Effects of uric acid-lowering therapy (ULT) on renal outcomes in CKD patients with asymptomatic hyperuricemia: a systematic review and meta-analysis.

BACKGROUND: It is well known that asymptomatic hyperuricemia and gout play an important role in patients with chronic kidney disease (CKD). However, the effect of uric acid-lowering therapy (ULT) on the prognosis of CKD patients with asymptomatic hyperuricemia remains controversial. Therefore, we aim to investigate the influence of ULT on renal outcomes in these patients. METHODS: Comprehensive searches were conducted in PubMed, EMBASE, China National Knowledge Internet (CNKI), and the Cochrane Library, up until January 2024. We included randomized controlled trials (RCTs) that evaluated the effects of ULT on renal outcomes in CKD patients with asymptomatic hyperuricemia. RESULTS: A total of 17 studies were included in the meta-analysis. Compared with placebo or no treatment, ULT preserved the loss of estimated glomerular filtrating rate (eGFR) (Weighted mean difference [WMD] and its 95% confidence intercal(CI): 2.07 [0.15,3.98] mL/min/1.73m2) at long-term subgroup. At the same time, short-term subgroup also proved the preserved loss of eGFR (WMD 5.74[2.09, 9.39] mL/min/1.73m2). Compared with placebo or no treatment, ULT also reduced the increase in serum creatinine (Scr) at short-term (WMD -44.48[-84.03,-4.92]µmol/L) subgroup and long-term (WMD -46.13[-65.64,-26.62]µmol/L) subgroup. ULT was associated with lower incidence of the events of doubling of Scr without dialysis (relative risk (RR) 0.32 [0.21, 0.49], p < 0.001). However, no difference was found for lower incidence of acute kidney injury (AKI) (p = 0.943). CONCLUSIONS: According to our study, ULT is beneficial for slowing CKD progression both in short to long-term follow-ups. Additionally, in patients younger than 60 years old, the protective effect of ULT on renal outcome is more pronounced. However, it showed no significant difference in the incidence of AKI. These findings underscore the importance of considering ULT in clinical strategies for CKD patients with asymptomatic hyperuricemia.

Enhancing milk quality and modulating rectal microbiota of dairy goats in starch-rich diet: the role of bile acid supplementation.

BACKGROUND: Diets rich in starch have been shown to increase a risk of reducing milk fat content in dairy goats. While bile acids (BAs) have been used as a lipid emulsifier in monogastric and aquatic animals, their effect on ruminants is not well understood. This study aimed to investigate the impact of BAs supplementation on various aspects of dairy goat physiology, including milk composition, rumen fermentation, gut microbiota, and BA metabolism. RESULTS: We randomly divided eighteen healthy primiparity lactating dairy goats (days in milk = 100 ± 6 d) into two groups and supplemented them with 0 or 4 g/d of BAs undergoing 5 weeks of feeding on a starch-rich diet. The results showed that BAs supplementation positively influenced milk yield and improved the quality of fatty acids in goat milk. BAs supplementation led to a reduction in saturated fatty acids (C16:0) and an increase in monounsaturated fatty acids (cis-9 C18:1), resulting in a healthier milk fatty acid profile. We observed a significant increase in plasma total bile acid concentration while the proportion of rumen short-chain fatty acids was not affected. Furthermore, BAs supplementation induced significant changes in the composition of the gut microbiota, favoring the enrichment of specific bacterial groups and altering the balance of microbial populations. Correlation analysis revealed associations between specific bacterial groups (Bacillus and Christensenellaceae R-7 group) and BA types, suggesting a role for the gut microbiota in BA metabolism. Functional prediction analysis revealed notable changes in pathways associated with lipid metabolism, suggesting that BAs supplementation has the potential to modulate lipid-related processes. CONCLUSION: These findings highlight the potential benefits of BAs supplementation in enhancing milk production, improving milk quality, and influencing metabolic pathways in dairy goats. Further research is warranted to elucidate the underlying mechanisms and explore the broader implications of these findings.

Numerical simulation and experimental verification of fatigue crack propagation in high-strength bolts based on fracture mechanics.

To investigate the fatigue crack propagation behavior of high-strength bolts for high-speed train brake discs, the fatigue crack propagation of high-strength bolts with initial defects under various load ratios was numerically simulated and experimentally verified based on fracture mechanics in this paper. Firstly, the fracture mechanics model of a three-dimensional hexahedral mesh with initial root defects was established using ABAQUS-FRANC3D interactive technology. Then the stress intensity factor (SIF) of the crack front was calculated by the stress superposition of the crack surface to simulate the coupling effect of preload and axial cyclic load. Based on it, fatigue crack propagation was simulated. Finally, the corresponding fatigue experiments on prefabricated crack bolts were carried out. The results show that mode I cracks dominate in the process of crack propagation. The stable crack propagation zones of the fractured high-strength bolts all show a semi-elliptical cross-section. The SIF of the crack front decreases with the increase of the load ratio, thus making the crack propagation life increase with the increase of the load ratio. The experimental outcomes are in great agreement with the simulation results, which verify that the numerical simulation method can effectively and accurately evaluate the fatigue life of high-strength bolts with initial defects and provides an effective means for predicting the fatigue crack propagation life of the same type high-strength bolts in engineering applications.

Crack propagation analysis and fatigue life assessment of high-strength bolts based on fracture mechanics.

To investigate the effect of initial cracks on the fatigue performance of high-strength bolts for high-speed train brake discs, the fatigue crack propagation behavior of high-strength bolts under the coupling action of preload and dynamic fatigue load was investigated experimentally and numerically based on the theory of linear elastic fracture mechanics. Firstly, fatigue tests of high-strength bolts with initial crack defects were carried out, and then a three-dimensional accurate numerical model with the hexahedral mesh for a bolt-nut was established by MATLAB, and the fatigue crack propagation behaviors were investigated using ABAQUS-FRANC3D interactive technology. In this paper, the effects of the initial crack state, the bolt preload, the axial excitation load, and the friction coefficient of the screw pair on crack propagation life were emphatically studied, and the simulated crack propagation trajectory and crack propagation life agreed well with the experimental results. The findings indicated that 0°-oriented cracks beginning at the maximum principal stress were predicted to have the shortest fatigue life. The crack propagation life was sensitive to the initial crack size, the coefficient of initial crack geometry, and the bolt preload, but not to the friction coefficient of the screw pair. Furthermore, when evaluating the effect of fatigue load on crack propagation, the load ratio, the mean load, and the load range should all be considered.

Eurycomanone stimulates bone mineralization in zebrafish larvae and promotes osteogenic differentiation of mesenchymal stem cells by upregulating AKT/GSK-3ß/ß-catenin signaling.

Background: Eurycomanone (EN) is a diterpenoid compound isolated from the roots of Eurycoma longifolia (E. longifolia). Previous studies have confirmed that E. longifolia can enhance bone regeneration and bone strength. We previously isolated and identified ten quassinoids from E. longifolia, and the result displayed that five aqueous extracts have the effects on promotion of bone formation, among whom EN showed the strongest activity. However, the molecular mechanism of EN on bone formation was unknown, and we further investigated in this study. Methods: After the verification of purity of extracted EN, following experiments were conducted. Firstly, the pharmacologic action of EN on normal bone mineralization and the therapeutic effect of EN on Dex-induced bone loss using zebrafish larvae. The mineralization area and integral optical density (IOD) were evaluated using alizarin red staining. Then the vital signaling pathways of EN relevant to OP was identified through network pharmacology analysis. Eventually in vitro, the effect of EN on cell viability, osteogenesis activities were investigated in human bone marrow mesenchymal stem cells (hMSCs) and C3H10 cells, and the molecular mechanisms by which applying AKT inhibitor A-443654 in hMSCs. Results: In zebrafish larvae, the administration in medium of EN (0.2, 1, and 5 µM) dramatically enhanced the skull mineralization area and integral optical density (IOD), and increased mRNA expressions of osteoblast formation genes (ALP, RUNX2a, SP7, OCN). Meanwhile, exposure of EN remarkably alleviated the inhibition of bone formation induced by dexamethasone (Dex), prominently improved the mineralization, up-regulated osteoblast-specific genes and down-regulated osteoclast-related genes (CTSK, RANKL, NFATc1, TRAF6) in Dex-treated bone loss zebrafish larvae. Network pharmacology outcomes showed the MAPK and PI3K-AKT signaling pathways are closely associated with 10 hub genes (especially AKT1), and AKT/GSK-3ß/ß-catenin was selected as the candidate analysis pathway. In hMSCs and C3H10 cells, results showed that EN at appropriate concentrations of 0.008-5 µM effectively increased the cell proliferation. In addition, EN (0.04, 0.2, and 1 µM) significantly stimulated osteogenic differentiation and mineralization as well as significantly increased the protein phosphorylation of AKT and GSK-3ß, and expression of ß-catenin, evidencing by the results of ALP and ARS staining, qPCR and western blotting. Whereas opposite results were presented in hMSCs when treated with AKT inhibitor A-443654, which effectively inhibited the pro-osteogenesis effect induced by EN, suggesting EN represent powerful potential in promoting osteogenesis of hMSCs, which may be closely related to the AKT/GSK-3ß/ß-catenin signaling pathway. Conclusions: Altogether, our findings indicate that EN possesses remarkable effect on bone formation via activating AKT/GSK-3ß/ß-catenin signaling pathway in most tested concentrations. The translational potential of this article: This study demonstrates EN is a new effective monomer in promoting bone formation, which may be a promising anabolic agent for osteoporosis (OP) treatment.

Role of C-Reactive Protein in Kidney Diseases.

Background: C-reactive protein (CRP) is an acute-phase protein and has been found to be a risk factor for acute kidney injury (AKI) and chronic kidney diseases (CKD). However, the role and mechanisms of CRP in AKI and CKD remain largely unclear. Summary: Clinically, elevated serum CRP is a risk factor or biomarker for patients with AKI and CKD. Interestingly, in critically ill COVID-19 patients, increased serum CRP is also associated with the development of AKI. Functionally, studies using human CRP transgenic mouse models find that CRP is pathogenic and can function as a mediator for AKI and CKD as mice overexpressing human CRP promote AKI and CKD. Mechanistically, CRP can promote AKI and CKD via NF-κB and Smad3-dependent mechanisms. We found that CRP can activate Smad3 signaling directly and cause AKI via the Smad3-p27-dependent G1 cell cycle arrest mechanism. Thus, targeting CRP-Smad3 signaling with a neutralizing antibody or Smad3 inhibitor can inhibit AKI. Key Messages: CRP acts not only as a biomarker but also as a mediator for AKI and CKD. CRP can activate Smad3 to induce cell death and cause progressive renal fibrosis. Thus, targeting CRP-Smad3 signaling may represent a promising therapy for AKI and CKD.

Microbial Enterotypes Shape the Divergence in Gut Fermentation, Host Metabolism, and Growth Rate of Young Goats.

Enterotypes can be useful tools for studying the gut microbial community landscape, which is thought to play a crucial role in animal performance. However, few studies have been carried out to identify enterotypes and their associations with growth performance in young goats. In this study, two enterotypes were categorized in 76 goats: cluster 1 (n = 39) and cluster 2 (n = 37). Compared to cluster 2, cluster 1 had greater growth rates, the concentrations of acetate, propionate, valerate, and total volatile fatty acids (VFA) in the gut. Several serum glycolipid metabolism parameters, including glucose, total cholesterol, high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C), were also increased in cluster 1, while serum IgG was decreased in cluster 1. Using α-diversity analysis, we found a microbiome with lower richness and diversity in cluster 1. Some gut bacteria, including Succinivibrio and several members of the Prevotellaceae family, were enriched in cluster 1, while Christensenellaceae R-7 group, Romboutsia, and Clostridium sensu stricto 1 were enriched in cluster 2. A co-occurrence network analysis revealed that the differential interaction patterns existed in two enterotypes, and microbial function prediction suggested that some nutrient metabolism-related pathways, including amino acid biosynthesis and starch and sucrose metabolism, were enriched in cluster 1. Furthermore, a correlation analysis showed that enterotype-related bacteria were closely correlated with gut fermentation, serum biochemistry, and growth rate. Overall, our data provide a new perspective for understanding enterotype characteristics in goats, offering insights into important microbial interaction mechanisms for improving the growth performance of ruminant animals. IMPORTANCE The intricate relationships between a host animal and its resident gut microbiomes provide opportunities for dealing with energy efficiency and production challenges in the livestock industry. Here, we applied the enterotype concept to the gut microbiome in young goats and found that it can be classified into two enterotypes which are apparently associated with divergences in gut fermentation, blood biochemistry, and goat growth rates. The microbial co-occurrence networks and function predictions differed between the two enterotypes, suggesting that the formation of host phenotype may be modified by different bacterial features and complex bacterial interactions. The characteristics of enterotypes related to growth performance in young goats may enable us to improve long-term production performance in goat industry by modulating the gut microbiome during early life.

Effect of Hydrothermal Cooking Combined with High-Pressure Homogenization and Enzymatic Hydrolysis on the Solubility and Stability of Peanut Protein at Low pH.

A novel method combining high-pressure homogenization with enzymatic hydrolysis and hydrothermal cooking (HTC) was applied in this study to modify the structure of peanut protein, thus improving its physicochemical properties. Results showed that after combined modification, the solubility of peanut protein at a pH range of 2-10 was significantly improved. Moreover, the Turbiscan stability index of modified protein in the acidic solution was significantly decreased, indicating its excellent stability in low pH. From SDS-PAGE (Sodium Dodecyl Sulfate PolyAcrylamide Gel Electrophoresis), the high molecular weight fractions in modified protein were dissociated and the low molecular weight fractions increased. The combined modification decreased the particle size of peanut protein from 74.82 to 21.74 µm and shifted the isoelectric point to a lower pH. The improvement of solubility was also confirmed from the decrease in surface hydrophobicity and changes in secondary structure. This study provides some references on the modification of plant protein as well as addresses the possibility of applying peanut protein to acidic beverages.

The relationship between MFN1 copy number variation and growth traits of beef cattle.

Copy number variation, as a kind of genetic submicroscopic structural variation, refers to the deletion or repetition of a large segment of genomic DNA, involving a segment size ranging from 50 bp to several MB. Mitochondrial fusion protein (MFN1) gene regulates the fusion of mitochondrial outer membrane in cells and maintains the dynamic needs of reticular mitochondria in cells. In this study, we conducted to tested the dstribution characteristics of MFN1-CNV in 522 cattles across Xianan cattle (XN), Pinan cattle (PN), Qinchuan cattle (QC), Jiaxian cattle (JX), Yunling cattle (YL), and correlated it with phenotypic traits. Then we observed the expression of MFN1 in various tissues of QC cattle (n = 3), and the expression levels were higher in lung and muscle. The results showed that there was significant correlation between MFN1 gene CNV and hucklebone width of QC cattle, hip width and height at sacrum of JX red cattle, chest width and rump length of YL cattle (P < 0.05). Individuals with duplication type were better than the type of normal or deletion in phenotypic traits. In conclusion, our data showed the correlation between MFN1 gene and growth traits of Chinese cattle. MFN1 gene can be used as a molecular marker for cattle selection and breeding, and accelerate the improvement of Chinese cattle.

Anti-Osteogenic Effect of Danshensu in Ankylosing Spondylitis: An in Vitro Study Based on Integrated Network Pharmacology.

Ankylosing spondylitis (AS) is a chronic inflammatory disease characterized by abnormal bone metabolism, with few effective treatments available. Danshensu [3-(3,4-dihydroxy-phenyl) lactic acid) is a bioactive compound from traditional Chinese medicine with a variety of pharmacologic effects. In the present study, we investigated the pharmacologic effect and molecular mechanism of Danshensu in AS. Potential targets of Danshensu were identified in four drugs-genes databases; and potential pharmacologic target genes in AS were identified in three diseases-genes databases. Differentially expressed genes related to AS were obtained from the Gene Expression Omnibus database. Overlapping targets of Danshensu and AS were determined and a disease-active ingredient-target interaction network was constructed with Cytoscape software. Enrichment analyses of the common targets were performed using Bioconductor. To test the validity of the constructed network, an in vitro model was established by treating osteoblasts from newborn rats with low concentrations of tumor necrosis factor (TNF)-α. Then, the in vitro model and AS fibroblasts were treated with Danshensu (1-10 µM). Osteogenesis was evaluated by alkaline phosphatase staining and activity assay, alizarin red staining, quantitative PCR, and western blotting. We identified 2944 AS-related genes and 406 Danshensu targets, including 47 that were common to both datasets. The main signaling pathways associated with the targets were the c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) pathways. A low concentration of TNF-α (0.01 ng/ml) promoted the differentiation of osteoblasts; this was inhibited by Danshensu, which had the same effect on AS fibroblasts but had the opposite effect on normal osteoblasts. Danshensu also decreased the phosphorylation of JNK and ERK in AS fibroblasts. There results provide evidence that Danshensu exerts an anti-osteogenic effect via suppression of JNK and ERK signaling, highlighting its therapeutic potential for the treatment of AS.

Electrophysiological correlates of visual attention span in Chinese adults with poor reading fluency.

Individuals with reading fluency difficulty (RFD) show an impairment in the simultaneous processing of multiple elements, which could be reflected in their visual attention span (VAS) capacity. However, the relationship between VAS impairment and RFD is still controversial. A series of processes underlie VAS, such as the early stage of visual attentional processing and the late stage of allocating and maintaining attentional resources. Therefore, the present study explored the relationships between VAS skills and RFD through the event-related potential (ERP) technique to disentangle the contributing cognitive processes regarding VAS from a temporal perspective. Eighteen Chinese adults with poor reading fluency and 18 age-matched normal readers participated. Their VAS skills were measured by a visual one-back task with symbols as nonverbal stimuli and key pressing as nonverbal responses, while relevant electrophysiological signals were recorded. The results showed that lower d' values and abnormal electrophysiological activities (especially weak amplitudes in the N1 and P3 components) in the VAS task were observed for the nonfluent readers compared with the controls. These findings suggested that the low VAS capacity in adults with poor reading fluency could be reflected by problems both in directing selective attention to visually discriminate stimuli within a multielement string at the early processing stage and in allocating attention to further encode targets at the late processing stage. Alternative explanations were further discussed. The current results provide theoretical explanations of the VAS-RFD relationship from a temporal perspective and provide insights for future remediation of reading fluency difficulty.

The association of transforming growth factor beta 1 gene polymorphisms with arthritis: a systematic review and meta-analysis.

The objective of this study was to explore the association between transformation growth factor beta 1 (TGF-ß1) gene polymorphisms and different types of arthritis. PubMed, Medline, Web of Science, Cochrane Library, Biosis and four Chinese databases: China Biology Medicine, China National Knowledge Infrastructure, Wanfang and CQVIP, were searched. Studies that analyzed the association of the TGF-ß1 polymorphisms with different types of arthritis were included. OR, 95% confidence interval and P value were calculated in three models including allele, dominant and recessive models, using D + L method. The Newcastle-Ottawa Scale was used to assess the quality of the included studies. TGF-ß1 869T > C polymorphism was significantly associated with rheumatoid arthritis (RA) in allele and recessive models, but not in dominant model (allele model T vs. C: OR = 1.30, 95% CI = 1.13-1.49, P < 0.001; recessive model CC vs. TT + TC: OR = 0.57, 95% CI = 0.43-0.76, P < 0.001; dominant model TT vs. TC + CC: OR = 1.20, 95% CI = 0.99-1.45, P = 0.063). Additionally, allele and recessive models showed that TGF-ß1 -509C > T was significantly correlated with RA susceptibility, while dominant model revealed nonsignificant correlation (allele model: C vs. T: OR = 1.51; 95% CI = 1.00-2.28; P = 0.049; recessive model: TT vs. CC + TC: OR = 0.52, 95% CI = 0.37-0.72, P = 0.000; dominant model: CC vs. TT + TC: OR = 1.48; 95% CI = 0.79-2.76; P = 0.223). However, no significant association was found between TGF-ß1 polymorphisms and ankylosing spondylitis (AS) or osteoarthritis (OA) risk. This study demonstrated that 869T > C, -509 C > T polymorphisms of TGF-ß1 gene were associated with increased susceptibility of RA, while polymorphisms of TGF-ß1 gene were not associated with OA and AS. These findings suggest that studying TGF-ß1 genotype may be useful in the prevention and management of RA. However, more studies are needed to evaluate the association of TGF-ß1 gene polymorphisms with the susceptibility of OA and AS.

Genetic variant of SPARC gene and its association with growth traits in Chinese cattle.

SPARC is a cysteine-rich acidic secreted protein. It is a non-collagen component of bone, which is widely distributed in humans and animals and plays an important role. SPARC has been found in a variety of human cancers (breast cancer, stomach cancer, ovarian cancer, etc.) and diabetes-related research. Especially the muscle and fat metabolism are closely related. In this study, we used a DNA pool to detect a new SNP site (g.12454T  >  C). A total of 616 samples of four breeds of Qinchuan cattle (QC, n = 176 ), Xianan cattle (XN, n = 160 ), Pinan cattle (PN, n = 136 ) and Jiaxian cattle (JX, n = 144 ) were analyzed and identified with ARMS-PCR. In addition, we correlated SNP with growth traits and showed significant correlation with growth traits such as rump length, hip width, and body length ( p < 0.05 ). Moreover, we tested the SPARC gene expression level in different tissues belonging to XN adult cattle ( n = 3 ) and found its high expression in muscle tissues (relative to the kidney). Further, we found the SNP is able to increase the SPARC expression level in skeletal muscle ( n = 12 ). According to statistical data, this SNP site may be applied to a molecular marker of an early marker-assisted selection for early growth of beef cattle.

Improving sentence reading performance in Chinese children with developmental dyslexia by training based on visual attention span.

Deficits in the visual attention span (VAS) are thought to hamper reading performance in dyslexic individuals. However, the causal relationship between VAS deficits and reading disability remains unclear. The present study attempts to address this issue by using a VAS-based intervention to explore the possible influence of VAS on reading processes in Chinese children with dyslexia. Given the influence of the heterogeneity of dyslexia on intervention effects, VAS-impaired dyslexic and VAS-intact dyslexic individuals were separately trained. Therefore, there were five groups of participants in this study, including 10 trained dyslexic individuals with VAS deficits and 10 untrained dyslexic individuals with VAS dysfunction as the baseline reference, 10 trained and 10 untrained dyslexic individuals with an intact VAS, and fourteen age-matched normal readers for reference of normal level. All participants completed reading measures and a visual 1-back task, reflecting VAS capacity with non-verbal stimuli and non-verbal responses, before and after VAS-based training. VAS-based training tasks included a length estimation task regarding the bottom-up attention, visual search and digit cancelling tasks targeting top-down attentional modulation, and visual tracking tasks to train eye-movement control. The results showed that visual training only helped improve VAS skills in VAS-impaired dyslexic individuals receiving training. Meanwhile, their silent sentence reading accuracy improved after training, and there was a significant relationship between training improvements in VAS function and reading performance. The current findings suggest that VAS-based training has a far-transfer effect on linguistic level (i.e., fluent reading). These findings suggest the possibility that VAS-related training may help children with dyslexia improve their reading skills.

Separation and determination of polyurethane amine catalysts in polyether polyols by using UHPLC-Q-TOF-MS on a reversed-phase/cation-exchange mixed-mode column.

A simple, selective, and accurate ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry method was established and validated for the efficient separation and quantification of polyurethane amine catalysts in polyether polyols. Amine catalysts were primarily separated in polyether polyol-based sample by solid-phase extraction, and further baseline separated on a reversed-phase/cation-exchange mixed-mode column (SiELC Primesep™ 200) using 0.1% trifluoroacetic acid/acetonitrile as a mobile phase in gradient elution mode at a flow rate of 0.2 mL/min. High-resolution quadrupole time-of-flight mass spectrometry analysis in electrospray ionization positive mode allowed the identification as N,N'-bis[3-(dimethylamino)propyl]urea, N-[2-(2-dimethylaminoethoxy)ethyl]-N-methyl-1,3-propanediamine, and N,N,N',N'-tetramethyldipropylenetriamine. The method was validated and presented good linearity for all the analytes in blank matrices within the concentration range of 0.20-5.0 or 0.1-2.0 µg/mL with the correlation coefficients (R2 ) ranging from 0.986 to 0.997. Method recovery ranged within 81-105% at all three levels (80, 100, and 120% of the original amount) with relative standard deviations of 1.0-6.2%. The limits of detection were in the range of 0.007-0.051 µg/mL. Good precision was obtained with relative standard deviation below 3.2 and 0.72% for peak area and retention time of three amines, respectively.

Insights into the Key Compounds of Durian (Durio zibethinus L. 'Monthong') Pulp Odor by Odorant Quantitation and Aroma Simulation Experiments.

Sixteen compounds, previously identified as potent odorants by application of an aroma extract dilution analysis and the gas chromatography-olfactometry analysis of static headspace samples, were quantitated in the pulp of durians, variety Monthong, and odor activity values (OAVs) were calculated by dividing the concentrations obtained by the odor thresholds of the compounds in water. In combination with data recently reported for hydrogen sulfide and short-chain alkanethiols, OAVs > 1 were obtained for 19 compounds, among which ethyl (2S)-2-methylbutanoate (fruity; OAV 1700000), ethanethiol (rotten onion; OAV 480000), and 1-(ethylsulfanyl)ethane-1-thiol (roasted onion; OAV 250000) were the most potent, followed by methanethiol (rotten, cabbage; OAV 45000), ethane-1,1-dithiol (sulfury, durian; OAV 23000), and ethyl 2-methylpropanoate (fruity; OAV 22000). Aroma simulation and omission experiments revealed that the overall odor of durian pulp could be mimicked by only two compounds, namely, ethyl (2S)-2-methylbutanoate and 1-(ethylsulfanyl)ethane-1-thiol, when combined in their natural concentrations.

Identification of (S,S)-γ-glutamyl-(cis-S-1-propenyl)thioglycine, a naturally occurring norcysteine derivative, from the Chinese vegetable Toona sinensis.

Extracts of Toona sinensis shoots were studied to identify the precursors of volatile sulfur-containing flavor molecules. T. sinensis was found to contain new compounds (S,S)-γ-glutamyl-(cis-S-1-propenyl)thioglycine, 1, (S,S)-γ-glutamyl-(trans-S-1-propenyl)thioglycine, 2, and γ-glutamyl-(cis-S-1-propenyl)-cysteine, 3. The structures of these compounds were determined by interpretation of multistage mass spectrometric (MS(n)), 1D, and 2D NMR data. The absolute configuration of 1 was established by comparison of experimental with computed infrared and vibrational circular dichroism spectra. Because of the flexibility of the molecule and the novelty of the structure, the configuration was further confirmed by X-ray crystallography. Compounds 1 and 2 are the first examples of norcysteine-containing metabolites reported from nature. They may release thiols via cleavage of the amide bond by proteases, followed by spontaneous decomposition of the resulting unstable alk(en)yl norcysteine moiety.

Characterization of the major odor-active compounds in Thai durian ( Durio zibethinus L. 'Monthong') by aroma extract dilution analysis and headspace gas chromatography-olfactometry.

An aroma extract dilution analysis applied on the volatile fraction isolated from Thai durian by solvent extraction and solvent-assisted flavor evaporation resulted in 44 odor-active compounds in the flavor dilution (FD) factor range of 1-16384, 41 of which could be identified and 24 that had not been reported in durian before. High FD factors were found for ethyl (2S)-2-methylbutanoate (fruity; FD 16384), ethyl cinnamate (honey; FD 4096), and 1-(ethylsulfanyl)ethanethiol (roasted onion; FD 1024), followed by 1-(ethyldisulfanyl)-1-(ethylsulfanyl)ethane (sulfury, onion), 2(5)-ethyl-4-hydroxy-5(2)-methylfuran-3(2H)-one (caramel), 3-hydroxy-4,5-dimethylfuran-2(5H)-one (soup seasoning), ethyl 2-methylpropanoate (fruity), ethyl butanoate (fruity), 3-methylbut-2-ene-1-thiol (skunky), ethane-1,1-dithiol (sulfury, durian), 1-(methylsulfanyl)ethanethiol (roasted onion), 1-(ethylsulfanyl)propane-1-thiol (roasted onion), and 4-hydroxy-2,5-dimethylfuran-3(2H)-one (caramel). Among the highly volatile compounds screened by static headspace gas chromatography-olfactometry, hydrogen sulfide (rotten egg), acetaldehyde (fresh, fruity), methanethiol (rotten, cabbage), ethanethiol (rotten, onion), and propane-1-thiol (rotten, durian) were found as additional potent odor-active compounds. Fourteen of the 41 characterized durian odorants showed an alkane-1,1-dithiol, 1-(alkylsulfanyl)alkane-1-thiol, or 1,1-bis(alkylsulfanyl)alkane structure derived from acetaldehyde, propanal, hydrogen sulfide, and alkane-1-thiols. Among these, 1-(propylsulfanyl)ethanethiol, 1-{[1-(methylsulfanyl)ethyl]sulfanyl}ethanethiol, and 1-{[1-(ethylsulfanyl)ethyl]sulfanyl}ethanethiol were reported for the first time in a natural product.