Figure 1 - available from: Scientific Reports
This content is subject to copyright. Terms and conditions apply.
Source publication
The enzyme browning reaction results in grey speckles on tobacco leaves, which impairs the value and industrial usability of tobacco leaves. To demonstrate the influences of different browning degrees (BDs) of tobacco leaves on the usability of different cultivars and positions and identified structure of brown (grey) matter, we selected three flue...
Contexts in source publication
Context 1
... with grey speckled or browning leaves, in undesirable in flue-cured tobacco ( Fig. 1) and it not only affects the supply of tobacco leaves, but also inhibits sustainable development of tobacco production; however, the influences of grey speckles on usability of tobacco leaves in different cultivars and positions and the structure of grey matters from enzymatic browning reactions remains unclear. Based on this, we aim ...
Context 2
... to Table 2, BD, cultivar, position, and their interaction show significant effects on the total nitrogen content (P < 0.05). Figure 10 shows that, at the same BD of less than 25%, total nitrogen contents in lower leaves of the K326 cultivar are significantly lower than that in middle leaves. When BD varies from 25% to 50%, the total nitrogen contents in middle and upper leaves of the K326 cultivar are significantly higher than that in lower leaves. ...
Context 3
... accordance with Table 2, cultivar and position, as well as their interaction exert significant influences on nicotine content (P < 0.05) and interaction between BD and cultivar also significantly affects the nicotine content. Figure 11 shows that, at the same BD of less than 25%, the nicotine contents in lower leaves of the K326 cultivar are significantly lower than those in middle and upper leaves, while nicotine contents in middle and lower leaves of the Hongda and Yunyan87 cultivars are significantly lower than that in upper leaves. When BD ranges from 50% to 75%, nicotine contents in lower leaves of the K326 and Yunyan87 cultivars are significantly lower than those in middle and upper leaves. ...
Context 4
... shown in Table 2, BD and position exert significant effects (P < 0.05) on the polyphenol content and BD has a synergistic effect with position. Figure 12 shows that the polyphenol content in different positions of the three flue-cured tobacco cultivars reduces with increasing BD. ...
Context 5
... has a synergistic effect with position. Figure 13 shows that the shatter resistance index (screen aperture < 1 mm) of tobacco leaves in different positions of each cultivar increase with increasing BD, while the shatter resistance index (screen aperture ≥ 2 mm) of tobacco leaves in different positions of each cultivar decrease with increasing BD. When the BD is less than 25%, the shatter resistance index (screen aperture ≥ 2 mm) in different positions of each cultivar is significantly greater than that when the BD exceeds 75%; however, when the BD is less than 25%, the shatter resistance index (screen aperture < 1 mm) in different positions of each cultivar is significantly lower than that when the BD exceeds 75%. ...
Context 6
... interactions of BD and cultivar, cultivar and position, and the three combined also significantly affect the sensory evaluation score. Figure 14 shows that the sensory evaluation score in each position of different cultivars decreases with increasing BD. At the same BD, when is less than 25%, the sensory evaluation score of upper leaves of the K326 cultivar is significantly higher Starch Total sugar Reducing sugar Protein Total nitrogen Nicotine Total polyphenols ------------------------------Probability of a greater F value------------------------------Browning degree (B) 3 <0.0001 ...
Context 7
... chloride to methanol of 5:1 and a ratio www.nature.com/scientificreports www.nature.com/scientificreports/ of methylene chloride, methanol and formic acid of 5:1:0.1, ethanol extracts were separated and divided through a methylene chloride/methanol system and finally 220 mg of component Fr.Ab1a was separated and purified by utilising gel LH-20 (Fig. 15). Based on comparative analysis, it is known that parts with grey speckles and parts without grey speckles on tobacco leaves have different components (Fig. 16) and the components in the grey speckles are marked in red circles in Fig. 16. Sample Fr. Ab1a was separated using the Agilent1200 high-performance liquid chromatograph with an ...
Context 8
... 5:1:0.1, ethanol extracts were separated and divided through a methylene chloride/methanol system and finally 220 mg of component Fr.Ab1a was separated and purified by utilising gel LH-20 (Fig. 15). Based on comparative analysis, it is known that parts with grey speckles and parts without grey speckles on tobacco leaves have different components (Fig. 16) and the components in the grey speckles are marked in red circles in Fig. 16. Sample Fr. Ab1a was separated using the Agilent1200 high-performance liquid chromatograph with an ultraviolet detector and YMC-pack ODS-A columns with a particle size of 5 μm and dimensions of 10 × 250 mm and passed through a system containing 35% MeCN/H 2 O ...
Context 9
... system and finally 220 mg of component Fr.Ab1a was separated and purified by utilising gel LH-20 (Fig. 15). Based on comparative analysis, it is known that parts with grey speckles and parts without grey speckles on tobacco leaves have different components (Fig. 16) and the components in the grey speckles are marked in red circles in Fig. 16. Sample Fr. Ab1a was separated using the Agilent1200 high-performance liquid chromatograph with an ultraviolet detector and YMC-pack ODS-A columns with a particle size of 5 μm and dimensions of 10 × 250 mm and passed through a system containing 35% MeCN/H 2 O solution at a flow rate of 2.0 mL/min. On this basis, 9.7 mg of the component ...
Context 10
... Figure 16 shows that the component from leaves with grey speckles has strong chromophores. After extracting extraction and separating tobacco with grey speckled leaves, the main chemical component, 9.7 mg of YC-ZJF was isolated from the tobacco with grey speckled leaves by repeated high-performance liquid chromatography (HPLC). ...
Context 11
... from leaves with grey speckles has strong chromophores. After extracting extraction and separating tobacco with grey speckled leaves, the main chemical component, 9.7 mg of YC-ZJF was isolated from the tobacco with grey speckled leaves by repeated high-performance liquid chromatography (HPLC). The structure of the isolated compound (YC-ZJF) (Fig. 17) was determined to be 3-acetyl-6,7-dimethoxycoumarin as evinced by analysing its 1-d and 2-d NMR spectra (Figs. 18-24). Interestingly, 3-acetyl-6,7-dimethoxycoumarin was only reported as a synthetic compound, instead of a natural product (Takadate et al., 1995). Thus, 3-acetyl-6,7-dimethoxycoumarin should be an artifact during ...
Context 12
... grey speckled leaves, the main chemical component, 9.7 mg of YC-ZJF was isolated from the tobacco with grey speckled leaves by repeated high-performance liquid chromatography (HPLC). The structure of the isolated compound (YC-ZJF) (Fig. 17) was determined to be 3-acetyl-6,7-dimethoxycoumarin as evinced by analysing its 1-d and 2-d NMR spectra (Figs. 18-24). Interestingly, 3-acetyl-6,7-dimethoxycoumarin was only reported as a synthetic compound, instead of a natural product (Takadate et al., 1995). Thus, 3-acetyl-6,7-dimethoxycoumarin should be an artifact during flue-curing of tobacco, therefore, 3-acetyl-6,7-dimethoxycoumarin should be one of the main components or related components in ...
Citations
... Leaf maturation and senescence is an important process in plants, especially for the quality of cigar tobacco leaves [20]. So far in China, cigar harvesting time depends on the farmer's experience which easily causes uneven in cigar quality. ...
... Research suggests that high nicotine levels in tobacco increase its harshness and spiciness. The sugars, particularly reducing sugars, in the leaves can neutralize alkaline components in smoke by producing an acidic reaction during combustion, maintaining the smoke's pH within a suitable range [20]. Apropriate sugar-nicotine ratios enable tobacco to maintain good taste as well as avor [20 23]. ...
... Subsequently, as the leaves mature and age, their chemical components gradually transform and decompose, with sugars breaking down more rapidly, leading to a decrease in sugars and nitrogen content. Additionally, an optimal potassium content in the leaves can enhance their combustibility [20]. In contrast, chlorine can suppress the burning of tobacco leaves [25]. ...
The timing of maturity significantly impacts the quality of cigar tobacco leaves, with both premature and delayed maturation leading to quality degradation. Despite the known association between maturity and physiological metabolic activities, there is a paucity of concrete evidence detailing the physiological behavior of cigar leaves harvested at varying times. This research involved a comprehensive physiological and metabolomic examination of the cigar tobacco variety CX-014, cultivated in Danjiangkou City, Hubei Province. The study focused on leaves picked at 35 (T1), 42 (T2), 49 (T3), and 56 (T4) days following the removal of the apical inflorescence. As the harvest period progressed, the leaves’ hue transitioned from green to yellow, displaying white mature spots. Between T1 and T2, there was an uptick in pigment indices (like chlorophyll a and b) and photosynthetic traits (such as stomatal conductance), which then diminished in the T3 and T4 samples. Optimal levels of sugar-to-nicotine and potassium-to-chlorine ratios—key indicators of smoking quality and tobacco combustibility—were observed at T3, suggesting a more balanced chemical composition in the leaves harvested at this stage. Metabolomic analysis revealed 2,153 distinct metabolites, with the most significant changes occurring between T2 and T3, highlighting critical physiological transformations during this interval. Pathway enrichment analysis via KEGG pinpointed notable shifts in amino acid synthesis pathways, particularly those involving tryptophan, alanine, and aspartate. Tryptophan metabolism and zeatin biosynthesis were substantially altered, with compounds like indolepyruvic acid, N-formylpurine nucleotide, isopentenyladenine nucleotide, and dihydrozeatin showing marked reductions at T3. This study also explored how the timing of lower leaf harvest influences the physiological processes of middle leaves, finding that a plethora of metabolites associated with the breakdown of arachidonic acid—a primitive metazoan signaler implicated in plant stress and defense networks—were abundant in T3 leaves when lower leaves were harvested 43 to 38 days prior. These findings suggest that the harvest timing of lower leaves may sway the maturation physiology and environmental adaptability of middle leaves. Overall, this investigation sheds light on the intricate physiological dynamics of cigar leaves throughout maturation and pinpoints crucial metabolites that signify pivotal metabolic pathways.
... The plant nitrogen was determined by the Kjeldahl method. The equations are as follows [29]: ...
Long-term rotary tillage leads to thinning of the soil layer and low nitrogen use efficiency of crops, resulting in a decrease in crop yield and quality. Therefore, a new alternative method to improve nitrogen use efficiency of crops needs to be found urgently. Here, we analyzed the effects of a new smash ridge tillage method combined with reduced nitrogen application on tobacco growth and development, and nitrogen use efficiency and its economic benefits. The results showed that, compared with conventional tillage and nitrogen application of 180 kg N ha−1, smash ridge tillage and a 30% reduction in nitrogen rate resulted in greater root length density, more primary lateral roots and greater rooting depth in the subsoil. It is also beneficial to maintain a high level of biomass and nitrogen accumulation in the later growth period, increasing the output value of tobacco by CNY 1588.35 ha−1 and reducing the cost by CNY 974.1 ha−1 on average in two years. In conclusion, our study highlights the economic benefits of smash ridge tillage and nitrogen reduction for tobacco growth and development, and considers them an effective method for improving agricultural productivity and nitrogen use efficiency.
... At the same time, because of the decrease in chlorophyll content of cold-injured tobacco leaves, the yellowing rate of tobacco leaves is faster than the rate of water loss, and the two cannot be coordinated, which also brings difficulties to fluecuring. Many enzymatic browning reactions occur easily because of the damage of cell membranes, which leads to the formation of browning tobacco (Chen et al., 2019). ...
Salicylic acid (SA) can induce plants to actively enhance abiotic stress resistance. Spraying SA to prevent cold stress in flue-cured tobacco fields can provide theoretical support and practical guidance for the actual protection from cold stress in fields at high altitude in Yunnan. The experiment was performed in Jianchuan County Yunnan Province, China. Honghuadajinyuan, a flue-cured tobacco variety with cold resistance, was used as the research object. SA was tested at two concentrations (0.05 [SA-1] and 0.1 [SA-1] mol L–1) relative to an untreated control (Control) to compare the quality of fresh tobacco leaves, curing characteristics, enzyme activity of antioxidants, and quality of the first-cured tobacco leaves. The tissue structure thickness, SPAD, and plastid pigment content of fresh tobacco leaves were least in the control; there was no significant difference between SA-1 and SA-2. The change of moisture content during curing was SA-1 > SA-2 > Control, and the water loss rate was Control > SA-2 > SA-1, and both varied greatly at 38–48°C. In each curing stage, the carbon and nitrogen metabolites and polyphenols changed most rapidly at 38°C, and the sugar metabolites changed as follows: Control > SA-1 > SA-2. The activities of the antioxidant enzymes superoxide dismutase, peroxidase, and catalase in fresh tobacco leaves were SA-1 > SA-2 > Control. Malondialdehyde content and the inactivation rate of antioxidant enzymes during curing was Control > SA-2 > SA-1. The economic character and sensory smoking quality of flue-cured tobacco leaves were SA-1 > SA-2 > Control. In high-altitude tobacco planting areas prone to cold stress in the field, early warning weather forecast and field spraying 0.05 mol L–1 SA are beneficial to protect and improve the quality of fresh tobacco leaves, curing characteristics, antioxidant system enzyme activities, and the quality of flue-cured tobacco leaves.
The surface color of cigar tobacco leaves (CTLs) is largely determined by the browning response and is one of the most important quality traits affecting consumer preferences. The physiological changes and metabolic network of browning in CTLs after harvest have not been reported. We investigated the molecular mechanism of browning in CTLs by comparing the physiological characteristics and metabolites of CTLs browning at five postharvest periods. Phenotypic traits and browning-related enzyme activity data indicated that the browning reaction was most intense at approximately 12 d when polyphenol oxidase and peroxidase activities reached their maximum. Postharvest CTLs polyphenols, polyacids, and carbon and nitrogen compounds were rapidly degraded during the yellowing phase, and the biosynthesis rate of polyphenols and carotenoids was greater than the degradation rate during the browning phase. Metabolomic analysis discovered 2027 metabolites that were annotated mainly to lipids and lipid-like molecules, organic acids and their derivatives, and organic heterocyclic components. Hierarchical cluster analysis discovered glutamate, serine, threonine, ornithine, and arginine as the major amino acids involved in the browning reaction. KEGG pathway enrichment analysis indicated that the metabolic pathways with important effects on enzymatic browning were phenylpropanoid biosynthesis, flavonoid biosynthesis, isoquinoline alkaloid biosynthesis, phenylalanine metabolism, and linoleic acid metabolism. The metabolic pathway network was mined, and the main polyphenols involved in the browning reaction of CTLs were found to be cyanidin, rutin, caffeoylquinic acid, kaempferol, naringin, and neohesperidin. This study provides a reference for the browning physiology and metabolism network of postharvest CTLs.
Graphical Abstract
Tobacco leaves, as raw materials, undergo complex processing before the final product is obtained. During the flue-curing process, inadequate control of environmental factors such as temperature, humidity or water loss rate, may lead to enzymatic browning occur caused by starvation metabolism of tobacco leaves, and therefore large amount of internal chemical substances consumed and changed, leading to excessive darker color and affecting the quality of products. This study aimed to investigate the mechanisms and material basis of browning, as well as the relationship between browning and internal substances changes. The microstructural changes of tobacco leaves under transmission electron microscopy were observed, quantitative proteomic and untargeted metabonomic methods were conducted in browning and normal tobacco leaves. In the results, 106 differential proteins and 576 differential metabolites were identified, with differential proteins mainly involved in biosynthesis and metabolism of polysaccharides, lipid, as well as the regulation of chlorophyll degradation and polyphenol oxidation related proteins. Differential metabolites were mainly enriched in purine metabolism, histidine metabolism and isoflavone biosynthesis pathway, with more secondary metabolites biosynthesis pathway enrichment. Moreover, tyrosine metabolism and phenylpropane biosynthesis metabolism were identified as the mainly differential proteins and metabolites pathways. Additionally, two metabolites, resveratrol and iridin, that exhibited strong free radicals scavenging activity and good antioxidant properties were uncovered. Taken together, these findings demonstrated changes of chemical substances and differences of proteins and metabolites between browning and normal tobacco leaves under specific conditions, and provided a theoretical reference for exploring optimized conditions and controlling material changes during the processing of tobacco to inhibit browning.
Metabolic enzyme activity and microbial composition of the air-curing and fermentation processes determine the quality of cigar tobacco leaves (CTLs). In this study, we reveal the evolution of the dominant microorganisms and microbial community structure at different stages of the air-curing and fermentation processes of CTLs. The results showed that the changes in metabolic enzymes occurred mainly during the air-curing phase, with polyphenol oxidase (PPO) being the most active at the browning phase. Pseudomonas, Bacteroides, Vibrio, Monographella, Bipolaris, and Aspergillus were the key microorganisms in the air-curing and fermentation processes. Principal coordinate analysis revealed significant separation of microbial communities between the air-curing and fermentation phases. Redundancy analysis showed that bacteria such as Proteobacteria, Firmicutes, Bacteroidota, and Acidobacteriota and fungi such as Ascomycota and Basidiomycota were correlated with enzyme activity and temperature and humidity. Bacteria mainly act in sugar metabolism, lipid metabolism, and amino acid metabolism, while fungi mainly degrade lignin, cellulose, and pectin through saprophytic action. Spearman correlation network analysis showed that Firmicutes, Proteobacteria, and Actinobacteria were the key bacterial taxa, while Dothideomycetes, Sordariomycetes, and Eurotiomycetes were the key fungal taxa. This research provides the basis for improving the quality of cigars by improving the air-curing and fermentation processes.
Key points
• Changes in POD and PPO activity control the color change of CTLs at the air-curing stage.
• Monographella, Aspergillus, Pseudomonas, and Vibrio play an important role in air-curing and fermentation.
• Environmental temperature and humidity mainly affect the fermentation process, whereas bacteria such as Proteobacteria, Firmicutes, Bacteroidota, and Acidobacteriota and fungi such as Ascomycota and Basidiomycota are associated with enzyme activity and temperature and humidity.
Graphical Abstract
The quality of fermented plant products is closely related to microbial metabolism. Here, the associations of bacterial communities, metabolites, and functional genes were explored using multi-omics techniques based on plant leaf fermentation systems. The results showed significant changes in the structure of the microbial community, with a significant decrease in Firmicutes and a significant increase in Proteobacteria. In addition, the concentration of metabolites with antibacterial, antioxidant and aroma properties increased significantly, enhancing the quality of the fermented plant leaves. Integrated macrogenomic and metabolomic analyses indicated that amino acid metabolism could be key metabolic pathway affecting fermentation quality. Actinobacteria, Proteobacteria, Firmicutes were actively involved in tyrosine metabolism (ko00350) and phenylalanine metabolism (ko00360), and are presumed to be the major groups responsible for synthesizing growth and flavor compounds. This study emphasized the important role of microorganisms in the changes of metabolites during the fermentation of plant leaves.
