Search Results (10)

The composition of the surface, optical response, and size of the carbon dots synthesized from Valencia orange peels (Citrus sinensis L. Osbeck) were studied. The peels used in the hydrothermal synthesis were at three ripeness stages, and the synthesis was carried out at 220 °C and 3 MPa. Infrared spectroscopy results showed that carbon dots synthesized from the peels of unripe oranges are functionalized with oxygenated groups, and the carbonization process was effective. Instead, carbon dots obtained from peels of ripe oranges exhibit a nitrogen-functionalized surface. These results were confirmed by the bond-breakdown analysis in photoelectron spectroscopy. Additionally, the self-doped surface modified the optical response of the carbon dots, exhibiting an enhancement of the absorption band located at 283 nm corresponding to the contribution from n-π* transitions in nitrogen. Also, the excitation and emission wavelengths present a red shift for the ripe peels. Based on the above and the transmission electron microscopy results, it is concluded that the emission mechanism is associated with surface states and not particle size. Statistical analysis yielded an average size of less than 10 nm, regardless of the orange peels’ ripeness stage. It was observed that the CDs-N3 sample has more crystalline nuclei, which is justified because ripe peels follow a shorter carbonization pathway. Full article

Carotenoids are an important class of natural compounds, essential for human nutrition, acting in plants as pigments and apocarotenoid precursors. Tomato is a key model for carotenoid metabolism, as genetic variation strongly affects carotenoid composition during fruit ripening. To date, most of the enzymes involved in the carotenoid pathway were mainly characterized by linking gain- or loss-of-function phenotypes to their genetic basis (e.g., mutation in a single gene), with limited integration into pathway-wide analyses. Here we report an extensive biochemical and molecular characterization of a collection of tomato carotenoid mutants—apricot (at), yellow flesh (r), tangerine (t), Delta (Del) and Beta (B)—throughout three different stages of fruit ripening (mature green, breaker, red ripe). Using correlation-based integrative analyses, we integrated targeted isoprenoid metabolomics (carotenoids, chlorophylls, tocochromanols, quinones, abscisic acid) with gene expression profiling and correlation-based analyses. The pronounced, stage-dependent remodeling of the isoprenoid profiles exceeded the expected changes in substrates/products and was accompanied by significant transcriptional changes, largely independent of the position of the mutated step in the pathway. This integration highlighted metabolite/transcript regulatory links and the central role of lycopene cyclization in isoprenoid metabolism rewiring, thus improving our understanding of mechanisms controlling their accumulation during tomato fruit ripening. Full article

Tomato (Solanum lycopersicum) is a globally important vegetable crop, with fruit quality being a major focus of research. Starch serves as the primary carbohydrate reserve during early fruit development and functions as a key carbon precursor for flavor compound biosynthesis in later stages. To elucidate the role of starch accumulation in determining ripe fruit quality, we analyzed the relationship between starch content in mature green fruits and flavor-related traits across eight tomato cultivars. The results demonstrated that starch content at the mature green stage showed a significantly positive correlation with total soluble solids (TSS) content (r = 0.922) and a significantly positive correlation with total acidity content (r = 0.783) in red-ripe fruits. Furthermore, the expression levels of starch synthesis gene AGPS1 and degradation gene PWD at the mature green stage were both significantly positively correlated with the final fruit TSS levels. These findings highlight the important role of starch accumulation during the mature green stage in shaping final fruit quality, providing a theoretical basis for breeding high-quality tomato varieties. Full article

As a uniquely Chinese post-fermented tea, Pu-erh tea undergoes profound changes in quality and flavor during aging, a process primarily driven by microbially mediated metabolic transformations. However, the patterns of microbe–metabolite co-evolution spanning a century-long timescale remain unclear. This study employed three samples—S (1920 raw Pu-erh tea), Y (1999 raw Pu-erh tea), and Q (2024 ripe Pu-erh tea)—integrating non-targeted metabolomics and microbiomics technologies to systematically analyze the characteristics of metabolites and microbial communities in century-old Pu-erh tea. The study elucidated the metabolic characteristics at the endpoint of long-term natural aging: the specific enrichment of hydrolyzable tannins, sucrose, and bipyrrole aromatic derivatives, providing a chemical basis for its unique “century-old charm”. Microbial community analysis indicated that long-term aging leads to simplified bacterial communities but increased fungal evenness, with the century-old sample specifically enriching for Thermodesulfobacterium and a large number of unclassified fungi. Multivariate statistics further constructed a microbe–metabolite interaction network, confirming significant correlations between key bacterial genera such as Paenibacillus and Bacillus and flavor precursors like sugars and phenolic acids. Full article

Salt stress causes osmotic stress and ion toxicity, often inhibiting plant growth and metabolism. However, salt-stressed tomato plants accumulate ascorbic acid, resulting in fruits with high commercial value. However, it was not well understood how mannose, the material for the synthesis of ascorbic acid, and its metabolism are affected under salt stress conditions. In this study, we found that tomatoes grown under salinity stress had increased levels of ascorbic acid, which correlated with decreased levels of mannan in the skin and seeds. Expression analysis of the ascorbic acid synthase gene showed increased expression in early ripening stages under salt stress. In addition, the expression of cellulose synthase-like A (CSLA), genes involved in mannan metabolism, increased significantly during mid-ripening in the control condition. Since ascorbic acid and mannan share mannose as a precursor, they are likely to compete for it. This suggests that salt-stressed tomatoes may be deficient in both ascorbic acid and mannose, thereby affecting mannan synthesis. To investigate this trade-off, we developed a culture system with added mannose. The results showed that in salt-stressed tomatoes supplemented with mannose, ascorbic acid levels in unripe green peels reached those of fully ripe fruit, highlighting the influence of mannose availability on ascorbic acid accumulation. Full article

Thevetia thevetioides is a species within the Apocynaceae family known for containing cardenolide-glycosides, commonly referred to as cardiac glycosides, which are characteristic of this genus. The seeds of the Thevetia species are frequently used as a model source for studying cardiac steroids, as these glycosides can be more readily extracted from the oil-rich seeds than from the plant’s green tissues. In this work, the cardenolide profile of ripe and immature seeds was determined and compared to establish the main differences. Ripe seeds contain six related cardenolides and triosides, with thevetin B being the predominant component. In contrast, immature seeds exhibit a total of thirteen cardiac glycosides, including monoglycosides such as neriifolin and peruvosides A, B, and C, as well as diglycosides like thevebiosides A, B, and C. Some of these compounds have previously been identified as degradation products of more complex cardiac glycosides; however, their presence in immature seeds, as described in this study, suggests that they may serve as biosynthetic precursors to the triosides observed in mature seeds. The glycoside patterns observed via HPTLC are associated with specific chemical structures characteristic of this genus, typically featuring thevetose or acetyl-thevetose at the first position, followed by glucose or gentibiose in di- or trisaccharides, independent of the trioside aglycones identified: digitoxigenin, cannogenin, or yccotligenin. Ripe seeds predominantly contain triosides, including thevetin B, C, and A, the latter of which has not been previously reported. Full article

Pre-harvest application of elicitors improves grape quality, specifically the phenolic compounds and color characteristics. Limited research has been conducted on the impact of elicitors on the C6 compounds found in grapes. This is due to lack of comprehensive studies examining the combined effects of bound aroma compounds, enzyme activity, and substrate availability. This study aimed to assess the impact of benzothiadiazole (BTH) on the physicochemical properties and C6 compounds of Cabernet Gernischt grapes during ripening. Compared with the control group (CK), BTH treatment significantly increased the 100-berry weight, skin/berry ratio, pH, total phenolic content, and total flavonoid content in ripe grapes. Additionally, BTH treatment led to significant reductions in reducing sugar, total soluble solids, titratable acidity, linoleic acid, linolenic acid, and free C6 aldehydes. Furthermore, BTH treatment significantly decreased the contents of free C6 alcohols and increased the levels of free and bound C6 esters. BTH treatment also increased the activities of lipoxygenase, alcohol dehydrogenase, and alcohol acetyltransferase enzymes, while it decreased the activity of hydroperoxide lyase enzyme. The application of BTH resulted in changes to the physicochemical properties and levels of C6 compounds in Cabernet Gernischt grapes by up-regulating enzyme activity and down-regulating precursors. Full article

The aim of this article was to assess the influence of the harvest date on the composition of amino acids and derived aromatic compounds in grape-mistelle and wine of the Moristel variety, in different vineyards. Two vineyards were sampled in 2016 and another one in 2017. At each sampling point, grapes were collected, destemmed, crushed and divided into four aliquots. The first three were fermented, and the latter was treated with ethanol, to produce 1-week macerates containing 15% ethanol (v/v)-mistelles. Overall, 10 mistelles and 33 wines were produced. Amino acids, Strecker aldehydes and aroma compounds were analysed. Amino acid profiles are characteristic of the vineyard and level of ripeness, converging with maturation. In fermentation, major amino acids, except proline, are consumed at a relatively fixed and specific tax, while consumption of 13 amino acids is determined by the ratios of alanine, glutamic acid, serine and threonine, with γ-aminobutyric acid. After fermentation, amino acid precursors to Strecker aldehydes are maxima in unripe and overripe samples, while Strecker aldehydes are maxima in unripe wines. No direct correlations between precursor amino acids in mistelle and aromatic compounds in wine have been found. Nevertheless, must amino acid profiles could determine wine aroma composition. Full article

Plant species are precursors of a wide variety of secondary metabolites that, besides being useful for themselves, can also be used by humans for their consumption and economic benefit. Pepper (Capsicum annuum L.) fruit is not only a common food and spice source, it also stands out for containing high amounts of antioxidants (such as vitamins C and A), polyphenols and capsaicinoids. Particular attention has been paid to capsaicin, whose anti-inflammatory, antiproliferative and analgesic activities have been reported in the literature. Due to the potential interest in pepper metabolites for human use, in this project, we carried out an investigation to identify new bioactive compounds of this crop. To achieve this, we applied a metabolomic approach, using an HPLC (high-performance liquid chromatography) separative technique coupled to metabolite identification by high resolution mass spectrometry (HRMS). After chromatographic analysis and data processing against metabolic databases, 12 differential bioactive compounds were identified in sweet pepper fruits, including quercetin and its derivatives, L-tryptophan, phytosphingosin, FAD, gingerglycolipid A, tetrahydropentoxylin, blumenol C glucoside, colnelenic acid and capsoside A. The abundance of these metabolites varied depending on the ripening stage of the fruits, either immature green or ripe red. We also studied the variation of these 12 metabolites upon treatment with exogenous nitric oxide (NO), a free radical gas involved in a good number of physiological processes in higher plants such as germination, growth, flowering, senescence, and fruit ripening, among others. Overall, it was found that the content of the analyzed metabolites depended on the ripening stage and on the presence of NO. The metabolic pattern followed by quercetin and its derivatives, as a consequence of the ripening stage and NO treatment, was also corroborated by transcriptomic analysis of genes involved in the synthesis of these compounds. This opens new research perspectives on the pepper fruit’s bioactive compounds with nutraceutical potentiality, where biotechnological strategies can be applied for optimizing the level of these beneficial compounds. Full article

Chocolate production suffered a vast impact with the emergence of the “witches’ broom” disease in cocoa plants. To recover cocoa production, many disease-resistant hybrid plants have been developed. However, some different cocoa hybrids produce cocoa beans that generate chocolate with variable quality. Fermentation of cocoa beans is a microbiological process that can be applied for the production of chocolate flavor precursors, leading to overcoming the problem of variable chocolate quality. The aim of this work was to use a cocktail of microorganisms as a starter culture on the fermentation of the ripe cocoa pods from PH15 cocoa hybrid, and evaluate its influence on the microbial communities present on the fermentative process on the compounds involved during the fermentation, and to perform the chocolate sensorial characterization. According to the results obtained, different volatile compounds were identified in fermented beans and in the chocolate produced. Bitterness was the dominant taste found in non-inoculated chocolate, while chocolate made with inoculated beans showed bitter, sweet, and cocoa tastes. 2,3-Butanediol and 2,3-dimethylpyrazine were considered as volatile compounds making the difference on the flavor of both chocolates. Saccharomyces cerevisiae UFLA CCMA 0200, Lactobacillus plantarum CCMA 0238, and Acetobacter pasteurianus CCMA 0241 are proposed as starter cultures for cocoa fermentation. Full article