Production of dihydroxylated betalains and dopamine in cell suspension cultures of Celosia argentea var. plumosa

BpCYP76AD15 is involved in betaxanthin biosynthesis in bougainvillea callus

MAIN CONCLUSION

BpCYP76AD15 is involved in betaxanthin biosynthesis in callus, but not in bracts, in bougainvillea. Bougainvillea (Bougainvillea peruviana) is a climbing tropical ornamental tree belonging to Nyctaginaceae. Pigments that are conferring colorful bracts in bougainvillea are betalains, and that conferring yellow color are betaxanthins. In general, for red-to-purple betacyanin biosynthesis, α clade CYP76AD that has tyrosine hydroxylase and DOPA oxygenase activity is required, while for betaxanthin biosynthesis, β clade CYP76AD that has only tyrosine hydroxylase is required. To date, betaxanthin biosynthesis pathway genes have not been identified yet in bougainvillea. Since bougainvillea is phylogenetically close to four-O-clock (Mirabilis jalapa), and it was reported that β clade CYP76AD, MjCYP76AD15, is involved in floral betaxanthin biosynthesis in four-O-clock. Thus, we hypothesized that orthologous gene of MjCYP76AD15 in bougainvillea might be involved in bract betaxanthin biosynthesis. To test the hypothesis, we attempted to identify β clade CYP76AD gene from yellow bracts by RNA-seq; however, we could not. Instead, we found that callus accumulated betaxanthin and that β clade CYP76AD gene, BpCYP76AD15, were expressed in callus. We validated BpCYP76AD15 function by transgenic approach (agro-infiltration and over-expression in transgenic tobacco), and it was suggested that BpCYP76AD15 is involved in betaxanthin biosynthesis in callus, but not in bracts in bougainvillea. Interestingly, our data also indicate the existence of two pathways for betaxanthin biosynthesis (β clade CYP76AD-dependent and -independent), and the latter pathway is important for betaxanthin biosynthesis in bougainvillea bracts.

Antioxidant and Anticancer Potential of Bioactive Compounds from Rhinacanthus nasutus Cell Suspension Culture

The potential benefits of natural plant extracts have received attention in recent years, encouraging the development of natural products that effectively treat various diseases. This is the first report on establishing callus and cell suspension cultures of Rhinacanthus nasutus (L.) Kurz. A yellow friable callus was successfully induced from in vitro leaf explants on Murashige and Skoog medium supplemented with 1 mg/L 2,4-dichlorophenoxyacetic acid and 1 mg/L 1-naphthalene acetic acid. A selected friable callus line was used to establish the cell suspension culture with the same medium. The antioxidant assays showed that the leaf- and ethanolic-suspension-cultured cell (SCC) extracts exhibited high antioxidant potential. In addition, the in vitro cytotoxicity revealed by the MTT assay demonstrated potent antiproliferative effects against the oral cancer cell lines ORL-48 and ORL-136 in a dose-dependent manner. Several groups of compounds, including terpenoids, phenolics, flavonoids, quinones, and stilbenes, were identified by UHPLC–QToF–MS, with the same compounds detected in leaf and SCC extracts, including austroinulin, lucidenic acid, esculetin, embelin, and quercetin 3-(2″-p-hydroxybenzoyl-4″-p-coumarylrhamnoside). The present study suggests the value of further investigations for phytochemical production using R. nasutus cell suspension culture.

Highly sensitive and selective detection of dopamine with boron and sulfur co-doped graphene quantum dots

In this work, we report, the synthesis of Boron and Sulfur co-doped graphene quantum dots (BS-GQDs) and its applicability as a label-free fluorescence sensing probe for the highly sensitive and selective detection of dopamine (DA). Upon addition of DA, the fluorescence intensity of BS-GQDs were effectively quenched over a wide concentration range of DA (0–340 μM) with an ultra-low detection limit of 3.6 μM. The quenching mechanism involved photoinduced electron transfer process from BS-GQDs to dopamine-quinone, produced by the oxidization of DA under alkaline conditions. The proposed sensing mechanism was probed using a detailed study of UV–Vis absorbance, steady state and time resolved fluorescence spectroscopy. The high selectivity of the fluorescent sensor towards DA is established. Our study opens up the possibility of designing a low-cost biosensor which will be suitable for detecting DA in real samples.

A dopamine-based biosynthetic pathway produces decarboxylated betalains in Chenopodium quinoa

Betalains are the nitrogenous pigments that replace anthocyanins in the plant order Caryophyllales. Here, we describe unconventional decarboxylated betalains in quinoa (Chenopodium quinoa) grains. Decarboxylated betalains are derived from a previously unconsidered activity of the 4,5-DOPA-extradiol-dioxygenase enzyme (DODA), which has been identified as the key enzymatic step in the established biosynthetic pathway of betalains. Here, dopamine is fully characterized as an alternative substrate of the DODA enzyme able to yield an intermediate and structural unit of plant pigments: 6-decarboxy-betalamic acid, which is proposed and described. To characterize this activity, quinoa grains of different colors were analyzed in depth by chromatography, time-of-flight mass spectrometry, and reactions were performed in enzymatic assays and bioreactors. The enzymatic-chemical scheme proposed leads to an uncharacterized family of 6-decarboxylated betalains produced by a hitherto unknown enzymatic activity. All intermediate compounds as well as the final products of the dopamine-based biosynthetic pathway of pigments have been unambiguously determined and the reactions have been characterized from the enzymatic and functional perspectives. Results evidence a palette of molecules in quinoa grains of physiological relevance and which explain minor betalains described in plants of the Caryophyllales order. An entire family of betalains is anticipated.

Establishment of a Cell Suspension Culture of Ageratina pichinchensis (Kunth) for the Improved Production of Anti-Inflammatory Compounds

Ageratina pichinchensis (Kunth) is a plant used in traditional Mexican medicine to treat multiple ailments. However, there have not been biotechnological studies on producing compounds in in vitro cultures. The aim of this study was to establish a cell suspension culture of A. pichinchensis, quantify the anti-inflammatory constituents 2,3-dihydrobenzofuran (2) and 3-epilupeol (3), evaluate the anti-inflammatory potential of its extracts, and perform a phytochemical analysis. Cell suspension cultures were established in a MS culture medium of 30-g L⁻¹ sucrose, 1.0-mg L⁻¹ α-naphthaleneacetic acid, and 0.1-mg L⁻¹ 6-furfurylaminopurine. The ethyl acetate extract of the cell culture analyzed by gas chromatography (GC) revealed that the maximum production of anti-inflammatory compounds 2 and 3 occurs on days eight and 16, respectively, improving the time and previously reported yields in callus cultures. The anti-inflammatory activity of these extracts exhibited a significant inhibition of nitric oxide (NO) production. Furthermore, a phytochemical study of the ethyl acetate (EtOAc) and methanol (MeOH) extracts from day 20 led to the identification of 17 known compounds. The structures of the compounds were assigned by an analysis of 1D and 2D NMR data and the remainder by GC–MS. This is the first report of the production of (-)-Artemesinol, (-)-Artemesinol glucoside, encecalin, and 3,5-diprenyl-acetophenone by a cell suspension culture of A. pichinchensis.

Therapeutic Application of Betalains: A Review

Anthocyanins, betalains, riboflavin, carotenoids, chlorophylls and caramel are the basic natural food colorants used in modern food manufacture. Betalains, which are composed of red–violet betacyanin and yellow betaxanthins, are water-soluble pigments that color flowers and fruits. Betalains are pigments primarily produced by plants of the order Caryophyllales. Because of their anti-inflammatory, cognitive impairment, anticancer and anti-hepatitis properties, betalains are useful as pharmaceutical agents and dietary supplements. Betalains also exhibit antimicrobial and antimalarial effects, and as an example, betalain-rich Amaranthus spinosus displays prominent antimalarial activity. Studies also confirmed the antidiabetic effect of betalains, which reduced glycemia by 40% without causing weight loss or liver impairment. These findings show that betalain colorants may be a promising alternative to the synthetic dyes currently used as food additives.

Light Emission in Betalains: From Fluorescent Flowers to Biotechnological Applications

The discovery of visible fluorescence in the plant pigments betalains revealed the existence of fluorescent patterns in flowers of plants of the order Caryophyllales, where betalains substitute anthocyanins. The serendipitous initial discovery led to a systemized characterization of the role of different substructures on the photophysical phenomenon. Strong fluorescence is general to all members of the family of betaxanthins linked to the structural property that the betalamic acid moiety is connected to an amine group. This property has led to bioinspired tailor-made probes and to the development of novel biotechnological applications in screening techniques or microscopy labeling. Here, we comprehensively review the photophysics, photochemistry, and photobiology of betalain fluorescence and describe all current applications.

Development of Fluorescent Reagent Based on Ligand Exchange Reaction for the Highly Sensitive and Selective Detection of Dopamine in the Serum

A new fluorescent probe (BDP-Fe2+) was developed for targeting dopamine, with a boron-dipyrromethenyl (BDP) group as the fluorophore and a Fe2+ complex as the ligand exchange site. The free form of BDP-Fe2+ in solution displayed weak fluorescence emission, while it showed strong fluorescence emission after interaction with dopamine due to the release of Fe2+ from BDP-Fe2+, confirming the binding of Fe2+ to dopamine. The increase in fluorescence intensity was concentration-dependent, and a good linear relationship was observed between the fluorescence intensity and dopamine concentration. The detection limit of dopamine by BDP-Fe2+ was 1.1 nM, indicating a 20-fold higher sensitivity than that of previously reported compounds. The reaction of BDP-Fe2+ with dopamine was not affected by the presence of foreign substances, allowing the highly selective detection of dopamine in the human serum sample. The results of this study indicate that the novel compound BDP-Fe2+ is a reliable fluorescent molecular probe for the detection of dopamine and can be widely employed in diverse scientific areas.

Scaled-up biotechnological production of individual betalains in a microbial system

The recent interest in plant pigment betalains as bioactive compounds and chemopreventive agents has led to the search for a reliable and scalable process to obtain them. The cloning of the novel and efficient enzyme 4,5-DOPA-extradiol dioxygenase from Gluconacetobacter diazotrophicus in an expression vector, and the subsequent heterologous expression in Escherichia coli cultures has led to the start-up of a biotechnological production system of individual pigments. The aim of this study was to search for the optimal conditions for the production of betalamic acid in microbial factories and the scaled-up obtention of the derived pigments. Four different betaxanthins and two betacyanins were obtained after the addition of non-transformable amines and amino acids and their condensation with the betalamic acid produced by the dioxygenase. The scaled-up obtention and purification of betalains improved the yields of the previous methodologies reaching quantities by up to 150 mg of pure compounds.

Study on Betalains in Celosia cristata Linn. Callus Culture and Identification of New Malonylated Amaranthins

Betacyanins and betaxanthins were characterized and determined in an intensely pigmented red-colored callus culture of Celosia cristata L. (Amaranthaceae). A new malonyl derivative, 6'- O-malonyl-amaranthin (celoscristatin) was isolated and identified by spectroscopic and mass spectrometric techniques. Its stereoisomer, 4'- O-malonyl-amaranthin (celoscristatin acyl-migrated), as well as its 15 R diastereomer were also detected in the callus as a result of the malonyl group migration in celoscristatin/isoceloscristatin, respectively. Amaranthin occurs in the callus as the major betacyanin, followed by celoscristatin, betanin, phyllocactin, and other minor betacyanins. The effect of different carbon sources on the growth rates of the Celosia callus as well as on betalains profiles in the callus cultures was studied. High dopamine content in the callus culture was determined and compared with the content in C. cristata inflorescences. The dopamine-based betalain (miraxanthin V) was detected as the main betaxanthin in the callus, however, at a concentration level much lower than that of the identified betacyanins. The studied callus culture of C. cristata can accumulate betalains in amounts which approach the quantities produced by most known high-yielding plant species.

Betalains in Some Species of the Amaranthaceae Family: A Review

Natural pigments are largely distributed in the plant kingdom. They belong to diverse groups, with distinct biochemical pathways. Betalains with colours that range from yellow to red-violet can de divided into two main subgroups: betaxanthins and betacyanins. These types of pigments are confined into 13 families of the order Caryophyllales and in some genera of higher fungi (Amanita muscaria, Hygrocybe and Hygrophorus). The Amaranthaceae family includes diverse genera in which betalains are present: Alternanthera, Amaranthus, Beta, Chenopodium, Celosia and Gomphrena. The biosynthesis of betalains and their general biological properties were reviwed in the present work. In addition, the types of betalains present in some species of the aforementioned genera, their stability and production, as well as biological attributes, were reviewed.

Fusarium oxysporum cell elicitor enhances betalain content in the cell suspension culture of Celosia cristata

We started a cell suspension culture from magenta coloured calli of cockscomb to study the effect of biotic and abiotic elicitors on the biosynthesis of betalain pigments. The cultures were grown in a flask containing 30 ml MS media fortified with 13.5 μM 2,4-D and 0.44 μM BAP. These cultures were elicited during its log-phase of growth using fungal elicitors (prepared from mycelia of Fusarium oxysporum), yeast extract, copper sulphate and cobalt chloride. The elicitation reduced the cell count, cell viability and percent pigmented cell in the suspension culture. Similarly, it also resulted in reduced betalain content by all the elicitors except 0.125 × 10^-3% fungal elicitor. Rather, fungal elicitor at this concentration significantly enhanced the amaranthin, betanin, betalamic acid and betaxanthin content in the culture. Besides this, copper sulphate doubled the pigment contribution (ratio of particular pigment content to total pigment content) of betaxanthin at all the concentrations. Therefore, we conclude that fungal elicitor can further be investigated to enhance the content of betalain pigments in suspension culture at a larger scale.

Development of Betalain Producing Callus Lines from Colored Quinoa Varieties (Chenopodium quinoa Willd)

Betalains are water-soluble plant pigments of hydrophilic nature with promising bioactive potential. Among the scarce edible sources of betalains is the grain crop quinoa (Chenopodium quinoa Willd), with violet, red, and yellow grains being colored by these pigments. In this work, callus cultures have been developed from differently colored plant varieties. Stable callus lines exhibited color and pigment production when maintained on Murashige and Skoog medium supplemented with the plant growth regulators 6-benzylaminopurine (8.88 μM) and 2,4-dichlorophenoxyacetic acid (6.79 μM) with a reduction of the nitrogen source to 5.91 mM. Pigment analysis by HPLC-DAD and ESI-MS/MS fully describes the content of individual pigments in the cell lines and allows the first report on the pigments present in quinoa seedlings. Phyllocactin and vulgaxanthin I are described as novel pigments in the species and show the potential of C. quinoa culture lines in the production of compounds of nutritional value.

"La Vie en Rose": Biosynthesis, Sources, and Applications of Betalain Pigments

Betalains are tyrosine-derived red-violet and yellow pigments found exclusively in plants of the Caryophyllales order, which have drawn both scientific and economic interest. Nevertheless, research into betalain chemistry, biochemistry, and function has been limited as comparison with other major classes of plant pigments such as anthocyanins and carotenoids. The core biosynthetic pathway of this pigment class has only been fully elucidated in the past few years, opening up the possibility for betalain pigment engineering in plants and microbes. In this review, we discuss betalain metabolism in light of recent advances in the field, with a current survey of characterized genes and enzymes that take part in betalain biosynthesis, catabolism, and transcriptional regulation, and an outlook of what is yet to be discovered. A broad view of currently used and potential new sources for betalains, including utilization of natural sources or metabolic engineering, is provided together with a summary of potential applications of betalains in research and commercial use.

Statistical experimental designs for the production of secondary metabolites in plant cell suspension cultures

Statistical experimental designs, also known as the "design of experiments" (DoE) approach, are widely used to improve not only technical processes but also to answer questions in the agricultural, medical and social sciences. Although many articles have been published about the application of DoE in these fields, few studies have addressed the use of DoE in the plant sciences, particularly in the context of plant cell suspension cultures (PCSCs). Compounds derived from PCSCs can be developed as pharmaceuticals, chemical feedstocks and cosmetic ingredients, and statistical experimental designs can be used to improve the productivity of the cells and the yield and/or quality of the target compounds in a cost efficient manner. In this article, we summarize recent findings concerning the application of statistical approaches to improve the performance of PCSCs and discuss the potential future applications of this approach.