Volatile Metabolites Research Articles

Erratum: Comparative Analysis of Heavy Metal Exposure Concentrations and Volatile Organic Compound Metabolites among Residents in the Affected Area According to Residential Distance from a Coal-fired Power Plant

Erratum: Comparative Analysis of Heavy Metal Exposure Concentrations and Volatile Organic Compound Metabolites among Residents in the Affected Area According to Residential Distance from a Coal-fired Power Plant

The Effect of Reduced Nitrogen Fertilizer Application on japonica Rice Based on Volatile Metabolomics Analysis.

Nitrogen is critical for rice yield and quality, but its overuse can be detrimental to efficiency and the environment. To identify changes in the quality of rice in response to the reduced application of nitrogen fertilizer, we carried out a comprehensive metabolomics study of SuiJing 18 using volatile metabolomics methods. Our results showed that SuiJing 18 had a total of 358 volatile metabolites, mainly lipids (16.25%), terpenoids (15.41%), heterocyclic compounds (15.13%), and hydrocarbons (13.45%). SuiJing 18 underwent significant changes in response to the reduced application of nitrogen fertilizer. Key sweet volatile compounds such as 4-methyl-benzeneacetaldehyde, hexyl acetate, and 2-methylnaphthalene were present at significantly higher levels when nitrogen fertilizer was applied at a rate of 68 kg of pure nitrogen per hectare, and their flavor characteristics also differed significantly from the compounds resulting from the other two treatments. Focusing on 16 differential volatile metabolites, we further investigated their effects on flavor and quality, thus laying the foundation for a greater understanding of the biomarkers associated with changes in rice quality. This study contributes to a better understanding of the mechanisms underlying changes in rice quality after reduced nitrogen fertilizer application.

In vitro and in vivo study of the antagonistic effects of a Trichoderma strain against four isolates of Fusarium that are pathogenic to chickpea.

This study investigated the antagonistic activity of Trichoderma asperellum against chickpea Fusarium wilt through in vitro and in vivo experiments. The dual culture test showed that Trichoderma had a significant inhibitory effect on the growth of the tested Fusarium isolates, with an inhibition rate ranging from 71.33% to 80.66%. The volatile and non-volatile metabolites produced by Trichoderma also showed antagonistic effects, with a growth inhibition rate ranging from 47.33% to 51.33% and a colonization rate ranging from 60% to 67%. In vivo experiments demonstrated that treating chickpea seeds with Trichoderma asperellum 48 h after inoculation with Fusarium significantly enhanced chickpea growth compared to seeds inoculated with Fusarium alone. Arial part length enhancement ranged between 69.3% and 92,19% while root length increased by 61,9% and 127%, this implied a significant improvement in biomass. These findings highlight Trichoderma's potential in controlling chickpea Fusarium wilt and enhancing plant growth, making it an environmentally friendly method in sustainable agriculture and crop protection.

Plant-to-plant defence induction in cotton is mediated by delayed release of volatiles upon herbivory.

Caterpillar feeding immediately triggers the release of volatile compounds stored in the leaves of cotton plants. Additionally, after 1 d of herbivory, the leaves release other newly synthesised volatiles. We investigated whether these volatiles affect chemical defences in neighbouring plants and whether such temporal shifts in emissions matter for signalling between plants. Undamaged receiver plants were exposed to volatiles from plants infested with Spodoptera caterpillars. For receiver plants, we measured changes in defence-related traits such as volatile emissions, secondary metabolites, phytohormones, gene expression, and caterpillar feeding preference. Then, we compared the effects of volatiles emitted before and after 24 h of damage on neighbouring plant defences. Genes that were upregulated in receiver plants following exposure to volatiles from damaged plants were the same as those activated directly by herbivory on a plant. Only volatiles emitted after 24 h of damage, including newly produced volatiles, were found to increase phytohormone levels, upregulate defence genes, and enhance resistance to caterpillars. These results indicate that the defence induction by volatiles is a specific response to de novo synthesised volatiles, suggesting that these compounds are honest signals of herbivore attack. These findings point to an adaptive origin of airborne signalling between plants.

Investigation of the Effect of Fragrance-Enhancing Temperature on the Taste and Aroma of Black Tea from the Cultivar Camellia sinensis (L.) O. Kuntze cv. Huangjinya Using Metabolomics and Sensory Histology Techniques

Huangjinya has recently seen widespread adoption in key tea-producing areas of China, celebrated for its unique varietal traits. Its leaves are also used to produce black tea with distinctive sensory characteristics. The fragrance-enhancing (EF) process is essential in crafting Huangjinya black tea (HJYBT) and is significant in flavor development. However, the impact of EF on non-volatile metabolites (NVMs), volatile metabolites (VMs), and their interactions remains poorly understood. This study aims to investigate how EF temperatures (60 °C, 70 °C, 80 °C, 90 °C, and 110 °C) influence HJYBT flavor transformation. Quantitative descriptive analysis revealed that EF improved the color, aroma, and appearance of tea leaves. Moreover, after an EF temperature of 80 °C, the HJYBT exhibited lower bitterness and astringency, whereas floral, sweet, and fruity aromas became stronger. However, when EF temperatures exceeded 90 °C, a pronounced burnt aroma developed, with HJYBT at 100 °C exhibiting caramel and roasted notes. Partial least squares discriminant analysis indicated that geraniol and linalool contribute to floral and fruity aromas, while 2-ethyl-6-methyl-pyrazine, furfural, and myrcene are key volatiles for caramel and roast aromas. Heptanal, methyl salicylate, α-citral, 1-hexanol, and (E)-3-hexen-1-ol were found to modify the green and grassy odor. Overall, HJYBT treated at 80 °C EF exhibited the highest umami, sweetness, floral and fruity aromas, and overall taste, exhibiting the least astringency, bitterness, and green and grassy notes. These results provide a significant theoretical basis for enhancing HJYBT quality and selecting the optimal EF method.

Metabolomic profiling of in vitro and in situ grown Nilgiris tea reveals unique signatures for breeding decaffeinated varieties

This study was begun by establishing an in vitro culture in UPASI 9, a Nilgiris tea clone (Camellia sinensis) by optimising various factors. Anatomical studies demonstrated that use of lower carbendazim concentration for sterilisation (0.2%) produced viable and healthy explants for callus initiation. To confirm the genetic consistency of the regenerated plants, gene-specific SSR markers were developed and utilised. GC-MS was employed to analyse volatile metabolites extracted from callus, stem, micro shoots, and leaves of the UPASI 9 tea genotype. The results revealed distinct compositions of metabolites in each sample. More interestingly, caffeine was exclusively detected in leaf samples but absent in all other investigated tissues, despite the presence of Tea Caffeine Synthase (TCS) gene-specific SSRs. Thus, this study provided unique information on the absence of caffeine in in vitro grown Nilgiris tea clone, UPASI 9, as decaffeinated tea has a unique niche in the global market.

Flavor properties of post-heated fermented milk revealed by a comprehensive analysis based on volatile and non-volatile metabolites and sensory evaluation

Existing research on the post-heating processing of fermented milk has primarily focused on single post-heating treatments and the texture, while research on how changes in metabolites during different post-heating treatments affect flavor and sensory properties is limited. This study investigates the changes in volatile metabolites in fermented milk treated at different post-heating temperatures to determine the characteristic aroma types and analyzes the changes in non-volatile metabolites associated with aroma-active compounds or their precursors to clarify the causes of the altered flavor and sensory properties. The results showed that in the 65°C and 75°C treatments, 63 volatile compounds were produced by Strecker degradation, lipid oxidation and esterification to produce ketones and aldehydes. Significantly higher odor activity values for 2,3-butanedione, hexanoic acid, and esters and significantly lower odor activity values for 2-heptanone enhanced the frankincense odors and creaminess of the post-heated fermented milk. With temperatures increasing to 95°C, the increased ketones were primarily 2-heptanone, 2-nonanone, and 2-undecanone that originated from the oxidative decomposition of unsaturated phospholipids at high temperatures. The Maillard reaction of dipeptides produces nitrogenous heterocycles that trigger a caramelized flavor, while organic acids interact with proteins to form complexes that produce astringent flavors. These increase the oxidative off-flavors and reduce the overall palatability. These findings provide a scientific basis for optimizing the post-heating temperature process of fermented milk.

Contribution of polyvinylpolypyrrolidone (PVPP) treatment to the distribution of polyphenols and the evolution of esters and higher alcohols in Rosa roxburghii Tratt wine

Polyvinylpolypyrrolidone (PVPP) is commonly employed for fining in fruit wine brewing. This study aimed to investigate the impact of PVPP pretreatment on the formation of fermentation aroma and polyphenol distribution in Rosa roxburghii Tratt (RRT) wine. A significant effect of PVPP on polyphenol adsorption was observed, and polyphenol families or subfamilies such as flavanols and flavonols showed specific affinity for PVPP, decreasing by over 19 % and 30 %, respectively. Furthermore, it was the first time to demonstrate a significant enhancement in the ester content of the corresponding RRT wine after PVPP treatment, particularly in imparting sweet and fruity esters (increased by over 40 %). In contrast, the RRT wine treated with PVPP exhibited a significant reduction of over 20 % in the concentration of higher alcohols, particularly reflected in the green and chemical aromas. This indicates that PVPP treatment could promote the transformation of RRT wine aroma from green and chemical to sweet and fruity. Correlation analysis revealed a positive relationship between the concentration of higher alcohols and most phenolic compounds in RRT wine, while quercetin 3-glucoside, rutin, and polydatin were negatively correlated with esters that can impart fruit flavor and floral aroma to fruit wine. As a practical insight into fruit wine fermentation, PVPP fining before fermentation is more likely to alter the phenolic compositions of RRT wine, thereby influencing its aroma characteristics. Specifically, polyphenols associated with energy metabolism of yeast could have stimulated the formed fluxes of esters. The association between the formation of esters and higher alcohols with phenolic compounds will provide new information on the impact of clarification treatments on yeast-derived volatile metabolites in RRT wine and hold promise in improving the aroma of RRT wine by modulating polyphenol composition through pre-clarification.

Plant Factory Speed Breeding Significantly Shortens Rice Generation Time and Enhances Metabolic Diversity

Rice (Oryza sativa L.) plays a pivotal role in global food security, yet its breeding is constrained by its long generation time and seasonality. To enhance rice breeding efficiency and meet future food demands, we have developed a vertical hydroponic breeding system integrated with light-emitting diodes (LEDs) lighting in a closed plant factory (PF), which significantly accelerates rice growth and generation advancement. The results show that indica rice can be harvested as early as after 63 days of cultivation, a 50% reduction compared with field cultivation, enabling the annual harvesting of 5–6 generations within the PF. A hyperspectral imaging system (HSI) and attenuated total reflectance infrared (ATR-IR) spectroscopy were further employed to characterize the chemical composition of the PF- and field-cultivated rice. Metabolomics analysis with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and gas chromatography-mass spectrometry (GC-MS) revealed that, compared with the field-cultivated rice, the PF-cultivated rice exhibited an up-regulation of total phenolic acids along with 68 non-volatile and 19 volatile metabolites, such as isovitexin, succinic acid, and methylillicinone F. Overall, this study reveals the unique metabolic profile of PF-cultivated rice and highlights the potential of PFs to accelerate the breeding of crops such as rice, offering an innovative agricultural strategy to support food security in the face of global population growth and climate change.

Bacteroides vesicles promote functional alterations in the gut microbiota composition.

Inflammatory bowel diseases are characterized by chronic intestinal inflammation and alterations in the gut microbiota composition. Bacteroides fragilis, which secretes outer membrane vesicles (OMVs) with polysaccharide A (PSA), can moderate the inflammatory response and possibly alter the microbiota composition. In this study, we created a murine model of chronic sodium dextran sulfate (DSS)-induced intestinal colitis and treated it with B. fragilis OMVs. We monitored the efficiency of OMV therapy by determining the disease activity index (DAI) and performing histological examination (HE) of the intestine before and after vesicle exposure. We also analyzed the microbiota composition using 16S rRNA gene sequencing. Finally, we evaluated the volatile compound composition in the animals' stools by HS-GC/MS to assess the functional activity of the microbiota. We observed more effective intestinal repair after OMV treatment according to the DAI and HE. A metabolomic study also revealed changes in the functional activity of the microbiota, with a predominance of phenol and pentanoic acid in the control group compared to the group treated with DSS and the group treated with OMVs (DSS OMVs). We also observed a positive correlation of these metabolites with Saccharibacteria and Acetivibrio in the control group, whereas in the DSS group, there was a negative correlation of phenol and pentanoic acid with Lactococcus and Romboutsia. According to the metabolome and sequencing data, the microbiota composition of the DSS-treated OMV group was intermediate between that of the control and DSS groups. OMVs not only have an anti-inflammatory effect but also contribute to the recovery of the microbiota composition.IMPORTANCEBacteroides fragilis vesicles contain superficially localized polysaccharide A (PSA), which has unique immune-modulating properties. Isolated PSA can prevent chemically induced colitis in a murine model. Outer membrane vesicles (OMVs) also contain digestive enzymes and volatile metabolites that can complement the anti-inflammatory properties of PSA. OMVs showed high therapeutic activity against sodium dextran sulfate-induced colitis, as confirmed by histological assays. 16S rRNA sequencing of fecal samples from different inflammatory stages, supplemented with comprehensive metabolome analysis of volatile compounds conducted by HS-GC/MS, revealed structural and functional alterations in the microbiota composition under the influence of OMVs. Correlation analysis of the OMV-treated and untreated experimental animal groups revealed associations of phenol and pentanoic acid with Lactococcus, Romboutsia, Saccharibacteria, and Acetivibrio.

Temperature-Dependent Metabolic Interactions Between Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus in Milk Fermentation: Insights from GC-IMS Metabolomics

Streptococcus (S.) thermophilus and Lactobacillus (L.) delbrueckii ssp. bulgaricus are widely used as a combined starter culture for milk fermentation, often at temperatures of 37°C and 42°C. To investigate the metabolic interplay between these 2 species during the fermentation process, this study examined the growth and fermentation characteristics of different S. thermophilus strains cocultured with L. delbrueckii ssp. bulgaricus ND02 at these 2 temperature conditions. Gas chromatography-ion mobility spectrometry (GC-IMS) metabolomics was employed to analyze changes in the milk metabolome during 3 key fermentation stages: initiation (F0, pH 6.50 ± 0.02), curdling (F1, pH 5.20 ± 0.02), and endpoint (F2, pH 4.50 ± 0.02). The results showed that 42°C fermentation promoted rapid bacterial growth, with significantly reduced fermentation time compared with 37°C. Interestingly, 37°C fermentation favored the enrichment of volatile fatty acids like 2-methylpropanoic acid, 3-methylbutanoic acid, and ethyl acetate. In contrast, 42°C fermentation led to increased levels of ketones such as acetone, 2-hexanone, 2-pentanone, and 2-heptanone. Sensory evaluation indicated that the 42°C fermented milk had higher overall scores. Discriminatory flavor metabolites were more abundant during the later fermentation stage (F1 to F2), while the underlying metabolic pathways became increasingly active. These findings provide insights into the dynamic changes in volatile metabolite profiles of fermented milk produced under different temperature and time conditions using varied starter culture combinations. The results are valuable for optimizing dairy fermentation processes and product quality.

Effects of volatile fatty acids on soil properties, microbial communities, and volatile metabolites in wheat rhizosphere of loess

The Loess Plateau faces critical challenges due to soil degradation. In this context, using volatile fatty acids (VFAs) from biowaste as readily available soil conditioners offer promising sustainable solutions to restore soil quality and enhance agricultural productivity. The study examined how applying different VFAs as soil amendments in arid and high-salt loess soil affected wheat plant growth, soil properties, soil microbial community diversity, volatile metabolites in soil and root exudate. The non-targeted analysis was used to identify and classify 49 soil volatile organic compounds (VOCs) and 63 root exudate VOCs to seek further specific functional volatile metabolites and explore the interaction mechanisms among plants, microorganisms, and soil. The results showed that acetic acid increased soil EC by 21.0% and decreased soil organic matter by 14.4%. Propionic acid reduced soil organic matter by 14.7%. Valeric acid increased the average root diameter by 15.1%. Further analysis revealed that rhizosphere bacterial communities, but not fungal communities, showed greater sensitivity to VFAs application. Bacterial α diversity was significantly reduced in the acetic acid treatment. The main contribution of VOCs in soil with acetic acid and propionic acid applications was alcohol, and its relative percentage was 50.06% and 43.54%, respectively, which has a significantly negative correlation with the α diversity of soil bacteria. On the contrary, the content of acylamides in soil with butyric acid and valeric acid applications was higher and significantly positively correlated with the average root diameter. It was concluded that soil microbial communities respond rapidly to acetic acid, propionic acid, butyric, and valeric acid applications by adjusting the concentration of alcohols and acylamides as secondary metabolites, respectively. This study revealed the close relationship between VFAs application type and soil properties, soil microbial community diversity, soil VOCs, and root exudates VOCs. VFAs derived from biowaste will contribute to restoring loess soil quality and achieving sustainable agriculture.

Comprehensive investigation on the flavor difference in five types of tea from JMD (Camellia sinensis 'Jinmudan').

Jinmudan (JMD) is a high-aroma variety widely cultivated in China. The current study primarily focuses on the key volatile metabolites in JMD black and oolong teas,and investigates the impact of processing technologies on the aroma quality of JMD tea. However, few studies have explored the suitabilityof JMD for producing a certain type of tea or the characteristic quality differences among various JMD teas using multivariate statistical analysis methods. The principal volatile metabolites contributing to the floral quality of JMD tea are linalool, geraniol, indole and phenethyl alcohol. In JMD black tea (BT), the key volatile metabolites include methyl salicylate, geraniol, (E)-β-ocimene and phenethyl alcohol. In JMD oolong tea (OT), the key volatile metabolites include indole, linalyl valerate and phenethyl alcohol. In JMD yellow tea (YT), the key volatile metabolites include methyl salicylate, geraniol and terpinolene. In JMD white tea (WT), the key volatile metabolites include methyl salicylate, geraniol and terpinolene. In JMD green tea (GT), the key volatile metabolites include (E)-β-ocimene, indole and geraniol. Comparative analysis and KEGG pathway enrichment analysis revealed that flavonoid biosynthesis is the primary metabolic pathway responsible for the taste differences among various tea types. GT exhibited higher levels of phloretin, dihydromyricetin and galangin. The contents of vitexin, tricetin in YT were relatively higher. The contents of aromadendrin and naringenin in BT were higher, while OT contained higher levels of kaempferol. Additionally, WT showed higher contents of 3-O-acetylpinobanksin and 3,5,7-pinobanksin. This study explained the reasons for the quality differences of different JMD tea and provided a reliable theoretical basis for the adaptability of JMD tea. © 2024 Society of Chemical Industry.

Spatio-Temporal Variations of Volatile Metabolites as an Eco-Physiological Response of a Native Species in the Tropical Forest.

This study evaluates the essential oil (EO) composition of Piper rivinoides Kunth, a shrub native to the Brazilian tropical rainforest, across different plant parts and developmental phases. The aim was to explore the chemical diversity of EO and its reflection in the plant's ecological interactions and adaptations. Plant organs (roots, stems, branches, and leaves) at different developmental phases were subjected to hydrodistillation followed by chemical analysis using Gas Chromatography-Mass Spectrometry (GC-MS) and Gas Chromatography-Flame Ionization Detector (GC-FID). The results revealed a relevant variation in EO yield and composition among different plant parts and developmental phases. Leaves showed the highest yield and chemical diversity, with α-pinene and β-pinene as major constituents, while roots and stems were characterized by a predominance of arylpropanoids, particularly apiol. The chemical diversity in leaves increased with plant maturity, indicating a dynamic adaptation to environmental interactions. The study underscores the importance of considering the ontogeny of plant parts in understanding the ecological roles and potential applications of P. rivinoides in medicine and agriculture. The findings contribute to the overall knowledge of Piperaceae chemodiversity and ecological adaptations, offering insights into the plant's interaction with its environment and its potential uses based on chemical composition.

Comparative Metabolomic Responses of Three Rhododendron Cultivars to the Azalea Lace Bug (Stephanitis pyrioides).

Rhododendron, with its high ornamental value and ecological benefits, is severely impacted by the azalea lace bug (Stephanitis pyrioides), one of its primary pests. This study utilized three Rhododendron cultivars, 'Zihe', 'Yanzhimi', and 'Taile', to conduct a non-targeted metabolomic analysis of leaf samples before and after azalea lace bug stress using headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME/GCMS) and liquid chromatography-mass spectrometry (LCMS). A total of 81 volatile metabolites across 11 categories and 448 nonvolatile metabolites across 55 categories were detected. Significant differences in metabolic profiles were observed among the different cultivars after pest stress. A total of 47 volatile compounds and 49 nonvolatile metabolites were upregulated in the most susceptible cultivar 'Zihe', including terpenes, alcohols, nucleotides, amino acids, and carbohydrates, which are involved in energy production and secondary metabolism. Conversely, 'Yanzhimi' showed a downtrend in both the differential volatiles and metabolites related to purine metabolism and zeatin biosynthesis under pest stress. The resistant cultivar 'Taile' exhibited moderate changes, with 17 volatile compounds and 17 nonvolatile compounds being upregulated and enriched in the biosynthesis of amino acids, pentose, glucuronate interconversions, carbon metabolism, etc. The phenylalanine metabolic pathway played an important role in the pest resistance of different susceptible cultivars, and relevant metabolites such as phenylethyl alcohol, methyl salicylate, and apigenin may be involved in the plant's resistance response. The results of this study provide a new perspective on the metabolomics of Rhododendron-insect interactions and offer references for the development of pest control strategies.

Proanthocyanidins as the marker of amomum fruit from three botanical origins based on comprehensive profiling with LC-MS and GC-MS combined with chemometrics.

Amomum fruit, also known as Sharen, serves as both a functional food and a traditional Chinese medicine with significant pharmacological activities. However, there are three botanical origins of Amomum fruit: Amomum villosum Lour. (AVL), Amomum villosum Lour. var. xanthioides T. L. (AVX), and Amomum longiligulare T. L. Wu (ALW). Conducting a comprehensive chemical composition analysis of Amomum fruit from three botanical origins aims to identify potential differences in metabolic characteristics. To annotate the metabolic characteristic ions of multi-origin Amomum fruit, we employed metabolomic techniques, including ultra-high-performance liquid chromatography (LC) coupled with linear ion trap-Orbitrap-tandem mass spectrometry (MS) and gas chromatography-MS, in conjunction with feature-based molecular networking technology. Additionally, chemometrics was utilized to examine the correlations between the various botanical origins. A total of 201 non-volatile and 151 volatile metabolites were annotated, and most of the proanthocyanidins and flavonoids were identified by feature-based molecular networking. Additionally, 61 non-volatile and 45 volatile feature ions were screened out for classification. Principal component analysis, orthogonal projection to latent structures discrimination analysis, and heat map analysis were employed to clearly distinguish the metabolite profiles of Amomum fruit from different origins. Hierarchical clustering analysis indicated that proanthocyanidins C1 and C2, as well as proanthocyanins oligomers, show significant differential expression between AVX and AVL, which could be the new quality markers for the classification. Classification of the botanical origin of Amomum fruit based on LC-MS characteristic ions proved to be more advantageous. This study introduces new strategies and technical support for the quality control of Amomum fruit and facilitates the identification of unknown compounds for future research.

Regulatory mechanism of methyl jasmonate and methyl dihydrojasmonate in enhancing aroma in 'Cabernet Gernischt' via the lipoxygenase pathway.

The present study explored the effects of pre-harvest methyl jasmonates spraying on the volatiles of 'Cabernet Gernischt' grapes through the lipoxygenase pathway. Headspace solid-phase microextraction combined with gas chromatography-mass spectrometry and an enzyme-linked immunosorbent assay were utilized to analyze volatile metabolites and key enzyme activities following methyl jasmonates application. Total RNA extraction and cDNA library construction were followed by transcriptome sequencing. The application of 0.1 mmol L-1 methyl jasmonate and 5 mmol L-1 methyl dihydrojasmonate significantly increased the levels of C6 compounds in 'Cabernet Gernischt' berries, and also enhanced the utilization of unsaturated fatty acids as precursors in the lipoxygenase-hydroperoxides lyase pathway. The up-regulated expression of VvADH1, VvADH2, VvHPL and VvLOX2S genes led to modulations in enzyme activity, thereby enhancing the berries's aromatic profile. There was a significant correlation between linoleic and linolenic acids (i.e. the precursors of the lipoxygenase pathway) and the activities and metabolites of key enzymes. The optimal concentration of methyl jasmonates treatment favorably influences the accumulation of green leaf volatiles in 'Cabernet Gernischt' grape. © 2024 Society of Chemical Industry.

Investigation of the impact of papain on the volatile and non-volatile metabolites of soybean meal yogurt.

Soybean meal yogurt was prepared from soybean meal using papain and Bifidobacterium animalis subsp. lactis. A non-targeted metabolomics approach was employed to analyze the relevance of papain to the differences in volatile and non-volatile metabolites of soybean meal yogurt. The results showed that the main up-regulated metabolites and metabolic pathways after enzymatic digestion were dominated by amino acids and their derivatives. Conversely, the main down-regulated metabolites and pathways were predominantly associated with flavonoid metabolism. Amino acids and their derivatives, as well as flavonoids, were found to be highly correlated with the formation of sweet, umami, astringent, and bitterness. The addition of papain enriched the content of aromatic compounds in soybean meal yogurt. Aromatic components such as 2-heptanone, naphthalene, and p-xylene increased in concentration. Synthetic peptide of aspartate and serine, gramine, geissospermine, N-desmethyl vinblastine, and 3,7-dihydroxyflavone were the major non-volatile differential metabolites distinguishing the soybean meal yogurt. This study provided a comprehensive analysis of the metabolic traits of products co-fermented by papain and Bifidobacterium animalis subsp. lactis, offering insights for the application of papain in fermented goods. © 2024 Society of Chemical Industry.

Integrated Analysis of the Transcriptome and Metabolome Reveals Genes Involved in the Synthesis of Terpenoids in Rhododendron fortunei Lindl.

Rhododendron, a globally popular ornamental flower, is nevertheless limited in our understanding of the mechanisms underlying its fragrance formation. Notably, terpenoids are the most prevalent volatile metabolite produced by plants. In this study, gas chromatography–mass spectrometry (GC–MS), liquid chromatography–mass spectrometry (LC–MS) and transcriptomics sequencing were conducted to analyze the synthesis mechanisms of terpenoid fragrance compounds of petals in fragrant R. fortunei Lindl. (YJ) and non-fragrant R. “Nova Zembla” (NW). The results identified that (-)-myrtenol, linalool, pinene, myrtenyl acetate, and terpineol were key floral aroma substances in YJ. Furthermore, an analysis of KEGG enrichment and differentially expressed genes (DEGs) revealed that the bud and decay stages exhibited the highest number of enriched DEGs among different aroma types, indicating these as critical stages for the synthesis of terpenoid floral compounds. In this study, a structural gene, denoted as RfFDPS, was identified as a negative regulatory gene for monoterpene accumulation and a positive regulatory gene for sesquiterpene accumulation in YJ. Utilizing subcellular localization technology, we determined that RfFDPS proteins are located in the cytoplasm. A functional analysis through transient expression and gene silencing of RfFDPS demonstrated its ability to regulate the accumulation of monoterpenes and sesquiterpenes. The overexpression of RfFDPS led to an increase in the expression of structural genes related to terpenoid synthesis, resulting in a decrease in monoterpenes and an increase in sesquiterpenes. Conversely, gene silencing had the opposite effect. In conclusion, RfFDPS plays a pivotal role in the synthesis and release of terpenoid volatile compounds in YJ petals, laying a solid theoretical foundation for the cultivation and enhancement of aromatic R. species.

Metabolomics analysis of bioactive compositions of Michelia macclurei Dany and its antioxidant and enzyme inhibitory activities.

Michelia macclurei Dandy is a traditional Chinese medicinal plant, but little is understood about the bioactive compositions and biological potential of its different parts, limiting their applications. This study aims to identify the bioactive compositions and analyze differences in accumulation patterns from different parts of Michelia macclurei (heartwood, sapwood, bark, root, leaf, and fruit) using metabolomics. It also seeks to explore their biological potential and analyze the relationship between the bioactive compositions and biological potential. A total of 63 volatile metabolites (VMs) were identified by gas chromatography-mass spectrometry (GC-MS) in six parts, and the VMs in each part were dominated by sesquiterpenes and their derivatives (71.40-88.32%). Six parts of Michelia macclurei contained structurally diverse non-volatile metabolites (NVMs) with a total of 207 bioactive compounds, including 92 alkaloids, 30 flavonoids, 19 lignans, and 18 organic acids, utilizing ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) analysis. Multivariate statistical analysis showed that the accumulation patterns of bioactive compositions differed significantly among the different parts, and the 25 VMs and 72 NVMs could be considered potential markers for distinguishing the different parts of Michelia macclurei. The excellent antioxidant and enzyme inhibitory capacity of extracts of all six parts was indicated by in vitro bioactivity assays. Pearson's correlation analysis showed that the bioactive compositions in the six parts were significantly correlated with antioxidant and enzyme inhibitory activities. This study offers helpful information on the distribution of bioactive compositions in different parts of Michelia macclurei and confirms the excellent antioxidant, and enzyme inhibitory potential of its extracts, which could provide scientific evidence for its potential applications in the pharmaceutical industry, cosmetics, and functional foods. © 2024 Society of Chemical Industry.