Blue Flowers Research Articles

Cold plasma at various voltage, gas flow rate, and time assisted extraction of blue pea flower: Quantitative UPLC-ESI/MS/MS analysis of bioactive compounds, phenolics, and anthocyanin content

Butterfly pea (Clitoria ternatea) is a rich source of anthocyanins and has gained popularity as an herbal tea. This study aimed to investigate the effects of sample preparation (powder vs. aqueous solution) and cold plasma treatment (with varying voltages, times, and gas flow rates) on the extractability and stability of bioactive compounds in butterfly pea flowers. Quantitative analysis using liquid chromatography-tandem mass spectrometry was conducted to assess the yield, bioactive compounds, and composition of the extracts. Additionally, response surface methodology and principal component analysis (PCA) were employed to elucidate the impact of experimental variables on extract characteristics. Results indicated significant concentrations of delphinidin, cyanidin, and their derivatives in all extracts. Aqueous samples treated at higher voltages and for longer durations exhibited increased total anthocyanin (+92 % for 5 min at 180 V) and phenolic content (+32 % for 3 min at 100 V). PCA revealed strong correlations between independent variables and biochemical properties, highlighting the importance of optimizing treatment parameters. Furthermore, anthocyanins with increased side chains were observed to be more resistant to degradation under gas flow rate and plasma effects. Powder samples experienced more significant degradation due to increased free radical generation. These findings elucidated the interaction between plasma and the plant matrix, demonstrating the potential of cold plasma technology for enhancing extraction and promoting more sustainable food production.

Clitoria ternatea L. (Butterfly Pea) Flower Against Endometrial Pain: Integrating Preliminary In Vivo and In Vitro Experimentations Supported by Network Pharmacology, Molecular Docking, and Molecular Dynamics Simulation Studies

Clitoria ternatea L. (CT) is a perennial herbaceous plant with deep blue flowers native to tropical Asia. This work explores the endometrial pain (EP) regulation of CT flower through a multifaceted approach. Phytochemical screening unveiled the presence of alkaloids, steroids, flavonoids, glycosides, and tannins in CT flower methanolic extract (ME). In the in vitro membrane stabilizing experiment, the ME demonstrated 91.47% suppression of heat-induced hemolysis. Upon carrageenan-induced paw edema assay conducted on male Swiss albino mice at doses of 200 mg/kg and 400 mg/kg, 65.28% and 81.89% inhibition rates, respectively, of paw edema were reported. For the same doses, upon acetic acid-induced-writhing assay, 75.6% and 76.78% inhibition rates, respectively, were observed. For network pharmacology analyses, a protein–protein interaction network was constructed for 92 overlapping gene targets of CT and EP, followed by GO and KEGG pathway enrichment analyses. Network pharmacology-based investigation identified the anti-EP activity of CT to be mostly regulated by the proteins SRC homology, ESR1, and PI3KR1. Physicochemical, pharmacokinetic, and toxicity property predictions for the compounds with stable ligand–target interactions and a molecular dynamics simulation for the highest interacting complex further validated these findings. This work affirmed the anti-EP role of CT flower against EP, suggesting a probable molecular mechanism involved.

Functional and transcriptional regulation of the anthocyanidin acyl modifier gene Gs5AT of Gentiana sino-ornata.

The Chinese gentian, Gentiana sino-ornata produces brilliant blue flowers. To investigate the biological function and transcriptional regulation mechanism of the anthocyanin 5-O-acyltransferase gene (Gs5AT ) in the corolla, it is beneficial to analyse the mechanism of blue flower colour presentation. In this investigation, we obtained the CDS and promoter sequences of the gene Gs5AT . Yeast one-hybrid experiments were used to identify the transcription factor GsbHLH7 that activates the gene Gs5AT . According to quantitive reverse transcription polymerase chain reaction analysis, the expression of the gene Gs5AT was significantly and positively correlated with the gene GsbHLH7 . The colour phenotype of the flowers was significantly altered by the virus-induced gene silencing transduction of Gs5AT and GsbHLH7 , with GsbHLH7 silencing producing more pronounced changes in the corolla colour than Gs5AT . The expression of GsF3'5'H , GsDFR , GsANS , Gs3GT , and Gs5GT all fell to varying degrees after GsbHLH7 silencing, indicating that GsbHLH7 may regulate transcription of these genes as well as Gs5AT . The results of this study indicate that Gs5AT was positively regulated by the GsbHLH7 , and thus affects the colour presentation of the blue corolla.

“Apotheosis of Poesy”: The blue flower as a Romantic theory of the novel

“Apotheosis of Poesy”: The blue flower as a Romantic theory of the novel

Enhanced performance of dye-sensitized solar cells via anthocyanin, chlorophyll, benzothiadiazole and diphenylacridine co-sensitizers and amine-based co-adsorbents

Anthocyanin (ANT) and chlorophyll (CHL) natural dyes extracted from blue butterfly pea flowers and spinach leaves and two synthetic metal-free dyes (BIM33 and C1) were evaluated as sensitizers/co-sensitizers in dye-sensitized solar cells (DSSCs). To suppress the possible dye aggregation, triethylamine (TEA) and diethylenetriamine (DETA) were utilized as alternative co-adsorbents to the commonly used chenodeoxycholic acid (CDCA). Furthermore, CHL, BIM33, and C1 were co-sensitized with ANT to achieve panchromatic light absorption and, hence, enhance the photovoltaic performance. Therefore, the power conversion efficiencies (PCEs) of DSSCs based on the dyes were significantly improved from 1.19–5.01 % to 2.39–6.31 % by the co-sensitization and utilization of co-adsorbents. Meanwhile, the efficiencies of DSSCs based on TEA or DETA were superior to those based on CDCA under the same conditions. This study provides effective strategies for improving the performance of DSSCs based on environment-friendly dyes.

A vacuolar protein MaSCPL1 mediates anthocyanin acylation modifications in blue-flowered grape hyacinth

The grape hyacinth is renowned for its profuse blue flowers, which confer substantial scientific and ornamental significance as well as considerable potential for industrial applications. The serine carboxypeptidase-like acyltransferases (SCPL-ATs) family is crucial for the blue flower coloration. To elucidate SCPL-ATs involved in anthocyanin modification in grape hyacinth, we performed a transcriptomic analysis of grape hyacinth SCPL-ATs. Through gene expression profiling, we identified a promising candidate gene, MaSCPL1, whose expression patterns corresponded with variations in anthocyanin content throughout petal coloration. Subsequently, the functional role of the MaSCPL1 gene was validated using the native petal regeneration system, and the silencing of MaSCPL1 led to a decreased total anthocyanin content and Dp3MG content in grape hyacinth petals. Furthermore, we employed yeast one-hybrid (Y1H), electrophoretic mobility shift assay (EMSA), and dual-luciferase assays to explore the regulatory interactions between the anthocyanin biosynthesis transcription factor MaMybA and the MaSCPL1 promoter. Our findings indicate that MaMybA can bind to the MaSCPL1 promoter and significantly activate its expression. Furthermore, the MaMybA-RNAi resulted in a substantial multifold reduction in the expression of MaSCPL1, implying that the regulation of MaSCPL1 expression is mediated by MaMybA. This study revealed the MaSCPL1 gene has been associated with anthocyanin acylated modification in grape hyacinth and elucidated the important role of the MaMybA-MaSCPL1 module in colouration grape hyacinth.

Downregulation of a Phi class glutathione S-transferase gene in transgenic torenia yielded pale flower color.

The members of glutathione S-transferase (GST) belonging to the Phi class of the GST family are known to play a role in anthocyanin transport to the vacuole. We isolated a GST orthologue from the torenia petal cDNA library. Transgenic plants transcribing GST double stranded RNA were generated from a torenia cultivar having blue flowers. These plants exhibited a range of flower colors, from blue to almost white. Quantitative RT-PCR confirmed the downregulation of the GST transcript, accompanied by a decrease in anthocyanin levels in the petals of the transgenic plants, whereas flavone levels remained unchanged. These results suggest that GST is involved in anthocyanin transport in torenia petals, and that anthocyanins and flavones are likely transported to the vacuole through different mechanisms.

Diverse Flowering Response to Blue Light Manipulation: Application of Electric Lighting in Controlled-Environment Plant Production

Blue light is an important light wavelength in regulating plant flowering. In a controlled environment (CE) plant production systems, blue light can be manipulated easily and even precisely through electric lighting, especially with the advancement of light-emitted diode (LED) technologies. However, the results of previous studies in the literature about blue-light-mediated flowering are inconsistent, which would limit its practical application in CE plant production while implying that an in-depth study of the relevant physiological mechanism is necessary in the future. This review consolidates and analyzes the diverse findings from previous studies on blue light-mediated plant flowering in varying high-value crops from ornamental plants to fruits, vegetables, and specialty crops. By synthesizing the contrasting results, we proposed the possible explanations and even the underlying mechanisms related to blue light intensity and exposure duration, its co-action with other light wavelengths, background environment conditions, and the involved photoreceptors. We have also identified the knowledge gaps based on these studies and outlined future directions for research and potential application in this promising field. This review provides valuable insights into the important and diverse role of blue light in plant flowering and offers a foundation for further investigations to optimize plant flowering through lighting technologies.

Biological activity of the Clitoria ternatea flower aqueous extract planted in Binh Duong province, Vietnam

Clitoria ternatea L. is commonly called the blue pea flower, an herbaceous plant that is used for traditional medicine, natural food colorants and beverages thanks to its antioxidant properties and the consequent health benefits. This study aimed to evaluate the bioactivity and safety of Clitoria ternatea flower (CTF) aqueous extracts. In this study, we evaluated the biological activity of CTF aqueous extracts at concentrations from 20 to 120 µg/mL through the test of 1,1-diphenyl-2-picrylhydrazyl (DPPH), ACE inhibition, antibacterial activity and cell viability assay to test for HEK.293 nephrotoxicity. The results indicated that CTF aqueous extract exhibited the highest antioxidant activity and ACE inhibitor activity at the concentration of 120 µg/mL. Besides, the antibacterial activity of the aqueous extract against Staphylococcus aureus and Bacillus sp. at 80 µg/ mL concentration was similar to that of 120 µg/mL. The aqueous extract at 120 µg/mL did not exhibit cytotoxic effects on HEK.293 cells. The results of this study suggested that CTF can be used as a natural beverage, a kind of tea to improve human health.

Identification of novel flower anthocyanins of Delphinium grandiflorum cultivars

Flower color is one of the most important properties of ornamental flowers. Information on the kinds of pigments that flowers can biosynthesize is useful for breeding cultivars focused on flower colors. The flower colors of regular ornamental delphinium cultivars are blue, violet, purple, pink, and white. The pigments of these flowers are delphinidin-based anthocyanins. It has been reported that the typical modification in delphinium anthocyanins involves the transfer of glucose and p-hydroxybenzoic acid molecules to the 7-position of delphinidin one by one, and it was predicted that other unidentified anthocyanins are present in addition to the already reported ones. Recently, light pink flowers that accumulate pelargonidin-based anthocyanins were reported from cultivars derived from Delphinium grandiflorum. Converting delphinidin-based anthocyanins to pelargonidin-based ones is considered key to producing red flowers in delphinium. Hence, we investigated anthocyanins of blue, mauve, light pink, and white flowers of D. grandiflorum cultivars. We isolated anthocyanins and analyzed them using HPLC, TLC, UV–vis spectra, FABMS, and NMR. Using these methods, we identified two novel delphinidin-based anthocyanins and three novel pelargonidin-based anthocyanins: delphinidin 3-O-[6-O-(α-rhamnopyranosyl)-β-glucopyranoside]-7-O-[6-O-(p-hydroxybenzoyl)-β-glucopyranoside] (2), pelargonidin 3-O-[6-O-(α-rhamnopyranosyl)-β-glucopyranoside]-7-O-[6-O-(4-O-(6-O-(p-hydroxybenzoyl)-β-glucopyranosyl)-p-hydroxybenzoyl)-β-glucopyranoside] (5, rubrodelphin), pelargonidin 3-O-[6-O-(α-rhamnopyranosyl)-β-glucopyranoside]-7-O-[3-O-(β-glucopyranosyl)-6-O-(4-O-(6-O-(p-hydroxybenzoyl)-β-glucopyranosyl)-p-hydroxybenzoyl)-β-glucopyranoside] (6), delphinidin 3-O-[6-O-(α-rhamnopyranosyl)-β-glucopyranoside]-7-O-[3-O-(3-O-(6-O-(p-hydroxybenzoyl)-β-glucopyranosyl)-β-glucopyranosyl)-6-O-(4-O-(6-O-(p-hydroxybenzoyl)-β-glucopyranosyl)-p-hydroxybenzoyl)-β-glucopyranoside] (7), and pelargonidin 3-O-[6-O-(α-rhamnopyranosyl)-β-glucopyranoside]-7-O-[3-O-(3-O-(6-O-(4-O-(6-O-(p-hydroxybenzoyl)-β-glucopyranosyl)-p-hydroxybenzoyl)-β-glucopyranosyl)-β-glucopyranosyl)-6-O-(4-O-(6-O-(p-hydroxybenzoyl)-β-glucopyranosyl)-p-hydroxybenzoyl)-β-glucopyranoside] (9, rosedelphin), along with four known anthocyanins. The flowers of five blue cultivars accumulated cyanodelphin (8) as the dominant pigment. The shapes of visible absorption spectra of these five blue flowers were similar, indicating that the color and the absorption spectra were the typical ones for delphinium blue color produced by 8. The mauve flower color was due to a mixture of delphinidin-based anthocyanins in various polyacylated levels at the 7-position. The light pink flowers accumulated pelargonidin-based anthocyanins 5, 6, and 9. These pigment structures showed that the pelargonidin-based anthocyanins modified in the same way as in the originally biosynthesized delphinidin-based anthocyanins even though aglycone was replaced by pelargonidin in these anthocyanins.

Application of anthocyanins from blue pea flower in yoghurt and fermented milk: An alternate natural blue colour to spirulina

Studies investigating the application of blue pea flower anthocyanins in fermented dairy products are limited. In this study, the application of anthocyanin extracts from blue pea flower (Clitoria ternatea) in yoghurt and fermented milk at 1 and 2% (w/v) concentrations was investigated and compared to a commercial blue colourant from spirulina. The total anthocyanin content (TAC), antioxidant activity (DPPH free radical and ferric reducing antioxidant power assays), pH, titratable acidity, syneresis, colour, and viable cell count were measured at 6 days intervals for 30 days at 4 °C storage. The TAC of yoghurt with blue pea flower anthocyanin extract demonstrated high stability, but the TAC of fermented milk with blue pea flower anthocyanin extract decreased significantly. The yoghurt and fermented milk with blue pea flower anthocyanin extract demonstrated higher antioxidant activity than the negative control and samples containing spirulina. The total colour change (ΔE) of yoghurt with blue pea flower anthocyanin extract was less than that of yoghurt containing spirulina during storage. However, the colour of fermented milk with blue pea flower anthocyanin extract was less stable than samples containing spirulina. The average colour acceptability of yoghurt and fermented milk containing 2% (w/v) blue pea flower anthocyanin extracts and those containing spirulina colourant was not significantly different. Therefore, an anthocyanin extract from blue pea flowers at 2% (w/v) concentration was a better blue colourant than spirulina in yoghurt. Spirulina was a better colourant compared to blue pea flower anthocyanins for fermented milk.

Formulation and Evaluation of Herbal Sunscreen Utilizing Blue Pea Flower Extract

This thesis presents the formulation and evaluation of a novel herbal sunscreen incorporating Blue Pea Flower (Clitoria ternatea) extract as the primary active ingredient. With increasing concerns about the adverse effects of synthetic sunscreens and the growing interest in natural alternatives, the study aims to explore the photoprotective properties of Blue Pea Flower extract, known for its rich anthocyanin and antioxidant content. The research begins with the extraction of Blue Pea Flower bioactive compounds through optimized solvent extraction methods. The formulated herbal sunscreen is developed by incorporating the extract into a suitable base, considering stability, safety, and efficacy. Key evaluation parameters include in vitro Sun Protection Factor (SPF) determination, photostability studies, and assessments of skin compatibility. Characterization of the Blue Pea Flower extract reveals essential bioactive compounds, establishing a foundation for understanding its potential benefits. The herbal sunscreen's physical characteristics and stability are analyzed to ensure a reliable and effective formulation. In vitro SPF testing assesses the photoprotective efficacy, while photostability studies gauge the product's robustness under sun exposure conditions. Safety evaluations, including skin irritation tests and biocompatibility studies, contribute crucial data on the product's safety profile. The results provide insights into the effectiveness of Blue Pea Flower extract as a natural photoprotective agent and the overall suitability of the herbal sunscreen formulation. Comparisons with synthetic sunscreens highlight the potential advantages of the herbal formulation in terms of efficacy and safety. Recommendations for formulation optimization and future research directions are discussed, emphasizing the significance of eco-friendly and sustainable alternatives in the sunscreen industry. In conclusion, this research offers a comprehensive exploration of Blue Pea Flower extract's potential in herbal sunscreen formulations. The findings contribute to the understanding of natural photoprotective agents, fostering the development of safer and environmentally conscious sun protection products.

‘Blossom Buddies’ − How do flower colour combinations affect emotional response and influence therapeutic landscape design?

Natural landscapes are linked to health and well-being outcomes. This research investigated emotional responses to colour in the landscape. An online questionnaire (with 715 respondents) was employed to capture participants' preferences and positive psychological reactions to key flower colours and combinations. Images were created using combinations of pansy flowers in various colours. Flower combinations explored the effects of complementary, analogous and warm/cool colour harmonies. Orange flowers (a warm colour) provided a strong uplifting emotion in participants: an emotional response that was maintained even when up to 50 % of the orange flowers were replaced by the complementary (and cool) colour of blue. In contrast, the relaxing effect of 100 % blue flowers was lost when 25 % or more of the flowers were replaced by orange. Using analogous cool colours, it was evident blue provided more feelings of relaxation than purple, and adding purple to a blue combination (50:50) reduced the capacity of the floral composition to promote relaxation. The colour found to be most relaxing, however, was white; but again mixing this colour with either blue or purple tended to reduce its capacity to relax. Thus, the study suggests that certain patterns of colours and combinations provide a generic response in enhancing emotional well-being of individuals; a point that can be exploited in designed therapeutic landscapes. The data also indicated, however, that cool colours scored quite highly for positive uplifting emotion (mean score > 6.5) and people’s favourite cool colour/combination was often described as uplifting (7.4), indicating the subjective nature of colour preference and emotional response. Thus, whilst understanding key principles about colour and therapeutic responses, designers also need to take account of personal preference and should provide some variety of colours/colour combinations in different parts of a garden/park. These findings provide valuable insights for horticultural design practices, emphasizing the importance of colour selection and user preferences in creating supportive environments for mental well-being.

Phytochemical Characterization, Antioxidant, and Anti-Proliferative Activities of Wild and Cultivated Nigella damascena Species Collected in Sicily (Italy).

The use of Nigella damascena seeds in the culinary field or as aerial parts infusions in the pharmaceutical and cosmetic fields is widely reported. The biological activity of this plant, as demonstrated over the years, is closely related to its phytochemical content. This investigation focused on the comparative study of the same plants of N. damascena, one totally wild (WND), while the other two, one with white flowers (CWND) and the other with blue flowers (CBND), were subject to cultivation, irrigation, and manual weeding. Using the potential of 1D and 2D-NMR spectroscopy, coupled with MS/MS spectrometric studies, the three methanolic extracts of N. damascena were investigated. Chemical studies have highlighted the presence of triterpene saponin compounds and various glycosylated flavonoids. Finally, the in vitro antiproliferative and antioxidant activities of the three individual extracts were evaluated. The antiproliferative activity performed on U-937, HL-60, and MCF-7 tumor cell lines highlighted a greater anticancer effect of the CBND and CWND extracts compared to the data obtained using WND. The antioxidant activity, however, performed to quantify ROS generation is comparable among the extracts used.

Floral pigments and their perception by avian pollinators in three Chilean Puya species.

The Chilean Puya species, Puya coerulea var. violacea and P. chilensis bear blue and pale-yellow flowers, respectively, while P. alpestris considered to be their hybrid-derived species has unique turquoise flowers. In this study, the chemical basis underlying the different coloration of the three Puya species was explored. We first isolated and identified three anthocyanins: delphinidin 3,3',5'-tri-O-glucoside, delphinidin 3,3'-di-O-glucoside and delphinidin 3-O-glucoside; seven flavonols: quercetin 3-O-rutinoside-3'-O-glucoside, quercetin 3,3'-di-O-glucoside, quercetin 3-O-rutinoside, isorhamnetin 3-O-rutinoside, myricetin 3,3',5'-tri-O-glucoside, myricetin 3,3'-di-O-glucoside and laricitrin 3,5'-di-O-glucoside; and six flavones: luteolin 4'-O-glucoside, apigenin 4'-O-glucoside, tricetin 4'-O-glucoside, tricetin 3',5'-di-O-glucoside, tricetin 3'-O-glucoside and selagin 5'-O-glucoside, which is a previously undescribed flavone, from their petals. We also compared compositions of floral flavonoid and their aglycone among these species, which suggested that the turquoise species P. alpestris has an essentially intermediate composition between the blue and pale-yellow species. The vacuolar pH was relatively higher in the turquoise (pH 6.2) and pale-yellow (pH 6.2) flower species, while that of blue flower species was usual (pH 5.2). The flower color was reconstructed in vitro using isolated anthocyanin, flavonol and flavone at neutral and acidic pH, and its color was analyzed by reflectance spectra and the visual modeling of their avian pollinators. The modeling demonstrated that the higher pH of the turquoise and pale-yellow species enhances the chromatic contrast and spectral purity. The precise regulation of flower color by flavonoid composition and vacuolar pH may be adapted to the visual perception of their avian pollinator vision.

Regulation of blue infertile flower pigmentation by WD40 transcription factor HmWDR68 in Hydrangea macrophylla 'forever summer'.

WD40 transcription factors are crucial in plant growth and developmental, significantly impacting plant growth regulation. This study investigates the WD40 transcription factor HmWDR68's role in developing the distinctive blue infertile flower colors in Hydrangea macrophylla 'Forever Summer'. The HmWDR68 gene was isolated by PCR, revealing an open reading frame of 1026 base pairs, which encodes 341 amino acids. Characterized by four WD40 motifs, HmWDR68 is a member of the WD40 family. Phylogenetic analysis indicates that HmWDR68 shares high homology with PsWD40 in Camellia sinensis and CsWD40 in Paeonia suffruticosa, both of which are integral in anthocyanin synthesis regulation. Quantitative real-time PCR (qRT-PCR) analysis demonstrated that HmWDR68 expression in the blue infertile flowers of 'Forever Summer' hydrangea was significantly higher compared to other tissues and organs. Additionally, in various hydrangea varieties with differently colored infertile flowers, HmWDR68 expression was markedly elevated in comparison to other hydrangea varieties, correlating with the development of blue infertile flowers. Pearson correlation analysis revealed a significant association between HmWDR68 expression and the concentration of delphinidin 3-O-glucoside, as well as key genes involved in anthocyanin biosynthesis (HmF3H, HmC3'5'H, HmDFR, and HmANS) in the blue infertile flowers of 'Forever Summer' hydrangea (P < 0.01). These findings suggest HmWDR68 may specifically regulate blue infertile flower formation in hydrangea by enhancing delphinidin-3-O-glucoside synthesis, modulating expression of HmF3H, HmC3'5'H, HmDFR and HmANS. This study provides insights into HmWDR68's role in hydrangea's blue flowers development, offering a foundation for further research in this field.

Co60 gamma irradiation reduces rooting ability in M1V1 Salvia uliginosa while inducing leaf variegation

Purpose Salvia uliginosa is a desirable ornamental shrub for the landscape with blue flowers and the ability to attract pollinators, but limited variation is commercially available in this species. Mutation breeding is a valuable tool to induce variation in ornamental species. However, many deleterious effects are associated with mutation breeding, including reduced rooting ability of vegetative cuttings. Materials and methods Cuttings of S. uliginosa were randomly assigned into groups of 10 and exposed to 0, 10, 20, 30, 40, or 50 Gy of gamma rays from a cobalt-60 source to determine an appropriate treatment rate. A follow-up experiment treated 25 S. uliginosa cuttings at 35 Gy to induce favorable mutations. Results and conclusions Root quality, survival, and plant height were reduced at higher levels of gamma radiation in the M1V1. However, rooting ability was not impacted in M1V2 selections. Additionally, one mutant was isolated from the 35 Gy treatment with variegated leaves for a mutation rate of 4%. Our research determined a treatment rate that induced a dominant mutation in S. uliginosa while minimizing the deleterious influence of gamma radiation.

Tracing the genealogy of research on the mechanism of blue flower coloration by anthocyanin based on Keita Shibata's work.

K. Shibata is the ancestor of the research on anthocyanins in Japan and proposed metal complex theory against the pH theory by R. Willstätter. Shibata's successors, S. Hattori and K. Hayashi, made efforts to clarify blue flower coloration by metal complexation and found commelinin, a self-assembled supramolecular metal complex pigment, in blue dayflower, Tsuyukusa. The author introduces two key reports on blue flower coloration published in the Proceedings of the Japan Academy and describes the subsequent development of the study.

Flavonoid extracts from chrysanthemum with appropriate anthocyanins turn blue when exposed to iron ions

Although some species that accumulate only cyanidin (Cy) in nature can produce blue flowers through iron ions, there has been no evidence of blue chrysanthemums being generated in this manner. This study revealed that flavonoid extracts from the ray florets of the chrysanthemum cultivar ‘Wandai Fengguang’ turned blue when exposed to Fe3+. Samples that could turn blue were labeled as CB (Cy-determined blue flowers), while samples that did not turn blue were labeled as CN (Cy-determined non-blue flowers). After a series of experiments, a stable screening system was established using flavonoid extracts containing NaAc buffer at pH 5.5 and a total anthocyanin concentration (TAC) of 30 μmol·L−1, and the addition of Fe3+ from 0 to 0.25 μmol·L−1 allowed for the selection of five CB samples from 39 chrysanthemum cultivars. All five CB samples exhibited flower color phenotypes that belonged to Cluster-I with redness (a∗) values ranging from 29.03 to 45.99, yellowness (b∗) values from −11.31 to 3.77, and brightness (L∗) values from 29.07 to 45.99. Additionally, the ratio of TAC to total luteolin concentration (TLC) was found to be a critical factor for distinguishing between CB and CN samples. To realize the desired blue hue in the flavonoid extracts with the participation of Fe3+, a TAC to TLC ratio of 2.25 and above is required. Moreover, the protoplasts and ray florets of CB samples that turned blue with the involvement of Fe2+ showed great potential for cultivating blue chrysanthemums through ferric–anthocyanin chelate. Overall, this study reveals that blue flowers can be cultivated through the increase in the iron ion concentration, combined with the accumulation of Cy.

Characterization of the varied output from the anthocyanin pathway in Phalaenopsis-type Dendrobium hybrids and its relationship with flower coloration

Floral color is an important Phalaenopsis-type Dendrobium hybrids (Den-Phals) trait in the flower markets. Anthocyanins are key pigments contributing to purple, pink, and violet floral color. However, the impact of anthocyanin composition on flower coloration has not yet been fully elucidated. In this study, the flower color characteristics of 62 Den-Phals were evaluated. Most flowers contained purple, while pure blue, orange, and red floral colors were scarce. In total 35 anthocyanins were identified and two acylated pelargonidin glycosides were tentatively characterized using ultra-performance liquid chromatography (UPLC)-mass spectrum (MS) analysis. Unfortunately, the major anthocyanin components remained unidentified. However, the hydrolysis anthocyanins to their anthocyanidins suggested that the cyanidin was the major component in most hybrids with a relative content over 85 %. Pelargonidin was almost the only pigment in reddish pink flowers. The slightly higher peonidin content was found in purple-violet flowers (up to 6.23 %). The trend indicated that with the increase of total anthocyanidin and cyanidin pigments, the floral color deepened and turned to purple. Flavones or flavonols as co-pigments contributed to brighter and yellower color. From the above results, the varied output from the anthocyanin biosynthetic pathway among Den-Phals was used to identify the rate-limiting steps involved and a strategy for the cultivation of pure red, blue, and violet flowers is proposed. The study provides a basis for screening excellent germplasm and improving floral color in Den-Phals.