Chili pepper fruits: presumed precursors of fatty acids characteristic for capsaicinoids

Haplotype analysis, regulatory elements and docking simulation of structural models of different AT3 copies in the genus Capsicum

Capsaicinoids are responsible for the pungency in Capsicum species. These are synthesized by the Capsaicin synthase (CS) encoded by the AT3 gene, which catalyzes the transference of an acyl moiety from a branched-chain fatty acid-CoA ester to the vanillylamine to produce capsaicinoids. Some AT3 gene copies have been identified on the Capsicum genome. The absence of capsaicinoid in some nonpungent accessions is related to mutant AT3 alleles. The differences between CS protein copies can affect the tridimensional structure of the protein and the affinity for its substrates, and this could affect fruit pungency. This study characterized 32 AT3 sequences covering Capsicum pungent and non-pungent accessions. These were clustered in AT3-D1 and AT3-D2 groups and representative sequences were analyzed. Genomic upstream analysis shows different regulatory elements, mainly responsive to light and abiotic stress. AT3-D1 and AT3-D2 gene expression was confirmed in fruit tissues of C. annuum. Amino acid substitutions close to the predictable HXXXD and DFGWG motifs were also identified. AT3 sequences were modeled showing a BAHD acyltransferase structure with two connected domains. A pocket with different shape, size and composition between AT3 models was found inside the protein, with the conserved motif HXXXD exposed to it, and a channel for their accessibility. CS substrates exhibit high interaction energies with the His and Asp conserved residues. AT3 models have different interaction affinities with the (E)-8-methylnon-6-enoyl-CoA, 8-methylnonanoyl-CoA and vanillylamine substrates. These results suggested that AT3-D1 and AT3-D2 sequences encode CS enzymes with different regulatory factors and substratum affinities.Communicated by Ramaswamy H. Sarma.

Capsaicinoids and Their Effects on Cancer: The "Double-Edged Sword" Postulate from the Molecular Scale

Capsaicinoids are a unique chemical species resulting from a particular biosynthesis pathway of hot chilies (Capsicum spp.) that gives rise to 22 analogous compounds, all of which are TRPV1 agonists and, therefore, responsible for the pungency of Capsicum fruits. In addition to their human consumption, numerous ethnopharmacological uses of chili have emerged throughout history. Today, more than 25 years of basic research accredit a multifaceted bioactivity mainly to capsaicin, highlighting its antitumor properties mediated by cytotoxicity and immunological adjuvancy against at least 74 varieties of cancer, while non-cancer cells tend to have greater tolerance. However, despite the progress regarding the understanding of its mechanisms of action, the benefit and safety of capsaicinoids' pharmacological use remain subjects of discussion, since CAP also promotes epithelial-mesenchymal transition, in an ambivalence that has been referred to as "the double-edge sword". Here, we update the comparative discussion of relevant reports about capsaicinoids' bioactivity in a plethora of experimental models of cancer in terms of selectivity, efficacy, and safety. Through an integration of the underlying mechanisms, as well as inherent aspects of cancer biology, we propose mechanistic models regarding the dichotomy of their effects. Finally, we discuss a selection of in vivo evidence concerning capsaicinoids' immunomodulatory properties against cancer.

Towards engineered yeast as production platform for capsaicinoids

Capsaicinoids are bioactive alkaloids produced by the chili pepper fruit and are known to be the most potent agonists of the human pain receptor TRPV1 (Transient Receptor Potential Cation Channel Subfamily V Member 1). They are currently produced by extraction from chili pepper fruit or by chemical synthesis. Transfer of the biosynthetic route to a microbial host could enable more efficient capsaicinoid production by fermentation and may also enable the use of synthetic biology to create a diversity of new compounds with potentially improved properties. This review summarises the current state of the art on the biosynthesis of capsaicinoid precursors in baker's yeast, Saccharomyces cerevisiae, and discusses bioengineering strategies for achieving total synthesis from sugar.

Transcriptional Regulation of Ripening in Chili Pepper Fruits (Capsicum spp.)

Chili peppers represent a very important horticultural crop that is cultivated and commercialized worldwide. The ripening process makes the fruit palatable, desirable, and attractive, thus increasing its quality and nutritional value. This process includes visual changes, such as fruit coloration, flavor, aroma, and texture. Fruit ripening involves a sequence of physiological, biochemical, and molecular changes that must be finely regulated at the transcriptional level. In this review, we integrate current knowledge about the transcription factors involved in the regulation of different stages of the chili pepper ripening process.

Patterns and compound specific stable carbon isotope analysis (δ13 C) of capsaicinoids in Cayenne chilli fruits of different ripening stages

INTRODUCTION

Capsaicinoids are alkaloids of high pungency which are exclusively formed by fruits of the genus Capsicum. Capsaicinoid content and composition of Capsicum fruits are influenced by ripening.

OBJECTIVE

Determination of changes in content and pattern of individual capsaicinoids in chilli pods with fruit ripening. Compound specific stable carbon isotope analysis (δ¹³ C values (‰), CSIA) was used for a better understanding of capsaicinoid development during fruit ripening.

METHODOLOGY

Cayenne chillies (Capsicum annuum) were grown in a glasshouse and harvested from different plants at four ripening stages (unripe, semi-ripe, ripe, overripe). Nine capsaicinoids (one verified by synthesis) were quantified by gas chromatography with mass spectrometry (GC-MS). For CSIA, an acetylation method for derivatising capsaicinoids was developed.

RESULTS

Variations in the patterns of the nine capsaicinoids were not relatable to a distinct ripening stage and also total contents varied extensively from plant to plant. However, changes in total capsaicinoid concentrations were systematic. In almost all plants, maximum values were reached in unripe fruits, then decreased to semi-ripe samples and increased again in the following ripening process. Likewise, δ¹³ C values of individual capsaicinoids were always by ~2‰ heavier in unripe than in semi-ripe or ripe fruits. However, direction of changes in sum-δ¹³ C values (‰) (taking contributions of all capsaicinoids together) could not be explained by corresponding variations in capsaicinoid concentrations.

CONCLUSIONS

Both quantification and δ¹³ C values (‰) verified the presence of ripening-related changes in the capsaicinoid content which may be caused by simultaneously proceeding reactions like synthesis, storage and degradation of capsaicinoids.

Flavor components, precursors, formation mechanisms, production and characterization methods: garlic, onion, and chili pepper flavors

There is an enormous demand in the food industry to shift toward natural flavors. However, most flavor molecules are significantly unstable outside their original sources. Moreover, limited studies are focused on the flavor formation mechanisms, regeneration methods, and stability, which could help facilitate this replacement by establishing a link between food processing conditions and flavor generation.This scoping review summarizes major findings related to the identification of garlic, onion, and chili pepper flavors and their precursor molecules, formation mechanisms, generation of flavors and precursors, characterization methods, and precursor stability under thermal food processing conditions. The findings confirmed that the allium flavors could be generated by alliin and isoalliin precursors through thermal processing. Also, the literature lacks detailed knowledge about chili pepper flavor's precursors, and only capsaicinoids have been reported as a thermally stable chili pepper flavor.Although numerous studies have focused on this area, there is still a lack of detailed applicable knowledge. Future investigations can be framed into (1) Development of efficient methods to generate flavors during food processing; (2) Improvement of flavors' stability; (3) Understanding the interactions of flavors and their precursors with other food ingredients and additives; and (4) Characterization of the organoleptic properties of flavors.

Capsaicin intake and oral carcinogenesis: A systematic review

Background

Chili is the most heavily and frequently consumed spice, either as a flavouring or colouring agent, and it is also a major source of pro-vitamin A, vitamin E and C. The main capsinoidcapsaicinoid found in chili peppers is capsaicin. It has been demonstrated that capsaicin acts as a cancer-suppressing agent through its antioxidant and anti-inflammatory effects, by blocking several signal transduction pathways. Oral squamous cell carcinoma is one of the most prevalent cancer worldwide. It is noteworthy that in countries where populations of diverse ethnic groups co-exist, differences have been observed in terms of incidence of oral cancer. The variances in their diet could explain, at least in part, these differences. The objective of this systematic review is to explore if there is evidence of a possible relationship between capsaicin intake and the incidence of oral squamous cell carcinoma, and discuss such association.

Material and Methods

A bibliographical search was made in PubMed, Scopus and Web of Science databases, and finally 7 experimental studies were included; OHAT risk of bias tool was used to assess their quality.

Results

allAll the studies confirm that capsaicin is a chemopreventive agent that prevents the development of oral cancer, through inhibition of malignant cell proliferation and increase of apoptosis.

Conclusions

More human studies are needed in order to clarify the real link between consumption of chili (capsaicin) and the prevalence of oral cancer.

Key words:Chili, capsaicin, oral epithelial dysplasia, oral cancer, cell proliferation, apoptosis.

Higher Bioavailability of Calcium in Chickens With a Novel In-Feed Pharmaceutical Formulation

Egg production and egg shell quality decrease toward the end of the first laying cycle in hens (approximately by week 80). Even so, farmers often choose to work a second cycle with them. Defective egg shell production has been mainly linked to a decrease in gastrointestinal absorption of calcium. Here we studied pharmaceutically-designed modified-release small pellets (FOLAs) containing calcium to improve calcium bioavailability (F). The influence of FOLA alone or with capsicum-oleoresin was studied in a total of 400 Bovans-White hens randomly divided into four groups of 20 laying hens each and with five replicates per group (n = 100) as follows: (1) control group (GC) receiving a diet containing basal levels of 4.1% of calcium-carbonate; (2) group GF treated as GC but with the same dose of calcium-carbonate in FOLA; (3) group GFc5 was treated as GF but with 6 ppm of capsicum-oleoresin (500,000 Scoville Heat Units [SHU]); and (4) group GFc10 treated as GFc5 but with 1,000,000 SHU capsicum-oleoresin. Plasma concentrations of calcium were determined during 5 days at predetermined times sampling more often on days 1 and 5 for blood plasma kinetics of calcium. Relative bioavailability (Fr) values based on the area under the serum calcium concentration vs. time curve (AUC) were obtained and compared to GC. The AUC was statistically different among all groups (P < 0.5), but the GFc10 had the greatest Fr (194%), with serum calcium concentrations ranging from 25.37 to 31.2 μg/dL. Calcium residence time (RT) between GC and GF showed no statistical differences while GFc5 and GFc10 had statistically superior RT values. Simultaneously, the number of shell-less eggs per group and their thickness was evaluated by utilizing the same groups but with 150 hens per group on 6 days. Shell-less eggs decreased to zero in Group GFc10 and produced eggs with the greatest shell thickness from day 2 onwards. The inclusion of calcium-carbonate in the pharmaceutical form FOLA induced higher serum calcium concentrations (GF, GFc5, and GFc10) particularly during the night-phase of the hen's cycle—this coincides with the time at which egg shell formation occurs.

Capsaicin—the major bioactive ingredient of chili peppers: bio-efficacy and delivery systems

The mechanisms of bio-efficacy of capsaicin and delivery systems with enhanced bioavailability were reviewed.

Milagro F, Sánchez J, de la Garza AL, Castro H. miRNAs and Novel Food Compounds Related to the Browning Process

Obesity prevalence is rapidly increasing worldwide. With the discovery of brown adipose tissue (BAT) in adult humans, BAT activation has emerged as a potential strategy for increasing energy expenditure. Recently, the presence of a third type of fat, referred to as beige or brite (brown in white), has been recognized to be present in certain kinds of white adipose tissue (WAT) depots. It has been suggested that WAT can undergo the process of browning in response to stimuli that induce and enhance the expression of thermogenesis: a metabolic feature typically associated with BAT. MicroRNAs (miRNAs) are small transcriptional regulators that control gene expression in a variety of tissues, including WAT and BAT. Likewise, it was shown that several food compounds could influence miRNAs associated with browning, thus, potentially contributing to the management of excessive adipose tissue accumulation (obesity) through specific nutritional and dietetic approaches. Therefore, this has created significant excitement towards the development of a promising dietary strategy to promote browning/beiging in WAT to potentially contribute to combat the growing epidemic of obesity. For this reason, we summarize the current knowledge about miRNAs and food compounds that could be applied in promoting adipose browning, as well as the cellular mechanisms involved.

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.

Insecticidal Activity of Natural Capsaicinoids Against Several Agricultural Insects

In this paper, the insecticidal activity of natural capsaicinoids (NC) and reference ingredients (imidacloprid, abamectin, and pyridaben, which are active ingredients of commercial pesticides) against 14 agricultural insects was studied in both the laboratory and field. The results of insecticidal activity in the laboratory showed that the median lethal concentration (LC50) and 90% lethal concentration values of the NC against 14 agricultural insects were greater than those of reference ingredients and the NC had a weaker relative toxicity than the corresponding reference ingredients. The NC showed impressive insecticidal activity when it was used to control Aphis gossypii from Cucumis sativus (LC50 152.82 mg L−1) but unimpressive insecticidal activity when used against Ectropis obliqua hypulina and Pieris rapae (LC50 1557.47 and 1502.48 mg L−1, respectively), which revealed that the insecticidal spectrum of NC was confined. Field experiments showed that the control effect of successively spraying the NC 2 times against insects was significantly higher than the effect of spraying 1 time.

Food Ingredients Involved in White-to-Brown Adipose Tissue Conversion and in Calorie Burning

Obesity is the consequence of chronic positive energy balance and considered a leading risk factor for cardiovascular and metabolic diseases. Due to its epidemic trends among children and adults, there is an increasing interest in implementing new therapeutic interventions to tackle overweight and obesity. Activation of brown adipose tissue (BAT) represents today a promising strategy to enhance energy expenditure (EE) through heat production. More recently, “browning” of white adipose tissue (WAT) has gained increasing attention in research area as an alternative method in stimulating energy dissipation. This minireview aims to summarize the current knowledge of some dietary compounds that have been shown to promote BAT activation and WAT browning with subsequent beneficial health effects.

Hesperidin and capsaicin, but not the combination, prevent hepatic steatosis and other metabolic syndrome-related alterations in western diet-fed rats

We aimed to assess the potential effects of hesperidin and capsaicin, independently and in combination, to prevent the development of obesity and its related metabolic alterations in rats fed an obesogenic diet. Three-month-old male Wistar rats were divided into 5 groups: Control (animals fed a standard diet), WD (animals fed a high fat/sucrose (western) diet), HESP (animals fed a western diet + hesperidin (100 mg/kg/day)), CAP (animals fed a western diet + capsaicin (4 mg/kg/day)), and HESP + CAP (animals fed a western diet + hesperidin (100 mg/kg/day) + capsaicin (4 mg/kg/day)). Hesperidin and capsaicin were administered by gavage. Capsaicin decreased body fat gain and prevented insulin resistance, whereas hesperidin showed little effect on body fat gain and no apparent effects on insulin resistance. No additive effects were observed with the combination. Capsaicin and hesperidin, separately, improved blood lipid profile, diminished hepatic lipid accumulation, and prevented non-alcoholic steatohepatitis in western diet-fed rats, but the combination showed lower effects. Hesperidin alone, and to a lesser extent capsaicin or the combination, displayed hypotensive effects in western diet-fed rats. In conclusion, capsaicin and hesperidin, separately, exhibit health beneficial effects on metabolic syndrome-related alterations in western diet-fed rats, but the effects are mitigated with the combination.

Molecular mechanisms of the anti-obesity effect of bioactive ingredients in common spices: a review

The mechanisms of the anti-obesity effects of bioactive compounds in common spices in adipocytes, animal models and human participants have been reviewed.

Capsaicin and nonivamide similarly modulate outcome measures of mitochondrial energy metabolism in HepG2 and 3T3-L1 cells

Nonivamide, a less pungent capsaicin analog, has similar effects on the outcome measures of energy metabolism to capsaicin.

Extraction, bioavailability, and bioefficacy of capsaicinoids

Capsaicinoids are active constituents responsible for the pungent and spicy flavor in chili peppers. During the past few decades, various extraction methods of capsaicinoids from peppers have been developed with high yields. Through biological studies, pharmacological benefits have been reported such as pain relief, antiinflammation, anticancer, cardioprotection, as well as weight loss. In this paper, the extraction methods and bioavailability of capsaicinoids are reviewed and discussed. In addition, the pharmacological effects and their underlying mechanisms are also studied.

Discovery of putative capsaicin biosynthetic genes by RNA-Seq and digital gene expression analysis of pepper

The Indian pepper ‘Guijiangwang’ (Capsicum frutescens L.), one of the world’s hottest chili peppers, is rich in capsaicinoids. The accumulation of the alkaloid capsaicin and its analogs in the epidermal cells of the placenta contribute to the pungency of Capsicum fruits. To identify putative genes involved in capsaicin biosynthesis, RNA-Seq was used to analyze the pepper’s expression profiles over five developmental stages. Five cDNA libraries were constructed from the total RNA of placental tissue and sequenced using an Illumina HiSeq 2000. More than 19 million clean reads were obtained from each library, and greater than 50% of the reads were assignable to reference genes. Digital gene expression (DGE) profile analysis using Solexa sequencing was performed at five fruit developmental stages and resulted in the identification of 135 genes of known function; their expression patterns were compared to the capsaicin accumulation pattern. Ten genes of known function were identified as most likely to be involved in regulating capsaicin synthesis. Additionally, 20 new candidate genes were identified related to capsaicin synthesis. We use a combination of RNA-Seq and DGE analyses to contribute to the understanding of the biosynthetic regulatory mechanism(s) of secondary metabolites in a nonmodel plant and to identify candidate enzyme-encoding genes.

Capsaicin: Current Understanding of Its Mechanisms and Therapy of Pain and Other Pre-Clinical and Clinical Uses

In this review, we discuss the importance of capsaicin to the current understanding of neuronal modulation of pain and explore the mechanisms of capsaicin-induced pain. We will focus on the analgesic effects of capsaicin and its clinical applicability in treating pain. Furthermore, we will draw attention to the rationale for other clinical therapeutic uses and implications of capsaicin in diseases such as obesity, diabetes, cardiovascular conditions, cancer, airway diseases, itch, gastric, and urological disorders.

(1) H and (13) C NMR data on natural and synthetic capsaicinoids

Capsaicinoids are the compounds responsible for the pungency of chili peppers. These substances have attracted the attention of many research groups in recent decades because of their antinociceptive, analgesic, anti-inflammatory, and anti-obesity properties, among others. There are nearly 160 capsaicinoids reported in the literature. Approximately 25 of them are natural products, while the rest are synthetic or semi-synthetic products. A large amount of NMR data for the capsaicinoids is dispersed throughout literature. Therefore, there is a need to organize all this NMR data in a systematic and orderly way. This review summarizes the (1) H and (13) C NMR data on 159 natural and synthetic capsaicinoids, with a brief discussion of some typical and relevant aspects of these NMR data. Copyright © 2015 John Wiley & Sons, Ltd.

Identification of QTLs for capsaicinoids, fruit quality, and plant architecture-related traits in an interspecific Capsicum RIL population

Quantitative trait loci (QTL) analyses in pepper are common for horticultural, disease resistance, and fruit quality traits; although none of the studies to date have used sequence-based markers associated with genes. In this study we measured plant architectural, phenological, and fruit quality traits in a pepper mapping population consisting of 92 recombinant inbred lines derived from a cross between Capsicum frutescens acc. 2814-6 and C. annuum var. NuMexRNAKY. Phenotypic measurements were correlated to loci in a high-density EST-based genetic map. In total, 96 QTL were identified for 38 traits, including 12 QTL associated with capsaicinoid levels. Twenty-one loci showed correlation among seemingly unrelated phenotypic categories, highlighting tight linkage or shared genetics between previously unassociated traits in pepper.

Molecular biology of capsaicinoid biosynthesis in chili pepper (Capsicum spp.)

Capsicum species produce fruits that synthesize and accumulate unique hot compounds known as capsaicinoids in placental tissues. The capsaicinoid biosynthetic pathway has been established, but the enzymes and genes participating in this process have not been extensively studied or characterized. Capsaicinoids are synthesized through the convergence of two biosynthetic pathways: the phenylpropanoid and the branched-chain fatty acid pathways, which provide the precursors phenylalanine, and valine or leucine, respectively. Capsaicinoid biosynthesis and accumulation is a genetically determined trait in chili pepper fruits as different cultivars or genotypes exhibit differences in pungency; furthermore, this characteristic is also developmentally and environmentally regulated. The establishment of cDNA libraries and comparative gene expression studies in pungent and non-pungent chili pepper fruits has identified candidate genes possibly involved in capsaicinoid biosynthesis. Genetic and molecular approaches have also contributed to the knowledge of this biosynthetic pathway; however, more studies are necessary for a better understanding of the regulatory process that accounts for different accumulation levels of capsaicinoids in chili pepper fruits.

Chemical and pharmacological aspects of capsaicin

Capsaicin is a unique alkaloid found primarily in the fruit of the Capsicum genus and is what provides its spicy flavor. Generally extracted directly from fruit, high demand has driven the use of established methods to increase production through extraction and characterization. Over time these methods have improved, usually be applying existing techniques in conjunction. An increasingly wide range of potential applications has increased interest in capsaicin. Especially compelling are the promising results of medical studies showing possible beneficial effects in many diseases. Capsaicin’s pungency has limited its use in clinical trials to support its biological activity. Characterization and extraction/ synthesis of non-pungent analogues is in progress. A review is made of capsaicin research focusing mainly on its production, synthesis, characterization and pharmacology, including some of its main potential clinical uses in humans.

Recent advances in the study on capsaicinoids and capsinoids

Chili peppers are the major source of nature capsaicinoids, which consist of capsaicin, dihydrocapsaicin, nordihydrocapsaicin, homodihydrocapsaicin, and homocapsaicin, etc. Capsaicinoids are found to exert multiple pharmacological and physiological effects including the activities of analgesia, anticancer, anti-inflammation, antioxidant and anti-obesity. Therefore, capsaicinoids may have the potential value in clinic for pain relief, cancer prevention and weight loss. In addition, capsaicinoids also display the benefits on cardiovascular and gastrointestinal system. It has been shown that capsaicinoids are potential agonists of capsaicin receptor or transient receptor potential vanilloid subfamily member 1 (TRPV1). They could exert the effects not only through the receptor-dependent pathway but also through the receptor-independent one. CH-19 Sweet peppers are the source of nature capsinoids, which share similar structure with capsaicinoids and consist of capsiate, dihydrocapsiate, and nordihydrocapsiate, etc, Comparing with capsaicinoids, capsinoids are less pungent and easily broken down in the normal aqueous conditions. So far, it has been found that capsinoids possess the biological properties of antitumor, antioxidant and anti-obesity. Since capsinoids are less toxic than capsaicinoids, therefore, capsinoids may have the advantages over capsaicinoids in clinical applications such as cancer prevention and weight loss.

Chili pepper fruits: content and pattern of capsaicinoids in single fruits of different ages

The content of capsaicinoids differs widely in fruits of an individual plant. This is shown for Capsicum annuum var. Cayenne and var. DeArbol and Capsicum frutescens var. Hot Siberian, respectively. Three age groups, (i) very young, (ii) medium age, and (iii) older fruits, were studied. A consistent dependence on the node position on the plant for fruit weight and capsaicinoid content of the individual fruits was not observed. These traits do not develop concomitantly and are influenced differently by environmental factors. Therefore, the expression as capsaicinoid content per fruit leads to a different conclusion than a comparison of concentration values (mg/kg). This is exemplified for C. frutescens var. Hot Siberian grown in two consecutive years with fruits of lower fruit weight but the same capsaicinoid accumulation in the second year. Higher values for pungency (expressed as mg/kg) would have been the result from the analysis of bulked material. The fatty acid pattern of capsaicinoids is uniform for all fruits from one plant, irrespective of the large variation of total capsaicinoid content.