Metabolite biodiversity in pepper (Capsicum) fruits of thirty-two diverse accessions: variation in health-related compounds and implications for breeding

Phytochemical Assessment of Native Ecuadorian Peppers (Capsicum spp.) and Correlation Analysis to Fruit Phenomics

In this work, the impact of pepper (Capsicum spp.) fruits morphology on their composition for health-promoting compounds was investigated. For that purpose, pepper accessions from Ecuador, one of the hotspots in Capsicum's origin, were analyzed for ascorbic acid, polyphenols, capsaicinoids, and prevention of cholesterol oxidation. Plant and fruit phenomics were assessed with conventional descriptors and Tomato Analyzer digital traits. Significant differences among accessions and species revealed a large diversity within the collection. The Capsicum frutescens group displayed the highest levels of capsaicinoids, whereas the polyphenols shortly varied among the five domesticated species. Capsicum pubescens exhibited the lowest content of ascorbic acid. The conventional descriptors describing the magnitude of plants and fruits, as well as digital attributes under the categories of size, shape index, and latitudinal section, mostly explained the variance among Capsicum groups. Correlation test revealed that phytochemical components were negatively correlated with the morphometric fruit attributes, suggesting that huge fruits contained lower amounts of nutraceutical compounds. Multivariate analysis showed that parameters related to fruit size, shape, and nutraceutical composition primarily contribute to the arrangement of pepper accessions. Such results suggested that those traits have been subjected to higher selection pressures imposed by humans.

Cross-Species Comparison of Fruit-Metabolomics to Elucidate Metabolic Regulation of Fruit Polyphenolics Among Solanaceous Crops

Many solanaceous crops are an important part of the human daily diet. Fruit polyphenolics are plant specialized metabolites that are recognized for their human health benefits and their defensive role against plant abiotic and biotic stressors. Flavonoids and chlorogenates are the major polyphenolic compounds found in solanaceous fruits that vary in quantity, physiological function, and structural diversity among and within plant species. Despite their biological significance, the elucidation of metabolic shifts of polyphenols during fruit ripening in different fruit tissues, has not yet been well-characterized in solanaceous crops, especially at a cross-species and cross-cultivar level. Here, we performed a cross-species comparison of fruit-metabolomics to elucidate the metabolic regulation of fruit polyphenolics from three representative crops of Solanaceae (tomato, eggplant, and pepper), and a cross-cultivar comparison among different pepper cultivars (Capsicum annuum cv.) using liquid chromatography-mass spectrometry (LC-MS). We observed a metabolic trade-off between hydroxycinnamates and flavonoids in pungent pepper and anthocyanin-type pepper cultivars and identified metabolic signatures of fruit polyphenolics in each species from each different tissue-type and fruit ripening stage. Our results provide additional information for metabolomics-assisted crop improvement of solanaceous fruits towards their improved nutritive properties and enhanced stress tolerance.

Phytochemical Profile of Capsicum annuum L. cv Senise, Incorporation into Liposomes, and Evaluation of Cellular Antioxidant Activity

Overproduction of oxidants in the human body is responsible for oxidative stress, which is associated with several diseases. High intake of vegetables and fruits can reduce the risk of chronic diseases, as they are sources of bioactive compounds capable of contrasting the free radical effects involved in cancer, obesity, diabetes, and neurodegenerative and cardiovascular diseases. Capsicum annuum L. cv Senise is a sweet pepper that is grown in the Basilicata region (Italy). It is an important source of polyphenols, carotenoids, and capsinoids and can play a key role in human health. In this study, an ethanol extract was obtained from C. annuum dried peppers and the analysis of the phytochemical composition was performed by LC-ESI/LTQ Orbitrap/MS. The extract was incorporated into liposomes, which showed small size (~80 nm), good homogeneity, negative surface charge, and good stability in storage. The biological activity of the extract was evaluated in the human hepatoma (HepG2) cell line, used as model cells. The extract showed no cytotoxic activity and reduced the intracellular reactive oxygen species (ROS) level in stressed cells. The antioxidant activity was further improved when the extract was loaded into liposomes. Moreover, the extract promoted the expression of endogenous antioxidants, such as catalase, superoxide dismutase, and glutathione peroxidase through the Nrf-2 pathway evaluated by RT-PCR.

The rin, nor and Cnr spontaneous mutations inhibit tomato fruit ripening in additive and epistatic manners

Tomato fruit ripening is regulated by transcription factors (TFs), their downstream effector genes, and the ethylene biosynthesis and signalling pathway. Spontaneous non-ripening mutants ripening inhibitor (rin), non-ripening (nor) and Colorless non-ripening (Cnr) correspond with mutations in or near the TF-encoding genes MADS-RIN, NAC-NOR and SPL-CNR, respectively. Here, we produced heterozygous single and double mutants of rin, nor and Cnr and evaluated their functions and genetic interactions in the same genetic background. We showed how these mutations interact at the level of phenotype, individual effector gene expression, and sensory and quality aspects, in a dose-dependent manner. Rin and nor have broadly similar quantitative effects on all aspects, demonstrating their additivity in fruit ripening regulation. We also found that the Cnr allele is epistatic to rin and nor and that its pleiotropic effects on fruit size and volatile production, in contrast to the well-known dominant effect on ripening, are incompletely dominant, or recessive.

Targeted UHPLC-HRMS (Orbitrap) Polyphenolic and Capsaicinoid Profiling for the Chemometric Characterization and Classification of Paprika with Protected Designation of Origin (PDO) Attributes

Society’s interest in the quality of food products with certain attributes has increased, the attribute of a Protected Designation of Origin (PDO) being an effective tool to guarantee the quality and geographical origin of a given food product. In Spain, two paprika production areas with PDO (La Vera and Murcia) are recognized. In the present work, targeted UHPLC-HRMS polyphenolic and capsaicinoid profiling through the TraceFinder^TM screening software, using homemade accurate mass databases, was proposed as a source of chemical descriptors, to address the characterization, classification, and authentication of paprika. A total of 126 paprika samples from different production regions—Spain (La Vera PDO and Murcia PDO) and the Czech Republic, each including different flavor varieties, were analyzed. UHPLC-HRMS polyphenolic profiles showed to be good chemical descriptors to achieve paprika classification and authentication, based on the production region, through principal component analysis and partial least squares regression-discriminant analysis, with classification rates of 82%, 86%, and 100% for La Vera PDO, Murcia PDO, and the Czech Republic, respectively. In addition, a perfect classification was also accomplished among the flavor varieties for the Murcia PDO and Czech Republic samples. By employing the UHPLC-HRMS polyphenolic and capsaicinoid profiles as chemical descriptors, acceptable discrimination among La Vera PDO flavor varieties was also achieved.

Factors affecting the capsaicinoid profile of hot peppers and biological activity of their non-pungent analogs (Capsinoids) present in sweet peppers

Capsaicinoids are acid amides of C₉-C₁₁ branched-chain fatty acids and vanillylamine and constitute important chemical compounds of Capsicum annuum together with their non-pungent analogs (capsinoids) which have an impressive list of health benefit properties (i.e., analgesia, anti-obesity, thermogenic, cardiovascular, gastrointestinal, antioxidant, anti-bacterial, anti-virulence, anti-inflamatory, anti-diabetic, inhibits angiogenesis, and improves glucose metabolism) . In this review, the state of art on how capsaicinoids are affected by different pre- and postharvest factors is discussed together with their biological activity. For instance, high light intensity and heat treatments may reduce capsaicinoid content in fruits probably due to the loss of activity of capsaicin synthase (CS) and phenylalanine ammonia lyase (PAL). The pungency in peppers varies also with environment, genotype or cultivar, node position, fruiting and maturity stages, nitrogen and potassium contents. As the fruit mature, capsaicinoid levels increase. Fruits from the second node tend to have higher accumulation of pungency than those of other positions and the pungency decreases linearly as the node position increase. Sodium hydroxide treatment reduces the pungency of pepper fruit as it hydrolyzes and modifies one of the features (vanillyl group, the acid-amide linkage and alkyl side chain) of capsaicin molecule. Salt and water stress increase PAL and capsaicin synthase activity and increase the capsaicinoid accumulation in fruit, by negatively regulating peroxidase activity at appropriate levels. Future research must be directed in better understanding the changes of capsinoids during pre and post-harvest management, the causal drivers of the loss of activity of the aminotransferase gene (pAMT) and if possible, studies with genetically modified sweet peppers with functional pAMT. Available data provided in this review can be used in different agricultural programs related to developing new cultivars with specific pungency levels. The contents of capsaicinoids and capsinoids in both fresh fruits and marketed products are also of remarkable importance considering the preferences of certain niches in market where higher added-value products might be commercialized.

Nitrogen Source Affects the Composition of Metabolites in Pepper (Capsicum annuum L.) and Regulates the Synthesis of Capsaicinoids through the GOGAT-GS Pathway

Phytochemical analyses of pepper fruit metabolites have been reported; however, much less is known about the influence of different forms of nitrogen (N), which is critical for plant growth and fruit quality formation. The "Longjiao No. 5" variety (Capsicum annuum L.) grown in Northwestern China was profiled using liquid chromatography-mass spectrometry (LC-MS) coupled with multivariate data analysis to explore the composition of different metabolites in pericarp and placenta, and to investigate the effect of three ammonium (NH4+)-to-nitrate (NO3-) ratios (0:100, 25:75, and 50:50). A total of 215 metabolites were obtained by qualitative analysis, where 31 metabolites were the major differential metabolite components of pepper fruits between placenta and pericarp, and 25 among N treatments. The addition of ammonium up-regulated carbohydrates, such as α-lactose and sucrose, as well as phenylalanine lyase (PAL) of placenta tissue. The supply of 25% NH4+-N and 75% NO3--N exhibited a relatively higher levels of ascorbic acid in pericarp and amino acids, capsaicin, and dihydrocapsaicin in placenta, and led to higher fruit weight among the ammonium-to-nitrate ratios. The expression and activities of glutamic acid synthetase (GOGAT) and glutamine synthetase (GS) that are involved in ammonium assimilation were affected by adjusting the ammonium-N proportion, and they were significantly positively correlated with capsaicin, dihydrocapsaicin contents, capsaicinoid synthetase (CS), as well as the relative expression levels of genes related to capsaicinoid biosynthesis, such as acyltransferase 3 (AT3) and acyl-ACP thioesterase (FatA).

Grown to be Blue-Antioxidant Properties and Health Effects of Colored Vegetables. Part II: Leafy, Fruit, and Other Vegetables

The current trend for substituting synthetic compounds with natural ones in the design and production of functional and healthy foods has increased the research interest about natural colorants. Although coloring agents from plant origin are already used in the food and beverage industry, the market and consumer demands for novel and diverse food products are increasing and new plant sources are explored. Fresh vegetables are considered a good source of such compounds, especially when considering the great color diversity that exists among the various species or even the cultivars within the same species. In the present review we aim to present the most common species of colored vegetables, focusing on leafy and fruit vegetables, as well as on vegetables where other plant parts are commercially used, with special attention to blue color. The compounds that are responsible for the uncommon colors will be also presented and their beneficial health effects and antioxidant properties will be unraveled.

Determination of Phenolic Compounds in Paprika by Ultrahigh Performance Liquid Chromatography-Tandem Mass Spectrometry: Application to Product Designation of Origin Authentication by Chemometrics

An ultrahigh performance liquid chromatography-electrospray-tandem mass spectrometry method was developed for the determination of 36 phenolic compounds in paprika. The proposed method showed good method performance with limits of quantitation between 0.03 and 50 μg/L for 16 compounds and between 50 μg/L and 1 mg/L for 12 compounds. Good linearity (R² > 0.995), run-to-run and day-to-day precisions (%RSD values < 12.3 and < 19.2%, respectively), and trueness (relative errors < 15.0%) were obtained. The proposed method was applied to the analysis of 111 paprika samples from different production regions: Spain (La Vera PDO and Murcia PDO) and Czech Republic, each one including different flavor varieties (sweet, bittersweet, and spicy). Phenolic profiles and concentration levels showed to be good chemical descriptors to achieve paprika classification and authentication according to the production region by principal component analysis and partial least squares regression-discriminant analysis. In addition, perfect classification among flavor varieties for Murcia PDO and Czech Republic samples was also obtained.

Integrative analysis of metabolome and transcriptome reveals the mechanism of color formation in pepper fruit (Capsicum annuum L.)

To understand the mechanism of the color formation of pepper fruit, integrative analysis of the metabolome and transcriptome profiles was performed in pepper varieties with 4 different fruit colors. A total of 188 flavonoids were identified, and most of the anthocyanins, flavonols and flavones showed markedly higher abundances in purple variety than in other varieties, which was linked to the high expression of flavonoid synthesis and regulatory genes. Using weighted gene co-expression network analyses, modules related to flavonoid synthesis and candidate genes that regulate flavonoid synthesis and transport were identified. Furthermore, the analysis of 12 carotenoids showed that the content of xanthophylls at 50 days after anthesis was significantly different between the four pepper varieties, which was resulted from the differential expressions of genes downstream of the carotenoid pathway. Our results provide new insights into the understanding of the synthesis and accumulation of flavonoids and carotenoids in pepper fruit.

Carotenoids of Capsicum Fruits: Pigment Profile and Health-Promoting Functional Attributes

Pepper of the Capsicum species is a common ingredient in various food preparations by different cultures worldwide. The Capsicum is recognised by its five main domesticated species, namely Capsicum annuum, C. baccatum, C. chinense, C. frutescens and C. pubescens. The genetic diversity in Capsicum offers fruits in wide ranges of morphology and carotenoid profile. Carotenoids enhance the value of pepper from a nutritional standpoint, despite being commonly prized for the pharmacologically active pungent capsaicinoids. Carotenoids of pepper comprise mainly of the unique, powerful and highly stable capsanthin and capsoroubin, together with β-carotene, β-cryptoxanthin, lutein, zeaxanthin, antheraxanthin and violaxanthin. These carotenoids are present at diverse profile and varying levels, biosynthetically connected to the fruit maturity stages. This review describes the health-promoting functional attributes of the carotenoids that are mainly associated with their excellent role as lipophilic antioxidants. Capsicum as a great source of carotenoids is discussed in the aspects of main domesticated species, biosynthesis, pigment profile, antioxidant activity and safety. Findings from a number of in vitro, in vivo and clinical studies provided appreciable evidence on the protective effects of pepper’s carotenoids against degenerative diseases. Hence, pepper with its functional carotenoids might be recommended in health-promoting and disease preventing strategies.

Jasmonate-Inducible R2R3-MYB Transcription Factor Regulates Capsaicinoid Biosynthesis and Stamen Development in Capsicum

Jasmonates (JAs) play an important role in plant developmental processes and regulate the biosynthesis of various specialized metabolites, and transcription factors are crucial in mediating JA signaling to regulate these processes. Capsaicinoids (Caps) are intriguing specialized metabolites produced uniquely by Capsicum species that give their fruits a pungent flavor to defend against herbivory and pathogens. In this study, we identify a R2R3-MYB transcription factor CaMYB108 and demonstrate its roles in regulating the biosynthesis of Caps and stamen development. Transcriptional analysis indicated that CaMYB108 was preferentially expressed in the flower and fruit, while the subcellular localization of CaMYB108 was shown to be the nucleus. Virus-induced gene silencing of CaMYB108 led to the expression of capsaicinoid biosynthetic genes (CBGs), and the contents of Caps dramatically reduce. Moreover, the CaMYB108-silenced plants showed delayed anther dehiscence and reduced pollen viability. Transient overexpression of CaMYB108 caused the expression of CBGs to be upregulated, and the Caps content significantly increased. The results of dual-luciferase reporter assays showed that CaMYB108 targeted CBG promoters. In addition, the expression of CaMYB108 and CBGs was inducible by methyl jasmonate and was consistent with the increased content of Caps. Overall, our results indicate that CaMYB108 is involved in the regulation of Caps biosynthesis and stamen development.

Placenta, Pericarp, and Seeds of Tabasco Chili Pepper Fruits Show a Contrasting Diversity of Bioactive Metabolites

Chili pepper (Capsicum spp.) is one of the most important horticultural crops worldwide, and its unique organoleptic properties and health benefits have been established for centuries. However, there is little knowledge about how metabolites are distributed throughout fruit parts. This work focuses on the use of liquid chromatography coupled with high resolution mass spectrometry (UHPLC-ESI-HRMS) to estimate the global metabolite profiles of the pericarp, placenta, and seeds of Tabasco pepper fruits (Capsicum frutescens L.) at the red mature stage of ripening. Our main results putatively identified 60 differential compounds between these tissues and seeds. Firstly, we found that pericarp has a higher content of glycosides, showing on average a fold change of 5 and a fold change of 14 for terpenoids when compared with other parts of the fruit. While placenta was the richest tissue in capsaicinoid-related compounds, alkaloids, and tocopherols, with a 35, 3, and 7 fold change, respectively. However, the seeds were richer in fatty acids and saponins with fold changes of 86 and 224, respectively. Therefore, our study demonstrates that a non-targeted metabolomic approach may help to improve our understanding of unexplored areas of plant metabolism and also may be the starting point for a detailed analysis in complex plant parts, such as fruits.

Biochemistry and molecular biology of capsaicinoid biosynthesis: recent advances and perspectives

The most widely known characteristic of chili pepper fruits is their capacity to produce capsaicinoids, which are responsible for the pungent sensation. The capsaicinoids have several uses in different areas, such as the pharmaceutical, cosmetic and agronomic industries, among others. They are synthesized by the condensation of vanillylamine (derived from phenylalanine) with a branched-chain fatty acid (from valine or leucine precursors), and they generally accumulate in the placental tissue of the chili pepper fruits. The pungency grade depends on the genotype of the plant but is also affected by external stimuli. In recent years, new structural and regulatory genes have been hypothesized to participate in the capsaicinoid biosynthetic pathway. Moreover, the role of some of these genes has been investigated. Substantial progress has been made in discerning the molecular biology of this pathway; however, many questions remain unsolved. We previously reviewed some aspects of the biochemistry and molecular biology of capsaicinoid biosynthesis (Aza-González et al. Plant Cell Rep 30:695-706. Aza-González et al., Plant Cell Rep 30:695-706, 2011), and in this review, we describe advances made by different researchers since our previous review, including the contribution of omics to the knowledge of this pathway.

Ozonation of Hot Red Pepper Fruits Increases Their Antioxidant Activity and Changes Some Antioxidant Contents

The effect of treatment of pepper fruits with gaseous ozone and storage time following the ozonation process on changes in the content of lipophilic fraction is analyzed for the first time in this paper. The aim of the present study was to assess the impact of ozone treatment on the composition of lipophilic compound fraction and its antioxidant activity (AA). Pepper fruits of cv. Cyklon were ozonated for 1 and 3 h immediately after harvesting. Then, the fruits were stored for 30 days under refrigeration conditions. The total content of phenolic compounds and the AA of the lipophilic fraction isolated from the pericarp and placenta of the fruits were investigated after 10, 20, and 30 days of storage. Additionally, quantitative high-performance liquid chromatography diode array detection analysis of individual phenolic compounds was performed. The results revealed that the content and activity of secondary metabolites varied during storage, with the highest values recorded on the 20th day after harvest, both in control and ozonated fruits, regardless of the ozone dosage used. Treatment of the fruits with ozone for 3 h, but not for 1 h, exhibited a positive effect on the phenolic composition and AA during the prolonged storage of pepper fruits. Three hours of ozonation seems to be the appropriate time to increase the persistence of pepper fruits during storage.

Influence of drying techniques and growing location on the chemical composition of sweet pepper (Capsicum annuum L., var. Senise)

The aim of this work was the comprehensive characterization of dried Senise pepper, a tasty landrace, to verify the suitability of common industrial processing and different growing locations to its production. Fruits from experimental CREA fields of Battipaglia (southern Italy) and Montanaso (northern Italy), dried using a solar dryer or a forced air oven, were compared with lyophilized and commercial samples. Solar dried samples showed a retention of glucose, while fructose levels decreased. Citric acid was the main acid in all samples, showing a differentiated behavior upon processing, with higher content in Battipaglia samples. The ascorbic acid showed the highest correlation with antioxidant assays, and both drying methods decreased its content, with better retention in Battipaglia samples. Drying did not markedly affect carotenoid levels, showing higher content in Battipaglia peppers. Both drying technique and mostly growing location influenced the volatile profile, with higher apocarotenoid content in Battipaglia samples. PRACTICAL APPLICATIONS: The use of Senise red pepper, a tasty landrace awarded in 1996 with the PGI certification mark, is spreading even outside Italy due to the renewed interest for high quality products with excellent taste and healthy properties. These peppers are mostly sun-dried following a traditional procedure and consumed as spice. New approaches regarding the type of drying and the growing location of this spice, together with the knowledge about the changes in quality indexes with processing, can be useful for a better exploitation of this product, increasing its market availability and lowering the cost of production.

Association between vitamin content, plant morphology and geographical origin in a worldwide collection of the orphan crop Gynandropsis gynandra (Cleomaceae)

The variability in nutrient content and morphology in Gynandropsis gynandra is associated with the geographic origin of the accessions and provides a basis for breeding for higher levels of vitamin C, carotenoids or tocopherols in higher-yielding cultivars. We examined the variation in carotenoids, tocopherols and ascorbic acid as well as morphological traits in a worldwide germplasm of 76 accessions of the orphan leafy vegetable Gynandropsis gynandra (Cleomaceae) using greenhouse experiments and high-performance liquid chromatography analysis. The levels of carotenoids and tocopherols accumulating in the leaves varied significantly across accessions and were linked with the geographical origin and morphological variation. The main carotenoids included lutein, β-carotene, α-carotene and violaxanthin. A twofold to threefold variation was observed for these compounds. The main tocopherols detected were α-tocopherol and γ-tocopherol with a 20-fold variation. A ninefold variation in vitamin C concentration and independent of geographical origin was observed. Overall, the accessions were grouped into three clusters based on variation in nutrient content and morphology. West African accessions were short plants with small leaves and with high tocopherol contents and relatively low carotenoid contents, Asian accessions were short plants with broad leaves and with relatively low carotenoid and high tocopherol contents, while East-Southern African plants were tall with high contents of both carotenoids and chlorophylls and low tocopherol contents. Carotenoids were positively correlated with plant height as well as foliar and floral traits but negatively correlated with tocopherols. The absence of a significant correlation between vitamin C and other traits indicated that breeding for high carotenoids or tocopherols content may be coupled with improved leaf yield and vitamin C content. Our study provides baseline information on the natural variation available for traits of interest for breeding for enhanced crop yield and nutrient content in Gynandropsis gynandra.

Transcriptional Regulation of Ascorbic Acid During Fruit Ripening in Pepper (Capsicum annuum) Varieties with Low and High Antioxidants Content

Research on plant antioxidants, such as ascorbic acid (AsA) and polyphenols, is of increasing interest in plant science because of the health benefits and preventive role in chronic diseases of these natural compounds. Pepper (Capiscum annuum L.) is a major dietary source of antioxidants, especially AsA. Although considerable advance has been made, our understanding of AsA biosynthesis and its regulation in higher plants is not yet exhaustive. For instance, while it is accepted that AsA content in cells is regulated at different levels (e.g., transcriptional and post-transcriptional), their relative prominence is not fully understood. In this work, we identified and studied two pepper varieties with low and high levels of AsA to shed light on the transcriptional mechanisms that can account for the observed phenotypes. We quantified AsA and polyphenols in leaves and during fruit maturation, and concurrently, we analyzed the transcription of 14 genes involved in AsA biosynthesis, degradation, and recycling. The differential transcriptional analysis indicated that the higher expression of genes involved in AsA accumulation is a likely explanation for the observed differences in fruits. This was also supported by the identification of gene-metabolite relations, which deserve further investigation. Our results provide new insights into AsA differential accumulation in pepper varieties and highlight the phenotypic diversity in local germplasm, a knowledge that may ultimately contribute to the increased level of health-related phytochemicals.

Natural variations in the MYB transcription factor MYB31 determine the evolution of extremely pungent peppers

Plants produce countless specialized metabolites crucial for their development and fitness, and many are useful bioactive compounds. Capsaicinoids are intriguing genus-specialized metabolites that confer a pungent flavor to Capsicum fruits, and they are widely applied in different areas. Among the five domesticated Capsicum species, Capsicum chinense has a high content of capsaicinoids, which results in an extremely hot flavor. However, the species-specific upregulation of capsaicinoid-biosynthetic genes (CBGs) and the evolution of extremely pungent peppers are not well understood. We conducted genetic and functional analyses demonstrating that the quantitative trait locus Capsaicinoid1 (Cap1), which is identical to Pun3 contributes to the level of pungency. The Cap1/Pun3 locus encodes the Solanaceae-specific MYB transcription factor MYB31. Capsicum species have evolved placenta-specific expression of MYB31, which directly activates expression of CBGs and results in genus-specialized metabolite production. The capsaicinoid content depends on MYB31 expression. Natural variations in the MYB31 promoter increase MYB31 expression in C. chinense via the binding of the placenta-specific expression of transcriptional activator WRKY9 and augmentation of CBG expression, which promotes capsaicinoid biosynthesis. Our findings provide insights into the evolution of extremely pungent C. chinense, which is due to natural variations in the master regulator, and offers targets for engineering or selecting flavor in Capsicum.

Characterization, processing potential and drivers for preference of pepper cultivars in the production of sweet or spicy jellies

Due to the importance of studying alternatives to reduce pepper post-harvest loss and verify the processing potential of the several cultivars/varieties available, the objective of this study was to characterize common peppers in Brazil, and to evaluate their potential for further processing into jelly form. More specifically, the most-consumed species and varieties in Brazil were investigated, that is: Habanero, Cheiro do Norte, Biquinho, Malagueta, Cayenne, Paprika and Dedo de Moça. Additionally, the drivers of liking for pepper jelly were sought so as to understand the desirable characteristics of this product. The different peppers were initially assessed by the following physical and physicochemical analyses: length, diameter, unit mass, total soluble solids, total titratable acidity, pH, color, total phenolic content, antioxidant activity, and vitamin C levels. Jellies made with different pepper types were also analyzed for total titratable acidity, pH, color, and texture profile, and a sensory study was conducted to elucidate the drivers of liking. As expected, different pepper types varied in physical and physicochemical properties, and the resulting jellies also differed in terms of physical, physicochemical, textural and sensory characteristics. In general, less pungent peppers (Biquinho, Paprika and Cheiro do Norte) were the most suitable for processing to produce jellies with more desirable attributes for consumers: reddish color, characteristic flavor and aroma of a pepper, sweet taste, and low pungency.

Potential Phytopharmacy and Food Applications of Capsicum spp.: A Comprehensive Review

Capsicum genus (Solanaceae) is native to the Americas. Today, it is an important agricultural crop cultivated around the world, not only due to its economic importance, but also for the nutritional value of the fruits. Among their phytochemical constituents, capsaicinoids are characteristic and responsible of the pungency of sharp-tasting cultivars. Moreover, Capsicum and capsaicinoids (mainly, capsaicin) have been largely studied because of their health benefits. Thus, this study reviews the scientific knowledge about Capsicum spp. and their phytochemicals against cancer, diabetes, gastrointestinal diseases, pain, and metabolic syndrome, as well as their antioxidant and antimicrobial activity. These bioactivities can be the basis of the formulation of functional ingredients and natural preservatives containing Capsicum extracts or isolated compounds.

Untargeted Metabolomics Analysis of Eggplant (Solanum melongena L.) Fruit and Its Correlation to Fruit Morphologies

Eggplant is one of the most widely cultivated vegetables in the world and has high biodiversity in terms of fruit shape, size, and color. Therefore, fruit morphology and nutrient content become important considerations for both consumers and breeders who develop new eggplant-based products. To gain insight on the diversity of eggplant metabolites, twenty-one eggplant accessions were analyzed by untargeted metabolomics using GC-MS and LC-MS. The dataset of eggplant fruit morphologies, and metabolites specific to different eggplant fruit accessions were used for correlation analysis. Untargeted metabolomics analysis using LC-MS and GC-MS was able to detect 136 and 207 peaks, respectively. Fifty-one (51) metabolites from the LC-MS analysis and 207 metabolites from the GC-MS analysis were putatively identified, which included alkaloids, terpenes, terpenoids, fatty acids, and flavonoids. Spearman correlation analysis revealed that 14 fruit morphologies were correlated with several metabolites. This information will be very useful for the development of strategies for eggplant breeding.

Quantitation of capsiate and dihydrocapsiate and tentative identification of minor capsinoids in pepper fruits (Capsicum spp.) by HPLC-ESI-MS/MS(QTOF)

A highly sensitive, selective method has been developed and validated for determination of capsiate and dihydrocapsiate for the first time using HPLC-ESI/MS(QTOF). For both capsinoids, LODs and LOQs were 0.02 and 0.05 µmol/l, respectively. The intra- and interday repeatability values (RSD %) were 0.26-0.41% for retention time, and 2.25-2.11% for peak area. Recoveries were up to 98% and 97% for capsiate and dihydrocapsiate, respectively. This method was successfully applied to quantify capsiate and dihydrocapsiate in eight pepper fruit accessions. Capsinoids were found in the range of 1.21-544.59 μg/g DW for capsiate and of 0.61-81.95 μg/g DW for dihydrocapsiate. In the 'Tabasco' accession, capsiate and dihydrocapsiate were quantified for the first time, ranging from 3.09 to 58.76 and 1.80 to 6.94 μg/g DW, respectively. Additionally, the ESI-MS/MS(QTOF) analysis has allowed the tentative identification of two other minor capsinoids by exact mass and fragmentation pattern, in the 'Bhut Jolokia' accession.

The genus Capsicum: a phytochemical review of bioactive secondary metabolites

The Capsicum genus is one of the most popular plants consumed and cultivated worldwide, containing approximately 50 000 varieties of pepper. Due to its wide biodiversity, the chemical composition within the genus also presents a great variability. Its major applications are in food and pharmacological industry, as pepper presents a chemical composition rich in capsaicinoids, carotenoids, flavonoids and volatile compounds which is attributed to the ability of the fruit to remove insipidity, produce aromas and act against oxidative diseases. Due the existence of several cultivars there is a huge intraspecific chemical variability within each species, which can be considered as an obstacle when selecting and cultivating a species to be applied as a natural product source for a specific objective. The usage of pepper-based products in different industrial areas requires pre-established ranges of chemical compounds, such as capsaicinoids, which in high concentration are toxic when consumed by humans. Applying a pepper with a chemical profile closely related to the concentration that is required after industrial processing can improve efficacy and effectiveness of the process. An insight into the chemical characteristics of major secondary bioactive compounds within Capsicum, the factors that affect their concentration and their chemosystematic implication are reported and discussed.

Occurrence of variable levels of health-promoting fruit compounds in horn-shaped Italian sweet pepper varieties assessed by a comprehensive approach

BACKGROUND

Cultivated pepper is a rich source of diverse bioactive compounds with potential properties related to the prevention of major degenerative and proliferative diseases. In the present study, 15 sweet pepper varieties, highly appreciated on the Italian market, were assessed for variation in the content of ascorbic acid, isoprenoids and flavonoids, as well as morpho-agronomic performances and molecular diversity.

RESULTS

The collection under study showed a wide variability for all traits considered. Traditional cultivars, although less productive, were characterized by a high content of β-carotene and ascorbic acid, reaching maximum concentrations of 230.5 mg kg^-1 fresh weight (fw) and 2750 mg kg^-1 fw, respectively. Strong correlations were demonstrated between neoxanthin and luteolins. Fruit weight was positively correlated with α-tocopherol content and negatively correlated with luteolins content. The genotyping by sequencing platform allowed the identification of 1833 single nucleotide polymorphism, which better defined the relationships among cultivars, based on provenance and improvement rate.

CONCLUSIONS

The present study provides an overview of the variability in the expression of fruit nutritional traits in a collection of horn-shaped pepper cultivars, integrating agronomic and molecular data. The impact for breeding and consumers is discussed. © 2017 Society of Chemical Industry.

Nitro-oxidative metabolism during fruit ripening

Pepper (Capsicum annuum L.) and tomato (Solanum lycopersicum L.), which belong to the Solanaceae family, are among the most cultivated and consumed fleshy fruits worldwide and constitute excellent sources of many essential nutrients, such as vitamins A, C, and E, calcium, and carotenoids. While fruit ripening is a highly regulated and complex process, tomato and pepper have been classified as climacteric and non-climacteric fruits, respectively. These fruits differ greatly in shape, color composition, flavor, and several other features which undergo drastic changes during the ripening process. Such ripening-related metabolic and developmental changes require extensive alterations in many cellular and biochemical processes, which ultimately leads to fully ripe fruits with nutritional and organoleptic features that are attractive to both natural dispersers and human consumers. Recent data show that reactive oxygen and nitrogen species (ROS/RNS) are involved in fruit ripening, during which molecules, such as hydrogen peroxide (H2O2), NADPH, nitric oxide (NO), peroxynitrite (ONOO-), and S-nitrosothiols (SNOs), interact to regulate protein functions through post-translational modifications. In light of these recent discoveries, this review provides an update on the nitro-oxidative metabolism during the ripening of two of the most economically important fruits, discusses the signaling roles played by ROS/RNS in controlling this complex physiological process, and highlights the potential biotechnological applications of these substances to promote further improvements in fruit ripening regulation and nutritional quality. In addition, we suggest that the term 'nitro-oxidative eustress' with regard to fruit ripening would be more appropriate than nitro-oxidative stress, which ultimately favors the consolidation of the plant species.

Significance of Genetic, Environmental, and Pre- and Postharvest Factors Affecting Carotenoid Contents in Crops: A Review

Carotenoids are a diverse group of tetraterpenoid pigments that play indispensable roles in plants and animals. The biosynthesis of carotenoids in plants is strictly regulated at the transcriptional and post-transcriptional levels in accordance with inherited genetic signals and developmental requirements and in response to external environmental stimulants. The alteration in the biosynthesis of carotenoids under the influence of external environmental stimulants, such as high light, drought, salinity, and chilling stresses, has been shown to significantly influence the nutritional value of crop plants. In addition to these stimulants, several pre- and postharvesting cultivation practices significantly influence carotenoid compositions and contents. Thus, this review discusses how various environmental stimulants and pre- and postharvesting factors can be positively modulated for the enhanced biosynthesis and accumulation of carotenoids in the edible parts of crop plants, such as the leaves, roots, tubers, flowers, fruit, and seeds. In addition, future research directions in this context are identified.

Synthesis of (±)-3,4-dimethoxybenzyl-4-methyloctanoate as a novel internal standard for capsinoid determination by HPLC-ESI-MS/MS(QTOF)

Capsinoids exhibit health-promoting properties and are therefore compounds of interest for medical and food sciences. They are minor compounds present in relatively high concentrations in only a few number of pepper cultivars. It is desirable to quantify capsinoids to provide selected cultivars with high capsinoid contents, which can then be employed as health food product. Quantifying low concentrations of capsinoids from pepper fruit requires a precise and selective analytical technique such as HPLC coupled to electrospray ionization - mass spectrometry, with development of an internal standard essential. In this work, the synthesis method of a novel compound analogue of capsinoids, the (±)-3,4-dimethoxybenzyl-4-methyloctanoate, which could be a suitable internal standard for capsinoid determination by electrospray ionization - mass spectrometry is described.

(±)-3,4-dimethoxybenzyl-4-methyloctanoate was stable under the analysis conditions and exerted chemical and physical properties similar to those of capsinoids. This internal standard will provide an accurate capsinoid determination by electrospray ionization - mass spectrometry, thus facilitating the pepper breeding programs, screening pepper cultivars and a better understanding of capsinoid biosynthetic pathway.

Metabolite Profiling of Peppers of Various Colors Reveals Relationships Between Tocopherol, Carotenoid, and Phytosterol Content

Peppers are widely consumed in Korea; the varietal development of peppers with increased content of beneficial plant metabolites is, therefore, of considerable interest. This requires a comprehensive understanding of the metabolic profile of pepper plants and the factors affecting this profile. To this end, we determined the content of various metabolites, such as hydrophilic and lipophilic compounds, phenolic acids, carotenoids, and capsaicinoids in peppers of various colors (green, red, pale green, and violet peppers) and in a high-pungency (green) pepper. We also performed principal component analysis (PCA), Pearson's correlation analysis, and hierarchical clustering analysis (HCA) to determine the relationships among these metabolites in peppers. PCA results indicated no significant variances among the 3 sample replicates. The HCA showed correlations between the metabolites resulting from common or closely linked biosynthesis pathways. Our results showed that carotenoids correlated positively with tocopherols and negatively with phytosterols; our findings also indicated a close relationship between the methylerythritol 4-phosphate and mevalonic acid biosynthesis pathways, providing evidence in favor of an earlier hypothesis regarding crosstalk across the chloroplast membrane. We, thus, demonstrate that metabolic profiling combined with multivariate analysis is a useful tool for analyzing metabolic networks.

PRACTICAL APPLICATION

A total of 71 metabolites were measured in 5 peppers of different colors. The metabolic profiling with multivariate analysis revealed that tocopherol content had a positive correlation with the carotenoid content and a negative correlation with the phytosterol content. The results of this study may help in breeding programs to produce new germplasm with enhanced nutritional quality.

Untargeted Metabolomic Analysis of Capsicum spp. by GC-MS

INTRODUCTION

In order to conserve the biodiversity of Capsicum species and find genotypes with potential to be utilised commercially, Embrapa Clima Temperado maintains an active germplasm collection (AGC) that requires characterisation, enabling genotype selection and support for breeding programmes.

OBJECTIVE

The objective of this study was to characterise pepper accessions from the Embrapa Clima Temperado AGC and differentiate species based on their metabolic profile using an untargeted metabolomics approach.

MATERIAL AND METHODS

Cold (-20°C) methanol extraction residue of freeze-dried fruit samples was partitioned into water/methanol (A) and chloroform (B) fractions. The polar fraction (A) was derivatised and both fractions (A and B) were analysed by gas chromatography coupled to mass spectrometry (GC-MS). Data from each fraction was analysed using a multivariate principal component analysis (PCA) with XCMS software.

RESULTS

Amino acids, sugars, organic acids, capsaicinoids, and hydrocarbons were identified. Outlying accessions including P116 (C. chinense), P46, and P76 (C. annuum) were observed in a PCA plot mainly due to their high sucrose and fructose contents. PCA also indicated a separation of P221 (C. annuum) and P200 (C. chinense), because of their high dihydrocapsaicin content.

CONCLUSIONS

Although the metabolic profiling did not allow for grouping by species, it permitted the simultaneous identification and quantification of several compounds complementing and expanding the metabolic database of the studied Capsicum spp. in the AGC. Copyright © 2017 John Wiley & Sons, Ltd.

Untargeted metabolomic analysis of tomato pollen development and heat stress response

Pollen development metabolomics. Developing pollen is among the plant structures most sensitive to high temperatures, and a decrease in pollen viability is often associated with an alteration of metabolite content. Most of the metabolic studies of pollen have focused on a specific group of compounds, which limits the identification of physiologically important metabolites. To get a better insight into pollen development and the pollen heat stress response, we used a liquid chromatography-mass spectrometry platform to detect secondary metabolites in pollen of tomato (Solanum lycopersicum L.) at three developmental stages under control conditions and after a short heat stress at 38 °C. Under control conditions, the young microspores accumulated a large amount of alkaloids and polyamines, whereas the mature pollen strongly accumulated flavonoids. The heat stress treatment led to accumulation of flavonoids in the microspore. The biological role of the detected metabolites is discussed. This study provides the first untargeted metabolomic analysis of developing pollen under a changing environment that can serve as reference for further studies.

Difference in capsaicinoid biosynthesis gene expression in the pericarp reveals elevation of capsaicinoid contents in chili peppers (Capsicum chinense)

This research reveals that the up-regulated expression of multiple capsaicinoid biosynthetic genes in pericarp tissue leads to the elevation of total capsaicinoid content in chili pepper fruit. Capsaicinoids are health-functional compounds that are produced uniquely in chili pepper fruits. A high capsaicinoid level is one of the major parameters determining the commercial quality and health-promoting properties of chili peppers. To investigate the mechanisms responsible for its high contents, we compared an extremely pungent cultivar 'Trinidad Moruga Scorpion Yellow' (MY) with other cultivars of different pungency levels (Fushimi-amanaga, Takanotsume, Red Habanero). Capsaicinoid concentrations were markedly higher in MY fruit (23.9 mg/g DW) than in other pungent cultivars including 'Red Habanero' (HB) fruit (14.3 mg/g DW). Comparative analysis of MY and HB reveals that both cultivars accumulated similar capsaicinoid concentrations in the placental septum, with that in the HB pericarp (1.8 mg/g DW) being markedly lower than that in the placental septum (69.1 mg/g DW). The capsaicinoid concentration in HB fruit is dependent on the placental septum, as reported in other accessions. Therefore, even though placental septum tissue contains high capsaicinoid concentrations, those in the pericarp and seeds attenuated its total content. In contrast, the MY pericarp exhibited a markedly higher concentration (23.2 mg/g DW). A qRT-PCR analysis revealed that multiple capsaicinoid biosynthetic pathway genes (Pun1, pAMT, KAS, and BCAT) were strongly up-regulated in placental septum of pungent cultivars. The genes were expressed exclusively in the MY pericarp, but were barely detected in the pericarps of other pungent cultivars. Collectively, the present study indicates that the up-regulated expression of these genes not only in placental septum but also in pericarp plays an important role in driving capsaicinoid accumulation in the whole fruit.

Comparative Analysis of Fruit Metabolites and Pungency Candidate Genes Expression between Bhut Jolokia and Other Capsicum Species

Bhut jolokia, commonly known as Ghost chili, a native Capsicum species found in North East India was recorded as the naturally occurring hottest chili in the world by the Guinness Book of World Records in 2006. Although few studies have reported variation in pungency content of this particular species, no study till date has reported detailed expression analysis of candidate genes involved in capsaicinoids (pungency) biosynthesis pathway and other fruit metabolites. Therefore, the present study was designed to evaluate the diversity of fruit morphology, fruiting habit, capsaicinoids and other metabolite contents in 136 different genotypes mainly collected from North East India. Significant intra and inter-specific variations for fruit morphological traits, fruiting habits and 65 fruit metabolites were observed in the collected Capsicum germplasm belonging to three Capsicum species i.e., Capsicum chinense (Bhut jolokia, 63 accessions), C. frutescens (17 accessions) and C. annuum (56 accessions). The pungency level, measured in Scoville Heat Unit (SHU) and antioxidant activity measured by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay showed maximum levels in C. chinense accessions followed by C. frutescens accessions, while C. annuum accessions showed the lowest value for both the traits. The number of different fruit metabolites detected did not vary significantly among the different species but the metabolite such as benzoic acid hydroxyl esters identified in large percentage in majority of C. annuum genotypes was totally absent in the C. chinense genotypes and sparingly present in few genotypes of C. frutescens. Significant correlations were observed between fruit metabolites capsaicin, dihydrocapsaicin, hexadecanoic acid, cyclopentane, α-tocopherol and antioxidant activity. Furthermore, comparative expression analysis (through qRT-PCR) of candidate genes involved in capsaicinoid biosynthesis pathway revealed many fold higher expression of majority of the genes in C. chinense compared to C. frutescens and C. annuum suggesting that the possible reason for extremely high pungency might be due to the higher level of candidate gene(s) expression although nucleotide variation in pungency related genes may also be involved in imparting variations in level of pungency.

Genetic diversity and population structure analysis to construct a core collection from a large Capsicum germplasm

Background

Conservation of genetic diversity is an essential prerequisite for developing new cultivars with desirable agronomic traits. Although a large number of germplasm collections have been established worldwide, many of them face major difficulties due to large size and a lack of adequate information about population structure and genetic diversity. Core collection with a minimum number of accessions and maximum genetic diversity of pepper species and its wild relatives will facilitate easy access to genetic material as well as the use of hidden genetic diversity in Capsicum.

Results

To explore genetic diversity and population structure, we investigated patterns of molecular diversity using a transcriptome-based 48 single nucleotide polymorphisms (SNPs) in a large germplasm collection comprising 3,821 accessions. Among the 11 species examined, Capsicum annuum showed the highest genetic diversity (H_E = 0.44, I = 0.69), whereas the wild species C. galapagoense showed the lowest genetic diversity (H_E = 0.06, I = 0.07). The Capsicum germplasm collection was divided into 10 clusters (cluster 1 to 10) based on population structure analysis, and five groups (group A to E) based on phylogenetic analysis. Capsicum accessions from the five distinct groups in an unrooted phylogenetic tree showed taxonomic distinctness and reflected their geographic origins. Most of the accessions from European countries are distributed in the A and B groups, whereas the accessions from Asian countries are mainly distributed in C and D groups. Five different sampling strategies with diverse genetic clustering methods were used to select the optimal method for constructing the core collection. Using a number of allelic variations based on 48 SNP markers and 32 different phenotypic/morphological traits, a core collection ‘CC240’ with a total of 240 accessions (5.2 %) was selected from within the entire Capsicum germplasm. Compared to the other core collections, CC240 displayed higher genetic diversity (I = 0.95) and genetic evenness (J’ = 0.80), and represented a wider range of phenotypic variation (MD = 9.45 %, CR = 98.40 %).

Conclusions

A total of 240 accessions were selected from 3,821 Capsicum accessions based on transcriptome-based 48 SNP markers with genome-wide distribution and 32 traits using a systematic approach. This core collection will be a primary resource for pepper breeders and researchers for further genetic association and functional analyses.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-016-0452-8) contains supplementary material, which is available to authorized users.

Vitamin Variation in Capsicum Spp. Provides Opportunities to Improve Nutritional Value of Human Diets

Chile peppers, native to the Americas, have spread around the world and have been integrated into the diets of many cultures. Much like their heat content, nutritional content can vary dramatically between different pepper types. In this study, a diverse set of chile pepper types were examined for nutrient content. Some pepper types were found to have high levels of vitamin A, vitamin C, or folate. Correlations between nutrient content, species, cultivation status, or geographic region were limited. Varietal selection or plant breeding offer tools to augment nutrient content in peppers. Integration of nutrient rich pepper types into diets that already include peppers could help combat nutrient deficiencies by providing a significant portion of recommended daily nutrients.

Metabolomics Provides Quality Characterization of Commercial Gochujang (Fermented Pepper Paste)

To identify the major factors contributing to the quality of commercial gochujang (fermented red pepper paste), metabolites were profiled by mass spectrometry. In principal component analysis, cereal type (wheat, brown rice, and white rice) and species of hot pepper (Capsicumannuum, C. annuum cv. Chung-yang, and C. frutescens) affected clustering patterns. Relative amino acid and citric acid levels were significantly higher in wheat gochujang than in rice gochujang. Sucrose, linoleic acid, oleic acid, and lysophospholipid levels were high in brown-rice gochujang, whereas glucose, maltose, and γ-aminobutyric acid levels were high in white-rice gochujang. The relative capsaicinoid and luteolin derivative contents in gochujang were affected by the hot pepper species used. Gochujang containing C. annuum cv. Chung-yang and C. frutescens showed high capsaicinoid levels. The luteolin derivative level was high in gochujang containing C. frutescens. These metabolite variations in commercial gochujang may be related to different physicochemical phenotypes and antioxidant activity.

Chronic ozone exposure alters the secondary metabolite profile, antioxidant potential, anti-inflammatory property, and quality of red pepper fruit from Capsicum baccatum

Tropospheric ozone (O3) background concentrations have increased since pre-industrial times, reaching phytotoxic concentrations in many regions globally. However, the effect of high O3 concentrations on quality of fruit and vegetables remains unknown. Here, we evaluated whether O3 pollution alters the quality of Capsicum baccatum peppers by changing the secondary compound profiles and biological activity of the fruit. C. baccatum pepper plants were exposed to ozone for 62 days in an open-top chamber at a mean O3 concentration of 171.6µg/m(3). Capsaicin levels decreased by 50% in the pericarp, but remained unchanged in the seeds. In contrast, the total carotenoid content increased by 52.8% in the pericarp. The content of total phenolic compounds increased by 17% in the pericarp. The total antioxidant potential decreased by 87% in seeds of O3-treated plants. The seeds contributed more than the pericarp to the total radical-trapping antioxidant potential and total antioxidant reactivity. O3 treatment impaired the ferric-reducing antioxidant power of the seeds and reduced NO(•)-scavenging activity in the pericarp. However, O3 treatment increased ferrous ion-chelating activity and hydroxyl radical-scavenging activity in the pericarp. Our results confirm that O3 alters the secondary metabolite profile of C. baccatum pepper fruits and, consequently, their biological activity profile.

Metabolomics reveal that amino acids are the main contributors to antioxidant activity in wheat and rice gochujangs (Korean fermented red pepper paste)

Metabolite profiling of gochujangs (Korean fermented red pepper paste) produced from different kinds of raw materials (WG, wheat gochujang; RG, rice gochujang) was performed using gas chromatography time-of-flight mass spectrometry (GC-TOF-MS) and ultra-performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC-Q-TOF-MS). Using principal component analysis (PCA), gochujang samples were differentiated based on the differences in starchy source and secondary materials used in their production. The content of amino acids and sugars was higher in WG, whereas the content of flavonoids, soyasaponins, and γ-aminobutyric acid (GABA) was higher in RG. The content of flavonoids and soyasaponins was related to the higher soybean koji content of RG. The level of antioxidant activity in WG was higher than that in RG and showed a strong positive correlation with amino acid content and a negative correlation with flavonoid content. Although the Trolox equivalent antioxidant capacity of flavonoids was only 10-fold higher than that of amino acids in an antioxidant activity assay, the total amino acid content was as much as several hundred fold higher than total flavonoid content in gochujang. This result suggests that the amino acids could be a main contributor to the antioxidant capacity in gochujang.