Development of a scalable, high-anthocyanin and low-acidity natural red food colorant from Hibiscus sabdariffa L

The hibiscus calyx contains 0.3-2.4% total anthocyanins, and is a promising source for naturally red food colorants. In this study, commercially available hibiscus calyces were subjected to ethanolic-aqueous extraction and chromatographic enrichment with the XAD-7HP resin, to create scalable, high-anthocyanin and low-acidity natural food colorants. Anthocyanins, organic and phenolic acids were monitored after each step using UHPLC-DAD and UHPLC-QQQ/MS. 75.67% total anthocyanins were recovered from calyces after double extractions, and the content increased by 8.50-14.90 times after the column enrichment, reaching 14.51-31.90% (by dry weight) in the final product. Chromatographic fractionation was also shown to effectively increase the total phenolic acids by 11.01-16.22 times, and remove an average of 98.58% of the total organic acids. High intensity redness at pH 2.5-3.5 indicated that the final product may be a promising, versatile natural food and beverage colorant in low pH products.

Research Progress on the Extraction and Purification of Anthocyanins and Their Interactions with Proteins

Anthocyanins, as the most critical water-soluble pigments in nature, are widely present in roots, stems, leaves, flowers, fruits, and fruit peels. Many studies have indicated that anthocyanins exhibit various biological activities including antioxidant, anti-inflammatory, anti-tumor, hypoglycemic, vision protection, and anti-aging. Hence, anthocyanins are widely used in food, medicine, and cosmetics. The green and efficient extraction and purification of anthocyanins are an important prerequisite for their further development and utilization. However, the poor stability and low bioavailability of anthocyanins limit their application. Protein, one of the three essential nutrients for the human body, has good biocompatibility and biodegradability. Proteins are commonly used in food processing, but their functional properties need to be improved. Notably, anthocyanins can interact with proteins through covalent and non-covalent means during food processing, which can effectively improve the stability of anthocyanins and enhance their bioavailability. Moreover, the interactions between proteins and anthocyanins can also improve the functional characteristics and enhance the nutritional quality of proteins. Hence, this article systematically reviews the extraction and purification methods for anthocyanins. Moreover, this review also systematically summarizes the effect of the interactions between anthocyanins and proteins on the bioavailability of anthocyanins and their impact on protein properties. Furthermore, we also introduce the application of the interaction between anthocyanins and proteins. The findings can provide a theoretical reference for the application of anthocyanins and proteins in food deep processing.

The Research Progress of Extraction, Purification and Analysis Methods of Phenolic Compounds from Blueberry: A Comprehensive Review

Blueberry is the source of a variety of bioactive substances, including phenolic compounds, such as anthocyanins, pterostilbene, phenolic acids, etc. Several studies have revealed that polyphenols in blueberry have important bioactivities in maintaining health, such as antioxidant and anti-tumor activities, immune regulation, the prevention of chronic diseases, etc. Therefore, these phenolic compounds in blueberries have been widely used in the field of healthcare, and the extraction, isolation, and purification of phenolic compounds are the prerequisites for their utilization. It is imperative to systematically review the research progress and prospects of phenolic compounds present in blueberries. Herein, the latest progress in the extraction, purification, and analysis of phenolic compounds from blueberries is reviewed, which can in turn provide a foundation for further research and usage of blueberries.

Anthocyanins in Different Food Matrices: Recent Updates on Extraction, Purification and Analysis Techniques

Anthocyanins (ANCs), a kind of natural pigments, are widely present in food substrates. Evidence has shown that ANCs can promote health in terms of anti-oxidation, anti-tumor, and anti-inflammation. However, the oxidative stability of ANCs limits accurate quantitation and analysis. Therefore, faster, more accurate, and highly sensitive extraction and determination methods are necessary for understanding the role of ANCs in medicine and food. This review presents an updated overview of pretreatment and detection techniques for ANCs in various food substrates since 2015. Liquid-liquid extraction and various green solvent extraction methods, such as accelerated solvents extraction, deep eutectic solvents extraction, ionic liquids extraction, and supercritical fluid extraction, are commonly used pretreatment methods for extraction and purification of ANCs. Liquid chromatography coupled with different detectors (tandem mass spectrometry and UV detectors) and spectrophotometry methods are some of the determination methods for ANC. This study has updated, compared, and discussed different pretreatment and analysis methods. Moreover, the advanced methods and development prospects in this field are comprehensively summarized, which can provide references for further utilization of ANCs.

Isolation, characterization of bamboo leaf flavonoids by size exclusion chromatography and their antioxidant properties

The utilization of bamboo industry exhibits varied but still needs to be improved. Bamboo leaf flavonoid (BLF) is an important resource of bamboo which has become a research focus. However, the isolation and purification techniques of four flavonoid carbon glycosides (orientin, isoorientin, vitexin, and isovitexin) from BLF were still confronted with difficulties due to their complex and similar structures, which obstructed the development of bamboo utilization. In this paper, a purification technology of four flavonoid carbon glycosides from BLF by Sephadex LH-20 was improved. The results were evaluated by HPLC and pharmacological activity. Specifically, the eluent, flow rate, and loading amount were investigated respectively. According to the results, the eluent would dominate the isolation effect among three factors. High concentration of isoorientin and four flavonoid carbon glycosides would be obtained under the optimized condition (The eluent was 70% methanol, the loading amount was 1.5 g, and the flow rate was 0.5 mL·min-1). Meanwhile, the link between flavonoid carbon glycosides content and their antioxidant activity in vitro was also revealed. Overall, the results suggested that BLF may serve as potential functional food additives and medicine.

Counter-Current Fractionation-Assisted Bioassay-Guided Separation of Active Compound from Blueberry and the Interaction between the Active Compound and α-Glucosidase

An efficient strategy for the selection of active compounds from blueberry based on counter-current fractionation and bioassay-guided separation was established in this study. Blueberry extract showed potential α-glucosidase inhibitory activity. After extraction by different solvents, the active components were enriched in water. The water extract was divided into six fractions via high-speed counter-current chromatography to further track the active components. Results indicated that the α-glucosidase inhibition rate of F4 was remarkable higher than the others. Cyanidin-3-glucoside (C3G) with a purity of 94.16% was successfully separated from F4 through column chromatography, and its structure was identified by ultraviolet spectral, Fourier-transformed infrared spectroscopy, high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry, ¹H nuclear magnetic resonance (NMR), and ¹³C NMR. The interaction mechanism between C3G and α-glucosidase was clearly characterized and described by spectroscopic methods, including fluorescence and circular dichroism (CD) in combination with molecular docking techniques. C3G could spontaneously bind with α-glucosidase to form complexes by hydrogen bonds. The secondary structure of α-glucosidase changed in varying degrees after complexation with C3G. The α-helical and β-turn contents of α-glucosidase decreased, whereas the β-sheet content and the irregular coil structures increased. Molecular docking speculated that C3G could form hydrogen bonds with α-glucosidase by binding to the active sit (Leu 313, Ser 157, Tyr 158, Phe 314, Arg 315, and two Asp 307). These findings may be useful for the development of functional foods to tackle type 2 diabetes.

Ultrasound-assisted enzymatic extraction of anthocyanins from grape skins: optimization, identification, and antitumor activity

Grape skins produced during the grape juice production and processing contain abundant anthocyanins and other active compounds. Consequently, this study optimized the extraction conditions for ultrasound-assisted enzymatic extraction (UAEE) of anthocyanins from grape skins via response surface methodology coupled with genetic algorithm. The optimum extraction parameters to achieve the highest anthocyanins yield (3.01 ± 0.04) mg/g from grape skins by UAEE were obtained under an extraction temperature of 50 °C, ultrasonic power of 400 W, pectinase dosage of 0.16%, and extraction time of 28 min. The AB-8 macroporous resin combined Sephadex LH-20 techniques were further employed to purify the anthocyanins extracts obtained under optimum extraction conditions (AEOEC), and the main anthocyanins were identified using high-performance liquid chromatography tandem mass spectrometry. The purified anthocyanins contained two anthocyanins in terms of delphinidin-3,5-O-diglucoside and cyanidin-3-O-rutinoside with purity of 91.35% and 92.64%, respectively. Ultimately, we further evaluated the antitumor activity of AEOEC and two purified anthocyanins on breast cancer. The results indicated that the antitumor effect of AEOEC on breast cancer MCF-7 cells was better than that of two purified anthocyanins. In addition, AEOEC could memorably increase intracellular reactive oxygen species levels and apoptosis of MCF-7 cells, and arrest MCF-7 cells in the G2/M phases. The findings provide an effective and feasible method for anthocyanins extraction and reduce the environmental burden of this waste.

Optimization Ultrasound-Assisted Deep Eutectic Solvent Extraction of Anthocyanins from Raspberry Using Response Surface Methodology Coupled with Genetic Algorithm

Raspberries have been reported to contain abundant anthocyanins and other active compounds. To extract anthocyanins from raspberries more efficiently, a novel procedure of ultrasound-assisted deep eutectic solvent extraction (UADESE) was proposed in this paper. The extraction process was optimized by response surface methodology coupled with a genetic algorithm. The optimum extraction parameters to achieve the highest yield of anthocyanins 1.378 ± 0.009 mg/g from raspberry powder via UADESE were obtained at a water content of 29%, ultrasonic power of 210 W, extraction temperature of 51 °C and extraction time of 32 min. The AB-8 macroporous resin combined with the high-speed counter current chromatography (HSCCC) method were further used to isolate and purify the anthocyanins extracts obtained under optimum extraction conditions, and the structure of purified anthocyanins components were identified by UV-Visible spectrophotometer (UV-Vis), high-performance liquid chromatography (HPLC), high-performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS/MS), ¹H nuclear magnetic resonance (NMR) and ¹³C-NMR spectra. The two anthocyanins (cyanidin-3-glucoside with a purity of 92.25% and cyanidin-3-rutinoside with a purity of 93.07%) identified were consistent with those present in raspberries. These findings provided an effective and feasible method for extraction, isolation and purification of anthocyanins from natural plant resources.