Comparative Study of Betacyanin Profile and Antimicrobial Activity of Red Pitahaya (Hylocereus polyrhizus) and Red Spinach (Amaranthus dubius)

Chenopodium quinoa Willd. and Amaranthus hybridus L.: Ancestral Andean Food Security and Modern Anticancer and Antimicrobial Activity

The species Chenopodium quinoa Willd. and Amaranthus hybridus L. are Andean staples, part of the traditional diet and gastronomy of the people of the highlands of Colombia, Ecuador, Peru, Bolivia, northern Argentina and Chile, with several ethnopharmacological uses, among them anticancer applications. This review aims to present updated information on the nutritional composition, phytochemistry, and antimicrobial and anticancer activity of Quinoa and Amaranth. Both species contribute to food security due to their essential amino acid contents, which are higher than those of most staples. It is highlighted that the biological activity, especially the antimicrobial activity in C. quinoa, and the anticancer activity in both species is related to the presence of phytochemicals present mostly in leaves and seeds. The biological activity of both species is consistent with their phytochemical composition, with phenolic acids, flavonoids, carotenoids, alkaloids, terpenoids, saponins and peptides being the main compound families of interest. Extracts of different plant organs of both species and peptide fractions have shown in vitro and, to a lesser degree, in vivo activity against a variety of bacteria and cancer cell lines. These findings confirm the antimicrobial and anticancer activity of both species, C. quinoa having more reported activity than A. hybridus through different compounds and mechanisms.

Anti-Amyloid β Aggregation Activity and Cell Viability Effect of Betacyanins from Red Pitahaya (Hylocereus polyrhizus) for Alzheimer's Disease

Betacyanin-rich extract from red beet (Beta vulgaris) was recently reported to inhibit amyloid β (Aβ) aggregation, a main pathological event in Alzheimer's disease. However, the anti-Aβ aggregation effect of individual betacyanin isolates has not been reported before. This study investigated the anti-Aβ aggregation activity and cytotoxicity of betacyanins from red pitahaya or red dragon fruit (Hylocereus polyrhizus). Betacyanin fraction (IC50 = 16.02 ± 1.15 µg/mL) and individual betacyanin isolates exhibited anti-Aβ aggregation activity in a concentration-dependent manner using a thioflavin T fluorescence assay. The highest to lowest IC50 was in the order of betanin (426.30 ± 29.55 µM), phyllocactin (175.22 ± 1.52 µM), and hylocerenin (131.73 ± 5.58 µM), following a trend of increase in functional groups of carboxyl, hydroxyl, and/or carbonyl. Further, the betacyanin fraction of 135.78 µg/mL and below, which were concentrations with an anti-Aβ aggregation effect, were validated as non-neurotoxic based on an in vitro cytotoxicity assay using human neuroblastoma (SH-SY5Y) cells. These findings highlight the potential neuroprotective activity of betacyanins for Alzheimer's disease.

Antimicrobial Activity of Catechol-Containing Biopolymer Poly[3-(3,4-dihydroxyphenyl)glyceric Acid] from Different Medicinal Plants of Boraginaceae Family

This study reports the antimicrobial activities of the biopolymers poly[3-(3,4-dihydoxyphenyl)glyceric acid] (PDHPGA) and poly[2-methoxycarbonyl-3-(3,4-dihydroxyphenyl)oxirane] (PMDHPO), extracted from the six plants of Boraginaceae family: Symphytum asperum (SA), S. caucasicum (SC), S. gr and iflorum (SG), Anchusa italica (AI), Cynoglosum officinale (CO), and Borago officinalis (BO) collected in various parts of Georgia. The study revealed that the antibacterial activities were moderate, and biopolymers from only three plants showed activities against all tested bacteria. Biopolymers from CO stems as well as SC and AI did not show any activity except low activity against a resistant P. aeruginosa strain, which was the most resistant among all three resistant strains. On the other hand, the antifungal activity was better compared to the antibacterial activity. Biopolymers from BO stems exhibited the best activities with MIC/MFC at 0.37-1.00 mg/mL and 0.75-1.5 mg/L, respectively, followed by those from SG stems. Biopolymers from SC and AI roots showed antifungal activities against all six fungi, in contrast to the antibacterial activity, while biopolymers from CO stems and SA roots had activities against four fungi and one fungus, respectively. The sugar-based catechol-containing biopolymers from BO stems demonstrated the best activities among all tested biopolymers against T. viride, P. funiculosum, P. cyclpoium var verucosum, and C. albicans (MIC 0.37 mg/mL). In addition, biopolymers from SG stems were half as active against A. fumigatus and T. viride as ketoconazole. Biopolymers from all plant materials except for CO stems showed higher potency than ketoconazole against T. viride. For the first time, it was shown that all plant materials exhibited better activity against C. albicans, one of the most dreadful fungal species.

Antimicrobial betalains

Betalains are nitrogen-containing plant pigments that can be red-violet (betacyanins) or yellow-orange (betaxanthins), currently employed as natural colourants in the food and cosmetic sectors. Betalains exhibit antimicrobial activity against a broad spectrum of microbes including multidrug-resistant bacteria, as well as single-species and dual-species biofilm-producing bacteria, which is highly significant given the current antimicrobial resistance issue reported by The World Health Organization. Research demonstrating antiviral activity against dengue virus, in silico studies including SARS-CoV-2, and anti-fungal effects of betalains highlight the diversity of their antimicrobial properties. Though limited in vivo studies have been conducted, antimalarial and anti-infective activities of betacyanin have been observed in living infection models. Cellular mechanisms of antimicrobial activity of betalains are yet unknown; however existing research has laid the framework for a potentially novel antimicrobial agent. This review covers an overview of betalains as antimicrobial agents and discussions to fully exploit their potential as therapeutic agents to treat infectious diseases.

Cactaceae plants as sources of active bioavailable phytochemicals

Arid-land plants from the Cactaceae family are endemic to the Americas and cultivated worldwide. Cactaceous plants and their fruits contain phenolic compounds, betalains, vitamins, carotenoids, minerals, and soluble fiber. Edible cactaceous matrices can be considered functional foods since their consumption may confer health benefits. These plants could be a source of novel bioactive compounds relevant to the area of phytomedicine. However, consumption of high concentrations of active molecules is not necessarily correlated to beneficial physiological effects because phytochemicals must be released from the food matrices under physiological conditions, resist digestion-associated chemical transformations, and remain in their active state in systemic circulation until the target tissues are reached. Notably, although digestion may either increase or decrease the bioactive phytochemicals' activity and stability, non-absorbed compounds may also be relevant for human health. Additionally, food matrices' type and composition and their technological processing operations may influence the compounds' release, stability, and accessibility. Thus, this review provides insights on the feasibility of using Cactaceae plants as sources of functional compounds. It is focused on compounds' bioactivity, bioaccessibility, and overall bioavailability after their metabolic transformation. Also, it addresses the influence of food processing on bioactive compounds. Many Cactaceae species are unexplored, and our understanding of how they confer health benefits is limited. To better understand the physiological relevance, nutraceutical potential, and therapeutic feasibility of cactaceous bioactive phytochemicals, future research should focus on the metabolic stability and safety of these compounds, as well as their assimilation mechanisms (absorption, distribution, and metabolic fate).

Antioxidant, cytotoxic, and antibacterial activities of Clitoria ternatea flower extracts and anthocyanin-rich fraction

Clitoria ternatea flower is a traditional medicinal herb that has been used as a natural food colourant. As there are limited studies on investigating the bioactivities of the anthocyanin-rich fraction of Clitoria ternatea flower, this study aimed to determine an efficient column chromatography method to obtain the anthocyanin-rich fraction from this flower and characterise its composition, antioxidant, antibacterial, and cytotoxic activities. Amberlite XAD-16 column chromatography was more efficient in enriching the total anthocyanin content (TAC) of the fraction with the highest TAC to total phenolic content (TPC) ratio of 1:6 than that using C18-OPN. A total of 11 ternatin anthocyanins were characterised in the anthocyanin-rich fraction by LC–MS analysis. The antioxidant activity of the anthocyanin-rich fraction was more potent in the chemical-based assay with an IC₅₀ value of 0.86 ± 0.07 mg/mL using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay than cellular antioxidant assay using RAW 264.7 macrophages. In vitro cytotoxicity assay using human embryonic kidney HEK-293 cell line showed the anthocyanin-rich fraction to be more toxic than the crude extracts. The anthocyanin-rich fraction had more potent antibacterial activity than the crude extracts against Bacillus cereus, Bacillus subtilis, and Escherichia coli. The anthocyanin-rich fraction of C. ternatea has the potential to be used and developed as a functional food ingredient or nutraceutical agent.

Evaluation of a Novel Phosphorylated Red Dragon Fruit Peel Pectin for Enhancement of Thermal Stability and Functional Activity

Red dragon fruit peel, as a fruit waste, is rich in plant-based nutritional pectins that can be applied as food additives. The present study aims to characterize a novel phosphorylated red dragon fruit peel pectin (PRDFP-P) and to explore its functional activities. The thermal analysis, morphology analysis, antibacterial, antioxidant and antitumor activities of PRDFP-P were evaluated. The results showed that the phosphorylated derivative PRDFP-P had typical phosphate groups. Compared with the native red dragon fruit peel pectin (PRDFP), PRDFP-P possessed superior thermal stability and exhibited significant inhibition effects on Escherichia coli and Staphylococcus aureus. Moreover, the phosphate groups on the derivative PRDFP-P chains remarkably enhanced the scavenging ability of hydroxyl radicals and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals. In addition, PRDFP-P showed a significant inhibition effect on growth of human hepatic carcinoma cells (HepG2) and the IC₅₀ value was determined to be 248.69 μg/mL (P < 0.05). Our results suggested that the phosphorylated derivative PRDFP-P might be potentially applied as stabilizing, thickening and gelling agents with functional activities in the food industry.

Betalain plant sources, biosynthesis, extraction, stability enhancement methods, bioactivity, and applications

Betalains are plant pigments with functional properties used mainly as food dyes. However, they have been shown to be unstable to different environmental factors. This paper provides a review of (1) Betalain plant sources within several plant families such as Amaranthaceae, Basellaceae, Cactaceae, Portulacaceae, and Nyctaginaceae, (2) The biosynthesis pathway of betalains for both betacyanins and betaxanthins, (3) Betalain extraction process, including non-conventional technologies like microwave-assisted, ultrasound-assisted, and pulsed electrical field extraction, (4) Factors affecting their stability, mainly temperature, water activity, light incidence, as well as oxygen concentration, metals, and the presence of antioxidants, as well as activation energy as a mean to assess stability, and novel food-processing technologies able to prevent betalain degradation, (5) Methods to increase shelf life, mainly encapsulation by spray drying, freeze-drying, double emulsions, ionic gelation, nanoliposomes, hydrogels, co-crystallization, and unexplored methods such as complex coacervation and electrospraying, (6) Biological properties of betalains such as their antioxidant, hepatoprotective, antitumoral, and anti-inflammatory activities, among others, and (7) Applications in foods and other products such as cosmetics, textiles and solar cells, among others. Additionally, study perspectives for further research are provided for each section.

Maturation Process, Nutritional Profile, Bioactivities and Utilisation in Food Products of Red Pitaya Fruits: A Review

Red pitaya (Hylocereus polyrhizus, red pulp with pink peel), also known as dragon fruit, is a well-known species of pitaya fruit. Pitaya seeds and peels have been reported to exhibit higher concentrations of total polyphenols, beta-cyanins and amino acid than pulp, while anthocyanins (i.e., cyanidin 3-glucoside, delphinidin 3-glucoside and pelargonidin 3-glucoside) were only detected in the pulp extracts. Beta-cyanins, phenolics and flavonoids were found to increase gradually during fruit maturation and pigmentation appeared earlier in the pulp than peel. The phytochemicals were extracted and purified by various techniques and broadly used as natural, low-cost, and beneficial healthy compounds in foods, including bakery, wine, dairy, meat and confectionery products. These bioactive components also exhibit regulative influences on the human gut microbiota, glycaemic response, lipid accumulation, inflammation, growth of microbials and mutagenicity, but the mechanisms are yet to be understood. The objective of this study was to systematically summarise the effect of red pitaya’s maturation process on the nutritional profile and techno-functionality in a variety of food products. The findings of this review provide valuable suggestions for the red pitaya fruit processing industry, leading to novel formulations supported by molecular research.

Underutilized plants of the Cactaceae family: Nutritional aspects and technological applications

This review examines the nutritional and functional aspects of some representatives of the Cactaceae family, as well as its technological potential in the most diverse industrial fields. The studied species are good sources of nutrients and phytochemicals of biological interest, such as phenolic compounds, carotenoids, betalains, phytosterols, tocopherols, etc. They also have shown great potential in preventing some diseases, including diabetes, obesity, cancer, and others. As to technological applications, the Cactaceae family can be explored in the production of food (e.g., cakes, yogurts, bread, ice cream, and juices), as natural dyes, sources of pectins, water treatment and in animal feed. In addition, they have great potential for many technological domains, including food chemistry, pharmacy, biotechnology, and many others.

Betacyanin-inhibited biofilm formation of co-culture of Staphylococcus aureus and Pseudomonas aeruginosa on different polymer surfaces

Staphylococcus aureus and Pseudomonas aeruginosa are bacteria that cause biofilm-associated infections. The aim of this study was to determine the activity of combined betacyanin fractions from Amaranthus dubius (red spinach) and Hylocereus polyrhizus (red pitahaya) against biofilms formed by co-culture of S. aureus and P. aeruginosa on different polymer surfaces. Various formulations containing different concentrations of the betacyanin fractions were investigated for biofilm-inhibiting activity on polystyrene surfaces using crystal violet assay and scanning electron microscopy. A combination of each betacyanin fraction (0.625 mg mL-1) reduced biofilm formation of five S. aureus strains and four P. aeruginosa strains from optical density values of 1.24-3.84 and 1.25-3.52 to 0.81-2.63 and 0.80-1.71, respectively. These combined fractions also significantly inhibited dual-species biofilms by 2.30 and reduced 1.0-1.3 log CFU cm-2 bacterial attachment on polymer surfaces such as polyvinyl chloride, polyethylene, polypropylene and silicone rubber. This study demonstrated an increase in biofilm-inhibiting activity against biofilms formed by two species using combined fractions than that by using single fractions. Betacyanins found in different plants could collectively be used to potentially decrease the risk of biofilm-associated infections caused by these bacteria on hydrophobic polymers.

Combined Transcriptome and Metabolome analysis of Pitaya fruit unveiled the mechanisms underlying Peel and pulp color formation

BACKGROUND

Elucidating the candidate genes and key metabolites responsible for pulp and peel coloration is essential for breeding pitaya fruit with new and improved appeal and high nutritional value. Here, we used transcriptome (RNA-Seq) and metabolome analysis (UPLC-MS/MS) to identify structural and regulatory genes and key metabolites associated with peel and pulp colors in three pitaya fruit types belonging to two different Hylocereus species.

RESULT

Our combined transcriptome and metabolome analyses suggest that the main strategy for obtaining red color is to increase tyrosine content for downstream steps in the betalain pathway. The upregulation of CYP76ADs is proposed as the color-breaking step leading to red or colorless pulp under the regulation by WRKY44 transcription factor. Supported by the differential accumulation of anthocyanin metabolites in red pulped pitaya fruit, our results showed the regulation of anthocyanin biosynthesis pathway in addition to betalain biosynthesis. However, no color-breaking step for the development of anthocyanins in red pulp was observed and no biosynthesis of anthocyanins in white pulp was found. Together, we propose that red pitaya pulp color is under the strict regulation of CYP76ADs by WRKYs and the anthocyanin coexistence with betalains is unneglectable. We ruled out the possibility of yellow peel color formation due to anthocyanins because of no differential regulation of chalcone synthase genes between yellow and green and no detection of naringenin chalcone in the metabolome. Similarly, the no differential regulation of key genes in the carotenoid pathway controlling yellow pigments proposed that the carotenoid pathway is not involved in yellow peel color formation.

CONCLUSIONS

Together, our results propose several candidate genes and metabolites controlling a single horticultural attribute i.e. color formation for further functional characterization. This study presents useful genomic resources and information for breeding pitaya fruit with commercially attractive peel and pulp colors. These findings will greatly complement the existing knowledge on the biosynthesis of natural pigments for their applications in food and health industry.

Phytoconstituents and pharmaco-therapeutic benefits of pitaya: A wonder fruit

Dragon fruit has caught the attention of many researchers in the last few years because of its vast therapeutic potential. The fruit is enriched with several phytochemical constituents having tremendous pharmacological properties. It is traditionally used as a coloring agent. Some newly explored therapeutic applications include its use as an antioxidant, antimicrobial, antidiabetic, anticancer, and nutraceutical. The phytoconstituents can be extracted from flesh, peel, and seeds of the fruit. The fruit is known to be a rich source of betacyanin, vitamin C, and lycopene. The current review is focused on phytochemical constituents of dragon fruit along with its pharmacological activities. It also sheds light on the safety aspects of the fruit. The review will pave a path for researchers to study this marvel fruit further for societal benefit. Advanced research on dragon fruit will unleash many more therapeutic benefits and can give mechanistic insight about its activities. PRACTICAL APPLICATIONS: Phytoconstituents play a vital role in the treatment of various diseases and for the improvement of human health, in general. Dragon fruit is known to be having antioxidant, anti-microbial, anti-diabetic, anti-cancer applications. The fruit can also be used as a nutraceutical (functional food). To grab all the benefits from this fruit, its phytoconstituents and pharmaco-therapeutic aspect have to be thoroughly studied. This review can be very useful for researchers across different fields like botany, agriculture, pharmacy, etc., to bridge the gap for collaborative work on dragon fruit, which will help in finding solutions for many modern diseases.

Could fruits be a reliable source of food colorants? Pros and cons of these natural additives

Color additives are important for the food industry to improve sensory quality lost during food process and to expand the variety of products. In general, artificial colorants have lower cost and better stability than the natural ones. Nevertheless, studies have reported their association with some health disorders. Furthermore, consumers have given greater attention to food products with health beneficial effects, which has provided a new perspective for the use of natural colorants. In this context, fruits are an excellent alternative source of natural compounds, that allow the obtainment of a wide range of colorant molecules, such as anthocyanins, betalains, carotenoids, and chlorophylls. Furthermore, in addition to their coloring ability, they comprise different bioactive properties. However, the extraction and application of natural colorants from fruits is still a challenge, since these compounds show some stability problems, in addition to issues related to the sustainability of raw-materials providing. To overcome these limitations, several studies have reported optimized extraction and stabilization procedures. In this review, the major pigments found in fruits and their extraction and stabilization techniques for uses as food additives will be looked over.

Plant Phenolics and Phenolic-Enriched Extracts as Antimicrobial Agents against Food-Contaminating Microorganisms

Phenolic compounds and extracts with bioactive properties can be obtained from many kinds of plant materials. These natural substances have gained attention in the food research as possible growth inhibitors of foodborne pathogenic and spoilage bacteria. Many phenolic-enriched plant extracts and individual phenolics have promising anti-quorum sensing potential as well and can suppress the biofilm formation and toxin production of food-related pathogens. Various studies have shown that plant phenolics can substitute or support the activity of synthetic food preservatives and disinfectants, which, by the way, can provoke serious concerns in consumers. In this review, we will provide a brief insight into the bioactive properties, i.e., the antimicrobial, anti-quorum sensing, anti-biofilm and anti-enterotoxin activities, of plant phenolic extracts and compounds, with special attention to pathogen microorganisms that have food relation. Carbohydrase aided applications to improve the antimicrobial properties of phenolic extracts are also discussed.

Antiviral activity of betacyanins from red pitahaya (Hylocereus polyrhizus) and red spinach (Amaranthus dubius) against dengue virus type 2 (GenBank accession no. MH488959)

This study investigated the antiviral activity of betacyanins from red pitahaya (Hylocereus polyrhizus) and red spinach (Amaranthus dubius) against dengue virus type 2 (DENV-2). The pulp of red pitahaya and the leaves of red spinach were extracted using methanol followed by sub-fractionation and Amberlite XAD16N column chromatography to obtain betacyanin fractions. The half maximum cytotoxicity concentration for betacyanin fractions from red pitahaya and red spinach on Vero cells were 4.346 and 2.287 mg ml-1, respectively. The half-maximal inhibitory concentration (IC50) of betacyanin fraction from red pitahaya was 125.8 μg ml-1 with selectivity index (SI) of 5.8. For betacyanin fraction from red spinach, the IC50 value was 14.62 µg ml-1 with SI of 28.51. Using the maximum non-toxic betacyanin concentration, direct virucidal effect against DENV-2 was obtained from betacyanin fraction from red pitahaya (IC50 of 126.70 μg ml-1; 95.0 % virus inhibition) and red spinach (IC50 value of 106.80 μg ml-1; 65.9 % of virus inhibition). Betacyanin fractions from red pitahaya and red spinach inhibited DENV-2 in vitro.

Metabolic Profiling of Pitaya (Hylocereus polyrhizus) during Fruit Development and Maturation

Pitaya (Hylocereus polyrhizus) has attracted much interest from consumers as it is a novelty fruit with high nutrient content and a tolerance to drought stress. As a group of attractive pigment- and health-promoting natural compounds, betalains represent a visual feature for pitaya fruit quality. However, little information on the correlation between betalains and relevant metabolites exists so far. Currently, color (Commission International del'Eclairage, CIE) parameters, betalain contents, and untargeted metabolic profiling (gas chromatography-time-of-flight-mass spectrometry, GC⁻MS and liquid chromatography tandem mass spectrometry, LC⁻MS) have been examined on 'Zihonglong' fruits at nine different developmental stages, and the variation character of the metabolite contents was simultaneously investigated between peel and pulp. Furthermore, principal component analysis (PCA) and partial least-squares discriminant analysis (PLS-DA) were used to explore metabolite profiles from the fruit samples. Our results demonstrated that the decrease of amino acid, accompanied by the increase of sugars and organic acid, might contribute to the formation of betalains. Notably, as one of four potential biomarker metabolites, citramalic acid might be related to betalain formation.

Biofilm inhibiting activity of betacyanins from red pitahaya (Hylocereus polyrhizus) and red spinach (Amaranthus dubius) against Staphylococcus aureus and Pseudomonas aeruginosa biofilms

AIMS

To investigate the biofilm inhibitory activity of betacyanins from red pitahaya (Hylocereus polyrhizus) and red spinach (Amaranthus dubius) against Staphylococcus aureus and Pseudomonas aeruginosa biofilms.

METHODS AND RESULTS

The pulp of red pitahaya and the leaves of red spinach were extracted using methanol followed by subfractionation to obtain betacyanin fraction. The anti-biofilm activity was examined using broth microdilution assay on polystyrene surfaces and expressed as minimum biofilm inhibitory concentration (MBIC). The betacyanin fraction from red spinach showed better anti-biofilm activity (MBIC: 0·313-1·25 mg ml^-1 ) against five Staph. aureus strains while the betacyanin fraction from red pitahaya showed better anti-biofilm activity (MBIC: 0·313-0·625 mg ml^-1 ) against four P. aeruginosa strains. Both betacyanin fraction significantly reduced hydrophobicity of Staph. aureus and P. aeruginosa strains. Numbers of Staph. aureus and P. aeruginosa attached to polystyrene were also reduced without affecting their cell viability.

CONCLUSION

Betacyanins can act as anti-biofilm agents against the initial step of biofilm formation, particularly on a hydrophobic surface like polystyrene.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is the first to investigate the use of betacyanin as a biofilm inhibitory agent. Betacyanin could potentially be used to reduce the risk of biofilm-associated infections.