Crocins with high levels of sugar conjugation contribute to the yellow colours of early-spring flowering crocus tepals

Comparative study on nutraceutical and sensorial characteristics of saffron (Crocus sativus L.) cultivated in Iran, Spain, and Türkiye

BACKGROUND

Quality properties of 14 saffron samples from Iran, Spain, and Türkiye were compared.

RESULTS

Significant differences were observed between anthocyanins, volatile compounds, fatty acids, total phenolic content, and antioxidant activity of saffron samples (P < 0.05). Besides, significant differences in color parameters were observed. Moreover, a total of 13 volatile compounds were identified in the saffron samples using. headspace-solid-phase microextraction-gas chromatography-mass spectrometry, safranal and α-isophorone being the two predominant aroma compounds. Regarding fatty acids, significant differences were seen in the fatty acid profiles of saffron samples (P < 0.05), while linoleic acid was the most concentrated fatty acid. In terms of sensory properties, different concentrations of safranal, α-isophorone and 4-ketoisophorone may lead to significant differences in the odor and taste attributes of saffron samples (P < 0.05).

CONCLUSION

Changes in corm origin along with climate and agricultural conditions may affect the quality characteristics of saffron cultivated in different geographical areas to a significant degree. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Metabolomic and transcriptomic analyses of yellow-flowered crocuses to infer alternative sources of saffron metabolites

BACKGROUND

The increasing demand for saffron metabolites in various commercial industries, including medicine, food, cosmetics, and dyeing, is driven by the discovery of their diverse applications. Saffron, derived from Crocus sativus stigmas, is the most expensive spice, and there is a need to explore additional sources to meet global consumption demands. In this study, we focused on yellow-flowering crocuses and examined their tepals to identify saffron-like compounds.

RESULTS

Through metabolomic and transcriptomic approaches, our investigation provides valuable insights into the biosynthesis of compounds in yellow-tepal crocuses that are similar to those found in saffron. The results of our study support the potential use of yellow-tepal crocuses as a source of various crocins (crocetin glycosylated derivatives) and flavonoids.

CONCLUSIONS

Our findings suggest that yellow-tepal crocuses have the potential to serve as a viable excessive source of some saffron metabolites. The identification of crocins and flavonoids in these crocuses highlights their suitability for meeting the demands of various industries that utilize saffron compounds. Further exploration and utilization of yellow-tepal crocuses could contribute to addressing the growing global demand for saffron-related products.

Saffron (Crocus sativus) and its constituents for pain management: A review of current evidence

Pain can become a chronic and deliberating experience with a significant burden. In preclinical and clinical studies, Saffron (Crocus sativus L.) has shown analgesic activities. Considering the unsatisfactory results of current therapeutic management for chronic pain conditions, we aimed to review saffron's analgesic activity and underlying mechanisms. Saffron showed antinociceptive activities in formalin-, carrageenan-, and capsaicin-induced experimental pain models. Saffron analgesic activities affected several targets, including ion channels of nociceptors; the adrenergic system and central histaminic system; inhibition of inflammatory pathways, apoptotic pathways, and oxidative stress; regulation of NO pathway, and the endocannabinoid system. Clinical studies showed analgesia of Saffron in rheumatoid arthritis, after-pain following childbirth, dysmenorrhea, and fibromyalgia. Our literature review showed that saffron can be beneficial as an adjunct therapy to commonly used analgesics in practice, particularly in chronic pain conditions.

Production of Saffron Apocarotenoids in Nicotiana benthamiana Plants Genome-Edited to Accumulate Zeaxanthin Precursor

Crocins are glycosylated apocarotenoids with strong coloring power and anti-oxidant, anticancer, and neuro-protective properties. We previously dissected the saffron crocin biosynthesis pathway, and demonstrated that the CsCCD2 enzyme, catalyzing the carotenoid cleavage step, shows a strong preference for the xanthophyll zeaxanthin in vitro and in bacterio. In order to investigate substrate specificity in planta and to establish a plant-based bio-factory system for crocin production, we compared wild-type Nicotiana benthamiana plants, accumulating various xanthophylls together with α- and β-carotene, with genome-edited lines, in which all the xanthophylls normally accumulated in leaves were replaced by a single xanthophyll, zeaxanthin. These plants were used as chassis for the production in leaves of saffron apocarotenoids (crocins, picrocrocin) using two transient expression methods to overexpress CsCCD2: agroinfiltration and inoculation with a viral vector derived from tobacco etch virus (TEV). The results indicated the superior performance of the zeaxanthin-accumulating line and of the use of the viral vector to express CsCCD2. The results also suggested a relaxed substrate specificity of CsCCD2 in planta, cleaving additional carotenoid substrates.

Saffron against Neuro-Cognitive Disorders: An Overview of Its Main Bioactive Compounds, Their Metabolic Fate and Potential Mechanisms of Neurological Protection

Saffron (Crocus sativus L.) is a spice used worldwide as a colouring and flavouring agent. Saffron is also a source of multiple bioactive constituents with potential health benefits. Notably, saffron displays consistent beneficial effects against a range of human neurological disorders (depression, anxiety, sleeping alterations). However, the specific compounds and biological mechanisms by which this protection may be achieved have not yet been elucidated. In this review, we have gathered the most updated evidence of the neurological benefits of saffron, as well as the current knowledge on the main saffron constituents, their bioavailability and the potential biological routes and postulated mechanisms by which the beneficial protective effect may occur. Our aim was to provide an overview of the neuroprotective effects attributed to this product and its main bioactive compounds and to highlight the main research gaps that need to be further pursued to achieve full evidence and understanding of the benefits of saffron. Overall, improved clinical trials and adequately designed pre-clinical studies are needed to support the evidence of saffron and of its main bioactive components (e.g., crocin, crocetin) as a therapeutic product to combat neurological disorders.

Farming for Pharming: Novel Hydroponic Process in Contained Environment for Efficient Pharma-Grade Production of Saffron

Soilless cultivation of saffron (Crocus sativus) in a controlled environment represents an interesting alternative to field cultivation, in order to obtain a standardized high-quality product and to optimize yields. In particular, pharma-grade saffron is fundamental for therapeutic applications of this spice, whose efficacy has been demonstrated in the treatment of macular diseases, such as Age-related Macular Degeneration (AMD). In this work, a hydroponic cultivation system was developed, specifically designed to meet the needs of C. sativus plant. Various cultivation recipes, different in spectrum and intensity of lighting, temperature, photoperiod and irrigation, have been adopted to study their effect on saffron production. The experimentation involved the cultivation of corms from two subsequent farm years, to identify and validate the optimal conditions, both in terms of quantitative yield and as accumulation of bioactive metabolites, with particular reference to crocins and picrocrocin, which define the 'pharma-grade' quality of saffron. Through HPLC analysis and chromatography it was possible to identify the cultivation parameters suitable for the production of saffron with neuroprotective properties, evaluated by comparison with an ISO standard and the REPRON^® procedure. Furthermore, the biochemical characterization was completed through NMR and high-resolution mass spectrometry analyses of saffron extracts. The whole experimental framework allowed to establish an optimized protocol to produce pharma-grade saffron, allowing up to 3.2 g/m² harvest (i.e., more than three times higher than field production in optimal conditions), which meets the standards of composition for the therapy of AMD.

Novel Insight into the Volatile Profile and Antioxidant Properties of Crocus sativus L. Flowers

The current production system of saffron spice generates hundreds of tons of waste. Thus, the aim of this study was to value both saffron and its floral by-products as a source of natural bioactive extracts, studying the in vitro antioxidant capacity, the composition of the volatile fraction by GC-MS/MS, and the determination of crocetins esters by HPLC-PDA. Saffron stigmas and floral by-products showed a high content of polyphenols and different antioxidant properties. Floral bio-residues (tepals, stamens, and styles) presented a high concentration of anthocyanins, and stigmas had high levels of flavonoids, β-carotene, and total crocins. In stigmas, 25 different volatile components were found, with safranal the most relevant. Floral by-products volatile composition consisted of 55 compounds with varying amounts depending on the drying treatment; all the samples presented acetic acid, 2(5H)-furanone, and phenylethyl alcohol. Therefore, saffron stigmas and flower by-products represent a sustainable source of bioactive ingredients for innovative healthy food formulations.

Gene prediction for leaf margin phenotype and fruit flesh color in pineapple (Ananas comosus) using haplotype-resolved genome sequencing

Pineapple (Ananas comosus (L.) Merr.) is one of the most economically important tropical fruit species. The major aim of the breeding programs in several countries, including Japan, is quality improvement, mainly for the fresh market. ‘Yugafu’, a Japanese cultivar with distinctive pipe-type leaf margin phenotype and white flesh color, is popular for fresh consumption. Therefore, genome sequencing of ‘Yugafu’ is expected to assist pineapple breeding. Here, we developed a haplotype-resolved assembly for the heterozygous genome of ‘Yugafu’ using long-read sequencing technology and obtained a pair of 25 pseudomolecule sequences inherited from the parental accessions ‘Cream pineapple’ and ‘HI101’. The causative genes for leaf margin and fruit flesh color were identified. Fine mapping revealed a 162-kb region on CLG23 for the leaf margin phenotype. In this region, 20 kb of inverted repeat was specifically observed in the ‘Cream pineapple’ derived allele, and the WUSCHEL-related homeobox 3 (AcWOX3) gene was predicted as the key gene for leaf margin morphogenesis. Dominantly repressed AcWOX3 via RNAi was suggested to be the cause of the pipe-type leaf margin phenotype. Quantitative trait locus (QTL) analysis revealed that the terminal region of CLG08 contributed to white flesh and low carotenoid content. Carotenoid cleaved dioxygenase 4 (AcCCD4), a key gene for carotenoid degradation underlying this QTL, was predicted as the key gene for white flesh color through expression analysis. These findings could assist in modern pineapple breeding and facilitate marker-assisted selection for important traits.

A New Glycosyltransferase Enzyme from Family 91, UGT91P3, Is Responsible for the Final Glucosylation Step of Crocins in Saffron (Crocus sativus L.)

Crocetin is an apocarotenoid formed from the oxidative cleavage of zeaxanthin, by the carotenoid cleavage enzymes CCD2 (in Crocus species) and specific CCD4 enzymes in Buddleja davidii and Gardenia jasminoides. Crocetin accumulates in the stigma of saffron in the form of glucosides and crocins, which contain one to five glucose molecules. Crocetin glycosylation was hypothesized to involve at least two enzymes from superfamily 1 UDP-sugar dependent glycosyltransferases. One of them, UGT74AD1, produces crocins with one and two glucose molecules, which are substrates for a second UGT, which could belong to the UGT79, 91, or 94 families. An in silico search of Crocus transcriptomes revealed six candidate UGT genes from family 91. The transcript profiles of one of them, UGT91P3, matched the metabolite profile of crocin accumulation, and were co-expressed with UGT74AD1. In addition, both UGTs interact in a two-hybrid assay. Recombinant UGT91P3 produced mostly crocins with four and five glucose molecules in vitro, and in a combined transient expression assay with CCD2 and UGT74AD1 enzymes in Nicotiana benthamiana. These results suggest a role of UGT91P3 in the biosynthesis of highly glucosylated crocins in saffron, and that it represents the last missing gene in crocins biosynthesis.

Identification and characterization of apocarotenoid modifiers and carotenogenic enzymes for biosynthesis of crocins in Buddleja davidii flowers

Crocetin biosynthesis in Buddleja davidii flowers proceeds through a zeaxanthin cleavage pathway catalyzed by two carotenoid cleavage dioxygenases (BdCCD4.1 and BdCCD4.3), followed by oxidation and glucosylation reactions that lead to the production of crocins. We isolated and analyzed the expression of 12 genes from the carotenoid pathway in B. davidii flowers and identified four candidate genes involved in the biosynthesis of crocins (BdALDH, BdUGT74BC1, BdUGT74BC2, and BdUGT94AA3). In addition, we characterized the profile of crocins and their carotenoid precursors, following their accumulation during flower development. Overall, seven different crocins, crocetin, and picrocrocin were identified in this study. The accumulation of these apocarotenoids parallels tissue development, reaching the highest concentration when the flower is fully open. Notably, the pathway was regulated mainly at the transcript level, with expression patterns of a large group of carotenoid precursor and apocarotenoid genes (BdPSY2, BdPDS2, BdZDS, BdLCY2, BdBCH, BdALDH, and BdUGT Genes) mimicking the accumulation of crocins. Finally, we used comparative correlation network analysis to study how the synthesis of these valuable apocarotenoids diverges among B. davidii, Gardenia jasminoides, and Crocus sativus, highlighting distinctive differences which could be the basis of the differential accumulation of crocins in the three species.

Efficient production of saffron crocins and picrocrocin in Nicotiana benthamiana using a virus-driven system

Crocins and picrocrocin are glycosylated apocarotenoids responsible, respectively, for the color and the unique taste of the saffron spice, known as red gold due to its high price. Several studies have also shown the health-promoting properties of these compounds. However, their high costs hamper the wide use of these metabolites in the pharmaceutical sector. We have developed a virus-driven system to produce remarkable amounts of crocins and picrocrocin in adult Nicotiana benthamiana plants in only two weeks. The system consists of viral clones derived from tobacco etch potyvirus that express specific carotenoid cleavage dioxygenase (CCD) enzymes from Crocus sativus and Buddleja davidii. Metabolic analyses of infected tissues demonstrated that the sole virus-driven expression of C. sativus CsCCD2L or B. davidii BdCCD4.1 resulted in the production of crocins, picrocrocin and safranal. Using the recombinant virus that expressed CsCCD2L, accumulations of 0.2% of crocins and 0.8% of picrocrocin in leaf dry weight were reached in only two weeks. In an attempt to improve apocarotenoid content in N. benthamiana, co-expression of CsCCD2L with other carotenogenic enzymes, such as Pantoea ananatis phytoene synthase (PaCrtB) and saffron β-carotene hydroxylase 2 (BCH2), was performed using the same viral system. This combinatorial approach led to an additional crocin increase up to 0.35% in leaves in which CsCCD2L and PaCrtB were co-expressed. Considering that saffron apocarotenoids are costly harvested from flower stigma once a year, and that Buddleja spp. flowers accumulate lower amounts, this system may be an attractive alternative for the sustainable production of these appreciated metabolites.

A review of medicinal plant of Middle East and North Africa (MENA) region as source in tuberculosis drug discovery

Tuberculosis (TB) is a disease that affects one-third of the world's population. Although currently available TB drugs have many side effects, such as nausea, headache and gastrointestinal discomfort, no new anti-TB drugs have been produced in the past 30 years. Therefore, the discovery of a new anti-TB agent with minimal or no side effects is urgently needed. Many previous works have reported the effects of medicinal plants against Mycobacterium tuberculosis (MTB). However, none have focused on medicinal plants from the Middle Eastern and North African (MENA) region. This review highlights the effects of medicinal plants from the MENA region on TB. Medicinal plants from the MENA region have been successfully used as traditional medicine and first aid against TB related problems. A total of 184 plants species representing 73 families were studied. Amongst these species, 93 species contained more active compounds with strong anti-MTB activity (crude extracts and/or bioactive compounds with activities of 0-100 µg/ml). The extract of Inula helenium, Khaya senegalensis, Premna odorata and Rosmarinus officinalis presented the strongest anti-MTB activity. In addition, Boswellia papyrifera (Del) Hochst olibanum, Eucalyptus camaldulensis Dehnh leaves (river red gum), Nigella sativa (black cumin) seeds and genus Cymbopogon exhibited anti-TB activity. The most potent bioactive compounds included alantolactone, octyl acetate, 1,8-cineole, thymoquinone, piperitone, α- verbenol, citral b and α-pinene. These compounds affect the permeability of microbial plasma membranes, thus kill the mycobacterium spp. As a conclusion, plant species collected from the MENA region are potential sources of novel drugs against TB.

Heterologous expression of xanthophyll esterase genes affects carotenoid accumulation in petunia corollas

The majority of carotenoids in petals are xanthophylls and most of these xanthophylls are esterified with fatty acids. Although petunia (Petunia x hybrida) is an important ornamental plant, it cannot accumulate enough carotenoids to have deep-yellow flowers. Our previous study suggested that low esterification activity causes low carotenoid accumulation in petunia corollas. Here, we introduced xanthophyll esterase (XES) from the petals of Ipomoea obscura, tomato (Solanum lycopersicum), and marigold (Tagetes erecta) into a pale-yellow-flowered cultivar of petunia to see whether these affect carotenoid accumulation in petunia corollas. Carotenoid contents and the proportions of esterified xanthophylls were elevated in the corollas of XES-overexpressing (XES-OX) transformants. Expression analysis showed that the transcript levels of endogenous carotenoid biosynthetic genes, which included geranylgeranyl diphosphate synthase 2, ζ-carotene desaturase, and lycopene β-ring cyclase in corolla tubes were upregulated in XES-OX plants. In addition, we discovered a difference in the composition of esterified xanthophylls among XES-OX plants, which may be caused by differences in the substrate specificity of their respective XESs. We conclude that esterification is an important process for carotenoid accumulation and XES is a useful tool for the quantitative and qualitative control of carotenoid accumulation in petals.

UGT709G1: a novel uridine diphosphate glycosyltransferase involved in the biosynthesis of picrocrocin, the precursor of safranal in saffron (Crocus sativus)

Saffron, a spice derived from the dried red stigmas of Crocus sativus, is one of the oldest natural food additives. The flowers have long red stigmas, which store significant quantities of the glycosylated apocarotenoids crocins and picrocrocin. The apocarotenoid biosynthetic pathway in saffron starts with the oxidative cleavage of zeaxanthin, from which crocins and picrocrocin are derived. In the processed stigmas, picrocrocin is converted to safranal, giving saffron its typical aroma. By a targeted search for differentially expressed uridine diphosphate glycosyltransferases (UGTs) in Crocus transcriptomes, a novel apocarotenoid glucosyltransferase (UGT709G1) from saffron was identified. Biochemical analyses revealed that UGT709G1 showed a high catalytic efficiency toward 2,6,6-trimethyl-4-hydroxy-1-carboxaldehyde-1-cyclohexene (HTCC), making it suited for the biosynthesis of picrocrocin, the precursor of safranal. The role of UGT709G1 in picrocrocin/safranal biosynthesis was supported by the absence or presence of gene expression in a screening for HTCC and picrocrocin production in different Crocus species and by a combined transient expression assay with CsCCD2L in Nicotiana benthamiana leaves. The identification of UGT709G1 completes one of the most highly valued specialized metabolic biosynthetic pathways in plants and provides novel perspectives on the industrial production of picrocrocin to be used as a flavor additive or as a pharmacological constituent.

In-depth analysis of crocetin ester glycosides from dried/processed stigmas of Crocus sativus L. by HPLC-ESI-MSn (n = 2, 3)

INTRODUCTION

Saffron stigmas from Crocus sativus L. (Iridaceae) are used as a drug in folk medicine, as a food additive and as a dying agent for at least 3500 years. Despite this long-term use the chemical composition of saffron seems still to be not fully known.

OBJECTIVE

An analytical strategy for detailed investigations of aqueous saffron extract is developed based on reverse-phase high-performance liquid chromatography electrospray ionisation (HPLC-ESI) multistage mass spectrometry (MSⁿ ) for crocins.

METHODS

Commercially available stigmas are analysed by reverse-phase HPLC in combination with ESI/three-dimensional (3D)-ion trap mass spectrometry (MS) and MSⁿ (n = 2 and 3). Sodium chloride is added to the analyte solution ready for injection to promote abundant [M + Na]⁺ adduct ions of crocins, being ideal precursor ions for low-energy collision-induced dissociation (CID)-MS^2/3 .

RESULTS

This strategy allows the detailed structural elucidation of known as well as previously unknown crocin derivatives (molecular mass of the aglycon, oligosaccharide chain length and linkage determination). The two isomeric trisaccharide substituents neapolitanose and gentiotriose are distinguished based on linkage-specific cross-ring cleavage for the first time. Furthermore, crocins containing up to six hexose units are also observed. Five novel crocin ester glycosides shifted by a mass difference of -40 Da indicate the presence of the here newly described C₁₇ -aglycon, termed norcrocetin (crocetin = C₂₀ ).

CONCLUSIONS

These findings indicate the action of at least two different carotenoid cleavage dioxygenases (CCD2 and tentatively CCD4) during biosynthesis of this new bis-apocarotenoid aglycon (norcrocetin) and the existence of even higher glycosylated crocin derivatives at trace level.

Multi-species transcriptome analyses for the regulation of crocins biosynthesis in Crocus

BACKGROUND

Crocins are soluble apocarotenoids that mainly accumulate in the stigma tissue of Crocus sativus and provide the characteristic red color to saffron spice, in addition to being responsible for many of the medicinal properties of saffron. Crocin biosynthesis and accumulation in saffron is developmentally controlled, and the concentration of crocins increases as the stigma develops. Until now, little has been known about the molecular mechanisms governing crocin biosynthesis and accumulation. This study aimed to identify the first set of gene regulatory processes implicated in apocarotenoid biosynthesis and accumulation.

RESULTS

A large-scale crocin-mediated RNA-seq analysis was performed on saffron and two other Crocus species at two early developmental stages coincident with the initiation of crocin biosynthesis and accumulation. Pairwise comparison of unigene abundance among the samples identified potential regulatory transcription factors (TFs) involved in crocin biosynthesis and accumulation. We found a total of 131 (up- and downregulated) TFs representing a broad range of TF families in the analyzed transcriptomes; by comparison with the transcriptomes from the same developmental stages from other Crocus species, a total of 11 TF were selected as candidate regulators controlling crocin biosynthesis and accumulation.

CONCLUSIONS

Our study generated gene expression profiles of stigmas at two key developmental stages for apocarotenoid accumulation in three different Crocus species. Differential gene expression analyses allowed the identification of transcription factors that provide evidence of environmental and developmental control of the apocarotenoid biosynthetic pathway at the molecular level.

Rapid isolation and characterization of crocins, picrocrocin, and crocetin from saffron using centrifugal partition chromatography and LC-MS

This study demonstrates a simple method for one-step isolation of the main secondary metabolites of a hydroalcoholic extract of Crocus sativus stigmas (saffron) using step-gradient centrifugal partition chromatography. The analysis was performed in dual and elution-extrusion mode, using five biphasic systems of the solvents heptane/ethyl acetate/butanol/ethanol/water in ratios of 4:10:0:4:10, 1:13:0:4:10, 1:12:1:4:10, 1:10:3:4:10, and 1:7:6:4:10. Five major crocins, picrocrocin, and crocetin were directly isolated in one step. Scaling up to preparative level, allowed the recovery of significantly high quantities of pure compounds, especially trans-crocin-4, saffron's principal crocin. Comparing dual-mode and elution-extrusion, in dual-mode, the trans-crocin-4 containing fractions were co-eluted with a high amount of free β-d-glucose. In contrast, absence of free β-d-glucose was observed in the corresponding trans-crocin-4 fractions obtained by the second method denoting its superiority against dual-mode. Initiating analysis with the 4^th solvent-system afforded selective isolation of trans-crocin-4, with reduction in experimental time and solvent consumption. Structure elucidation was performed by nuclear magnetic resonance spectroscopy, liquid chromatography with mass spectrometry, and high-resolution tandem mass spectrometry. The proposed methodology comprises an integrated approach for the purification and characterization of biologically active saffron components in a fast, selective, and environmentally friendly manner.

Transcriptome analysis in tissue sectors with contrasting crocins accumulation provides novel insights into apocarotenoid biosynthesis and regulation during chromoplast biogenesis

Crocins, the red soluble apocarotenoids of saffron, accumulate in the flowers of Crocus species in a developmental and tissue-specific manner. In Crocus sieberi, crocins accumulate in stigmas but also in a distinct yellow tepal sector, which we demonstrate contains chromoplast converted from amyloplasts. Secondary metabolites were analysed by LC-DAD-HRMS, revealing the progressive accumulation of crocetin and crocins in the yellow sector, which were also localized in situ by Raman microspectroscopy. To understand the underlying mechanisms of crocin biosynthesis, we sequenced the C. sieberi tepal transcriptome of two differentially pigmented sectors (yellow and white) at two developmental stages (6 and 8) by Illumina sequencing. A total of 154 million high-quality reads were generated and assembled into 248,099 transcripts. Differentially expressed gene analysis resulted in the identification of several potential candidate genes involved in crocin metabolism and regulation. The results provide a first profile of the molecular events related to the dynamics of crocetin and crocin accumulation during tepal development, and present new information concerning apocarotenoid biosynthesis regulators and their accumulation in Crocus. Further, reveals genes that were previously unknown to affect crocin formation, which could be used to improve crocin accumulation in Crocus plants and the commercial quality of saffron spice.

Evolutionarily distinct carotenoid cleavage dioxygenases are responsible for crocetin production in Buddleja davidii

Crocetin, one of the few colored apocarotenoids known in nature, is present in flowers and fruits and has long been used medicinally and as a colorant. Saffron is the main source of crocetin, although a few other plants produce lower amounts of this apocarotenoid. Notably, Buddleja davidii accumulates crocetin in its flowers. Recently, a carotenoid dioxygenase cleavage enzyme, CCD2, has been characterized as responsible for crocetin production in Crocus species. We searched for CCD2 homologues in B. davidii and identified several CCD enzymes from the CCD1 and CCD4 subfamilies. Unexpectedly, two out of the three CCD4 enzymes, namely BdCCD4.1 and BdCCD4.3, showed 7,8;7',8' activity in vitro and in vivo over zeaxanthin. In silico analyses of these enzymes and CCD2 allowed the determination of key residues for this activity. Both BdCCD4 genes are highly expressed during flower development and transcripts levels parallel the accumulation of crocins in the petals. Phylogenetic analysis showed that BdCCD4.2 grouped with almost all the characterized CCD4 enzymes, while BdCCD4.1 and BdCCD4.3 form a new sub-cluster together with CCD4 enzymes from certain Lamiales species. The present study indicates that convergent evolution led to the acquisition of 7,8;7',8' apocarotenoid cleavage activity in two separate CCD enzyme families.

Unraveling Massive Crocins Transport and Accumulation through Proteome and Microscopy Tools during the Development of Saffron Stigma

Crocins, the glucosides of crocetin, are present at high concentrations in saffron stigmas and accumulate in the vacuole. However, the biogenesis of the saffron chromoplast, the changes during the development of the stigma and the transport of crocins to the vacuole, are processes that remain poorly understood. We studied the process of chromoplast differentiation in saffron throughout stigma development by means of transmission electron microscopy. Our results provided an overview of a massive transport of crocins to the vacuole in the later developmental stages, when electron dense drops of a much greater size than plastoglobules (here defined "crocinoplast") were observed in the chromoplast, connected to the vacuole with a subsequent transfer of these large globules inside the vacuole. A proteome analysis of chromoplasts from saffron stigma allowed the identification of several well-known plastid proteins and new candidates involved in crocetin metabolism. Furthermore, expressions throughout five developmental stages of candidate genes responsible for carotenoid and apocarotenoid biogenesis, crocins transport to the vacuole and starch metabolism were analyzed. Correlation matrices and networks were exploited to identify a series of transcripts highly associated to crocetin (such as 1-Deoxy-d-xylulose 5-phosphate synthase (DXS), 1-Deoxy-d-xylulose 5-phosphate reductoisomerase (DXR), carotenoid isomerase (CRTISO), Crocetin glucosyltransferase 2 (UGT2), etc.) and crocin (e.g., ζ-carotene desaturase (ZDS) and plastid-lipid-associated proteins (PLAP2)) accumulation; in addition, candidate aldehyde dehydrogenase (ADH) genes were highlighted.

Carotenoid Cleavage Oxygenases from Microbes and Photosynthetic Organisms: Features and Functions

Apocarotenoids are carotenoid-derived compounds widespread in all major taxonomic groups, where they play important roles in different physiological processes. In addition, apocarotenoids include compounds with high economic value in food and cosmetics industries. Apocarotenoid biosynthesis starts with the action of carotenoid cleavage dioxygenases (CCDs), a family of non-heme iron enzymes that catalyze the oxidative cleavage of carbon-carbon double bonds in carotenoid backbones through a similar molecular mechanism, generating aldehyde or ketone groups in the cleaving ends. From the identification of the first CCD enzyme in plants, an increasing number of CCDs have been identified in many other species, including microorganisms, proving to be a ubiquitously distributed and evolutionarily conserved enzymatic family. This review focuses on CCDs from plants, algae, fungi, and bacteria, describing recent progress in their functions and regulatory mechanisms in relation to the different roles played by the apocarotenoids in these organisms.

Intron retention and rhythmic diel pattern regulation of carotenoid cleavage dioxygenase 2 during crocetin biosynthesis in saffron

The carotenoid cleavage dioxygenase 2, a new member of the CCD family, catalyzes the conversion of zeaxanthin into crocetin-dialdehyde in Crocus. CCD2 is expressed in flowers, being responsible for the yellow, orange and red colorations displayed by tepals and stigma. Three CsCCD2 genes were identified in Crocus sativus, the longest contains ten exons and the shorter is a truncated copy with no introns and which lacks one exon sequence. Analysis of RNA-seq datasets of three developmental stages of saffron stigma allowed the determination of alternative splicing in CsCCD2, being intron retention (IR) the prevalent form of alternative splicing in CsCCD2. Further, high IR was observed in tissues that do not accumulate crocetin. The analysis of one CsCCD2 promoter showed cis-regulatory motifs involved in the response to light, temperature, and circadian regulation. The light and circadian regulation are common elements shared with the previously characterized CsLycB2a promoter, and these shared common cis-acting elements may represent binding sites for transcription factors responsible for co-regulation of these genes during the development of the stigma in saffron. A daily coordinated rhythmic regulation for CsCCD2 and CsLycB2a was observed, with higher levels of mRNA occurring at low temperatures during darkness, confirming the results obtained in the in silico promoter analysis. In addition, to the light and temperature dependent regulation of CsCCD2 expression, the apocarotenoid β-cyclocitral up-regulated CsCCD2 expression and could acts as a mediator of chromoplast-to-nucleus signalling, coordinating the expression of CsCCD2 with the developmental state of the chromoplast in the developing stigma.

PEG functionalized selenium nanoparticles as a carrier of crocin to achieve anticancer synergism

Schematic representation of crocin extraction from saffron stigmas and possible mechanism of pH based crocin delivery system of PEG-SeNP induced apoptosis in lung cancer cell.

The carotenoid cleavage dioxygenase CCD2 catalysing the synthesis of crocetin in spring crocuses and saffron is a plastidial enzyme

The apocarotenoid crocetin and its glycosylated derivatives, crocins, confer the red colour to saffron. Crocetin biosynthesis in saffron is catalysed by the carotenoid cleavage dioxygenase CCD2 (AIG94929). No homologues have been identified in other plant species due to the very limited presence of crocetin and its derivatives in the plant kingdom. Spring Crocus species with yellow flowers accumulate crocins in the stigma and tepals. Four carotenoid CCDs, namely CaCCD1, CaCCD2 and CaCCD4a/b and CaCCD4c were first cloned and characterized. CaCCD2 was localized in plastids, and a longer CCD2 version, CsCCD2L, was also localized in this compartment. The activity of CaCCD2 was assessed in Escherichia coli and in a stable rice gene function characterization system, demonstrating the production of crocetin in both systems. The expression of all isolated CCDs was evaluated in stigma and tepals at three key developmental stages in relation with apocarotenoid accumulation. CaCCD2 expression parallels crocin accumulation, but C14 apocarotenoids most likely are associated to the CaCCD1 activity in Crocus ancyrensis flowers. The specific CCD2 localization and its membrane interaction will contribute to the development of a better understanding of the mechanism of crocetin biosynthesis and regulation in the chromoplast.

Saffron: Its Phytochemistry, Developmental Processes, and Biotechnological Prospects

The present state of knowledge concerning developmental processes and the secondary metabolism of saffron, Crocus sativus L. (Iridaceae), along with the genes involved in these processes so far known, is reviewed. Flowers and corms constitute the most valuable parts of saffron. Corm and flower development are two key aspects to be studied in saffron to increase the yield and quality of the spice, to raise its reproductive rate, and to implement new production systems. Important knowledge about the physiology of flowering and vegetative growth has been acquired in recent years, but there is still only limited information on molecular mechanisms controlling these processes. Although some genes involved in flower formation and meristem transition in other species have been isolated in saffron, the role of these genes in this species awaits further progress. Also, genes related with the synthesis pathway of abscisic acid and strigolactones, growth regulators related with bud endodormancy and apical dominance (paradormancy), have been isolated. However, the in-depth understanding of these processes as well as of corm development is far from being achieved. By contrast, saffron phytochemicals have been widely studied. The different flower tissues and the corm have been proved to be an important source of phytochemicals with pharmacological properties. The biotechnological prospects for saffron are here reviewed on the basis of the discovery of the enzymes involved in key aspects of saffron secondary metabolism, and we also analyze the possibility of transferring current knowledge about flowering and vegetative propagation in model species to the Crocus genus.

Petals of Crocus sativus L. as a potential source of the antioxidants crocin and kaempferol

Saffron from the province of L'Aquila, in the Abruzzo region of Italy, is highly prized and has been awarded a formal recognition by the European Union with EU Protected Designation of Origin (PDO) status. Despite this, the saffron regions are abandoned by the younger generations because the traditional cultivation of saffron (Crocus sativus L.) is labour intensive and yields only one crop of valuable saffron stamens per year. Petals of the saffron Crocus have had additional uses in traditional medicine and may add value to the crops for local farmers. This is especially important because the plant only flowers between October and November, and farmers will need to make the best use of the flowers harvested in this period. Recently, the petals of C. sativus L., which are considered a waste material in the production of saffron spice, were identified as a potential source of natural antioxidants. The antioxidants crocin and kaempferol were purified by flash column chromatography, and identified by thin layer chromatography (TLC), HPLC-DAD, infrared (IR), and nuclear magnetic resonance ((1)H &(13)C NMR) spectroscopy. The antioxidant activity was determined with the ABTS and DPPH tests. The antioxidant activities are mainly attributed to carotenoid and flavonoid compounds, notably glycosides of crocin and kaempferol. We found in dried petals 0.6% (w/w) and 12.6 (w/w) of crocin and kaempferol, respectively. Petals of C. sativus L. have commercial potential as a source for kaempferol and crocetin glycosides, natural compounds with antioxidant activity that are considered to be the active ingredients in saffron-based herbal medicine.

Structural characterization of highly glucosylated crocins and regulation of their biosynthesis during flower development in Crocus

Crocin biosynthesis in Crocus has been proposed to proceed through a zeaxanthin cleavage pathway catalyzed by carotenoid cleavage dioxygenase 2 (CCD2), and followed by glucosylation reactions catalyzed by CsGT2 (UGT74AD1). In Crocus ancyrensis flowers, crocins with eight (crocin-1), seven (crocin-2), and six glucose (crocin-3) moieties accumulated both in stigma and tepals. We have characterized the structure of these highly glucosylated crocins and follow up their accumulation by high-resolution liquid chromatography coupled with diode array detector along the development of both tissues, and coupled to the isolation and analysis of the expression of eighteen genes (PSY-I, PSY-II, PDS-(I-V), ISO-ZDS, ZDS, CtrISO, LYC-I and II, BCH, CaCCD2, UGT74AD2-5) related with the apocarotenoid metabolism in C. ancyrensis tepals and stigmas. Structure elucidation of crocin-1 and crocin-2 was done by the combined use of 1D and 2D [(1)H, (1)H] (gCOSY and TOCSY and ROESY) and [(1)H-(13)C] NMR experiments, revealing that for crocin-1 was all-trans-crocetin O-[β-D- Glucopyranosyl)-(1→4)-(β-D-glucopyranosyl)-(1→2)]-O-[β-D-glucopyranosyl-(1→6)]-β-D-glucopyranosyl diester, while crocin-2 showed an identical structure except for the absence of one glucose residue in one end of the molecule. Crocins accumulation was not synchronically regulated in stigma and tepals, although in both cases crocins accumulation parallels tissue development, decreasing at anthesis. The expression of the carotenogenic genes PSY, ZDS-V, BCH, and LCY-II was correlated with crocins accumulation. In addition, CaCCD2 and only one of the four glucosyltransferase encoding genes, UGT74AD2, were highly expressed, and the expression was correlated with high levels of crocins accumulation in stigma and tepals.