Antioxidative phytochemicals from Rhododendron oldhamii Maxim. leaf extracts reduce serum uric acid levels in potassium oxonate-induced hyperuricemic mice.

BACKGROUND: Some of the genus Rhododendron was used in traditional medicine for arthritis, acute and chronic bronchitis, asthma, pain, inflammation, rheumatism, hypertension and metabolic diseases and many species of the genus Rhododendron contain a large number of phenolic compounds and antioxidant properties that could be developed into pharmaceutical products. METHODS: In this study, the antioxidative phytochemicals of Rhododendron oldhamii Maxim. leaves were detected by an online HPLC-DPPH method. In addition, the anti-hyperuricemic effect of the active phytochemicals from R. oldhamii leaf extracts was investigated using potassium oxonate (PO)-induced acute hyperuricemia. RESULTS: Six phytochemicals, including (2R, 3R)-epicatechin (1), (2R, 3R)-taxifolin (2), (2R, 3R)-astilbin (3), hyposide (4), guaijaverin (5), and quercitrin (6), were isolated using the developed screening method. Of these, compounds 3, 4, 5, and 6 were found to be major bioactive phytochemicals, and their contents were determined to be 130.8 ± 10.9, 105.5 ± 8.5, 104.1 ± 4.7, and 108.6 ± 4.0 mg per gram of EtOAc fraction, respectively. In addition, the four major bioactive phytochemicals at the same dosage (100 mmol/kg) were administered to the abdominal cavity of potassium oxonate (PO)-induced hyperuricemic mice, and the serum uric acid level was measured after 3 h of administration. H&E staining showed that PO-induced kidney injury caused renal tubular epithelium nuclear condensation in the cortex areas or the appearance of numerous hyaline casts in the medulla areas; treatment with 100 mmol/kg of EtOAc fraction, (2R, 3R)-astilbin, hyposide, guaijaverin, and quercitrin significantly reduced kidney injury. In addition, the serum uric acid level was significantly suppressed by 54.1, 35.1, 56.3, 56.3, and 53.2 %, respectively, by the administrations of 100 mmol/kg EtOAc fraction and the derived major phytochemicals, (2R, 3R)-astilbin, hyposide, guaijaverin, and quercitrin, compared to the PO group. The administration of 10 mg/kg benzbromarone, a well-known uricosuric agent, significantly reduced the serum uric acid level by 45.5 % compared to the PO group. CONCLUSION: The in vivo decrease in uric acid was consistent with free radical scavenging activity, indicating that the major phytochemicals of R. oldhamii leave extracts and the derived phytochemicals possess potent hypouricemic effects, and they could be potential candidates for new hypouricemic agents.

Antioxidant activities and phytochemicals of leaf extracts from 10 native rhododendron species in taiwan.

Rhododendron, one of the most famous ornamental plants in the world, is traditionally a medicinal plant. However, the potential bioactivities of native Rhododendron in Taiwan have not been completely studied. In this study, the results revealed that Rhododendron pseudochrysanthum exhibited the best antioxidant activities among 10 native Rhododendron species in Taiwan. Furthermore, based on a bioactivity-guided isolation principle, nine specific phytochemicals were isolated and identified as (2R,3S)-catechin (1), (2R,3R)-epicatechin (1'), (2R,3R)-dihydromyricetin 3-O- ß -l-arabinopyranoside (2), (2S,3S)-taxifolin 3-O- ß -l-arabinopyranoside (2'), (2R,3R)-taxifolin 3-O- ß -l-arabinopyranoside (3), myricetin 3-O- ß -d-glucopyranoside (3'), rutin (4), hyperoside (5), and quercitrin (6). Of these compounds, 2 and 3 were found to be major bioactive compounds, and their concentrations in the n-butanol (BuOH) fraction were determined to be 52.0 and 67.3 mg per gram, respectively. These results demonstrated that methanolic extracts of Rhododendron pseudochrysanthum leaves have excellent antioxidant activities and great potential as a source for natural health products.

Assessment of Candida glabrata strain relatedness by pulsed-field gel electrophoresis and multilocus sequence typing.

In this study, 80 Candida glabrata isolates from intensive care unit and human immunodeficiency virus (HIV)-infected patients were typed by multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), and mating type class determination. Among the 25 patients with multiple isolates, 19 patients (76%) contained multiple isolates exhibiting identical or highly related PFGE and MLST genotypes, which may indicate the maintenance or microvariation of one C. glabrata strain in each patient. However, isolates from six patients (24%) displayed different sequence types, PFGE genotypes, or mating type classes, which may indicate colonization with more than one clone over time or strain replacement. High correlations among PFGE genotypes, sequence types, and mating types were found (P < 0.01). MLST exhibited less discriminatory power than PFGE with BssHII. The genotypes, sequence types, and mating type classes were independent of anatomic sources, drug susceptibility, and HIV infection status.

Multilocus sequence typing for analyses of clonality of Candida albicans strains in Taiwan.

Multilocus sequence typing (MLST) was used to characterize the genetic profiles of 51 Candida albicans isolates collected from 12 hospitals in Taiwan. Among the 51 isolates, 16 were epidemiologically unrelated, 28 were isolates from 11 critically ill, human immunodeficiency virus (HIV)-negative patients, and 7 were long-term serial isolates from 3 HIV-positive patients. Internal regions of seven housekeeping genes were sequenced. A total of 83 polymorphic nucleotide sites were identified. Ten to 20 different genotypes were observed at the different loci, resulting, when combined, in 45 unique genotype combinations or diploid sequence types (DSTs). Thirty (36.1%) of the 83 individual changes were synonymous and 53 (63.9%) were nonsynonymous. Due to the diploid nature of C. albicans, MLST was more discriminatory than the pulsed-field gel electrophoresis-BssHII-restricted fragment method in discriminating epidemiologically related strains. MLST is able to trace the microevolution over time of C. albicans isolates in the same patient. All but one of the DSTs of our Taiwanese strain collections were novel to the internet C. albicans DST database (http://test1.mlst.net/). The DSTs of C. albicans in Taiwan were analyzed together with those of the reference strains and of the strains from the United Kingdom and United States by unweighted-pair group method using average linkages and minimum spanning tree. Our result showed that the DNA type of each isolate was patient specific and associated with ABC type and decade of isolation but not associated with mating type, anatomical source of isolation, hospital origin, or fluconazole resistance patterns.

Mutations on CaENO1 in Candida albicans inhibit cell growth in the presence of glucose.

Enolase (2-phospho-D-glycerate hydrolase) is an enzymatic component of the glycolytic pathway and is conserved through evolution. The TR-CaENO1/Caeno1 stain, of which the expression of CaENO1 is under control of the tetracycline-regulatable (TR) expression system, is utilized for elucidating the functions of CaENO1 in Candida albicans. As expected, there was no detectable CaENO1 mRNA when the TR-CaENO1/Caeno1 cells grew on media containing doxycycline repressing the expression of TR-CaENO1.The TR-CaENO1/Caeno1 cells were arrested in media containing doxycycline in the presence of glucose but not in non-fermentable carbon sources, such as glycerol. Furthermore, the TR-CaENO1/Caeno1 cells were also arrested in media containing 4% serum. In this study, we have showed that CaENO1 is required for the cell growth of C. albicans in the presence of glucose. Our findings may help us to design new and more effective antifungal agents for preventing and treating bloodstream fungal infections by blocking the function(s) of enolases.