniculatone F was verified by ECD calculation. Termipaniculatones A and E showed obvious XO inhibitory activity with IC₅₀ values of 55.6 and 89.5 μM, respectively, which took effects via a mix-type mode. A molecular modeling study revealed that termipaniculatone A was well located into the active site of XO by interacting with Glu802, Arg880, Thr1010 and Val1011 residues. Termipaniculatone A showed anti-hyperuricemic effects by decreasing serum uric acid levels and inhibiting XO activity in both serum and liver on potassium oxonate (PO)-induced hyperuricemia mice, and anti-inflammatory activity through alleviating paw swelling on monosodium urate (MSU)-induced mice, at the concentration of 20 mg/kg. This is the first time to reveal the anti-hyperuricemic and anti-acute gouty arthritis potency of T. paniculata and the characteristic biflavonoids as active constituents, which provides valuable information for searching new XO inhibitors from natural sources.

Natural compounds with xanthine oxidase inhibitory activity: A review

Hyperuricemia (HUA), a disease due to an elevation of body uric acid level and responsible for various diseases such as gout, cardiovascular disorders, and renal failure, is a major ground debate for the medical science these days. Considering the risk factors linked with allopathic drugs for the treatment of this disease, the debate has now become a special issue. Previously, we critically discussed the role of dietary polyphenols in the treatment of HUA. Besides dietary food plants, many researchers figure out the tremendous effects of medicinal plants-derived phytochemicals against HUA. Keeping in mind all these aspects, we reviewed all possible managerial studies related to HUA through medicinal plants (isolated compounds). In the current review article, we comprehensively discussed various bioactive compounds, chemical structures, and structure-activity relationship with responsible key enzyme xanthine oxidase.

Actions of Inonotus obliquus against Hyperuricemia through XOD and Bioactives Screened by Molecular Modeling

Inonotus obliquus is an edible mushroom and also a remedy against various diseases, especially metabolic syndrome. In this paper we report the actions of an ethanol extract of I. obliquus (IOE) against hyperuricemia in hyperuricemic mice, and the screen of bioactives. The extract (IOE) was prepared by extracting I. obliquus at 65 °C with ethanol, and characterized by HPLC. IOE at low, middle, and high doses reduced serum uric acid (SUA) of hyperuricemic mice (353 μmol/L) to 215, 174, and 152 μmol/L (p < 0.01), respectively, showing similar hypouricemic effectiveness to the positive controls. IOE showed a non-toxic impact on kidney and liver functions. Of note, IOE suppressed xanthine oxidase (XOD) activity in serum and liver, and also down-regulated renal uric acid transporter 1 (URAT1). Four compounds hit highly against XOD in molecular docking. Overall, the four compounds all occupied the active tunnel, which may inhibit the substrate from entering. The IC₅₀ of betulin was assayed at 121.10 ± 4.57 μM, which was near to that of allopurinol (148.10 ± 5.27 μM). Betulin may be one of the anti-hyperuricemia bioactives in I. obliquus.

Nα-arylsulfonyl histamines as selective β-glucosidase inhibitors

N^α-benzenesulfonylhistamine, a new semi-synthetic β-glucosidase inhibitor, was obtained by bioactivity-guided isolation from a chemically engineered extract of Urtica urens L. prepared by reaction with benzenesulfonyl chloride. In order to identify better β-glucosidase inhibitors, a new series of N^α,N^τ-di-arylsulfonyl and N^α-arylsulfonyl histamine derivatives was prepared. Biological studies revealed that the β-glucosidase inhibition was in a micromolar range for several N^α-arylsulfonyl histamine compounds of the series, N^α-4-fluorobenzenesulfonyl histamine being the most powerful compound. Besides, this reversible and competitive inhibitor presented a good selectivity for β-glucosidase with respect to other target enzymes including α-glucosidase.

A selective β-glucosidase inhibitor was discovered using the chemically engineered extracts approach.

Identification of the biologically active constituents of Camellia japonica leaf and anti-hyperuricemic effect in vitro and in vivo

Camellia japonica L. is a plant of which the seeds are used as a folk medicine, and it is native to South Korea, Japan and China. In previous study, triterpenes, flavonoids, tannins and fatty acids which have antiviral, antioxidant and anti inflammatory activity were reported from C. japonica leaf and flower. In Korea, the seed from this plant is used as a traditional medicine and in folk remedies for the treatment of bleeding and inflammation. However, the major issue associated with the use of the seed as a medicinal and/or functional food ingredient is its application to the pharmaceutical and food industry. First, the productivity of seed extract is very much less than that of the leaf. Second, the beneficial usage of the seed extract as an alternative medicine and functional source is not yet clear. Thus, in this study, we focused on another part of the plant, the leaf, and found that the extract of Camellia japonica leaf has a high concentration of vitamin E, rutin and other biologically active compounds related to hyperuricemia. We aimed to investigate the biological activities, namely the antioxidant activities, xanthine oxidase (XO) inhibitory activity and anti‑hyperuricemic effects of extract from C. japonica leaf and the phytochemicals contained therein. Ethanol extracts of C. japonica leaf (ECJL) were prepared, and the extract was used with respect to antioxidant activities, total phenolic contents and XO inhibitory activity. The in vivo XO inhibitory activity and anti‑hyperuricemic effects of the extract were evaluated in mice with potassium oxonate‑induced hyperuricemia. To clarify the marker compounds that are responsible for the anti‑hyperuricemic effects, several key constituents were identified using gas chromatography‑mass spectrometry (GC‑MS) and and liquid chromatography-mass spectrometry (LC-MS). ECJL was found to have strong antioxidant activities, and in vitro XO inhibitory activity. The results of the in vivo experiments using mice demonstrated that ECJL at the doses of 100 and 300 mg/kg inhibited hepatic XO activity and significantly attenuated hyperuricemia. To the best of our knowledge, the present study is the first report on the XO inhibitory and anti-hyperuricemic effects of ECJL, which can be therapeutically applied in the treatment of hyperuricemia and gout.

Novel electrochemical xanthine biosensor based on chitosan-polypyrrole-gold nanoparticles hybrid bio-nanocomposite platform

The aim of this study was the electrochemical detection of the adenosine-3-phosphate degradation product, xanthine, using a new xanthine biosensor based on a hybrid bio-nanocomposite platform which has been successfully employed in the evaluation of meat freshness. In the design of the amperometric xanthine biosensor, chitosan-polypyrrole-gold nanoparticles fabricated by an in situ chemical synthesis method on a glassy carbon electrode surface was used to enhance electron transfer and to provide good enzyme affinity. Electrochemical studies were carried out by the modified electrode with immobilized xanthine oxidase on it, after which the biosensor was tested to ascertain the optimization parameters. The Biosensor exhibited a very good linear range of 1-200 μM, low detection limit of 0.25 μM, average response time of 8 seconds, and was not prone to significant interference from uric acid, ascorbic acid, glucose, and sodium benzoate. The resulting bio-nanocomposite xanthine biosensor was tested with fish, beef, and chicken real-sample measurements.

Myricetin inhibits the generation of superoxide anion by reduced form of xanthine oxidase

Myricetin, a plant-derived flavonol, was found to inhibit the formation of uric acid in a mixed-type manner with IC₅₀ value of (8.66±0.03)×10^-6molL^-1 and more potently inhibit the generation of superoxide anion (O₂^-) catalysed by xanthine oxidase (XOD) with IC₅₀ value of (4.55±0.02)×10^-6molL^-1. Inhibiting O₂^- generation by myricetin may be attributed to the reduced form of XOD with a substantially higher reduction potential for FADH/FADH₂ couple. Moreover, molecular docking verified that myricetin bound to the site around isoalloxazine ring in the flavin adenine dinucleotide (FAD) domain to block the diffusion of O₂^- out of the FAD site, resulting in the transfer of another electron from FADH₂ to O₂^- to form hydrogen peroxide. This study has provided new insight into the role of myricetin in inhibiting XOD catalysis, which may be beneficial to improve myricetin's potential application in functional foods.

Effects of extracts from Corylopsis coreana Uyeki (Hamamelidaceae) flos on xanthine oxidase activity and hyperuricemia

Objectives

This study aims to investigate xanthine oxidase (XO) inhibitory activity and antihyperuricemic effects of Corylopsis coreana Uyeki flos extracts and the phytochemicals contained therein.

Methods

Ethanolic extracts of the plant were prepared, and the extraction process was optimized with respect to flavonoid content and XO inhibitory activity. The optimized ethanolic extract was tested for its XO inhibitory activity and antihyperuricemic effects in potassium oxonate-induced hyperuricemic mice.

Key findings

The 80% ethanolic extract showed the highest total flavonoid content and in-vitro XO inhibitory activity. In-vivo studies demonstrated that the optimized 80% ethanolic extract could inhibit hepatic XO activity and significantly alleviate hyperuricemia at a relatively low oral dose (50 mg/kg) in mice. Additionally, an in-vitro enzyme inhibition study showed that phytochemicals such as bergenin, isosalipurposide, quercetin and quercitrin may be the key constituents responsible for the observed antihyperuricemic effects of the extract.

Conclusions

This study is the first report on the XO inhibitory and antihyperuricemic effects of C. coreana Uyeki flos extract, which can be therapeutically applied in treating hyperuricemia and gout.

Antineuroinflammatory and Antiproliferative Activities of Constituents from Tilia amurensis

As part of our ongoing search for bioactive constituents of natural Korean medicinal resources, we found in a preliminary study that the methanol (MeOH) extract from the trunks of Tilia amurensis RUPR. showed an inhibitory effect on nitric oxide (NO) production in an activated murine microglial cell line. A bioassay-guided fractionation and chemical investigation of the MeOH extract resulted in the isolation and identification of a new isoflavonoid glycoside, orobol 4'-O-β-D-apiofuranosyl-(1→6)-β-D-glucopyranoside (1) and 16 known compounds (2-17). The structure of the new compound was determined by spectroscopic methods, i.e., one-dimensional (1D) and two-dimensional (2D)-NMR techniques and high resolution (HR)-MS, and chemical methods. The antineuroinflammatory activities of the isolated compounds were determined by measuring NO levels in the medium using murine microglial BV-2 cells. Among them, 12 compounds, including compound 1 (most active with an IC50 value of 23.42 µM), inhibited NO production in lipopolysaccharide-stimulated BV-2 cells. Moreover, compounds 1-4 showed moderate antiproliferative activities against the SK-MEL-2 cell line, with IC50 values ranging from 12.31 to 19.67 µM.

Chemical diversification of essential oils, evaluation of complex mixtures and identification of a xanthine oxidase inhibitor

A set of chemically engineered essential oils has been generated through chemical diversification by reaction with bromine, leading to the discovery of a new brominated xanthine oxidase inhibitor.

Phenolic Compounds from the Roots of Rhodiola crenulata and Their Antioxidant and Inducing IFN-γ Production Activities

In the present study, two new phenolic compounds 1 and 11, a pair of lignan isomers 12 and 13 with their absolute configurations established for the first time, were isolated from the ethanol extract of the roots of Rhodiola crenulata, together with 13 known phenolic compounds, and their structures were elucidated via NMR, HRESIMS, UV, IR and CD analyses. All the isolated compounds were evaluated for their in vitro antioxidant activities using the 2,2-diphenyl-1-picryhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assays. Ten of them exhibited significant antioxidant activities compared to ascorbic acid. Furthermore, the inducibilities of the isolated compounds to IFN-γ production were also assessed. Compounds 1, 8, 9, 12, 13, 14 and 15 could moderately stimulate IFN-γ expression.

Diversity and antioxidant activity of culturable endophytic fungi from alpine plants of Rhodiola crenulata, R. angusta, and R. sachalinensis

Rhodiola spp. are rare and endangered alpine plants widely used as medicines and food additives by many civilizations since ancient times. Their main effective ingredients (such as salidroside and p-tyrosol) are praised to exhibit pharmacologic effects on high-altitude sickness and possess anti-aging and other adaptogenic capacities based on their antioxidant properties. In this study, 347 endophytic fungi were isolated from R. crenulata, R. angusta, and R. sachalinensis, and the molecular diversity and antioxidant activities of these fungi were investigated for the first time. These fungi were categorized into 180 morphotypes based on cultural characteristics, and their rRNA gene ITS sequences were analyzed by BLAST search in the GenBank database. Except for 12 unidentified fungi (6.67%), all others were affiliated to at least 57 genera in 20 orders of four phyla, namely, Ascomycota (88.89%), Basidiomycota (2.78%), Zygomycota (1.11%), and Glomeromycota (0.56%), which exhibited high abundance and diversity. Antioxidant assay showed that the DPPH radical-scavenging rates of 114 isolates (63.33%) were >50%, and those of five isolates (Rct45, Rct63, Rct64, Rac76, and Rsc57) were >90%. The EC50 values of five antioxidant assays suggested significant potential of these fungi on scavenging DPPH•, O2-•, and OH• radicals, as well as scavenging nitrite and chelating Fe2+, which showed preference and selection between endophytic fungi and their hosts. Further research also provided the first evidence that Rac12 could produce salidrosides and p-tyrosol. Results suggested that versatile endophytic fungi associated with Rhodiola known as antioxidants could be exploited as potential sources of novel antioxidant products.

Novel insights into the inhibitory mechanism of kaempferol on xanthine oxidase

Xanthine oxidase (XO), a key enzyme in purine catabolism, is widely distributed in human tissues. It can catalyze xanthine to generate uric acid and cause hyperuricemia and gout. Inhibition kinetics assay showed that kaempferol inhibited XO activity reversibly in a competitive manner. Strong fluorescence quenching and conformational changes of XO were found due to the formation of a kaempferol-XO complex, which was driven mainly by hydrophobic forces. The molecular docking further revealed that kaempferol inserted into the hydrophobic cavity of XO to interact with some amino acid residues. The main inhibition mechanism of kaempferol on XO activity may be due to the insertion of kaempferol into the active site of XO occupying the catalytic center of the enzyme to avoid the entrance of the substrate and inducing conformational changes of XO. In addition, luteolin exhibited a stronger synergistic effect with kaempferol than did morin at the lower concentration.

Effects of Rhodiola on production, health and gut development of broilers reared at high altitude in Tibet

Rhodiola has long been used as a traditional medicine to increase resistance to physical stress in humans in Tibet. The current study was designed to investigate whether Rhodiola crenulata (R. crenulata) could alleviate the negative effects of hypoxia on broiler chickens reared in Tibet Plateau. The effect of supplementing crushed roots of R. crenulata on production performance, health and intestinal morphology in commercial male broilers was investigated. Dietary treatments included CTL (basal diet), Low-R (basal diet + 0.5% R. crenulata) and High-R (basal diet + 1.5% R. crenulata). In comparison with broilers fed the control diet, Low-R had no effect on production performance while High-R significantly decreased average daily feed intake at d 14, 28 and 42, body weight at d 28 and 42 and gut development. Ascites induced mortality did not differ among treatments. Nevertheless Low-R significantly reduced non-ascites induced mortality and total mortality compared with broilers fed CTL and High-R diets. Broilers fed the High-R diet had significantly increased blood red blood cell counts and hemoglobin levels at 28 d compared with other treatments. Our results suggest that supplementation with Rhodiola might reduce the effects of hypoxia on broilers and consequently decrease mortality rate.

Inhibition of mammalian DNA polymerases and the suppression of inflammatory and allergic responses by tyrosol from used activated charcoal waste generated during sake production

The components adsorbed onto activated charcoal following the fermentation process of the Japanese rice wine "sake" have been studied with the aim of identifying suitable applications for this industrial food waste product. The absorbed materials were effectively extracted from the charcoal, and inhibited the activity of several mammalian DNA polymerases (pols). Subsequent purification of the extract afforded tyrosol [4-(2-hydroxyethyl)phenol] as the active component, which selectively inhibited the activity of 11 mammalian pols with IC50 values in the range of 34.3-46.1 μM. In contrast, this compound did not influence the activities of plant or prokaryotic pols or any of the other DNA metabolic enzymes tested. Tyrosol suppressed both anti-inflammatory and antiallergic effects in vivo, including 12-O-tetradecanoylphorbol-13-acetate-induced inflammatory mouse ear edema, and immunoglobulin E-induced passive cutaneous anaphylactic reaction in mice. These results suggested that this byproduct formed during the sake-brewing process could be used as an anti-inflammatory and/or antiallergic agent.