Degradation Of Flavonoids Research Articles

Multi-omics analysis of metabolic differences in rape bee pollen fermented by single and mixed lactic acid bacterial strains

Bee pollen is a nutrient-rich granule, but its hard cell wall limits the absorption of its nutrients by the human body. Fermenting bee pollen with lactic acid bacteria breaks down its cell wall and enhances its metabolite profile, improving nutrient availability. However, the differences in metabolites and cell wall disruption effects between mixed and single-strain fermentation have not been clarified. This study aimed to analyze the metabolites of Lactobacillus plantarum comprehensively fermented bee pollen (LPFP), Lactobacillus acidophilus fermented bee pollen (LAFP), and L. plantarum and L. acidophilus mixed fermented bee pollen (LMFP) using targeted and untargeted metabolomics as well as lipidomics, to explore the key metabolic pathways of LMFP. The results showed that under scanning electron microscopy (SEM), the cell wall of LMFP was more thoroughly disrupted. Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA) and metabolic pathway enrichment analysis indicated that the degradation of flavonoids in LMFP was reduced, while the contents of total phenols, total flavonoids, rutin, and other polyphenols were significantly increased. Meanwhile, the metabolism of sucrose and amino acids in LMFP was enhanced, which might have contributed to the production of flavor compounds. Additionally, compared to LAFP and LPFP, triglycerides (TG) in LMFP increased by 8.14% and 9.85%, respectively, while the proportion of phosphatidylcholine (PC) decreased by 0.62% and 2.88%. Overall, this study presents a comprehensive metabolic profile of LAFP, LPFP, and LMFP, demonstrating how fermentation strategies affect cell wall disruption and metabolite diversity, laying a foundation for enhancing bee pollen's nutritional and functional properties.

Novel enzymatic route to the synthesis of C-8 hydroxyflavonoids including flavonols and isoflavones

Flavin-dependent monooxygenases (FMOs) are a valuable group of biocatalysts that can regioselectively introduce a hydroxy group for the targeted modification of biologically active compounds. Here, we present the fdeE, the FMO from Herbaspirillum seropedicae SmR1 that is a part of the naringenin degradation pathway and is active towards a wide range of flavonoids—flavanones, flavones, isoflavones, and flavonols. Bioinformatics and biochemical analysis revealed a high similarity between the analyzed enzyme and other F8H FMOs what might indicate convergent evolutionary mechanism of flavonoid degradation pathway emergence by microorganism. A simple approach with the manipulation of the reaction environment allowed the stable formation of hydroxylation products, which showed very high reactivity in both in vivo and in vitro assays. This approach resulted in an 8-hydroxyquercetin—gossypetin titer of 0.16 g/L and additionally it is a first report of production of this compound.

Widely targeted metabolomics analysis of nutrient changes in a new black rice variety ‘Huamoxiang No.3’ (Oryza sativa L. var. Glutinosa Matsum) under different cooking modes

AbstractBackgroundBlack rice is rich in various nutrients, such as anthocyanins, which may undergo some changes during cooking. However, previous studies have been mainly focused on a single substance and paid less attention to the changes in overall nutrient components. Here, we performed widely targeted metabolomics analysis on the chemical compositional changes in a new black rice variety (‘Huamoxiang No.3’) under three cooking modes, including bottom heating (BH), induction heating (IH), and IH + pressure.ResultsAmong the detected 1458 metabolites, 276 and 108 metabolites were differential metabolites after cooking and in three cooking modes, respectively. Cooking increased the contents of most peptides, phenolic acids, and organic acid compounds but significantly decreased those of lipids and flavonoids, particularly anthocyanins. However, phenolic acids such as chlorogenic acid, erucic acid, and p‐coumaric acid increased significantly, possibly due to the release of bound phenols and degradation of flavonoids to phenolic acids, such as thermal degradation of C3G to protocatechuic acid and among the three heating modes, the IH + pressure mode resulted in the most significant changes.ConclusionAlthough cooking reduced the content of flavonoids and anthocyanins, the increase in phenolic acids and other substances contributed to the healthy effect of cooked black rice, and the content of these active substances increased more significantly in the IH + pressure mode.

Genomics and physiology of Catenibacillus, human gut bacteria capable of polyphenol C-deglycosylation and flavonoid degradation.

The genus Catenibacillus (family Lachnospiraceae, phylum Bacillota) includes only one cultivated species so far, Catenibacillus scindens, isolated from human faeces and capable of deglycosylating dietary polyphenols and degrading flavonoid aglycones. Another human intestinal Catenibacillus strain not taxonomically resolved at that time was recently genome-sequenced. We analysed the genome of this novel isolate, designated Catenibacillus decagia, and showed its ability to deglycosylate C-coupled flavone and xanthone glucosides and O-coupled flavonoid glycosides. Most of the resulting aglycones were further degraded to the corresponding phenolic acids. Including the recently sequenced genome of C. scindens and ten faecal metagenome-assembled genomes assigned to the genus Catenibacillus, we performed a comparative genome analysis and searched for genes encoding potential C-glycosidases and other polyphenol-converting enzymes. According to genome data and physiological characterization, the core metabolism of Catenibacillus strains is based on a fermentative lifestyle with butyrate production and hydrogen evolution. Both C. scindens and C. decagia encode a flavonoid O-glycosidase, a flavone reductase, a flavanone/flavanonol-cleaving reductase and a phloretin hydrolase. Several gene clusters encode enzymes similar to those of the flavonoid C-deglycosylation system of Dorea strain PUE (DgpBC), while separately located genes encode putative polyphenol-glucoside oxidases (DgpA) required for C-deglycosylation. The diversity of dgpA and dgpBC gene clusters might explain the broad C-glycoside substrate spectrum of C. scindens and C. decagia. The other Catenibacillus genomes encode only a few potential flavonoid-converting enzymes. Our results indicate that several Catenibacillus species are well-equipped to deglycosylate and degrade dietary plant polyphenols and might inhabit a corresponding, specific niche in the gut.

Biodegradation of flavonoids – Influences of structural features

Flavonoids, a class of natural products with a variety of applications in nutrition, pharmacy and as biopesticides, could substitute more harmful synthetic chemicals that persist in the environment. To gain a better understanding of the biodegradability of flavonoids and the influence of structural features, firstly, the ultimate biodegradation of 19 flavonoids was investigated with the Closed Bottle Test according to the OECD guideline 301 D. Secondly, regarding the fast abiotic degradation reported for several flavonoids with severe concentration decrease within hours and its possible impacts on the processes behind the ultimate biodegradation, primary degradation of 4 selected flavonoids was compared at conditions representing biodegradation, abiotic degradation, and mixed substrates by monitoring the flavonoids' concentrations with HPLC-UV/vis. Our results showed that 17 out of the 19 tested flavonoids were readily biodegradable. Structural features like a hydroxy group at C3, the C2–C3 bond order, a methoxy group in the B ring, and the position of the B ring in regard to the chromene core did not affect biodegradation of the tested flavonoids. Only flavone without any hydroxy groups and morin with an uncommon 2′,4′ pattern of hydroxy groups were non-readily biodegradable. Monitoring the concentration of 4 selected flavonoids by HPLC-UV/vis revealed that biodegradation occurred faster than abiotic degradation at CBT conditions with no other carbon sources present. The presence of an alternative carbon source tends to increase lag phases and decrease biodegradation rates. At this condition, abiotic degradation contributed to the degradation of unstable flavonoids. Overall, as a first tier to assess the environmental fate, our results indicate low risks for persistence of most flavonoids. Thus, flavonoids could represent benign substitutes for persistent synthetic chemicals.

The metabolites of flavonoids with typical structure enhanced bioactivity through gut microbiota

The degradation of flavonoids helps to elucidate the mechanism of their biological activity, thus guiding individuals to better ingestion and utilization of these compounds. In this study, seven kinds of flavonoids with typical structures were in vitro fermented by fresh feces, and the degradation process of flavonoids were monitored by HPLC, and the gut microbiota constitutes were analyzed by 16 S rRNA microbiota sequencing. Results indicated that all seven kinds of flavonoids could be degraded by intestinal microbiota. In addition, the degradation products of flavonoids showed excellent antioxidant and anti-inflammatory activity, especially the degradation products of epicatechin at 24 h exhibited the strongest scavenging capacity for FRAP and ABTS free radicals, which were 287.494 ± 16.941 μM and 567.344 ± 13.477 μM, respectively. Moreover, compared with the corresponding control group, flavonoid treatment changed the composition of the gut microbiota, mainly by significantly reducing the abundance of harmful bacteria, such as Proteobacteria, and increasing the abundance of beneficial bacteria, such as Flavonifractor. This paper might provide theoretical basis and technical support for the nutritional and pharmacological applications of flavonoids.

P1227 Revealing lower capacity of microbial metabolism of flavonoids and associated metabolic changes in Crohn’s disease

Abstract Background Recent studies highlight the role of interplay between oxidative stress, gut microbiota, and immune response in the etiology of Crohn’s disease (CD). Polyphenols are natural antioxidants which are mainly metabolized by gut microbiota and could modulate the composition of gut microbiota. However, it’s yet reported whether there is difference in polyphenol-degradation capacity of gut microbiota in CD and healthy controls (HCs). Methods A comprehensive literature search was conducted on microbial metabolic pathway of polyphenols and the responsible organisms and genes were recorded. The polyphenol-degrading genes were quantified using shortBRED in three clinical cohorts (the First Affiliated Hospital of Sun Yat-sen University (FAH) cohort, PRISM cohort, and HMP2 cohort). Microbiota abundance was analyzed in FAH and PRISM cohort. Polyphenol intake and serum metabolites were assessed in the FAH cohort. Enterotype analysis was performed in FAH cohort. Correlation analysis among polyphenol intake, gene abundance, serum metabolites and bacterial abundance was conducted. Results Phylogenetic tree revealed that reported polyphenol-degrading bacteria were mainly distributed to Actinobacteria and Firmicutes. The abundance of flavonoid degradation related genes (mainly flavone reductase, chalcone isomerase and phloretin hydrolase) was significantly decreased in patients with CD in FAH cohort, but not in PRISM and HMP cohort. Difference in abundance of polyphenol-degrading bacteria was observed between CD patients and HCs in FAH and PRISM cohort. In addition, lower polyphenols intake and serum hippuric acid (HA) level were detected in CD patients. Enterotype analysis revealed that CD patients were mainly distributed to Enterobacteriaceae- and Bacteroidaceae-dominated enterotype while HCs were mainly distributed to Ruminococcaceae- and Prevotellaceae-dominated enterotype. Serum HA level was higher in healthier enterotypes (Ruminococcaceae and Prevotellaceae dominant) and positively correlated with flavonoid-degrading organisms and butyric acid-producing organisms. No positive correlation between abundance of polyphenol-degradation genes and polyphenols intake was detected. Conclusion The current study summarized the polyphenol metabolic pathway mediated by gut microbiota and quantified genes responsible for polyphenol degradation. Our comprehensive analysis of diet-microbiota-gene-metabolite data revealed a lower capability of flavonoid degradation in gut microbiota and lower HA level in CD patients. Finally, our findings provide a foundation for future work exploring the polyphenol or polyphenol-degrading microbiota interventions in preclinical models of CD.

Biochemical investigations of polyphenol degradation enzymes in the phototrophic bacterium Rubrivivax gelatinosus.

Phloroglucinol (1,3,5-trihydroxybenzene) is an important intermediate in the degradation of flavonoids and tannins by anaerobic bacteria. Recent studies have shed light on the enzymatic mechanism of phloroglucinol degradation in butyrate-forming anaerobic bacteria, including environmental and intestinal bacteria such as Clostridium and Flavonifractor sp. Phloroglucinol degradation gene clusters have also been identified in other metabolically diverse bacteria, although the polyphenol metabolism of these microorganisms remain largely unexplored. Here, we describe biochemical studies of polyphenol degradation enzymes found in the purple non-sulfur bacterium Rubrivivax gelatinosus IL144, an anaerobic photoheterotroph reported to utilize diverse organic compounds as carbon sources for growth. In addition to the phloroglucinol reductase and dihydrophloroglucinol cyclohydrolase that catalyze phloroglucinol degradation, we characterize a Mn2+-dependent phloretin hydrolase that catalyzes the cleavage of phloretin into phloroglucinol and phloretic acid. We also report a Mn2+-dependent decarboxylase (DeC) that catalyzes the reversible decarboxylation of 2,4,6-trihydroxybenzoate to form phloroglucinol. A bioinformatics search led to the identification of DeC homologs in diverse soil and gut bacteria, and biochemical studies of a DeC homolog from the human gut bacterium Flavonifractor plautii demonstrated that it is also a 2,4,6-trihydroxybenzoate decarboxylase. Our study expands the range of enzymatic mechanisms for phloroglucinol formation, and provides further biochemical insight into polyphenol metabolism in the anaerobic biosphere.

Optimization of the molybdenum blue method for estimating the antioxidant activity of natural products

Context: The present experimental conditions of the molybdenum blue spectrophotometric method, used for antioxidant activity estimation, promote the degradation of flavonoids with potential interferences in the above determination. Aims: To evaluate the effects of physicochemical factors on the formation of the complex for optimizing the total antioxidant activity method to better estimate the antioxidant activity of natural products. Methods: A 34-1 fractional experimental design was applied. Independent variables were temperature, color development time, type of acid and acidity, and the dependent variable was the absorbance of the complex. The concentration of ammonium molybdate tetrahydrate and sodium hydrogen phosphate remained constant throughout the study. The effects of the reducing agent and its concentration were studied independently. The effect of acidity in a wide range of values, the color development time considering temperature, the influence of co-solvents, and the antioxidant activity of various natural metabolites were also evaluated. Results: Acid concentration and temperature greatly influenced the complex formation, making the type of acid and incubation time less significant. Ascorbic acid showed a shorter color development time than reference metabolites. Ethanol negatively influenced the amount of complex formed. The proposed conditions for developing this method were: type of acid, HCl or H2SO4; acid concentration 0.01 N; incubation temperature 65°C; and incubation time 40 min. Under these experimental conditions, the ranking order of antioxidant activity was pyrogallol>quercetin>ascorbic acid>gallic acid>rutin. Conclusions: The new experimental conditions for the molybdenum complex assay give a more reliable determination of the antioxidant activity of natural products.

Thermal degradation of (2R, 3R)-dihydromyricetin in neutral aqueous solution at 100 ℃

In the field of thermal degradation of flavonoids, current studies mainly focused on flavonols. However, the thermal degradation of dihydroflavonols in aqueous solution has received limited attention compared to flavonols. The single C2-C3 bonds of dihydroflavonols, which differs from the C2-C3 double bond in flavonols, may cause different degradation mechanisms. Dihydromyricetin (DMY) is a typical dihydroflavonol with six hydroxyl groups, and possesses various health effects. We explored the thermal degradation of DMY in neutral aqueous solution (pH 7) at 100 ℃. Ultra-performance liquid chromatography combined with photodiode array and electrospray ionization quadrupole-time-of-flight tandem mass spectrometric detection (UPLC-PDA-ESI-QTOF–MS/MS) provided suitable platform for exploring DMY degradation pathways, and negative ion mode was applied. Thermal treatment led to a decline in DMY level with time, accompanied by the appearance of various degradation products of DMY. Degradation mechanisms of DMY included isomerization, oxidation, hydroxylation, dimerization and ring cleavage. The pyrogallol-type ring B of DMY might be initially oxidized into ortho-quinone, which could further attack another DMY to form dimers. In addition, hydroxylation is likely to occur at C-2, C-3 of DMY or DMY dimers, which then further yields ring-cleavage products via breakage of the O1-C2 bond, C2-C3 bond, or C3-C4 bond. The 3-hydroxy-5-(3,3,5,7-tetrahydroxy-4-oxochroman-2-yl) cyclohexa-3,5-diene-1, 2-dione (m/z 333.0244) and unknown compound m/z 435.0925 were annotated as key intermediates in DMY degradation. Four phenolic acids, including 3,4,5-trihydroxybenzoic acid (m/z 169.0136, RT 1.4 min), 2,4,6-trihydroxyphenylglyoxylic acid (m/z 197.0084, RT 1.7 min), 2-oxo-2-(2,4,6-trihydroxyphenyl) acetaldehyde (m/z 181.0132, RT 2.4 min), and 2,4,6-trihydroxybenzoic acid (m/z 169.0139, RT 2.5 min) were identified as the major end products of DMY degradation. In addition, 5-((3,5dihydroxyphenoxy) methyl)-3-hydroxycyclohexa-3,5-diene-1,2-dione (m/z 261.0399, RT 11.7 min) and unidentified compound with m/z 329.0507 (RT 1.0 min) were also suggested to be end products of DMY degradation. These results provide novel insights on DMY stability and degradation products. Moreover, the heat treatment of DMY aqueous solution was found to gradually reduce the antioxidant activities of DMY, and even destroy the beneficial effect of DMY on the gut microbiota composition.

Effect of Aloe vera gel coating on organoleptic and nutritional quality of minimally processed carrot.

Demand for fresh vegetables has led to development studies in postharvest area mainly focused on minimizing and look for alternatives to chemical additives for food preservation. The use of natural derived edible coatings emerges as a promising alternative for maintaining quality of vegetables. The objective of this study was to evaluate the effect of Aloe vera gel in minimally processed carrot during postharvest storage. Samples with different degrees of processing were immersed in Aloe vera gel, packaged polyolefin bags, and stored in refrigerated chambers at 5 °C for 12 days. Different organoleptic and quality parameters were evaluated. In general, the samples treated with Aloe vera gel showed less quality loss and a lower increment in the bleaching index. Moreover, sensory analysis allowed to establish that carrots processed in slices and shredded and coated with the gel had a more flavorful taste and higher moisture content. Aloe vera treatment did not influence the microbiological growth of bacteria and fungi during storage. Regarding nutritional quality, the treated samples showed a higher accumulation or lower degradation of phenols, flavonoids, and carotenoids, probably generating in this way, a higher antioxidant capacity in these samples. Finally, Aloe vera gel treatment did not influence sugar dynamics in any of the samples. It can be concluded that the treatment with Aloe vera gel allows maintaining a better organoleptic and nutritional quality of carrots with different degrees of processing during refrigerated storage.

Kinetics of Flavonoid Degradation and Controlled Release from Functionalized Magnetic Nanoparticles.

Flavonoids are naturally occurring antioxidants that have been shown to protect cell membranes from oxidative stress and have a potential use in photodynamic cancer treatment. However, they degrade at physiological pH values, which is often neglected in drug release studies. Kinetic study of flavonoid oxidation can help to understand the mechanism of degradation and to correctly analyze flavonoid release data. Additionally, the incorporation of flavonoids into magnetic nanocarriers can be utilized to mitigate degradation and overcome their low solubility, while the release can be controlled using magnetic fields (MFs). An approach that combines alternating least squares (ALS) and multilinear regression to consider flavonoid autoxidation in release studies is presented. This approach can be used in general cases to account for the degradation of unstable drugs released from nanoparticles. The oxidation of quercetin, myricetin (MCE), and myricitrin (MCI) was studied in PBS buffer (pH = 7.4) using UV-vis spectrophotometry. ALS was used to determine the kinetic profiles and characteristic spectra, which were used to analyze UV-vis data of release from functionalized magnetic nanoparticles (MNPs). MNPs were selected for their unique magnetic properties, which can be exploited for both targeted drug delivery and control over the drug release. MNPs were prepared and characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, superconducting quantum interference device magnetometer, and electrophoretic mobility measurements. Autoxidation of all three flavonoids follows a two-step first-order kinetic model. MCE showed the fastest degradation, while the oxidation of MCI was the slowest. The flavonoids were successfully loaded into the prepared MNPs, and the drug release was described by the first-order and Korsmeyer-Peppas models. External MFs were utilized to control the release mechanism and the cumulative mass of the flavonoids released.

Exploring the mysterious effect of piling fermentation on Pu-erh tea quality formation: Microbial action and moist-heat action

Moist-heat action and microbial action are essential to the formation of Pu-erh tea’s quality. To explore the impact of piling fermentation (PF) environment on Pu-erh tea quality, samples subjected to spontaneous PF (SPPF) and sterile PF (STPF) from the same batch of raw material were processed, and their sensory quality and metabolic profile dynamics were determined. Sensory evaluation indicated that infusions of the SPPF samples were mainly brownish-red, stale-mellow taste, and stale aroma, whereas infusions of the STPF samples were mainly orange-red, sweet-mellow taste, and woody aroma. Metabolomics analysis identified 465 key metabolites, including 33 microbial markers and 39 moist-heat activity markers. Enzyme and pathway analyses revealed that the production of microbial enzymes accelerates the degradation of flavonoids, flavonols, and lipids and also indicated an exclusive influence of microorganisms on the lipid metabolite pathway. This study elucidated the mechanism underlying the formation of Pu-erh tea’s stale flavour.

Anaerobic phloroglucinol degradation by Clostridium scatologenes.

Polyphenols are abundant in nature, and their anaerobic biodegradation by gut and soil bacteria is a topic of great interest. The O2 requirement of phenol oxidases is thought to explain the microbial inertness of phenolic compounds in anoxic environments, such as peatlands, termed the enzyme latch hypothesis. A caveat of this model is that certain phenols are known to be degraded by strict anaerobic bacteria, although the biochemical basis for this process is incompletely understood. Here, we report the discovery and characterization of a gene cluster in the environmental bacterium Clostridium scatologenes for the degradation phloroglucinol (1,3,5-trihydroxybenzene), a key intermediate in the anaerobic degradation of flavonoids and tannins, which constitute the most abundant polyphenols in nature. The gene cluster encodes the key C-C cleavage enzyme dihydrophloroglucinol cyclohydrolase, as well as (S)-3-hydroxy-5-oxo-hexanoate dehydrogenase and triacetate acetoacetate-lyase, which enable phloroglucinol to be utilized as a carbon and energy source. Bioinformatics studies revealed the presence of this gene cluster in phylogenetically and metabolically diverse gut and environmental bacteria, with potential impacts on human health and carbon preservation in peat soils and other anaerobic environmental niches. IMPORTANCE This study provides novel insights into the microbiota's anaerobic metabolism of phloroglucinol, a critical intermediate in the degradation of polyphenols in plants. Elucidation of this anaerobic pathway reveals enzymatic mechanisms for the degradation of phloroglucinol into short-chain fatty acids and acetyl-CoA, which are used as a carbon and energy source for bacterium growth. Bioinformatics studies suggested the prevalence of this pathway in phylogenetically and metabolically diverse gut and environmental bacteria, with potential impacts on carbon preservation in peat soils and human gut health.

Cold plasma-assisted buckwheat grain dehulling and farinographical properties of dehulled buckwheat flour

The process of dehulling buckwheat grain should lead to less breaking of the buckwheat grain and improve the whole kernel recovery rate. However, heat treatment-based delhulling is associated with starch gelatinization, protein denaturation, and degradation of flavonoids. This study investigated a cold plasma-based rapid dehulling technology by analyzing the farinographical properties of dehulled buckwheat flour (BF). Cold plasma treatment-mediated etching and dehydration created cracks and pores on the surface of the hull, and the gap between the hull and the kernel increased, resulting in a decrease of the critical damage force of the hull by 58.3%. Compared with heat treatment, significant changes were observed in solubility, swelling power, color, iodine blue values, fatty acid and flavonoid contents, and crystal structure in cold plasma-treated dehulled BF. In conclusion, cold plasma can be used as an ancillary method of dehulling buckwheat for the production of high-quality BF.

Changes of Bioactive Components and Antioxidant Capacity of Pear Ferment in Simulated Gastrointestinal Digestion In Vitro.

Fruit ferment is rich in polyphenols, organic acids, enzymes, and other bioactive components, which contribute to their antioxidant ability. In this study, we investigated the effect of the simulated gastric and intestinal digestion in vitro on the total phenolic content (TPC), total flavonoid content (TFC), phenolic components content, organic acid content, protease activity, superoxide dismutase (SOD) activity, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (DPPH-RSA), hydroxyl (·OH) radical scavenging activity (·OH-RSA), and total reducing capacity in 'Xuehua' pear (Pyrus bretschneideri Rehd) ferment. The result showed that the TPC, TFC, protease activity, and phenolic components such as arbutin, protocatechuic acid, malic acid, and acetic acid showed a rising trend during the simulated gastric digestion in 'Xuehua' pear ferment, and these components might contribute to the increasing of ·OH-RSA and total reducing capacity. The SOD activity and epicatechin content showed an increasing trend at first and then a decreasing trend, which was likely associated with DPPH-RSA. During in vitro-simulated intestinal digestion, the majority of evaluated items reduced, except for protease activity, quercetin, and tartaric acid. The reason for the decreasing of bio-accessibility resulted from the inhibition of the digestive environment, and the transformation between substances, such as the conversion of hyperoside to quercetin. The correlation analysis indicated that the antioxidant capacity of 'Xuehua' pear ferment was mainly affected by its bioactive compounds and enzymes activity as well as the food matrices and digestive environment. The comparison between the digestive group with and without enzymes suggested that the simulated gastrointestinal digestion could boost the release and delay the degradation of phenolic components, flavonoids, and organic acid, protect protease and SOD activity, and stabilize DPPH-RSA, ·OH-RSA, and total reducing capacity in 'Xuehua' pear ferment; thus, the 'Xuehua' pear ferment could be considered as an easily digestible food.

Colonic Degradation as Reverse Process to Flavone Biosynthesis in Plants: Similarities and Differences.

For many years, it was thought that the main function of the colon is the reabsorption of water and salt and the elimination of unused food materials. Only very recently, a crucial role of the human intestinal microbiota in the metabolism of different food constituents, including plant foods-derived flavonoids, was discovered. Currently, the knowledge about colonic degradation of ingested flavonoids, involved bacteria and produced catabolites is rapidly increasing. In general, flavonoids unabsorbed in the small intestine reach the colon, where they are exposed to the gut microbiota. In this perspective article, colonic degradation of flavonoids is considered a reverse process to their biosynthesis in plants, with a special focus on the subclass of flavones. According to this approach: what is composed in plants, will be decomposed in the human colon. Several inverse similarities are highlighted, including hydrolysis of flavonoid glycosides as the first step in the gut degradation contrasted with the attachment of sugar moiety as the last reaction of flavonoid biosynthesis in plants, colonic reduction contrasted with plant introduction of C2-C3 double bond in the central heterocyclic ring, or microbial ring fission contrasted with plant ring closure of the heterocyclic ring of flavones. Despite these inverse similarities, precursors of flavonoid pathway in plants are different from the spectrum of gut microbial catabolites in humans. In the human colon, a wide variety of phenolic acids are produced from the ingested flavonoids, due to the diverse enzymatic capacity of intestinal microbiota. The bioactivities and potential health impacts of these catabolites are still largely unknown.

Convective Drying of Purple Basil (Ocimum basilicum L.) Leaves and Stability of Chlorophyll and Phenolic Compounds during the Process.

This study evaluated the effect of convective drying on the degradation of color and phenolic compounds of purple basil (Ocimum basilicum L.) leaves, and the hygroscopic behavior of dried leaves. The fresh leaves underwent drying at 40 °C, 50 °C, 60 °C, and 70 °C. Degradation of chlorophyll, flavonoids, and phenolic compounds were evaluated during drying and the hygroscopicity was evaluated through the moisture sorption isotherms. The drying mathematical modeling and the moisture sorption data were performed. The effective diffusivity for the drying increased from 4.93 × 10−10 m2/s at 40 °C to 18.96 × 10−10 m2/s at 70 °C, and the activation energy value (39.30 kJ/mol) showed that the leaves present temperature sensibility. The leaves dried at 40 °C had less degradation of phenolic compounds and color variation, but the drying process was too slow for practical purposes. Modified Page, Diffusion Approximation, and Verna models had excellent accuracy in drying kinetics. The isotherms showed that, in environments with relative humidity above 50%, the purple basil leaves are more susceptible to water gain, and at 8.83 g H2O/100 g db moisture, it guarantees the microbiological stability of the dried leaves. The Oswin model was the most suitable for estimating the moisture sorption isotherms of the dried leaves.

Multi-omics analyses reveal new insights into nutritional quality changes of alfalfa leaves during the flowering period.

High-quality alfalfa is an indispensable resource for animal husbandry and sustainable development. Its nutritional quality changes dramatically during its life cycle and, at present, no molecular mechanisms for nutrient metabolic variation in alfalfa leaves at different growth stages have been clearly reported. We have used correlation and network analyses of the alfalfa leaf metabolome, proteome, and transcriptome to explore chlorophyll, flavonoid, and amino acid content at two development stages: budding stage (BS) and full-bloom stage (FBS). A high correlation between the expression of biosynthetic genes and their metabolites revealed significant reductions in metabolite content as the plant matured from BS to FBS. l-Glutamate, the first molecule of chlorophyll biosynthesis, decreased, and the expression of HemA, which controls the transformation of glutamyl-tRNA to glutamate 1-semialdehyde, was down-regulated, leading to a reduction in leaf chlorophyll content. Flavonoids also decreased, driven at least in part by increased expression of the gene encoding CYP75B1: flavonoid 3'-monooxygenase, which catalyzes the hydroxylation of dihydroflavonols and flavonols, resulting in degradation of flavonoids. Expression of NITRILASE 2 (NIT2) and Methyltransferase B (metB), which regulate amino acid metabolism and influence the expression of genes of the glycolysis-TCA pathway, were down-regulated, causing amino acid content in alfalfa leaves to decrease at FBS. This study provides new insights into the complex regulatory network governing the content and decrease of chlorophyll, amino acids, flavonoids, and other nutrients in alfalfa leaves during maturation. These results further provide a theoretical basis for the generation of alfalfa varieties exhibiting higher nutritional quality, high-yield cultivation, and a timely harvest.

Transcriptional regulation of fleshy fruit texture.

Fleshy fruit texture is a critically important quality characteristic of ripe fruit. Softening is an irreversible process which operates in most fleshy fruits during ripening which, together with changes in color and taste, contributes to improvements in mouthfeel and general attractiveness. Softening results mainly from the expression of genes encoding enzymes responsible for cell wall modifications but starch degradation and high levels of flavonoids can also contribute to texture change. Some fleshy fruit undergo lignification during development and post-harvest, which negatively affects eating quality. Excessive softening can also lead to physical damage and infection, particularly during transport and storage which causes severe supply chain losses. Many transcription factors (TFs) that regulate fruit texture by controlling the expression of genes involved in cell wall and starch metabolism have been characterized. Some TFs directly regulate cell wall targets, while others act as part of a broader regulatory program governing several aspects of the ripening process. In this review, we focus on advances in our understanding of the transcriptional regulatory mechanisms governing fruit textural change during fruit development, ripening and post-harvest. Potential targets for breeding and future research directions for the control of texture and quality improvement are discussed.