Indole Acid Research Articles

Buqi-Huoxue-Tongnao decoction drives gut microbiota-derived indole lactic acid to attenuate ischemic stroke via the gut-brain axis

BackgroundIschemic stroke belongs to “apoplexy” and its pathogenesis is characterized by qi deficiency and blood stasis combining with phlegm-damp clouding orifices. Buqi-Huoxue-Tongnao decoction (BHTD) is a traditional Chinese medicine formula for qi deficiency, blood stasis and phlegm obstruction syndrome. However, its efficacy and potential mechanism on ischemic stroke are still unclear. This study aims to investigate the protective effect and potential mechanism of BHTD against ischemic stroke.Materials and methodsMiddle cerebral artery occlusion (MCAO) surgery was carried out to establish an ischemic stroke model in rats. Subsequently, the rats were gavaged with different doses of BHTD (2.59, 5.175, 10.35 g/kg) for 14 days. The protective effects of BHTD on the brain and gut were evaluated by neurological function scores, cerebral infarction area, levels of brain injury markers (S-100B, NGB), indicators of gut permeability (FD-4) and bacterial translocation (DAO, LPS, D-lactate), and tight junction proteins (Occludin, Claudin-1, ZO-1) in brain and colon. 16S rRNA gene sequencing and metabolomic analysis were utilized to analyze the effects on gut microecology and screen for marker metabolites to explore potential mechanisms of BHTD protection against ischemic stroke.ResultsBHTD could effectively mitigate brain impairment, including reducing neurological damage, decreasing cerebral infarction and repairing the blood–brain barrier, and BHTD showed the best effect at the dose of 10.35 g/kg. Moreover, BHTD reversed gut injury induced by ischemic stroke, as evidenced by decreased intestinal permeability, reduced intestinal bacterial translocation, and enhanced intestinal barrier integrity. In addition, BHTD rescued gut microbiota dysbiosis by increasing the abundance of beneficial bacteria, including Turicibacter and Faecalibaculum. Transplantation of the gut microbiota remodeled by BHTD into ischemic stroke rats recapitulated the protective effects of BHTD. Especially, BHTD upregulated tryptophan metabolism, which promoted gut microbiota to produce more indole lactic acid (ILA). Notably, supplementation with ILA by gavage could alleviate stroke injury, which suggested that driving the production of ILA in the gut might be a novel treatment for ischemic stroke.ConclusionBHTD could increase gut microbiota-derived indole lactic acid to attenuate ischemic stroke via the gut-brain axis. Our current finding provides evidence that traditional Chinese medicine can ameliorate central diseases through regulating the gut microbiology.

The interaction between Lactobacillus delbrueckii ssp. bulgaricus M-58 and Streptococcus thermophilus S10 can enhance the texture and flavor profile of fermented milk: Insights from metabolomics analysis

Lactobacillus delbrueckii ssp. bulgaricus M-58 (M58) and Streptococcus thermophilus S10 (S10) are both dairy starter strains known for their favorable fermentation characteristics. Therefore, this research aimed to study the effects of 1-d low-temperature ripening on the physicochemical properties and metabolomics of fermented milk. Initially, the performance of single (M58 or S10) and dual (M58+S10) strain fermentation was assessed, revealing that the M58+S10 combination resulted in a shortened fermentation time, a stable gel structure, and desirable viscosity, suggesting positive strain interactions. Subsequently, nontargeted metabolomics analyses using liquid chromatography-MS and GC-MS were performed to comparatively analyze M58+S10 fermented milk samples collected at the end of fermentation and after 1 d of low-temperature ripening. The results showed a significant increase in almost all small peptides and dodecanedioic acid in the samples after 1 d of ripening, although there was a substantial decrease in indole and amino acid metabolites. Moreover, notable increases were observed in high-quality flavor compounds, such as geraniol, delta-nonalactone, 1-hexanol,2-ethyl-, methyl jasmonate, and undecanal. This study provides valuable insights into the fermentation characteristics of the dual bacterial starter consisting of M58 and S10 strains and highlights the specific contribution of the low-temperature ripening step to the overall quality of fermented milk.

A gut microbial metabolite cocktail fights against obesity through modulating the gut microbiota and hepatic leptin signaling.

Excessive body weight and obesity elevate the risk of chronic non-communicable diseases. The judicious application of the gut microbiome, encompassing both microorganisms and their derived compounds, holds considerable promise in the treatment of obesity. In this study, we showed that a cocktail of gut microbiota-derived metabolites, comprising indole 3-propionic acid (IPA), sodium butyrate (SB) and valeric acid (VA), alleviated various symptoms of obesity in both male and female mice subjected to a high-fat diet (HFD). The 16S ribosomal RNA (rRNA) sequencing revealed that administering the cocktail via oral gavage retained the gut microbiota composition in obese mice. Fecal microbiota transplantation using cocktail-treated mice as donors mitigated the obesity phenotype of HFD-fed mice. Transcriptomic sequencing analysis showed that the cocktail preserved the gene expression profile of hepatic tissues in obese mice, especially up-regulated the expression level of leptin receptor. Gene delivery via in vivo fluid dynamics further validated that the anti-obesity efficacy of the cocktail was dependent on leptin signaling at least partly. The cocktail also inhibited the expression of appetite stimulators in hypothalamus. Together, the metabolite cocktail combated adiposity by retaining the gut microbiota configuration and activating the hepatic leptin signaling pathway. Our findings provide a sophisticated regulatory network between the gut microbiome and host, and highlight a cocktail of gut microbiota-derived metabolites, including IPA, SB, and VA, might be a prospective intervention for anti-obesity in a preclinical setting. © 2024 Society of Chemical Industry.

Construction of C5‐Indole Unnatural Amino Acid Motifs via Diastereoselective Pd(II)‐Catalyzed β‐C(sp3)‐H Functionalization

We report the construction of C5‐indole unnatural amino acid derivatives via the diastereoselective Pd(II)‐catalyzed prochiral β‐C(sp3)‐H arylation of racemic (DL), and enantiopure L‐ and D‐carboxamides of amino acids with 5‐iodoindoles. Independently, indole‐based compounds and amino acid motifs are important small molecules in organic synthesis and drug discovery research. This report aimed to contribute to enriching the library of indole‐based unnatural amino acid derivatives. The synthesis of examples of C5‐indole motif‐installed amino acid derivatives comprising norvaline, phenylalanine, leucine, norleucine, 2‐aminooctanoic acid having anti‐stereochemistry was accomplished. The synthesis of the C5‐indole motif‐containing non‐α‐amino acid (aminoalkanoic acid) derivatives was also reported. The C‐H arylation reactions of racemic and enantiopure carboxamides with 5‐iodoindoles afforded the corresponding indole unnatural amino acid derivatives with good diastereoselectivity (anti, dr >95:5 and enantiopurity (er up to 99:1). Removal of the directing group (8‐aminoquinoline), phthalimide group and preparation of indole amino acid esters and free amino group‐containing indole unnatural amino acid motifs were also shown. The utility of the methodology was shown by synthesizing indole motif‐containing pyrrolidone and peptide molecules. The stereochemistry of the major (anti) diastereomers was ascertained from the X‐ray structure of a representative compound.

A consortium of different Saccharomyces species enhances the content of bioactive tryptophan-derived compounds in wine fermentations

In recent years, the presence of molecules derived from aromatic amino acids in wines has been increasingly demonstrated to have a significant influence on wine quality and stability. In addition, interactions between different yeast species have been observed to influence these final properties. In this study, a screening of 81 yeast strains from different environments was carried out to establish a consortium that would promote the improvement of indolic compound levels in wine. Two strains, Saccharomyces uvarum and Saccharomyces eubayanus, with robust fermentative capacity were selected to be combined with a Saccharomyces cerevisiae strain with a predisposition towards the production of indolic compounds. Fermentation dynamics were studied in pure cultures, co-inoculations and sequential inoculations, analysing strain interactions and end-of-fermentation characteristics. Fermentations showing significant interactions were further analyzed for the resulting indolic compounds and aroma profile, with the aim of observing potential interactions and synergies resulting from the combination of different strains in the final wine. Sequential inoculation of S. cerevisiae after S. uvarum or S. eubayanus was observed to increase indolic compound levels, particularly serotonin and 3-indoleacetic acid. This study is the first to demonstrate how the formation of microbial consortia can serve as a useful strategy to enhance compounds with interesting properties in wine, paving the way for future studies and combinations.

Microbial metabolites as modulators of host physiology.

The gut microbiota is increasingly recognised as a key player in influencing human health and changes in the gut microbiota have been strongly linked with many non-communicable conditions in humans such as type 2 diabetes, obesity and cardiovascular disease. However, characterising the molecular mechanisms that underpin these associations remains an important challenge for researchers. The gut microbiota is a complex microbial community that acts as a metabolic interface to transform ingested food (and other xenobiotics) into metabolites that are detected in the host faeces, urine and blood. Many of these metabolites are only produced by microbes and there is accumulating evidence to suggest that these microbe-specific metabolites do act as effectors to influence human physiology. For example, the gut microbiota can digest dietary complex polysaccharides (such as fibre) into short-chain fatty acids (SCFA) such as acetate, propionate and butyrate that have a pervasive role in host physiology from nutrition to immune function. In this review we will outline our current understanding of the role of some key microbial metabolites, such as SCFA, indole and bile acids, in human health. Whilst many studies linking microbial metabolites with human health are correlative we will try to highlight examples where genetic evidence is available to support a specific role for a microbial metabolite in host health and well-being.

Dynamic gut microbiome-metabolome in cationic bovine serum albumin induced experimental immune-complex glomerulonephritis and effect of losartan and mycophenolate mofetil on microbiota modulation

Dynamic changes in gut dysbiosis and metabolomic dysregulation are associated with immune-complex glomerulonephritis (ICGN). However, an in-depth study on this topic is currently lacking. Herein, we report an ICGN model to address this gap. ICGN was induced via the intravenous injection of cationized bovine serum albumin (c-BSA) into Sprague-Dawley (SD) rats for two weeks, after which mycophenolate mofetil (MMF) and losartan were administered orally. Two and six weeks after ICGN establishment, fecal samples were collected and 16S ribosomal DNA (rDNA) sequencing and untargeted metabolomic were conducted. Fecal microbiota transplantation (FMT) was conducted to determine whether gut normalization caused by MMF and losartan contributed to their renal protective effects. A gradual decline in microbial diversity and richness was accompanied by a loss of renal function. Approximately 18 genera were found to have significantly different relative abundances between the early and later stages, and Marvinbryantia and Allobaculum were markedly upregulated in both stages. Untargeted metabolomics indicated that the tryptophan metabolism was enhanced in ICGN, characterized by the overproduction of indole and kynurenic acid, while the serotonin pathway was reduced. Administration of losartan and MMF ameliorated microbial dysbiosis and reduced the accumulation of indoxyl conjugates in feces. FMT using feces from animals administered MMF and losartan improved gut dysbiosis by decreasing the Firmicutes/Bacteroidetes (F/B) ratio but did not improve renal function. These findings indicate that ICGN induces serous gut dysbiosis, wherein an altered tryptophan metabolism may contribute to its progression. MMF and losartan significantly reversed the gut microbial and metabolomic dysbiosis, which partially contributed to their renoprotective effects.

The rhizomes of Atractylodes macrocephala relieve loperamide-induced constipation in rats by regulation of tryptophan metabolism

Ethnopharmacological relevanceConstipation is one of the most prevalent gastrointestinal tract diseases that seriously affects health-related quality of human life and requires effective treatments without side effect. The rhizome of Atractylodes macrocephala Koidz. (Compositae), called Atractylodes Macrocephala Rhizome (AMR), a commonly used traditional Chinese medicine, has been used to relieve the clinical symptoms of patients with constipation. Aim of the studyTo reveal the dose-dependent laxative effect and potential mechanism of AMR on loperamide-induced slow transit constipation (STC) rats. Materials and methodsLoperamide-induced constipation rat model was established and the dose-dependent laxative effect of AMR was investigated. Untargeted metabolomics based on an UPLC-Q/TOF-MS technique combined with western blot analysis was used to explain the potential mechanism of AMR relieve loperamide-induced constipation in rats. ResultsThe results showed that medium dose of AMR (AMR-M, 4.32 g raw herb/kg) and high dose of AMR (AMR-H, 8.64 g raw herb/kg) treatments significantly increased the fecal water content, Bristol score, gastrointestinal transit rate, and recovered the damaged colon tissues of constipated rats, but low dose of AMR (AMR-L, 2.16 g raw herb/kg) did not show laxative effect. Both AMR-M and AMR-H treatments also remarkably reduced the serum levels of vasoactive intestinal peptide (VIP), somatostatin (SS) and dopamine (DA), and increased the levels of motilin (MTL), gastrin (GAS) and 5-hydroxytryptamine (5-HT). Urine metabolomics revealed that constipation development was mainly ascribed to the perturbed tryptophan metabolism, and AMR-M and AMR-H markedly corrected the abnormal levels of five urine tryptophan metabolites, namely 4,6-dihydroxyquinoline, indole, 4,8-dihydroxyquinoline, 5-hydroxytryptamine, and kynurenic acid. Additionally, western blot analysis confirmed that the abnormal expression of rate-limiting enzyme involving in tryptophan metabolism, including tryptophan hydroxylase (TPH), monoamine oxidase (MAO) and indoleamine-2,3-dioxygenase (IDO) in the colon of constipated rats, were mediated by AMR-M and AMR-H. Conclusions: The findings provide insight into the mechanisms of STC and AMR could be developed as new therapeutic agent for prevention or healing of constipation.

Naphthyl-Substituted Indole and Pyrrole Carboxylic Acids as Effective Antibiotic Potentiators-Inhibitors of Bacterial Cystathionine γ-Lyase.

Over the past decades, the problem of bacterial resistance to most antibiotics has become a serious threat to patients' survival. Nevertheless, antibiotics of a novel class have not been approved since the 1980s. The development of antibiotic potentiators is an appealing alternative to the challenging process of searching for new antimicrobials. Production of H2S-one of the leading defense mechanisms crucial for bacterial survival-can be influenced by the inhibition of relevant enzymes: bacterial cystathionine γ-lyase (bCSE), bacterial cystathionine β-synthase (bCBS), or 3-mercaptopyruvate sulfurtransferase (MST). The first one makes the main contribution to H2S generation. Herein, we present data on the synthesis, in silico analyses, and enzymatic and microbiological assays of novel bCSE inhibitors. Combined molecular docking and molecular dynamics analyses revealed a novel binding mode of these ligands to bCSE. Lead compound 2a manifested strong potentiating activity when applied in combination with some commonly used antibiotics against multidrug-resistant Acinetobacter baumannii, Pseudomonas aeruginosa, and methicillin-resistant Staphylococcus aureus. The compound was found to have favorable in vitro absorption, distribution, metabolism, excretion, and toxicity parameters. The high effectiveness and safety of compound 2a makes it a promising candidate for enhancing the activity of antibiotics against high-priority pathogens.

Surgery-induced gut microbial dysbiosis promotes cognitive impairment via regulation of intestinal function and the metabolite palmitic amide

BackgroundPerioperative neurocognitive disorders (PND) are the most common postoperative complications with few therapeutic options. Gut microbial dysbiosis is associated with neurological diseases; however, the mechanisms by which the microbiota regulates postoperative gastrointestinal and cognitive function are incompletely understood.MethodsBehavioral testing, MiSeq 16S rRNA gene sequencing, non-target metabolism, intestinal permeability detection, protein assays, and immunofluorescence staining were employed to discern the impacts of surgery on microbial profiles, intestinal barriers, serum metabolism, and the brain. Interventions in mice included fecal microbiota transplantation, the anti-inflammatory agent dexamethasone, Lactobacillus supplementation, indole propionic acid supplementation, and palmitic amide administration.ResultsSurgery-induced cognitive impairment occurs predominantly in aged mice, and surgery-induced alterations in the microbiota composition profile exacerbate intestinal barrier disruption in aged mice. These adverse effects can be mitigated by transferring microbiota from young donors or by bolstering the intestinal barrier function using dexamethasone, Lactobacillus, or indole propionic acid. Moreover, microbiota composition profiles can be restored by transplanting feces from young mice to aged surgical mice, improving neuropathology and cognitive function, and these effects coincide with increased intestinal permeability. Metabolomic screening identified alterations in metabolites in mouse serum after surgery, especially the increase in palmitic amide. Palmitic amide levels in serum and brain can be decreased by transplanting feces from young mice to aged surgical mice. Oral palmitic amide exacerbates cognitive impairment and neuropathological changes in mice.ConclusionsGut microbial dysbiosis in mice after surgery is a key mechanism leading to cognition dysfunction, which disrupts the intestinal barrier and metabolic abnormalities, resulting in neuroinflammation and dendritic spine loss. Intestinal barrier damage and high level of palmitic amide in old mice may be the cause of high incidence of PND in the elderly. Preoperative microbiota regulation and intestinal barrier restoration may be of therapeutic benefit in preventing PND.9Ey9teFKZKXmrKtD72aS7bVideo

Functional Swiss-type cheeses promote beneficial effects in mice gut microbiome during homeostasis and inflammation

The impact of Functional foods on the gut microbiota is a fundamental question since shifts in bacterial composition are associated with inflammation progression. Therefore, this study investigated the effects of two types of cheeses fermented by probiotic bacteria in C57BL6 mice either in healthy conditions or in dextran sulfate sodium (DSS)-induced colitis. One cheese was fermented by Propionibacterium freudenreichii CIRM-BIA129. A second kind of cheese was made in industrial conditions to reproduce Emmental but using the above-mentioned strain in combination with Lactobacillusdelbrueckii CNRZ327 and Streptococcus thermophilus LMD-9 as starters. The gut microbiota was investigated by shotgun metagenomic sequencing and the taxonomic and functional profiles were assessed through sequence alignment to NCBI taxonomy and KEGG pathways databases. Our results suggest that both treatments did not disturb the microbial community ecology. Emmental intake increased symbionts as Romboutsia and Akkermansia muciniphila. Furthermore, metabolic pathway analysis suggests that A. muciniphila may produce bioactive metabolites as acetate and cooperate with other commensal species to produce indole and gamma-aminobutyric acid. Mice with colitis have restored some of the impaired microbiome metabolic functions when treated with cheese fermented only by Propionibacterium, while the Emmental cheese promoted the increase of Ligilactobacillus murinus. This taxon presented several genes with immunomodulatory activity potential. This study provides insights for engineering functional cheeses to increase beneficial bacteria in the gut. However, further studies are required to investigate their role in regulating the gut-brain axis. Moreover, possible anti-inflammatory mechanisms based on the promotion of Lg. murinus interaction with the host was suggested.

Faecal metabolome responses to an altered dietary protein:carbohydrate ratio in adult dogs

High-protein diets may aid weight loss and weight maintenance programs in both humans and dogs, although the effect of dietary protein levels on gut metabolism and functionality has not been studied in depth. The current study aimed to investigate the effect of an altered dietary protein:carbohydrate ratio on gut function in adult dogs by means of faecal metabolomic fingerprinting. More specifically, functional metabolic differences in dogs fed a high-protein/low-carbohydrate (HPLC) vs. low-protein/high-carbohydrate (LPHC) diet were studied by equally allocating twelve clinically healthy (6 lean and 6 obese) Beagles into two groups in a cross-over design, with each group receiving two isocaloric diets for four weeks. The faecal metabolome revealed that different protein:carbohydrate ratio can influence host and/or gut microbiome metabolism and function, while no effect was observed on the body condition. Targeted analysis demonstrated that the HPLC diet significantly increased the concentration of indole, spermidine, and pipecolinic acid and decreased the concentration of azelaic acid, D-fructose, mannose, and galactose (p < 0.05). Multivariate modelling (OPLS-DA) of the untargeted faecal metabolome revealed distinctly different metabolomic profiles following the HPLC vs. LPHC diet, with 18 altered pathways. The HPLC diet influenced amino acid and lipid metabolism, potentially promoting weight loss and immune function, whereas the LPHC diet affected carbohydrate fermentation and may promote anti-oxidative function.

The binding of a c-MYC promoter G-quadruplex to neurotransmitters: An analysis of G-quadruplex stabilization using DNA melting, fluorescence spectroscopy, surface-enhanced Raman scattering and molecular docking

The interactions of several neurotransmitter and neural hormone molecules with the c-MYC G-quadruplex DNA sequence were analyzed using a combination of spectroscopic and computational techniques. The interactions between indole, catecholamine, and amino acid neurotransmitters and DNA sequences could potentially add to the understanding of the role of G-quadruplex structures play in various diseases. Also, the interaction of the DNA sequence derived from the nuclear hypersensitivity element (NHE) III1 region of c-MYC oncogene (Pu22), 5′-TGAGGGTGGGTAGGGTGGGTAA-3′, has added significance in that these molecules may promote or inhibit the formation of G-quadruplex DNA which could lead to the development of promising drugs for anticancer therapy. The results showed that these molecules did not disrupt G-quadruplex formation even in the absence of quadruplex-stabilizing cations. There was also evidence of concentration-dependent binding and high binding affinities based on the Stern-Volmer model, and thermodynamically favorable interactions in the form of hydrogen-bonding and interactions involving the π system of the aromatic neurotransmitters.

Therapeutic potential of dietary phytochemicals from Drynaria quercifolia to modulate gut microbiome: an in silico approach

Drynaria quercifolia is one of the pioneer medicinal plants which exert many beneficial effects on humans. Fatty acids are hydrophobic ligands that act as membrane substrates, metabolic signalling molecules, and metabolic energy sources. It could enhance the mucus production in the intestine which maintain mucosal homeostasis. The inflammatory responses were also regulated by 5-HT receptors. Serotonin 2 A receptors are G-protein coupled receptors targeted by various types of ligands viz. antidepressants, antipsychotics and anti-migraine drugs. The interaction of mucin protein and fatty acid could increase the antimicrobial activity and anti-inflammatory activity of gut microbiome. In this study, dietary phytochemicals were extracted from D. quercifolia and characterized using GC-MS analysis. The result shows presence of 38 various compounds viz. decanoic acid, indole, and dodecanoic acid and etc., Among the all, dodecanoic acid showed good drug likeness and pharmaceutical properties. Target proteins viz. 3IFB (Intestinal fatty acid binding protein) and 7WC4 (5-hydroxytryptamine receptor 2 A) were docked with dodecanoic acid using Auto dock software. The fatty acids produced in the gut could interact with 3IFB and 7WC4 proteins to maintain intestinal integrity and improved gut-brain function respectively. Dodecanoic acid exhibits the highest binding energy with mutated 3IFB (-6.01) than native whereas 7WC4 native protein showed (-7.3 kal/mol) the highest affinity than mutated protein. Structural changes were predicted by using SOPMA and ProSA. Evaluation results indicate that 3IFB was having more stability, good quality, and enhanced affinity than 7WC4. Further, MD simulations were done for 3IFB to check the stability of protein-ligand complex using WebGro platform. The model was investigated by root mean square deviation and fluctuations. Therefore, dodecanoic acids have been considered as a potential agonists and offer opportunities for developing innovative medications for gastrointestinal diseases. Communicated by Ramaswamy H. Sarma

Heterocyclic and non-heterocyclic arena of monocarboxylate transporter inhibitors to battle tumorigenesis.

Monocarboxylate transporters (MCTs) have gained significant attention in cancer research due to their critical role in tumour metabolism. MCTs are legends for transporting lactate molecules in cancer cells, an oncometabolite and waste product of glycolysis, acting as an indispensable factor of tumour proliferation. Targeting MCTs with inhibitors has emerged as a promising strategy to combat tumorigenesis. This article summarizes the most recent research on MCT inhibitors in preventing carcinogenesis, covering both heterocyclic and non-heterocyclic compounds. Heterocyclic and non-heterocyclic compounds such as pteridine, pyrazole, indole, flavonoids, coumarin derivatives and cyanoacetic acid derivatives have been reported as potent MCT inhibitors. We examine the molecular underpinnings of MCTs in cancer metabolism, the design and synthesis of heterocyclic and non-heterocyclic MCT inhibitors, their impact on tumour cells and the microenvironment and their potential as therapeutic agents. Moreover, we explore the challenges associated with MCT inhibitor development and propose future directions for advancing this field. This write-up aims to provide researchers, scientists and clinicians with a comprehensive understanding of the heterocyclic and non-heterocyclic MCT inhibitors and their potential in combating tumorigenesis.

ATP-triggered, selective superoxide radical generating oxidase-mimetic cerium oxide nanozyme exhibiting efficient antibacterial activity at physiological pH

Bacterial infections are considered as one of the major health threats to the global population. The advent of bacterial species with antibiotic resistance has attracted significant efforts to develop novel materials and strategies to effectively avoid the resistance with enhanced antibacterial potential. In this work, we have developed oxidase-mimetic cerium oxide nanoparticles (CeO2 NPs), which exhibit nanozyme activity at physiological pH in the presence of adenosine triphosphate (ATP). The oxidase-mimetic activity was confirmed to involve superoxide radicals using p-benzoquinone and dihydroethidium. Using indole propionic acid, ethanol, and terephthalic acid, it was confirmed that the oxidase-mimetic activity of CeO2 NPs with ATP does not involve the formation of hydroxyl radicals. CeO2 NPs with ATP produced a strong antibacterial activity against Staphylococcus aureus and Escherichia coli within 3 – 6 hrs. The bacterial cell morphology analysis suggested that superoxide radicals generated during the oxidase-mimetic activity of CeO2 NPs with ATP cause distortion of paired and tetrad arrangement (Staphylococcus aureus), loss of cytoplasmic content, damage, and pore formation in the cell wall (Escherichia coli) that led to the death of bacteria. Further, the live/dead assay also concludes the time-dependent death of bacterial cells with the highest death in the cell population exposed to CeO2 NPs and ATP. Thus, the antibacterial activity at physiological pH by superoxide radical generating oxidase-mimetic CeO2 NPs could be further extended to other pathogenic bacterial species.

Determining the Relationship between Aroma and Quality of Bao-Chung Tea by Solid-Phase Microextraction (SPME) and Electronic Nose Analyses

Despite extensive studies, the relationship between the quality/quantity of tea odorants and oolong tea quality remains unclear. To investigate the key components affecting Bao-chung tea quality, we collected samples of different grades from a tea-tasting competition and determined the content and composition of volatile components and individual catechins using gas chromatography–mass spectrometry and high-performance liquid chromatography. We used an electronic nose (E-nose) to collect odor component signals and established a quality recognition model. The different tea grades did not significantly differ in catechin content, but their specific odor intensity and proportion of odor components varied significantly. Linear discriminant analysis showed that the intensity and proportion of volatile organic compounds could be used for distinguishing the different grades of Bao-chung tea. By combining different quantities of indole, linalool, and butanoic acid and proportions of p-cymene, cis-β-ocimene, nonanal, allo-ocimene, cis-jasmone, and α-farnesene, the ability to distinguish among Bao-chung tea grades was significantly improved. Our results revealed that the quality of Bao-chung tea should be evaluated based on the combined perception of odor component intensity and proportion rather than solely relying on the concentration or composition of specific compounds. Therefore, individuals can judge a Bao-chung tea grade based on the combined perception of odor component intensity and proportion. The E-nose can be used to identify Bao-chung tea grades based on its ability to determine the odorant composition.

Characterisation of Antennal Sensilla and Electroantennography Responses of the Dung Beetles Bubas bison, Onitis aygulus and Geotrupes spiniger (Coleoptera: Scarabaeoidea) to Dung Volatile Organic Compounds.

Locating sporadically distributed food resources and mate finding are strongly aided by volatile cues for most insects, including dung beetles. However, there is limited information on the olfactory ecology of dung beetles. We conducted a scanning electron microscopy study on the morphology and distribution of the antennal sensilla of three introduced dung beetle species in Australia: Geotrupes spiniger (Coleoptera: Geotrupidae), Bubas bison and Onitis aygulus (Coleoptera: Scarabaeidae). Three main morphological types of antennal sensilla were identified: sensilla trichodea (ST), sensilla basiconica (SB) and sensilla chaetica (SCh). Distinct variations of SB distribution were observed in B. bison and G. spiniger and on different lamellar surfaces in both sexes of all three species. Sexual dimorphism in antennal sensilla distribution or their abundance was not evident. To complement the morphological characterisation of sensilla, electroantennography (EAG) was carried out to construct EAG response profiles of the three species to selected dung volatiles. An initial study revealed that antennae of all species were sensitive to a mix of phenol, skatole, indole, p-cresol, butanone and butyric acid, common components of livestock dung headspace. In addition to these six compounds, dimethyl sulfide, dimethyl disulfide, eucalyptol and toluene were tested for antennal activity. All compounds evoked measurable EAG responses, confirming antennal sensitivity. Geotrupes spiniger exhibited significant responses to all the compounds compared to the control, whereas B. bison and O. aygulus only responded to a subset of compounds. A comparison of relative EAG amplitudes revealed highly significant responses to p-cresol in G. spiniger and to skatole in B. bison. Geotrupes spiniger displayed differential responses to all the compounds. Pooled EAG data suggest highly significant differences in responses among the three species and among compounds. Our findings suggest that a blend of volatiles may offer potential for the trapping of dung beetles, thereby avoiding the use of dung baits that are inconvenient, inconsistent and may pose a threat to farm biosecurity.

Evaluation of Antimicrobial, Anticholinesterase Potential of Indole Derivatives and Unexpectedly Synthesized Novel Benzodiazine: Characterization, DFT and Hirshfeld Charge Analysis

The pharmacological effectiveness of indoles, benzoxazepines and benzodiazepines initiated our synthesis of indole fused benoxazepine/benzodiazepine heterocycles, along with enhanced biological usefulness of the fused rings. Activated indoles 5, 6 and 7 were synthesized using modified Bischler indole synthesis rearrangement. Indole 5 was substituted with the trichloroacetyl group at the C7 position, yielding 8, exclusively due to the increased nucleophilic character of C7. When trichloroacylated indole 8 was treated with basified ethanol or excess amminia, indole acid 9 and amide 10 were yielded, respectively. Indole amide 10 was expected to give indole fused benoxazepine/benzodiazepine 11a/11b on treatment with alpha halo ester followed by a coupling agent, but when the reaction was tried, an unexpectedly rearranged novel product, 1,3-bezodiazine 12, was obtained. The synthetic compounds were screened for anticholinesterase and antibacterial potential; results showed all products to be very important candidates for both activities, and their potential can be explored further. In addition, 1,3-bezodiazine 12 was explored by DFT studies, Hirshfeld surface charge analysis and structural insight to obrain a good picture of the structure and reactivity of the products for the design of derivatised drugs from the novel compound.

Co-production of 7-chloro-tryptophan and indole pyruvic acid based on an efficient FAD/FADH2 regeneration system.

Efficient FAD/FADH2 regeneration is vital for enzymatic biocatalysis and metabolic pathway optimization. Here, we constructed an efficient and simple FAD/FADH2 regeneration system through a combination of L-amino acid deaminase (L-AAD) and halogenase (CombiAADHa), which was applied for catalyzing the conversion of an L-amino acid to halide and an α-keto acid. For cell-free biotransformation, the optimal activity ratio of L-AAD and halogenase was set between 1:50 and 1:60. Within 6h, 170mg/L of 7-chloro-tryptophan (7-Cl-Trp) and 193mg/L of indole pyruvic acid (IPA) were synthesized in the selected mono-amino acid system. For whole-cell biotransformation, 7-Cl-Trp and IPA synthesis was enhanced by 15% (from 96 to 110mg/L) and 12% (from 115 to 129mg/L), respectively, through expression fine-tuning and the strengthening of FAD/FADH2 supply. Finally, ultrasound treatment was applied to improve membrane permeability and adjust the activity ratio, resulting in 1.6-and 1.4-fold higher 7-Cl-Trp and IPA yields. The products were then purified. This system could also be applied to the synthesis of other halides and α-keto acids. KEY POINTS: • In this study, a whole cell FAD/FADH2 regeneration system co-expressingl-AAD and halogenase was constructed • This study found that the activity and ratio of enzyme and the concentration of cofactors had a significant effect on the catalytic process for the efficient co-production of 7-chlorotryptophan and indole pyruvate.