Quantification Of Anthocyanins Research Articles

Pigment Extraction Method for Anthocyanin Natural Resources in Indonesia: A Review

Anthocyanin is the pigment that still attracts attention from food industries because of its abundance in Indonesian plants. Anthocyanins are produced in a variety of colors with unique stability properties. Through a systematic review, this review studied 40 scientific reports conducted in Indonesia over the last 10 years. The research objects included fruits, flowers, seeds, peels, and roots from the islands of Java, Sumatra, Kalimantan, Sulawesi, and Nusa Tenggara. Several methods are used to extract solvent-based anthocyanin compounds, including maceration, microwave, and reflux-soxhlet extraction. Microwave extraction, including ultrasonic extraction, is recommended for anthocyanin extraction. Spectrophotometry with the pH differential method was chosen as the anthocyanin quantification procedure, using 500 and 700 nm wavelenghts.

Quantification of anthocyanins and phenolic compounds in an infusion made from dried acaí (Euterpe precatoria) pulp

Quantification of anthocyanins and phenolic compounds in an infusion made from dried acaí (<i>Euterpe precatoria</i>) pulp

OsGSTU34, a Bz2-like anthocyanin-related glutathione transferase transporter, is essential for rice (Oryza sativa L.) organs coloration

Anthocyanins are a flavonoid compound known as one of the most important chromogenic substances. They play several functions, including health promotion and sustaining plants during adverse conditions. They are synthesized at the endoplasmic reticulum and sequestered in the vacuole. In this work, we generated knock-out lines of OsGSTU34, a glutathione transporter's tau gene family, with no transgene line and off-target through CRISPR/Cas9 mutagenesis and highlighted the loss of pigmentation in rice flowers, leaves, stems, shoots, and caryopsis. The anthocyanin quantification in the wild-type BLWT and mutant line BLG34-8 caryopsis showed that cyanidin-3-O-glucoside (C3G) and peonidin-3-O-glucoside (P3G) were almost undetectable in the mutant line. A tandem mass tag (TMT) labeling proteomic analysis was conducted to elucidate the proteomic changes in the BLWT and BLG34-8. The result revealed that 1175 proteins were altered, including 408 that were down-regulated and 767 that were upregulated. The accumulation of the OsGSTU34-related protein (Q8L576), along with several anthocyanin-related proteins, was down-regulated. The enrichment analysis showed that the down-regulated proteins were enriched in different pathways, among which the phenylpropanoid biosynthesis pathway, flavonoid biosynthesis metabolites, and anthocyanin biosynthesis pathway. Protein interaction network prediction revealed that glutathione-S-transferase (Q8L576) was connected to the proteins involved in the flavonoid and anthocyanin biosynthesis pathways, such as flavanone 3-dioxygenase 1 (Q7XM21), leucoanthocyanidin dioxygenase 1 (Q93VC3), 4-coumarate-CoA ligase 2 (Q42982), phenylalanine ammonia-lyase (P14717), chalcone synthase 1 (Q2R3A1), and 4-coumarate-CoA ligase 5 (Q6ZAC1). However, the expression of the most important anthocyanin biosynthesis gene was not altered, suggesting that only the transport mechanism was affected. Our findings highlight new insight into the anthocyanin pigmentation in black rice and provide new perspectives for future research.

Mecanismos biocinéticos de antocianinas en frutos rojos producidos en el estado de Michoacán, México

Berry fruits are a rich source of phytonutrients, especially phenolic compounds such as flavonoids, which have antioxidant properties. Among these fruits, the most cultivated and consumed are those of the genus Fragaria (Strawberries) and Rubus (Raspberries, blackberries, dewberries), which have been widely studied for their beneficial effects on human and animal health. One of the most important bioactive compounds of these fruits are anthocyanins, which have shown potential benefits for health by their antimicrobial, anti-inflammatory and anticancer activity. Therefore, the study of anthocyanins is of great pharmaceutical and nutraceutical interest. The objective of this research is to analyze the biokinetic mechanisms of anthocyanins in Rubus adenotrichos and Fragaria x ananassa produced in the state of Michoacán, Mexico. For this purpose, research strategies that included the extraction and quantification of anthocyanins, as well as bioinformatic tools to understand their biosynthetic pathway in the mentioned fruits were used. The use of informatic platforms allowed to identify the regulatory genes and enzymes involved in the biosynthesis of anthocyanins in R. adenotrichos and F. x ananassa, finding that most are common, with some specific differences, and that there are only a few exceptions, such as the enzymes catechol-O-methyltransferase (OMT), UDP-glucosyltransferase (UGT) and beta-glucuronidase (GUSB), which only occur in Rubus adenotrichos and not in Fragaria x ananassa.

When Cannabis sativa L. Turns Purple: Biosynthesis and Accumulation of Anthocyanins.

Environmental cues elicit anthocyanin synthesis in plant vegetative and reproductive tissues. Their accumulation in different organs accounts for their diverse biological functions, mainly related to their antioxidant properties, and it depends on a temporally and spatially regulated mechanism controlled by the action of a well-known multi-transcription factor complex. Despite the highly recognizable value of Cannabis sativa L. as a natural biorefinery of phytochemicals, very little information is known on anthocyanin pigmentation in this species. In this work, a targeted quantification of anthocyanins via HPLC-MS/MS, combined with the transcriptional profile via RT-qPCR of genes encoding for structural and decorating enzymes and regulatory transcription factors in different C. sativa tissues, help gain insights into the anthocyanin pathway in this species. To the best of our knowledge, this is the first report on the identification of cyanidin-3-rutinoside (keracyanin) as the major anthocyanin in C. sativa vegetative and floral tissues. Keracyanin amounts were higher than in small berries, suggesting that Cannabis biomass is a valuable source of colored antioxidants to be exploited in diverse applications. Furthermore, a gene putatively encoding for an anthocyanin DTX35 type transporter and CsTTG1 were identified in silico and their transcriptional levels were assessed via RT-qPCR. The results allow us to provide the first model of anthocyanin regulation in C. sativa, opening a new research scenario in this species for both breeding purposes and phytochemical exploitation.

Image-based phenotyping to estimate anthocyanin concentrations in lettuce.

Anthocyanins provide blue, red, and purple color to fruits, vegetables, and flowers. Due to their benefits for human health and aesthetic appeal, anthocyanin content in crops affects consumer preference. Rapid, low-cost, and non-destructive phenotyping of anthocyanins is not well developed. Here, we introduce the normalized difference anthocyanin index (NDAI), which is based on the optical properties of anthocyanins: high absorptance in the green and low absorptance in the red part of the spectrum. NDAI is determined as (Ired - Igreen)/(Ired + Igreen), where I is the pixel intensity, a measure of reflectance. To test NDAI, leaf discs of two red lettuce (Lactuca sativa) cultivars 'Rouxai' and 'Teodore' with wide range of anthocyanin concentrations were imaged using a multispectral imaging system and the red and green images were used to calculate NDAI. NDAI and other commonly used indices for anthocyanin quantification were evaluated by comparing to with the measured anthocyanin concentration (n = 50). Statistical results showed that NDAI has advantages over other indices in terms of prediction of anthocyanin concentrations. Canopy NDAI, obtained using multispectral canopy imaging, was correlated (n = 108, R2 = 0.73) with the anthocyanin concentrations of the top canopy layer, which is visible in the images. Comparison of canopy NDAI from multispectral images and RGB images acquired using a Linux-based microcomputer with color camera, showed similar results in the prediction of anthocyanin concentration. Thus, a low-cost microcomputer with a camera can be used to build an automated phenotyping system for anthocyanin content.

Profiling and Quantification of Anthocyanins in Purple-Pericarp Sweetcorn and Purple-Pericarp Maize

Purple-pericarp sweetcorn accessions, derived from crossing purple-pericarp maize with white shrunken2 sweetcorn, were assessed for differences in anthocyanin profile at both sweetcorn eating stage and at full kernel maturity. The 'Tim1' sweetcorn line developed a similar total anthocyanin concentration to its 'Costa Rica' parent when assessed at sweetcorn-eating stage. At full maturity it surpassed the purple maize parent, but this was mainly due to the presence of starch diluting the anthocyanin concentration of the latter. The anthocyanin/colour relationship was affected by both total anthocyanin concentration and the ratio of cyanidin- to pelargonidin-based anthocyanins. Malonylation of anthocyanins was also found to vary and did not appear to be linked with either cyanidin:pelargonidin ratio or total anthocyanin concentration. In addition, anthocyanin synthesis was affected by kernel maturity at harvest, with colour development increasing in conjunction with a progression of anthocyanin development across the kernel surface. Pigmentation was present in the aleurone, pericarp and vitreous endosperm of kernels of the purple-pericarp maize parent and purple-pericarp sweetcorn accessions when fully mature, but pigmentation was only apparent in the pericarp at sweetcorn-eating stage. Importantly for consumers, anthocyanin pigmentation covered almost the entire kernel surface at sweetcorn-eating stage.

Extraction, Quantification and Characterization Techniques for Anthocyanin Compounds in Various Food Matrices—A Review

Anthocyanins are water-soluble pigments characterized by various intense colors found in fruits and vegetables. Scientific studies have shown growing evidence to support their health benefits. Therefore, estimating the anthocyanin content in food is essential to identify the ideal analytical method. Moreover, due to the instability of plant anthocyanins, it is important to select and optimize their extraction, separation and qualitative and quantitative analysis, steps that are indispensable and important in their study. The present article reviews the latest procedures for extracting anthocyanins from various food matrices and analytical methods for their quantification. Therefore, various forms of preliminary treatments of samples for anthocyanin extraction, extraction procedures for various fruits, vegetables and cereals, purification of samples and quantification of anthocyanins are highlighted and evaluated. Using ultrasound-assisted extraction (UAE) might be effective for anthocyanin extraction and the Amberlite XAD-7HP method is the most effective for purifying anthocyanins. Combining the liquid chromatography (LC) method with electrospray ionization (ESI) and mass spectrometry (MS) or quadrupole time-of-flight (QTOF) with mass spectrometry (MS) better quantifies the anthocyanins in the food complex samples. Therefore, the extraction and separation of anthocyanins and their qualitative and quantitative analyses are essential steps in their research. As a result, the study concentrates on a detailed characterization of various qualitative and quantitative analytical methodologies, while briefly describing the main anthocyanin extraction processes.

Identification and Quantification of Anthocyanin and Catechin Compounds in Purple Tea Leaves and Flakes.

Tea is the first most popular beverage worldwide and is available in several selections such as black (fully oxidized), Oolong (partially oxidized) and green (non-oxidized), in addition to purple tea, an emerging variety derived from the same tea plant (Camellia sinensis). This study investigated purple tea leaves (non-oxidized) and flakes (water extractable) to thoroughly identify their composition of anthocyanins and catechins and to study the effect of a water extraction process on their compositional properties in comparison with green tea. Anthocyanin and catechin compounds were separated and quantified using UPLC, and their identity was confirmed using LC-MS/MS in positive and negative ionization modes. Delphinidin was the principal anthocyaninidin in purple tea, while cyanidin came in second. The major anthocyanin pigments in purple tea were delphinidin-coumaroyl-hexoside followed by delphinidin-3-galactoside and cyanidin-coumaroyl-hexoside. The water extraction process resulted in substantial reductions in anthocyanins in purple tea flakes. There were no anthocyanin compounds detected in green tea samples. Both purple and green tea types were rich in catechins, with green tea containing higher concentrations than purple tea. The main catechin in purple or green tea was epigallocatechin gallate (EGCG) followed by either epicatechin gallate (ECG) or epigallocatechin (EGC), subject to tea type. The extraction process increased the concentration of catechins in both purple and green tea flakes. The results suggest that purple tea holds promise in making healthy brews, natural colorants and antioxidants and/or functional ingredients for beverages, cosmetics and healthcare industries due to its high content of anthocyanins and catechins.

Application of anthocyanins as indicators for alkalimetric titration

Along with synthetic substances, various naturally-occurring pigments can response to pH variations in solutions by changing their colour. Such substances include, for example, anthocyanins. In this study, the possibility of applying a set of anthocyanins obtained from berry extracts as a potential acid-base indicator. This indicator can be a good alternative to the widely-used phenolphthalein test. Aqueous and alcoholic extracts derived from the fruit of ashberry, sea-buckthorn, lingonberry, blueberry, currant, blackberry, cranberry, rose hip, cherry and hawthorn plants were studied. The presence of anthocyanins in the test samples was confirmed by chemical and physicochemical methods of analysis, including qualitative tests, ascending thin-layer chromatography and direct spectrophotometry. Quantification of anthocyanins was carried out by pH-differential spectrophotometry. Compared to alcoholic extracts, aqueous berry extracts were found to contain anthocyanins in far lesser amounts. In order to compare the pH indicator potential of phenolphthalein and the studied set of anthocyanins, the content of ascorbic acid in the test samples was assessed by direct alkalimetry. A control experiment was performed using a 5% ascorbic acid solution for injection. The pH value of aqueous and alcoholic solutions of all berry extracts was determined by an instrumental procedure. The pH of the extracts ranged from 2.95 to 5.04. The content of the total amount of anthocyanins in aqueous and alcoholic extracts of blackberries, cranberries, black currants, blueberries and lingonberries in terms of cyanidin-3-glucoside was determined both quantitatively and qualitatively. A good agreement was achieved between the results of alkalimetric titration performed using phenolphthalein and the set of anthocyanins extracted from blackcurrant berries with 95% ethanol.

A recessive mutation in muscadine grapes causes berry color-loss without influencing anthocyanin pathway

Anthocyanins, a major class of flavonoids, are important pigments of grape berries. Despite the recent discovery of the genetic cause underlying the loss of color, the metabolomic and molecular responses are unknown. Anthocyanin quantification among diverse berry color muscadines suggests that all genotypes could produce adequate anthocyanin quantities, irrespective of berry color. Transcriptome profiling of contrasting color muscadine genotypes proposes a potential deficiency that occurs within the anthocyanin transport and/or degradation mechanisms and might cause unpigmented berries. Genome-wide association studies highlighted a region on chromosome-4, comprising several genes encoding glutathione S-transferases involved in anthocyanin transport. Sequence comparison among genotypes reveals the presence of two GST4b alleles that differ by substituting the conserved amino acid residue Pro171-to-Leu. Molecular dynamics simulations demonstrate that GST4b2–Leu171 encodes an inactive protein due to modifications within the H-binding site. Population genotyping suggests the recessive inheritance of the unpigmented trait with a GST4b2/2 homozygous. A model defining colorless muscadines’ response to the mutation stimulus, avoiding the impact of trapped anthocyanins within the cytoplasm is established.

Agronomic and physicochemical parameters of must and wine as a function of changes in ‘Cabernet Sauvignon’ grapevine canopy

This study aimed to evaluate the influence of vegetative canopy height on the agronomic characteristics and grape must and wine physicochemical properties of a ‘Cabernet Sauvignon’ vineyard in an espalier-trained system. The evaluated parameters comprised agronomic characteristics of ‘Cabernet Sauvignon’ grapevines and physicochemical compositions of ‘Cabernet Sauvignon’ musts and wines, as well as their phenolic compositions (anthocyanins, stilbenes, and flavonoids), and impact on wine contents of methoxypyrazines (volatile compounds that impart vegetal or earthy odors to wine, which are considered undesirable in large intensity). To that end, four heights of the vegetative canopy were tested: 60 cm (T1), 80 cm (T2), 100 cm (T3), and 120 cm (T4). The experiment was carried out in a commercial vineyard in the region of “Campanha Gaúcha” (Dom Pedrito, Rio Grande do Sul State, Brazil) during the productive cycles of 2015/16, 2016/17, 2017/18, and 2018/19. The main agronomic parameters were measured: estimated productivity per plant and hectare, and mean weight and number of clusters. All wines were elaborated by the same traditional winemaking methods. The physicochemical analyses of must and wines were performed by infrared spectroscopy using Fourier Transform Infrared Spectrometer (FTIR), and the phenolic analysis by high-efficiency liquid chromatography and UV-Vis spectrophotometry. Methoxypyrazines were quantified using headspace solid-phase microextraction (HS-SPME), followed by gas chromatography-mass spectrometry (GC-MS). The results showed that treatments did not influence agronomic parameters. However, technological maturation (sugar accumulation) had interesting results for plants managed at higher canopy heights, with respective results obtained for wine. Treatments had little influence on individual quantification of anthocyanins, although cycles had a high influence on their profile. The wines had low concentrations of methoxypyrazines and did not differ among treatments.

Identification and quantification of anthocyanins of 62 blueberry cultivars via UPLC-MS

Blueberries are rich in anthocyanins, which are plant-specific secondary metabolites that are a good source of plant nutrients. Although anthocyanins have been investigated, there is a lack of comprehensive detailed research that includes large numbers of blueberry cultivars, and the anthocyanin compositions of some cultivars are still unknown. Consequently, we determined the anthocyanin compositions of 62 cultivars using ultra-performance liquid chromatography–mass spectrometry (UPLC–MS). In total, we identified 30 anthocyanins derived from five kinds of anthocyanidin. We also identified four glycosides having three kinds of modifications. Among the tested cultivars, ‘Rubel’ contained the highest anthocyanin content, at 534.158 mg/100 g fresh weight (FW), whereas ‘Puru’ contained the lowest anthocyanin content at 71.734 mg/100 g FW. ‘Malvidin-gal’ had the highest average content among all the anthocyanin monomers, at 48.95 mg/100 g FW. ‘HL9’ had the greatest methylation degree, at 79.39%, and ‘HL2’ had the greatest acetylation degree, at 25.14%. This study provides detailed anthocyanin compositions and modifications of different blueberry cultivars. These data will aid in breeding high-quality blueberry cultivars and in developing related healthy functional foods.

Quantification of anthocyanins in blueberries (Vaccinium spp.) by modified QuEChERS and liquid chromatography‐mass spectrometry

AbstractAnthocyanins are among the most extensively investigated class of bioflavonoids in plant and fruit products due to their widespread presence in nature and their antioxidant activity. A method based on a modified quick, easy, cheap, effective, rugged, and safe method (QuEChERS) was developed for the determination of six common types of anthocyanins in blueberries using liquid chromatography–tandem mass spectrometry (LC–MS/MS). The QuEChERS procedure was optimized in the dispersive solid‐phase extraction (d‐SPE) for obtaining the targeted anthocyanins. This method provided the quantitative ranges between 2.5 and 1,000 μg L−1 (R2 &gt; 0.9974) for the target analytes with satisfactory recoveries and precisions. The developed method was successfully applied to the analysis of anthocyanins in blueberries from different countries and the total anthocyanins concentrations were in the range from 926.5 to 2074.6 μg kg−1. This proposed method provided an efficient and sensitive approach for the qualitative and quantitative determination of the common anthocyanins in blueberry samples.

Identification and quantification of anthocyanins, flavonoids, and phenolic acids in flowers of Rhododendron arboreum and evaluation of their antioxidant potential.

The current study aimed to investigate the anthocyanins, non-anthocyanins (flavonoids and phenolic acids), and free radicals scavenging potential in the flowers of Rhododendron arboreum using ultra high performance liquid chromatography with ion mobility quadrupole time of flight tandem mass spectrometry. A total of 25 constituents including nine anthocyanins, six phenolic acids, and ten flavonoids were identified in the flower extract. The major anthocyanins identified were cyanidin-3-O-β-galactoside (1), cyanidin-3-O-α-arabinoside (4), and cyanidin-3-O-rhamnoside (8), while quercetin glycosides were the main identified flavonoids in R. arboreum flowers. Additionally, ultra high performance liquid chromatography methods were developed and validated for the quantification of nine compounds (anthocyanins, flavonoid glycosides, and phenolic acids); five of them were quantified using internal standards. The extracts were analyzed for total phenolics (123.6mg GAE/g), anthocyanin content (1.76% w/w), and evaluated for antioxidant properties against 2,2-diphenyl-1-picrylhydrazyl radical (IC50 : 102.06 and 96.92 μg/mL) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical cation (112.25 and 45.59 μM TE/g) assays. The profiling of R. arboreum for anthocyanins is reported for the first time. The findings suggest that the flowers are a promising source of bioactive constituents and could be used as functional food, antioxidants, and nutraceuticals.

Anthocyanin Extraction Method and Sample Preparation Affect Anthocyanin Yield of Strawberries

Anthocyanins are a group of pigments with antioxidant activities that are present naturally in plants. The role of the pigment in human health and its quantitative analysis has attracted a lot of attention globally. A well-known and accurate method of anthocyanin quantification is based on spectrophotometric methods. However, these methods are subject to interference from impurities and need to be optimized for different plant matrixes and extraction conditions. Two experiments were designed to study (1) the effect of plant preparation methods (eg, fresh, frozen, and freeze-dried puree) on anthocyanin yield and (2) the effect of five anthocyanin extraction methods on anthocyanin yield of freeze-dried strawberry puree. Sample preparation methods did not have any effect on anthocyanin yield. Freeze-dried samples were used for their stability (ease of use and flexibility) to compare extraction methods. The anthocyanin yield was affected by the extraction method. Two methods containing chloroform gave the highest anthocyanin yield. One method with methanol:water:HCl gave intermediate results, and the pH differential and the other method with methanol:water:HCl (80:20:1) gave the lowest anthocyanin yields. Processing time (incubation time) was lowest in the pH differential method; however, the haze produced in this method may interfere with the spectrophotometric assessment of anthocyanins.

Identification and quantification of anthocyanins in honeysuckle under the conditions of Tomsk Province

Background. Honeysuckle is a promising berry crop for food and medical uses, which has recently become increasingly popular. Searching for sources with high content of bioactive substances to obtain new fruit cultivars with improved chemical composition continues to be relevant. Anthocyanin content and composition in honeysuckle cultivars depend on many factors, including plant reproduction conditions (temperature and humidity). Studying chemical composition of Siberian honeysuckle cultivars grown under the conditions of Western Siberia will make it possible to identify sources of high BAS content for various uses.Materials and methods. The target materials of the study were fruits of 21 honeysuckle cultivars grown in Western Siberia before and after freezing. The qualitative and quantitative composition of anthocyanins was assessed in ethanol extracts of honeysuckle fruits using HPLC technique.Results. The content of anthocyanins was higher in the fruits of honeysuckle grown in Western Siberia compared with the published data for the same cultivars reproduced in Belgorod Province (Central Black Earth Region). After freezing, the anthocyanin level in honeysuckle fruits remained the same and in some cases even increased.Conclusions. The obtained data helped to ascertain that honeysuckle fruits reproduced in Western Siberia are valuable sources of such bioactive compounds as anthocyanins.

Melatonin triggers tissue-specific changes in anthocyanin and hormonal contents during postharvest decay of Angeleno plums

Plum is a stone fruit that stands out for having a short shelf-life because of its high susceptibility to rapid deterioration. Part of this deterioration is explained by fruit overripening. Recently, the role of melatonin in delaying postharvest decay has been investigated but its regulatory function during overripening is still under extensive debate. In this study, to understand physiological events taking place in plums overripening and elucidate the role of melatonin on the postharvest quality of these fruits and its relationship to other plant hormones, Angeleno plums were sprayed with 10−4 M of melatonin solution immediately after harvest. We carried out tissue-specific (mesocarp and exocarp) analysis of total phenols and anthocyanin quantification, as well as the evaluation of different phytohormones by LC-MS/MS and fruit quality parameters. Results showed that during postharvest, endogenous melatonin contents decreased both in the mesocarp and the exocarp of Angeleno plums. Likewise, plum firmness also decreased and a strong correlation was found for this parameter with jasmonic acid (JA) and cytokinins. Conversely, after exogenous melatonin application, endogenous melatonin content increased both in mesocarp and exocarp but it had a differential effect depending on the plum tissue. Indeed, total phenol and anthocyanin contents arose by 21% and 58%, respectively, in the mesocarp after melatonin treatment but no variations were found in the exocarp of Angeleno plums. Hormonal analysis of Angeleno mesocarp also revealed an increase in the JA and its precursor, 12-oxo-phytodienoic acid (OPDA), on the fourth day after melatonin application as well as a positive correlation between melatonin and gibberellin 1 (GA1). These results suggest that melatonin may be acting as a signal molecule increasing phenolic compounds contents through direct regulation and by signaling with other phytohormones. Therefore, this research provides valuable information for understanding the regulatory role of melatonin and its relationship with plant hormones during overripening to contribute to improve the postharvest quality of plums.

Handheld Multifunctional Fluorescence Imager for Non-invasive Plant Phenotyping.

Fluorescence imaging has shown great potential in non-invasive plant monitoring and analysis. However, current systems have several limitations, such as bulky size, high cost, contact measurement, and lack of multifunctionality, which may hinder its applications in a wide range of settings including indoor vertical farming. Herein, we developed a compact handheld fluorescence imager enabling multipurpose plant phenotyping, such as continuous photosynthetic activity monitoring and non-destructive anthocyanin quantification. The compact imager comprises of pulse-amplitude-modulated multi-color light emitting diodes (LEDs), optimized light illumination and collection, dedicated driver circuit board, miniaturized charge-coupled device camera, and associated image analytics. Experiments conducted in drought stressed lettuce proved that the novel imager could quantitatively evaluate the plant stress by the non-invasive measurement of photosynthetic activity efficiency. Moreover, a non-invasive and fast quantification of anthocyanins in green and red Batavia lettuce leaves had excellent correlation (>84%) with conventional destructive biochemical analysis. Preliminary experimental results emphasize the high throughput monitoring capability and multifunctionality of our novel handheld fluorescence imager, indicating its tremendous potential in modern agriculture.

Colorimetric selective quantification of anthocyanins with catechol/pyrogallol moiety in edible plants upon zinc complexation.

Here is examined the colour development from common anthocyanins (i.e., cyanidin, delphinidin, malvidin, and pelargonidin glycosides) and from anthocyanins-rich extracts (i.e., bilberries, strawberries, and raspberries), using zinc-anthocyanin complexes as molecular probe. We have observed the absorbance increase in the blue region in presence of large excess of zinc ion at acidic pH for cyanidin and delphinidin derivatives, likely due to quinoidal base stabilization from catechol and pyrogallol moiety. The assay condition were studied and applied to natural extracts containing these compounds. The same behaviour was observed for bilberry and, to a minor extent, for raspberry extracts, due to the larger cyanidin/delphinidin contents in the former than in the latter. Anthocyanin standard UV-Vis analysis in buffer has shown a very good linear correlation for cyanidin and delphinidin (R2=0.995 and 0.997, respectively), good precision (CV%=7.4% and 5.3% respectively), high sensitivity (Cyε600nm=8300M-1cm-1, LOD=0.264±0.005mgL-1, LOQ=0.478±0.007mgL-1, and Dpε600nm=15,900M-1cm-1, LOD=0.143±0.002mgL-1, LOQ=0.478±0.007mgL-1). The effectiveness of this colorimetric method for the selective quantification of catechol/pyrogallol-based anthocyanins has been demonstrated in the aforementioned complex real matrices and compared to LC-MS/MS analysis and pH-differential method, offering a valuable tool to characterize plant and food extracts particularly rich in zinc-coordinating anthocyanins.